钴掺杂稀磁氧化物的局域结构与磁学性能
|
摘要
稀磁氧化物是一种有重要前景的自旋源,是新一代自旋器件的重要支撑材料。制备具有室温铁磁性的稀磁氧化物,探索其磁性来源,并将其应用于自旋器件是自旋电子学领域的研究热点之一。本文采用磁控溅射、离子注入和脉冲激光沉积技术分别制备了Co掺杂ZnO和LiNbO_3稀磁氧化物材料,系统研究了掺杂浓度、基片类型及其温度、氧分压和沉积速率等工艺参数对稀磁氧化物局域结构和磁学性能的影响,重点探讨了磁性与Co的局域结构之间的关系、稀磁氧化物的磁性起源,并利用获得的稀磁氧化物材料,设计和构造了隧道结原型自旋器件,研究了隧道结的隧道磁电阻和相关的自旋极化、注入与传输现象。
研究结果表明,采用磁控溅射技术成功获得了居里温度在700K以上的Co掺杂ZnO稀磁材料,其磁矩与掺杂浓度、基片密切相关。在LiNbO_3铁电基片上的(4%) Co掺杂ZnO绝缘态薄膜中观察到6.1μB/Co的室温巨磁矩,发现磁性薄膜/铁电基片之间的逆磁电耦合能有效提高薄膜的磁性,在束缚磁极子机制的基础上发展了超耦合模型,并对巨磁矩现象进行了合理的解释。通过调控氧分压,实现了稀磁绝缘体与稀磁半导体Co掺杂ZnO单晶薄膜的可控生长。基于绝缘态的Co掺杂ZnO具有室温强磁性,以及分离结构缺陷与载流子浓度对磁性的影响,揭示了结构缺陷是稀磁氧化物室温铁磁性的真正起源,载流子调制机制中的载流子只是结构缺陷的副产物,从而对磁性机制进行了较完整的诠释。
利用所获得的Co掺杂ZnO稀磁材料,成功构造了全外延的(Zn,Co)O/ZnO/(Zn,Co)O隧道结。该隧道结在4K下磁场为2T时具有20.8%的正隧道磁电阻(TMR)。由于界面质量的改善与兼容性,TMR能保持到室温,说明实现了室温的自旋注入和传输。实验进一步发现双隧穿层的(Zn,Co)O基隧道结表现出反常的偏压相关隧道磁电阻曲线,不仅对深入认识自旋现象有重要意义,还将拓宽使用隧道结器件的偏压范围。
实验还表明(5%) Co掺杂LiNbO_3材料也具有很好的室温稀磁特性,验证了基于缺陷的束缚磁极子机制。Co掺杂LiNbO_3是一种室温单相多铁材料,它的铁磁和铁电居里温度非常接近,分别为540K和610K。
Diluted magnetic oxides (DMO) are promising spin sources, which are considered as important supporting materials for a new generation of spintronics. Preparing DMO with room temperature ferromagnetism (RTFM), exploring the origin of RTFM, and applicating DMO to spintronics are the hot topics in the field of spintronics. The effects of preparation parameters, such as doping concentration, substrate and its temperature, oxygen partial pressure and deposition rate, on the local structure and ferromagnetic ordering of DMO have been systematically studied. This dissertation discusses Co-doped ZnO and LiNbO_3 prepared by magnetron sputtering, as well as ion implantation and pulsed laser deposition, respectively. These researches concentrate on the correlations between magnetic properties and the local structure, the origin of RTFM in DMO. Employing the prepared DMO materials, magnetic tunnel junctions (MTJ) prototype spintronics are designed and fabricated, whose tunnel magnetoresistance (TMR) and the corresponding spin polarization, injection and trasnsport are explored.
The results show that the Co-doped ZnO films deposited by magnetron sputtering possess a Curie temperature higher than 700K, and the magnetic moments of Co are intimately correlated to the doping concentration and the substrate. A giant magnetic moment of 6.1μB/Co is observed in (4 at.%) Co-doped ZnO insulating films. Converse magnetoelectric coupling between Zn0.96Co0.04O films and ferroelectric substrates can effectively enhance the ferromagnetic ordering. A super coupling mechanism based on bound magnetic polarons (BMP) is developed to understand the giant magnetic moment. Taking advantage of modulating the oxygen partial pressure, diluted magnetic insulators (DMI) and semiconductors (DMS) in single-crystal Zn0.96Co0.04O films can be controllably synthesized. Based on the insulating Co-doped ZnO films showing robust RTFM, as well as separating the effects of carrier concentrations and structural defects on magnetization, we unambiguously demonstrate that RTFM is profoundly correlated with structural defects, and the carriers involved in carrier-mediated exchange are by-products of defects created in ZnO. The origin of RTFM in DMO is then clearly clarified.
Taking advantage of the prepared Co-doped ZnO films, fully epitaxial (Zn,Co)O/ZnO/(Zn,Co)O junctions are successfully fabricated. A positive TMR of 20.8% is obtained at 4 K and at 2 Tesla. Due to the improved crystallinity and compatibility of electrode/barrier interfaces, TMR can resist up to room temperature, indicating that spin injection and transport at room temperature are realized in the junctions. (Zn,Co)O-based MTJ with double-barriers show anomalous bias voltage dependent TMR, which are not only significant for deeply exploring spin phenomena, but also expand the range of bias voltage for using MTJ devices.
The results also show that (5%) Co-doped LiNbO_3 is a real DMO with RTFM, demonstrating that the bound magnetic polarons based on defects are the origin of RTFM in DMO. Co-doped LiNbO_3 is a room temperature single-phase multiferroic, which possesses very similar ferromagnetic and ferroelectric Curie temperature, i.e., 540 K and 610 K, respectively.
研究结果表明,采用磁控溅射技术成功获得了居里温度在700K以上的Co掺杂ZnO稀磁材料,其磁矩与掺杂浓度、基片密切相关。在LiNbO_3铁电基片上的(4%) Co掺杂ZnO绝缘态薄膜中观察到6.1μB/Co的室温巨磁矩,发现磁性薄膜/铁电基片之间的逆磁电耦合能有效提高薄膜的磁性,在束缚磁极子机制的基础上发展了超耦合模型,并对巨磁矩现象进行了合理的解释。通过调控氧分压,实现了稀磁绝缘体与稀磁半导体Co掺杂ZnO单晶薄膜的可控生长。基于绝缘态的Co掺杂ZnO具有室温强磁性,以及分离结构缺陷与载流子浓度对磁性的影响,揭示了结构缺陷是稀磁氧化物室温铁磁性的真正起源,载流子调制机制中的载流子只是结构缺陷的副产物,从而对磁性机制进行了较完整的诠释。
利用所获得的Co掺杂ZnO稀磁材料,成功构造了全外延的(Zn,Co)O/ZnO/(Zn,Co)O隧道结。该隧道结在4K下磁场为2T时具有20.8%的正隧道磁电阻(TMR)。由于界面质量的改善与兼容性,TMR能保持到室温,说明实现了室温的自旋注入和传输。实验进一步发现双隧穿层的(Zn,Co)O基隧道结表现出反常的偏压相关隧道磁电阻曲线,不仅对深入认识自旋现象有重要意义,还将拓宽使用隧道结器件的偏压范围。
实验还表明(5%) Co掺杂LiNbO_3材料也具有很好的室温稀磁特性,验证了基于缺陷的束缚磁极子机制。Co掺杂LiNbO_3是一种室温单相多铁材料,它的铁磁和铁电居里温度非常接近,分别为540K和610K。
Diluted magnetic oxides (DMO) are promising spin sources, which are considered as important supporting materials for a new generation of spintronics. Preparing DMO with room temperature ferromagnetism (RTFM), exploring the origin of RTFM, and applicating DMO to spintronics are the hot topics in the field of spintronics. The effects of preparation parameters, such as doping concentration, substrate and its temperature, oxygen partial pressure and deposition rate, on the local structure and ferromagnetic ordering of DMO have been systematically studied. This dissertation discusses Co-doped ZnO and LiNbO_3 prepared by magnetron sputtering, as well as ion implantation and pulsed laser deposition, respectively. These researches concentrate on the correlations between magnetic properties and the local structure, the origin of RTFM in DMO. Employing the prepared DMO materials, magnetic tunnel junctions (MTJ) prototype spintronics are designed and fabricated, whose tunnel magnetoresistance (TMR) and the corresponding spin polarization, injection and trasnsport are explored.
The results show that the Co-doped ZnO films deposited by magnetron sputtering possess a Curie temperature higher than 700K, and the magnetic moments of Co are intimately correlated to the doping concentration and the substrate. A giant magnetic moment of 6.1μB/Co is observed in (4 at.%) Co-doped ZnO insulating films. Converse magnetoelectric coupling between Zn0.96Co0.04O films and ferroelectric substrates can effectively enhance the ferromagnetic ordering. A super coupling mechanism based on bound magnetic polarons (BMP) is developed to understand the giant magnetic moment. Taking advantage of modulating the oxygen partial pressure, diluted magnetic insulators (DMI) and semiconductors (DMS) in single-crystal Zn0.96Co0.04O films can be controllably synthesized. Based on the insulating Co-doped ZnO films showing robust RTFM, as well as separating the effects of carrier concentrations and structural defects on magnetization, we unambiguously demonstrate that RTFM is profoundly correlated with structural defects, and the carriers involved in carrier-mediated exchange are by-products of defects created in ZnO. The origin of RTFM in DMO is then clearly clarified.
Taking advantage of the prepared Co-doped ZnO films, fully epitaxial (Zn,Co)O/ZnO/(Zn,Co)O junctions are successfully fabricated. A positive TMR of 20.8% is obtained at 4 K and at 2 Tesla. Due to the improved crystallinity and compatibility of electrode/barrier interfaces, TMR can resist up to room temperature, indicating that spin injection and transport at room temperature are realized in the junctions. (Zn,Co)O-based MTJ with double-barriers show anomalous bias voltage dependent TMR, which are not only significant for deeply exploring spin phenomena, but also expand the range of bias voltage for using MTJ devices.
The results also show that (5%) Co-doped LiNbO_3 is a real DMO with RTFM, demonstrating that the bound magnetic polarons based on defects are the origin of RTFM in DMO. Co-doped LiNbO_3 is a room temperature single-phase multiferroic, which possesses very similar ferromagnetic and ferroelectric Curie temperature, i.e., 540 K and 610 K, respectively.
引文
[1] Wolf S A, Awschalom D D, Buhrman R A, et al. Spintronics: A spin-based electronics vision for the future. Science, 2001, 294: 1488-1495.
[2] Zutic I, Fabian J, Das Sarma S. Spintronics: Fundamentals and application. Rev. Mod. Phys., 2004, 76(2): 323-410.
[3] Baibich M N, Brote J M, Fert A, et al. Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices. Phys. Rev. Lett., 1988, 61(21): 2472-2475.
[4] Binasch G, Grünberg P, Saurenbach F, et al. Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange. Phys. Rev. B, 1988, 39 (7): 4828-4830.
[5] Prinz G A. Magnetoelectronics. Science, 1998, 282: 1660-1663.
[6] Levy P M, Zhang S, Fert A. Electrical conductivity of magnetic multilayered structures. Phys. Rev. Lett., 1990, 65 (13): 1643-1646.
[7] Dieny B, Speriosu V S, Parkin S S P, et al. Giant magnetoresistive in soft ferromagnetic multilayers. Phys. Rev. B, 1991, 43 (1): 1297-1300.
[8] Helmolt R V, Wecker J, Holzapfel B, et al. Giant negative magnetoresistance in perovskitelike La2/3Ba1/3MnOx ferromagnetic films. Phys. Rev. Lett., 1993, 71 (14):2331-2333.
[9] Moodera J S, Kinder L R, Wong T M, et al. Large magnetoresistance at room temperature in ferromagnetic thin film tunnel junctions. Phys. Rev. Lett., 1995, 74: 3273-3276.
[10] Julliere M. Tunneling between ferromagnetic films. Phys. Lett., 1975, 54A (3): 225-226.
[11] De Teresa J M, Barthélémy A, Fert A, et al. Role of metal-oxide interface in determing the spin polarization of magnetic tunnel junctions. Science, 1999, 286: 507-509.
[12] Yuasa S, Nagahama T, Fukushima A, et al. Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions. Nat. Mater., 2004, 3: 868-871.
[13] Parkin S S P, Kaiser C, Panchula A, et al. Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers. Nat. Mater., 2004, 3: 862-867.
[14] Das Sarma S, Fabian J, Hu X, et al. Spin electronics and spin computation. Solid State Commun., 2001, 119: 207-215.
[15] Ohno Y, Young D K, Beschoten B, et al. Electrical spin injection in a ferromagnetic semiconductor. Nature, 1999, 402: 790-792.
[16] Ohno H, Shen A, Matsukura F. (Ga,Mn)As: A new diluted magnetic semiconductor based on GaAs. Appl. Phys. Lett., 1996, 69(3): 363-365.
[17] Fiederling R, Keim M, Reuscher G, et al. Injection and detection of a spin-polarized current in a light-emitting diode. Nature,1999,402: 787-789.
[18] Pan F, Song C, Liu X J, et al. Ferromagnetism and possible application in spintronics of transition-metal-doped ZnO films. Mater. Sci. Eng. R., 2008, 62: 1-35.
[19] Pearton S J, Abernathy C R, Norton D P, et al. Advances in wide bandgap materials for semiconductor spintronics. Mater. Sci. Eng. R., 2003, 40: 137-168.
[20] Jedema F J, Filip A T, Wees B J van, Electrical spin injection and accumulation at room temperature in an all-metal mesoscopic spin valve. Nature, 2001, 410: 345-348.
[21] Ohno H, Chiba D, Matsukura F, et al. Electric-field control of ferromagnetism. Nature, 2000, 408: 944-946.
[22] Allwood D A, Xiong G, Cooke M D, et al. Submicrometer ferromagnetic NOT gate and shife register. Science, 2002, 296: 2003-2006.
[23] Filip A T, LeClair P, Smits C J P, et al. Spin-injection device based on EuS magnetic tunnel barriers. Appl. Phys. Lett., 2002, 81(10): 1815-1817.
[24] Schmidt G, Ferrand D, Molenkamp L W, et al. Fundamental obstacle for electrical spin injection from a ferromagnetic metal into a diffusive semiconductor. Phys. Rev. B, 2000, 62: R4790-R4793.
[25] Awschalom D D, FlattéM E. Challenges for semiconductor spintronics. Nat. Phys., 2007, 3: 153-159.
[26] Fukumura T, Jin Z W, Ohtomo A, et al. An oxide-diluted magnetic semiconductor: Mn-doped ZnO. Appl. Phys. Lett., 1999, 75: 3366-3368.
[27] Fukumura T, et al. Magnetic properties of Mn-doped ZnO. Appl. Phys. Lett., 2001, 78: 958-960.
[28] Jin Z W, Murakami M, Fukumura T, et al. Combinatorial laser MBE synthesis of 3d ion doped epitaxial ZnO thin films. J. Cryst. Growth, 2000, 214/215: 55-58.
[29] Ando, K. et al. Magneto-optical properties of ZnO-based diluted magnetic semiconductors. J. Appl. Phys., 2001, 89: 7284.
[30] Ando K, Satio H, Jin Z W, et al. Large magneto-optical effect in an oxide diluted magnetic semiconductor Zn1-xCoxO. Appl. Phys. Lett., 2001, 78(18): 2700-2702.
[31] Ueda K, Tabata H, Kawai T. Magnetic and electric properties of transition-metal-doped ZnO films. Appl. Phys. Lett., 2001, 79: 988-990.
[32] Pearton S J, Abernathy C R, Overberg M E, et al. Wide band gap ferromagnetic semiconductors and oxides. J. Appl. Phys., 2003, 93(1): 1-13.
[33] Pearton S J, Heo W H, Ivill M, et al. Dilute magnetic semiconducting oxides. Semicond. Sci. Technol., 2004, 19: R59-R74.
[34] Pearton S J, Norton D P, Ip K. Recent progress in processing and properties of ZnO. Prog. Mater. Sci., 2005, 50: 293-340.
[35] Prellier W, Fouchet A, Mercey B. Oxide-diluted magnetic semiconductors: a review of the experimental status. J. Phys.: Condens. Matter, 2003, 15: R1583-R1601.
[36] Sharma P, Gupta A, Rao K V, et al. Ferromagnetism above room temperature in bulk and transparent thin films of Mn-doped ZnO. Nat. Mater., 2003, 2: 673-677.
[37] Radovanovic P V, Gamelin D R. High-temperature ferromagnetism in Ni2+-doped ZnO aggregates prepared from colloidal diluted magnetic semiconductor quantum dots. Phys. Rev. Lett., 2003, 91: 157202.
[38] Prellier W, Fouchet A, Mercey B, et al. Laser ablation of Co:ZnO films deposited from Zn and Co metal targets on (0001) Al2O3 substrates. Appl. Phys. Lett., 2003, 82(20): 3490-3492.
[39] Tuan A C , Bryan J D, Pakhomov A B, et al. Epitaxial growth and properties of cobalt-doped ZnO onα-Al2O3 single-crystal substrates. Phys. Rev. B, 2004, 70: 054424.
[40] Janisch R, Gopal P, Spaldin N A. Transition metal-doped TiO2 and ZnO-present status of the field. J. Phys.: Condens. Matter, 2005, 17: R657-R689.
[41] Fukumura T, Toyosaki H, Yamada Y. Magnetic oxide semiconductors. Semicond. Sci. Technol., 2005, 20: S103-S111.
[42] Coey J M D, Venkatesan M, Fitzgerald C B. Donor impurity band exchange in dilute ferromagnetic oxides. Nat. Mater., 2005, 4: 173-179.
[43] Ozgürü, Alivov Ya I, Liu C, et al. A comprehensive review of ZnO materials and devices. J. Appl. Phys., 2005, 98: 041301.
[44] Chambers S A. Ferromagnetism in doped thin-film oxide and nitride semiconductors and dielectrics. Surf. Sci. Rep., 2006, 61: 345-381.
[45] Pearton S J, Norton D P, Ivill M P, et al. ZnO doped with transition metal ions. IEEE Trans. Electron Devices, 2007, 54: 1040-1048.
[46] Ney A, Ollefs K, Ye S, et al. Absence of intrinsic ferromagnetic interactions of isolated and paired Co dopant atoms in Zn1-xCoxO with high structural perfection. Phys. Rev. Lett., 2008, 100: 157201.
[47] Behan A J, Mokhtari A, Blythe H J, et al. Two magnetic regimes in doped ZnO corresponding to a dilute magnetic semiconductor and a dilute magnetic insulator. Phys. Rev. Lett., 2008, 100: 047206.
[48] Rode K, Mattana R, Anane A, et al. Magnetism of (Zn,Co)O thin films probed by x-ray absorption spectroscopies. Appl. Phys. Lett., 2008, 92: 012509.
[49] Saito H, Zayets V, Yamagata S, et al. Room-temperature ferromagnetism in a II-VI diluted magnetic semiconductor Zn1-xCrxTe. Phys. Rev. Lett., 2003, 90: 207202.
[50] Kuroda S, Nishizawa N, Takita K, et al. Origin and control of high-temperature ferromagnetism in semiconductors. Nat. Mater., 2007, 6: 440-446.
[51] Radovanovic P V. Synthesis, spectroscopy and magnetism of diluted magnetic semiconductor nanocrystal. Ph. D. Thesis, University of Washington, Seattle, Washington, 2004.
[52] Matsumoto Y, Murakami M, Shono T, et al. Room-temperature ferromagnetism in transparent transition metal-doped titanium dioxide. Science, 291: 854-856.
[53] Shinde S R, Ogale S B, Higgins J S, et al. Co-occurrence of superparamagnetism and anomalous Hall effect in highly reduced cobalt-doped rutile TiO2-δfilms. Phys. Rev. Lett., 2004, 92: 166601.
[54] Shutthanandan V, Thevuthasan S, Heald S M, et al. Room-temperature ferromagnetism in ion-implanted Co-doped TiO2(110) rutile. Appl. Phys. Lett., 2004, 84(22): 4466-4468.
[55] Kaspar T C, Heald S M, Wang C M, et al. Negligible magnetism in excellent structural quality CrxTi1-xO2 anatase: Contrast with high-TC ferromagnetism in structurally defective CrxTi1-xO2. Phys. Rev. Lett. 2005, 95: 217203.
[56] Kaspar T C, Droubay T, Shutthanandan V, et al. Ferromagnetism and structure of epitaxial Cr-doped anatase TiO2 thin films. Phys. Rev. B, 2006, 73: 155327.
[57] Macdonald A H, Schiffer P, Samarth N. Ferromagnetic semiconductors: moving beyond (Ga,Mn)As. Nat. Mater., 2005, 4: 195-202.
[58] Wu R. Mn distribution and spin polarization in Ga1-xMnxAs. Phys. Rev. Lett., 2005, 94: 207201.
[59] Stotz J H, Hey R, Santos P, et al. Coherent spin transport through dynamic quantum dots. Nat. Mater., 2005, 4: 585-588.
[60] Jungwirth T, Sinova J, Ma?ek J, et al. Theory of ferromagnetic (III,Mn)V semiconductors. Rev. Mod. Phys., 2006, 78: 809-864.
[61] Theodoropoulou N, Hebard A F, Overberg M E, et al. Unconventional carrier-mediated ferromagnetism above room temperature in ion-implanted (Ga,Mn)P:C. Phys. Rev. Lett., 2002, 89(10): 107203.
[62] Kumar D, Antifakos J, Blamire M G, et al. High Curie temperatures in ferromagnetic Cr-doped AlN thin films. Appl. Phys. Lett., 2004, 84(24): 5004-5006.
[63] Park Y D, Hanbicki A T, Erwin S C, et al. A group-IV ferromagnetic semiconductor: MnxGe1-x. Science, 2002, 295: 651-654.
[64] Zhao Y G, Shinde S R, Ogale S B, et al. Co-doped La0.5Sr0.5TiO3: Diluted magnetic oxide system with high Curie temperature. Appl. Phys. Lett., 2004, 83(11): 2199-2201.
[65] Worledge D C, Geballe T H. Spin-polarized tunneling in La0.67Sr0.33MnO3. Appl. Phys. Lett., 2004, 76(7): 4466-4468.
[66] Lee J S, Khim Z G, Park Y D, et al. Magnetic properties of Co- and Mn-implanted BaTiO3, SrTiO3 and KTaO3. Solid-State Electron., 2003, 47: 2225-2230.
[67] Jungwirth T, Wang K Y, Ma?ek J, et al. Prospects for high temperature ferromagnetism in (Ga,Mn)As semiconductors. Phys. Rev. B, 2005, 72: 165204.
[68] Dietl T, Ohno H, Matsukura F, et al. Zener model description of ferromagnetism in zinc-blende magnetic semiconductors. Science, 2000, 287: 1019-1022.
[69] Esaki L, Stiles P J, von Molnar S. Magnetointernal field emission in junctions of magnetic insulators. Phys. Rev. Lett., 1967, 19: 852-854.
[70] Munekata H, Ohno H, von Molnar S, et al. Diluted magnetic semicondutors. Phys. Rev. Lett., 1989, 63(17): 1849-1852.
[71] Dietl T, Spalek J. Effect of thermodynamic fluctuations of magnetization on the bound magnetic polaron in dilute magnetic semiconductors. Phys. Rev. B, 1983, 28(3): 1548-1563.
[72] Story T, Galazka R R, Frankel R B, et al. Carrier-concentration-induced ferromagnetism in PbSnMnTe. Phys. Rev. Lett., 1986, 56(7): 777-779.
[73] Ohno H, Munekata, Penney T. Magnetotransport properties of p-type (In,Mn)As diluted magnetic III-V semiconductors. Phys. Rev. Lett., 1992, 68(17): 2664- 2667.
[74] Sato K, Katayama-Yoshida H. Material design for transparent ferromagnets with ZnO-based magnetic semiconductors. Jpn. J. Appl. Phys., 2000, 39: L555-L558.
[75] Hong N H, Sakai J, Prellier W, et al. Room temperature ferromagnetism in laser ablated transition-metal-doped TiO2 thin films on various types of substrates. J. Phys. D: Appl. Phys., 2005, 38: 816-821.
[76] Sudakar C, Thakur J S, Lawes G, et al. Ferromagnetism induced by planar nanoscale CuO inclusions in Cu-doped ZnO thin films. Phys. Rev. B, 2007, 75: 054423.
[77] Coey J M D, Douvalis A P, Fitzgerald C B, et al. Ferromagnetism in Fe-doped SnO2 thin films. Appl. Phys. Lett., 2004, 84(8): 1332-1334.
[78] Ogale S B, Choudhary R J, Buban J P, et al. High temperature ferromagnetism with a giant magnetic moment in transparent Co-doped SnO2-δ. Phys. Rev. Lett., 2003, 91: 077205.
[79] Tiwari A, Bhosle V M, Ramachandran S, et al. Ferromagnetism in Co doped CeO2: Observation of a giant magnetic moment with a high Curie temperature. Appl. Phys. Lett., 2006, 88: 142511.
[80] Sasaki T, Sonoda S, Yamamoto Y, et al. Magnetic and transport characteristics on high Curie temperature ferromagnet of Mn-doped GaN. J. Appl. Phys., 2002, 91(10): 7911-7913.
[81] Philip J, Punnoose A, Kim B I, et al. Carrier-controlled ferromagnetism in transparent oxide semiconductors. Nat. Mater., 2006, 5: 298.
[82] Ramachandra Rao M S, Kundaliya D C, Ogaleb S B, et al. Search for ferromagnetism in undoped and cobalt-doped HfO2-δ. Appl. Phys. Lett., 2006, 88: 142505.
[83] Park J H, Kim M G, Jang H M, et al. Co-metal clustering as the origin of ferromagnetism in Co-doped ZnO thin films. Appl. Phys. Lett., 2004, 84(4): 1338-1340.
[84] Huang J C A, Hsu H S. Inspection of magnetic semiconductor and clustering structure in CoFe-doped ZnO films by bias-dependent impedance spectroscopy. Appl. Phys. Lett., 2005, 87: 132503.
[85] MacManus-Driscoll J L, Khare N, Liu Y, et al. Structural evidence for Zn interstitionals in ferromagnetic Zn1-xCoxO films. Adv. Mat., 2007, 19: 2925-2929.
[86] Kundaliya D C, Ogale S B, Lofland S E, et al. On the origin of high-temperature ferromagnetism in the low-temperature-processed Mn–Zn–O system. Nat. Mater., 2004, 3, 709-714.
[87] Dietl T, Andrearczyk T, Lipińska A, et al. Origin of ferromagnetism in Zn1-xCoxO from magnetization and spin-dependent magnetoresistance measurements. Phys. Rev. B, 2007, 76: 155312.
[88] Kuroda S, Nishizawa N, Takita K, et al. Origin and control of high-temperature ferromagnetism in semiconductors. Nat. Mater., 2007, 6, 440-446.
[89] Schwartz D A, Gamelin D R. Reversible 300 K ferromagnetic ordering in a diluted magnetic semiconductor. Adv. Mater., 2004, 16(17): 2115-2119.
[90] Yan W, Sun Z, Liu Q, et al. Structures and magnetic properties of (Mn,N)-codoped ZnO thin films. Appl. Phys. Lett., 2007, 90: 242509.
[91] Spaldin N A. Search for ferromagnetism in transition-metal-doped piezoelectric ZnO. Phys. Rev. B, 2004, 69: 125201.
[92] Venkatesan M, Fitzgerald C B, Lunney J G, et al. Anisotropic ferromagnetism in substituted zinc oxide. Phys. Rev. Lett., 2004, 93: 177206.
[93] Coey J M D, Venkatesan M, Fitzgerald C B, et al. Anisotropy of the magnetization of a dilute magnetic oxide. J. Magn. Magn. Mater. 2005, 290-291, 1405-1407.
[94] Dorneles L S, O’Mahony D, Fitzgerald C B, et al. Structural and compositional analysis of transition-metal-doped ZnO and GaN PLD thin films. Appl. Surf. Sci., 2005, 248: 406-410.
[95] Saeki H, Tabata H, Kawai T. Magnetic and electric properties of vanadium doped ZnO films. Solid Solid Commun., 2001, 120: 439-443.
[96] Hong N H, Sakai J, Hassini A. Magnetic properties of V-doped ZnO thin films. J. Appl. Phys., 2005, 97: 10D312.
[97] Hong N H, Sakai J, Huong N T, et al. Role of defects in tuning ferromagnetism in diluted magnetic oxide thin films. Phys. Rev. B, 2005, 72: 045336.
[98] Liu H, Zhang X, Li L, et al. Role of point defects in room-temperature ferromagnetism Cr-doped ZnO. Appl. Phys. Lett., 2007, 91: 072511.
[99] Roberts B K, Pakhomov A B, Voll P, et al. Surface scalling of magnetism in Cr:ZnO dilute magnetic dielectric thin films. Appl. Phys. Lett., 2008, 92: 072511.
[100] García M A, Ruiz-González M L, Quesada A, et al. Interface double-exchange ferromagnetism in the Mn-Zn-O system: New class of biphase magnetism. Phys. Rev. Lett., 2005, 94: 217206.
[101] Park S Y, Kim P J, Lee Y P, et al. Realization of room-temperature ferromagnetism and of improved carrier mobility in Mn-doped ZnO film by oxygen deficiency, introduced by hydrogen and heat treatments. Adv. Mater., 2007, 19, 3496-3500.
[102] Wei X X, Song C, Geng KW, et al. Local Fe structure and ferromagnetism in Fe-doped ZnO films. J. Phys.: Condens. Matter, 2006, 18, 7471-7479.
[103] Sluiter M H F, Kawazoe Y, Sharma P, et al. First principles based design and experimental evidence for a ZnO-based ferromagnet at room temperature. Phys. Rev. Lett., 2005, 94: 187204.
[104] Kittilstved K R, Norberg N S, Gamelin D R. Chemical manipulation of high-TC ferromagnetism in ZnO diluted magnetic semiconductors. Phys. Rev. Lett., 2005, 94: 147209.
[105] Hsu H S, Huang J C A, Huang Y H, et al. Evidence of oxygen vacancy enhanced room-temperature ferromagnetism in Co-doped ZnO. Appl. Phys. Lett., 2006, 88: 242507.
[106] Liu X, Lin F, Sun L, et al. Doping concentration dependence of room-temperature ferromagnetism for Ni-doped ZnO thin films prepared by pulsed-laser deposition. Appl. Phys. Lett., 2006, 88: 062508.
[107] Hou D L, Ye X J, Meng H J, et al. Magnetic properties of n-type Cu-doped ZnO thin films. Appl. Phys. Lett., 2007, 90: 142502.
[108] Buchholz D B, Chang R P H, Song J H, et al. Room-temperature ferromagnetism in Cu-doped ZnO thin films. Appl. Phys. Lett., 2005, 87: 082504.
[109] Lee S, Shon Y, Lee S W, et al. Improved ferromagnetism of (Zn0.93Mn0.07)O through rapid thermal annealing. Appl. Phys. Lett., 2006, 88: 212513.
[110] Lee S J, Lee H S, Kim D Y, et al. Microstructural, optical, and magnetic properties of (Zn1-xMnx)O thin films grown on (0001) Al2O3 substrates. J. Cryst. Growth, 2005, 276: 121-127.
[111] Schmidt H, Diaconu M, Hochmuth H, et al. Weak ferromagnetism in textured Zn1-x(TM)xO thin films. Superlattices Microstruct., 2006, 39: 334-339.
[112] Ramachandran S, Tiwari A, Narayan J, et al. Epitaxial growth and properties of Zn1?xVxO diluted magnetic semiconductor thin films. Appl. Phys. Lett., 2005, 87: 172502.
[113] Kaspar T C, Droubay T, Li Y, et al. Lack of ferromagnetism in n-type cobalt-doped ZnO epitaxial thin films. New J. Phys., 2008, 10: 055010.
[114] Keavney D J, Buchholz D B, Ma Q, et al. Where does the spin reside in ferromagnetic Cu-doped ZnO? Appl. Phys. Lett., 2007, 91: 012501.
[115] Diana A, Schmerber G, Pierron-Bohnes V, et al. Magnetic perpendicular anisotropy in sputtered (Zn0.75Co0.25)O dilute magnetic semiconductor. J. Magn. Magn, Mater., 2005, 286: 37-40.
[116] Ziese M, Thornton M J. Spin electronics. Berlin: Springer, 2001.
[117] Schulthess H C, Temmerman W M, Szotek Z, et al. Electronic structure and exchange coupling of Mn impurities in III-V semiconductors. Nat. Mater. 2005, 4: 838-844.
[118] Kawakami R K, Kato Y, Hanson M, et al. Ferromagnetic imprinting of nuclear spins in semiconductors. Science, 2001, 294: 131-134.
[119] Malajovich I, Berry J J, Samarth N, et al. Persistent sourcing of coherent spins for multifunctional semiconductor spintronics. Nature, 2001, 411: 770-772.
[120] Ramachandran S, Tiwari A, Narayan J. Zn0.9Co0.1O-based diluted magnetic semiconducting thin films. Appl. Phys. Lett., 2004, 84(25): 5255-5257.
[121] Xu Q, Hartmann L, Schmidt H, et al. Metal-insulator transition in Co-doped ZnO: Magnetotransport properties. Phys. Rev. B, 2006, 73: 205342.
[122] Xu Q, Hartmann L, Schmidt H, et al. Magnetoresitance effects in Zn0.9Co0.1O films. J. Appl. Phys., 2006, 100: 013904.
[123] Xu Q, Hartmann L, Schmidt H, et al. Magnetoresitance and anomalous Hall effect in magnetic ZnO films. J. Appl. Phys., 2007, 101: 063908.
[124] Xu Q, Hartmann L, Schmidt H, et al. s-d exchange interaction induced magnetoresistance in magnetic ZnO. Phys. Rev. B, 2007, 76: 134417.
[125] Shinde S R, Ogale S B, Das Sarma S, et al. Ferromagnetism in laser deposited anatase Ti1-xCoxO2-δfilms. Phys. Rev. B, 2003, 67: 115211.
[126] Xu Q, Schmidt H, Zhou S, et al. Room temperature ferromagnetism in ZnO films due to defects. Appl. Phys. Lett. 2008, 92: 082508.
[127] Cheng X M, Chien C L. Magnetic properties of epitaxial Mn-doped ZnO thin films. J. Appl. Phys., 2003, 93(10): 7876-7878.
[128] Lin Y B, Xu J P, Zou W Q, et al. Effects of annealing and hydrogenation on the properties of ZnMnO polycrystalline films synthesized by plasma enhanced chemical vapour deposition. J. Phys. D: Appl. Phys. 40 (2007) 3674.-3677.
[129] Norton D P, Pearton S J, Hebard A F, et al. Ferromagnetism in Mn-implanted ZnO:Sn single crystals. Appl. Phys. Lett., 2003,82(2) 239-241.
[130] Potzger K, Zhou S, Reuther H, et al. Fe implanted ferromagnetic ZnO. Appl. Phys. Lett., 2006, 88, 052508.
[131] Lee H J, Jeong S Y, Cho C R, et al. Study of diluted magnetic semiconductor: Co-doped ZnO. Appl. Phys. Lett., 2002, 81(21): 4020-4022.
[132] Griffin K A, Pakhomov A B, Wang C M, et al. Intrinsic ferromagnetism in insulating cobalt doped anatase TiO2. Phys. Rev. Lett., 2005, 94: 157204.
[133] Belghazi Y, Schmerber G, Colis S, et al. Extrinsic origin of ferromagnetism in ZnO and Zn0.9Co0.1O magnetic semiconductor films prepared by sol-gel technique. Appl. Phys. Lett., 2006, 89: 122504.
[134] Che Mofor A, EI-Shaer A, Bakin A, et al. Magnetic property investigations on Mn-doped ZnO layers on sapphire. Appl. Phys. Lett., 2005, 87: 062501.
[135] Coey J M D. Dilute magnetic oxides. Curr. Opin. Solid State Mater. Sci., 2006, 10, 83-92.
[136] Kim J H, Kim H, Kim D, et al. Magnetic properties of epitaxially grown semiconducting Zn1-xCoxO thin filmsby pulsed laser deposition. J. Appl. Phys., 2002, 92(10): 6066-6071.
[137] Jung S W, An S J, Yi G C, et al. Ferromagentic properties of Zn1-xMnxO epitaxial thin films. Appl. Phys. Lett., 2002, 80(24): 4561-4563.
[138] Yin Z, Chen N, Chai C, et al. Structural and magnetic properties of insulating Zn1-xCoxO thin films. J. Appl. Phys., 2004, 96(9): 5093-5096.
[139] Cho Y M, Choo W K, Kim H, et al. Effects of rapid thermal annealing on the ferromagnetic properties of sputtered Zn1-x(Co0.5Fe0.5)xO thin films. Appl. Phys. Lett., 2002, 80(18): 3358-3360.
[140] Tay M, Wu Y, Han G C, et al. Ferromagnetism in inhomogeneous Zn1-xCoxO thin films. J. Appl. Phys., 2006, 100: 063910.
[141] Krishnamurthy S, McGuinness C, Dorneles L S, et al. Soft-x-ray spectroscopic investigation of ferromagnetic Co-doped ZnO. J. Appl. Phys., 2006, 99: 08M111
[142] Biegger E, Fonin M, Rüdiger U, et al. Defect induced low temperature ferromagnetism in Zn1-xCoxO films. J. Appl. Phys., 2007, 101: 073904.
[143] Ando K. Seeking room-temperature ferromagnetic semiconductors. Science, 2006, 312, 1883-1885.
[144] Kobayashi M, Ishida Y, Hwang J l, et al. Characterization of magnetic components in the diluted magnetic semiconductor Zn1-xCoxO by x-ray magnetic circular dichroism. Phys. Rev. B, 2005, 72: 201201(R).
[145] Neal J R, Behan A J, Ibrahim R M, et al. Room-temperature magneto-optics of ferromagnetic transition-metal-doped ZnO thin films. Phys. Rev. Lett., 2006, 96: 197608.
[146] Kim J Y, Park J H, Park B G, et al. Ferromagnetism induced by clustered Co in Co-doped anatase TiO2 thin films. Phys. Rev. Lett., 2003, 90: 017401.
[147] Diaconu M, Schmidt H, P?ppl A, et al. EPR study on magnetic Zn1-xMnxO. Superlattices Microstruct., 2005, 38: 413-420.
[148] Ahn G Y, Park S I, Shim I B, et al. M?ssbauer studies of ferromagnetism in Fe-doped ZnO magnetic semiconductor. J. Magn. Magn. Mater., 2004, 282: 166-169.
[149] Chattopadhyay A, Das Sarma S, Millis A J. Transition temperature of ferromagnetic semiconductors: A dynamical mean field study. Phys. Rev. Lett., 2001, 87: 227202.
[150] Walsh A, Da Silva J LF, Wei S H. Theoretical description of carrier mediated magnetism in cobalt doped ZnO. Phys. Rev. Lett., 2008, 100: 256401.
[151] Kaminski A, Das Sarma D. Polaron percolation in diluted magnetic semiconductors. Phys. Rev. Lett., 2002, 88: 247202.
[152] Cox P A. Transition metal oxides. Oxford: Clarendon press, 1992.
[153] Folk J A, Potoc R M, Marcus C M, et al. A gate-controlled bidirectional spin filter using quantum coherence. Science, 2003, 299: 679-682.
[154] Zhao T, Shinde S R, Ogale S B, et al. Electric field effect in diluted magnetic insulator anatase Co: TiO2. Phys. Rev. Lett., 2005, 94: 126601.
[155] Gould C, Pappert K, Schmidt G, et al. Magnetic anisotropies and (Ga,Mn)As-based spintronic devices. Adv. Mater., 2007, 19: 323-340.
[156] Chiba D, Sato Y, Kita T, et al. Current-driven magnetization reversal in a ferromagnetic semiconductor GaMnAs/GaAs/GaMnAs tunnel junction. Phys. Rev. Lett., 2004, 93(21): 216602.
[157] Tanaka M, Higo Y. Large tunneling magnetoresistance in GaMnAs/AlAs/ GaMnAs ferromagnetic semiconductor tunnel junctions. Phys. Rev. Lett., 2001, 87(2): 026602.
[158] Mattana R, George J M, Jaffrès H, et al. Electrical detection of spin accumulation in a p-type GaAs quantum well. Phys. Rev. Lett., 2003, 90: 166601.
[159] Herranz G, Ranchal R, Bibes M, et al. Co-doped (La, Sr)TiO3-δ: A high Curie temperaute diluted magnetic system with large spin polarization. Phys. Rev. Lett., 2006, 96: 027207.
[160] Toyosaki H, Fukumura T, Ueno K, et al. A ferromagnetic oxide semiconductor as spin injection electrode in magnetic tunnel junctions. Jpn. J. Appl. Phys., Part 2, 2005, 44: L896-L898.
[161] Toyosaki H, Fukumura T, Ueno K, et al. Ti1-xCoxO2-δ/AlOx/Fe0.1Co0.9 magentic tunnel junctions with varied AlOx thinckness. J. Appl. Phys., 2006, 99: 08M102.
[162] Wang W G, Ni C, Moriyama T, et al. Spin-polarized transport in hybrid (Zn,Cr)Te/Al2O3/Co magnetic tunnel junctions. Appl. Phys. Lett., 2006, 88: 202501.
[163] Nozaki T, Hirohata A, Tezuka N, et al. Bias voltage effect on tunnel magnetoresistance in fully epitaxial MgO double-barrier magnetic tunnel junctions. Appl. Phys. Lett., 2005, 86:082501.
[164] Ladak S, Hicken R J. Origin of large magnetocurrent in three-terminal double-barrier magnetic tunnel junctions. J. Appl. Phys., 2005, 97: 104512.
[165] Wang J, Neaton J B, Zheng H, et al. Epitaxial BiFeO3 multiferroic thin film heterostructures. Science, 2003, 299: 1719-1722.
[166] Béa H, Bibes M, Barthélémy A, et al. Influence of parasitic phases on the properties of BiFeO3 epitaxial thin films. Appl. Phys. Lett., 2005, 87: 072508.
[167] Lim S H, Murakami M, Sarney W L, et al. The effects of multiphase formation on strain relaxation and magnetization in multiferroic BiFeO3 thin films. Adv. Funct. Mater., 2007, 17: 2594-2599.
[168] Song C, Geng K W, Zeng F, et al. Giant magnetic moment in an anomalous ferromagnetic insulator: Co-doped ZnO. Phys. Rev. B, 2006, 73: 024405.
[169] Song C, Zeng F, Geng K W, et al. The magnetic properties of Co-doped ZnO diluted magnetic insulator films prepared by direct current reactive magnetron co-sputtering. J. Magn. Magn. Mater., 2007, 309: 25-30.
[170] Song C, Zeng F, Geng K W, et al. Substrate-dependent magnetization in Co-doped ZnO insulating films. Phys. Rev. B, 2007, 76: 045215.
[171] Song C, Liu X J, Geng K W, et al. Transition from diluted magnetic insulator to semiconductor in Co-doped ZnO transparent oxide. J. Appl. Phys., 2007, 101: 103903.
[172] Song C, Pan S N, Liu X J, et al. Evidence of structural defects enhanced room temperature ferromagnetism in Co-doped ZnO. J. Phys.: Condens. Matter, 2007, 19: 176229.
[173] Song C, Liu X J, Zeng F, et al. Epitaxial (Zn,Co)O/ZnO/(Zn,Co)O junction and its tunnel magnetoresistance. Appl. Phys. Lett., 2007, 91: 042106.
[174] Song C, Yang Y C, Li X W, et al. Anomalous voltage dependence of tunnel magnetoresistance in (Zn,Co)O-based junction with double-barrier. Appl. Phys. Lett., 2007, 91: 172109.
[175] Song C, Zeng F, Shen Y X, et al. Local Co structure and ferromagnetism in ion-implanted Co-doped LiNbO3. Phys. Rev. B, 2006, 73: 172412.
[176] Song C, Wang C Z, Yang Y C, et al. Room temperature ferromagnetism and ferroelectricity in cobalt-doped LiNbO3 films. Appl. Phys. Lett., 2008, 92: 262901.
[177] Song C, Wang C Z, Liu X J, et al. Room temperature ferromagnetism in single-crystal cobalt-doped LiNbO3 films. Cryst. Growth Des., in press.
[178] Ohkubo Y, Murakami T, Saito T, et al. Mechanism of the ferroelectric phase transitions in LiNbO3 and LiTaO3. Phys. Rev. B, 2002, 65: 052107.
[179] Prieto C, Zaldo C. Determination of the lattice site of Fe in photorefractive LiNbO3. Solid State Commun., 1992, 83: 819-821.
[180] Prieto C, Zaldo C, Fessler P, et al. Lattice position of Hf and Ta in LiNbO3: An extended x-ray-absorpt on fine-structure study. Phys. Rev. B, 1991, 43: 2594.
[181] Chen J J, Zeng F, Gao Y, et al. The effect of oxygen partial pressures on the microstructure,electrical and mechanical properties of high resistivity ZnO films. Appl. Surf. Sci., 2004, 223: 318-329.
[182] Ankudinov A L, Ravel B, Rehr J J, et al. Real-space multiple-scattering calculation and interpretation of x-ray-absorption near-edge structure. Phys. Rev. B, 1998, 58: 7565-7576.
[183] Rehr J J, Albers R C. Theoretical approaches to x-ray absorption fine structure. Rev. Mod. Phys., 2000, 72(3): 621-654.
[184] Kikkawa J M, Awschalom D D. Lateral drag of spin coherence in gallium arsenide. Nature, 1999, 397: 139-141.
[185] Paillard M, Marie X, Renucci P, et al. Spin relaxation quenching in semiconductor quantum dots. Phys. Rev. Lett., 2001, 86: 1634-1637.
[186] Moulder J F, Stickle W F, Sobol P E, et al. Hand-book of X-ray photoelectron spectroscopy. Eden Prairie: Perkin-Elmer, 1992.
[187] Fitzgerald C B, Venkatesan M, Lunney J G, et al. Cobalt-doped ZnO–a room temperature dilute magnetic semiconductor. Appl. Surf. Sci., 2005, 247: 493-496.
[188] Xu X H, Blythe H J, Ziese M, et al. Carrier-induced ferromagnetism in n-type ZnMnAlO and ZnCoAlO thin films at room temperature. New J. Phys., 2006, 8: 135.
[189] Theodoropoulou N, Misra V, Philip J, et al. High-temperature ferromagnetism in Zn1-xMnxO semiconductor thin films. J. Magn. Magn, Mater., 2006, 300: 407-411.
[190] Yang Z, Liu J L, Biasini M, et al. Electron concentration dependent magnetization and magnetic anisotropy in ZnO:Mn thin films. Appl. Phys. Lett., 2008, 92: 042111.
[191] Hong N H, Sakai J, Prellier W, et al. Transparent Cr-doped SnO2 thin films: ferromagnetism beyond room temperature with a giant magnetic moment. J. Phys.: Condens. Matter, 2005, 17: 1697-1702.
[192] Hong N H, Sakai J, Hassini A. Ferromagnetism at room temperature with a large magnetic moment in anatase V-doped TiO2 thin films. Appl. Phys. Lett., 2004, 84(14): 2602-2604.
[193] Sati P, Hayn R, Kuzian R, et al. Magnetic anisotropy of Co2+ as signature of intrinsic ferromagnetism in ZnO:Co. Phys. Rev. Lett., 2006, 96: 017203.
[194] Shang D S, Wang Q, Chen L D, et al. Effect of carrier trapping on the hysteresis current-voltage characteristics in Ag/La0.7Ca0.3MnO3/Pt heterostrucutes. Phys. Rev. B, 2006, 73: 245427.
[195] Edmonds K W, Binns C, Baker S H, et al. Doubling of the orbital magnetic moment in nanoscale Fe clusters. Phys. Rev. B, 1999, 60(1): 472-476.
[196] Kittel C. Introduction to solid state physics. New York: John Wiley & Sons, 1996.
[197] Wang X, Xu J, Zhang B, et al. Signature of intrinsic high-temperature ferromagnetism in cobalt-doped zinc oxide nanocrystals. Adv. Mater. 2006, 18: 2476-2480.
[198] Samanta K, Bhattacharya P, Katiyar R S, et al. Raman scattering studies in dilute magnetic semiconductor Zn1-xCoxO. Phys. Rev. B, 2006, 73: 245213.
[199] Liu X J, Song C, Yang P Y, et al. Substrate orientation-induced distinct ferromagnetic moment in Co:ZnO films. Appl. Surf. Sci., 2008, 254: 3167-3174.
[200] Rode K, Anane A, Mattana R, et al. Magnetic semiconductors based on cobalt substituted ZnO. J. Appl. Phys., 2003, 93: 7676-7678.
[201] Rode K, Mattana R, Anane A, et al. Magnetism of (Zn,Co)O thin films probed by x-ray absorption spectrocopies. Appl. Phys. Lett., 2008, 92: 012509.
[202] Ramachandran S, Narayan J, Prater J T. Effect of oxygen annealing on Mn doped ZnO diluted magnetic semiconductors. Appl. Phys. Lett., 2006, 88: 242503.
[203] Nielsen K, Bauer S, Lübbe M, et al. Ferromagnetism in epitaxial Zn0.95Co0.05O films grown on ZnO and Al2O3. Phys. Stat. Sol. A, 2006, 203: 3581-3596.
[204] Zhang Y B, Liu Q, Sritharan T, et al. Pulsed laser ablation of preferentially orientated ZnO:Co diluted magnetic semiconducting thin films on Si substrates. Appl. Phys. Lett., 2006, 89: 042510.
[205] Liu X J, Song C, Zeng F, et al. Enhancement of electrical and ferromagnetic properties by additional Al doping in Co:ZnO thin films. J. Phys.: Condens. Matter, 2007, 19: 296208.
[206] Liu X, Lin F, Sun L, et al. Doping concentration dependence of room-temperature ferromagnetism for Ni-doped ZnO thin films prepared by pulsed-laser depostion. Appl. Phys. Lett., 2006, 88: 062508.
[207] Harima H. Raman studies on spintronics materials based on wide bandgap semiconductors. J. Phys.: Condens. Matter, 2004, 16: S5653-S5660.
[208] Herng T S, Lau S P, Yu S F, et al. Zn-interstitial-enhanced ferromagnetism in Cu-doped ZnO films. J. Magn. Magn. Mater., 2007, 315: 107-110.
[209] Chakraborti D, Trichy G R, Prater J T, et al. The effect of oxygen annealing on ZnO:Cu and ZnO: (Cu, A l) diluted magnetic semiconductors. J. Phys. D: Appl. Phys., 2007, 40: 7606-7613.
[210] Verna A, Ottaviano L, Passacantando M, et al. Ferromagnetism in ion implanted amorphous and nanocrystalline MnxGe1-x. Phys. Rev. B, 2006, 74: 085204.
[211] Li X L, Wang Z L, Qin X F, et al. Enhancement of magnetic moment of Co-doped ZnO films by postannealing in vacuum. J. Appl. Phys., 2008, 103: 023911.
[212] Khare N, Kappers M J, Wei M, et al. Defect-induced ferromagnetism in Co-doped ZnO. Adv. Mater., 2006, 18: 1449-1452.
[213] Lin Y H, Ying M, Li M, et al. Room-temperature ferromagnetic and ferroelectric behavior in polycrystalline ZnO-based thin films. Appl. Phys. Lett., 2007, 90: 222110.
[214] Yang S G, Pakhomov A B, Hung S T, et al. Room temperature magnetism in sputtered (Zn,Co)O films. IEEE Trans. Magn., 2002, 38: 2877-2879.
[215] Zheng Y, Boulliard J C, Demaille D, et al. Study of ZnO crystals and Zn1-xMxO (M=Co, Mn) epilayers grown by pulsed laser deposition on ZnO ( 00 .1) substrate. J. Crystal Growth, 2005, 274: 156-166.
[216] Guo H, Burgess J, Street S, et al. Growth of epitaxial thin films of the ordered double perovskite La2NiMnO6 on different substrates. Appl. Phys. Lett., 2006, 89: 022509.
[217] Sakurai K, Kanehiro M, Nakahara K, et al. Effects of substrate offset angles on MBE growth of ZnO. J. Cryst. Growth, 2000, 214/215: 92-94.
[218] Mei Z X, Wang Y, Du X L, et al. Growth of In2O3 single-crystalline film on sapphire (0001) substrate by molecular beam epitaxy. J. Cryst. Growth, 2006, 289: 686-689.
[219] Ramesh R, Spaldin N A. Multiferroics: progress and prospects in thin films. Nat. Mater., 2007, 6: 21-29.
[220] Zheng H, Wang J, Lofland S E, et al. Multiferroic CoFe2O4-BaTiO3 nanostructures. Science, 2004, 303: 661-663.
[221] Duan C G, Jaswal S S, Tsymbal E Y. Predicted magnetoelectric effect in Fe/BaTiO3 multilayers: Ferroelectric control of magnetism. Phys. Rev. Lett., 2006, 97: 047201.
[222] Cheng Z, Wang X, Kannan C V, et al. Enhanced electrical polarization and ferromagnetic moment in a multiferroic BiFeO3/Bi3.25Sm0.75Ti2.98V0.02O12 double-layered thin film. Appl. Phys. Lett., 2006, 88: 132909.
[223] Zhou J P, He H C, Shi Z, et al. Magnetoelectric CoFe2O4/Pb(Zr0.52Ti0.48)O3 double-layer thin film prepared by pulsed-laser deposition. Appl. Phys. Lett., 2006, 88: 013111.
[224] Eerenstein W, Wiora M, Prieto J L, et al. Giant sharp and persistent converse magnetoelectric effects in multiferroic epitaxial heterostructures. Nat. Mater., 2007, 6: 348-351.
[225] Kim N, Kim H, Kim J W, et al. Modulation of the Curie temperature in ferromagentic/ferroelectric hybrid double quamtum wells. Phys. Rev. B, 2006, 73: 033318.
[226] Lee E C, Chang K J. Ferromagnetic versus antiferromagnetic interaction in Co-doped ZnO. Phys. Rev. B, 2004, 69: 085205.
[227] Zhang W, Wang X, Elliott M, et al. Stress effect and enhanced magnetoresistance in La0.67Sr0.33MnO3-δfilms. Phys. Rev. B, 1998, 58: 14143.
[228] Lee S, Lee H S, Hwang S J, et al. Effects of oxygen partial pressure during sputtering growth on physical properties of Zn0.93Mn0.07O thin films. J. Crystal growth, 2006, 286: 223-227.
[229] Droubay T, Heald S M, Shutthanandan V, et al. Cr-doped TiO2 anatase: A ferromagnetic insulator. J. Appl. Phys., 2005, 97: 046103.
[230] Toyosaki H, Fukumura T, Yamada Y, et al. Anomalous Hall effect governed by electron doping in a room-temperature transparent ferromagnetic semiconductor. Nat. Mater., 2004, 3: 221-224.
[231] Sakai K, Kakeno T, Ikari T, et al. Defect centers and optical absorption edge of degenerated semiconductor ZnO thin films grown by a reactive plasma deposition by means of piezoelectric photothermal spectroscopy. J. Appl. Phys., 2006, 99: 043508.
[232] Venkataraj S, Ohashi N, Sakaguchi I, et al. Structural and magnetic properties of Mn-ion implanted ZnO films. J. Appl. Phys., 2007, 102: 014905.
[233] Vaithianathan V, Lee B T, Chang C H, et al. Characterization of As-doped, p-type ZnO by x-ray absorption near-edge structure spectroscopy. Appl. Phys. Lett., 2006, 88: 112103.
[234] Ungureanu M, Schmidt H, von Wenckstern H, et al. A comparison between ZnO films doped with 3d and 4f magnetic ions. Thin Solid Films, 2007, 515: 8761-8763.
[235] Liu X J, Song C, Zeng F, et al. Influence of annealing on microstructure and magnetic properties of co-sputtered Co doped ZnO thin films. J. Phys. D: Appl. Phys., 2007, 40: 1608-1613.
[236] Kittilstved K R, Schwartz D A, Tuan A C, et al. Direct kinetic correlation of carriers and ferromagnetism in Co2+: ZnO. Phys. Rev. Lett., 2006, 97: 037203.
[237] Matsumura T, Okuyama D, Niioka S, et al. X-ray anomalous scattering of diluted magnetic oxide semiconductors: Possible evidence of lattice deformation for high temperature ferromagnetism. Phys. Rev. B, 2007, 76 : 115320.
[238] Chakraborti D, Ramachandran S, Trichy G, et al. Magnetic, electrical, and microstructural characterization of ZnO thin films codoped with Co and Cu. J. Appl. Phys., 2007, 101: 053918.
[239] Tiwari A, Snure M, Kumar D, et al. Ferromagnetism in Cu-doped ZnO films: Role of charge carriers. Appl. Phys. Lett., 2008, 92: 062509.
[240] Liu X C, Shi E W, Chen Z Z, et al. High-temperature ferromagnetism in (Co,Al)-codoped ZnO powders. Appl. Phys. Lett., 2006, 88: 252503.
[241] Ivill M, Pearton S J, Norton D P, et al. Magnetization dependence on electron density in epitaxial ZnO thin films doped with Mn and Sn. J. Appl. Phys., 2005, 97: 053904.
[242] Jayakumar O D, Gopalakrishnan I K, Kulshreshtha S K. Surfactant-assisted synthesis of Co- and Li-doped ZnO nanocrystalline samples showing room-temperature ferromagnetism. Adv. Mater., 2006, 18: 1857-1860.
[243] Tietze T, Gacic M, Schütz, et al. XMCD studies on Co and Li doped ZnO magnetic semiconductors. New J. Phys., 2008, 10: 055009.
[244] Liu X J, Song C, Zeng F, et al. Donor defects enhanced ferromagnetism in Co: ZnO films. Thin Solid Films, 2008, 516: 8757-8761.
[245] Xu H Y, Liu Y C, Xu C S, et al. Room-temperature ferromagnetism in (Mn,N)-codoped ZnO thin films prepared by reactive magnetron cosputtering. Appl. Phys. Lett., 2006, 88: 242502.
[246] Gu Z B, Lu M H, Wang J, et al. Structure, optical, and magnetic properties of sputtered manganese and nitrogen-codoped ZnO films. Appl. Phys. Lett., 2006, 88: 082111.
[247] Ivill M, Pearton S J, Heo Y W, et al. Magnetization dependence on carrier doping in epitaxial ZnO thin films doped with Mn and P. J. Appl. Phys., 2007, 101: 123909.
[248] Hong N H, BrizéV, Sakai J. Mn-doped ZnO and (Mn,Cu)-doped ZnO thin films: Does the Cu doping indeed play a key role in tuning the ferromagnetism. Appl. Phys. Lett., 2005, 86: 082505.
[249] Han S J, Song J W, Yang C H, et al. Key to room-temperature ferromagnetism in Fe-doped ZnO: Cu. Appl. Phys. Lett., 2002, 81: 4212-4214.
[250] Mokhtari A, Behan A J, Score D S, et al. Transport and magnetism studies of doped ZnO films. New J. Phys., submitted.
[251] Chun S H, Potashnik S J, Ku K C, et al. Spin-polarized tunneling in hybrid metal-semiconductor magnetic tunnel junctions. Phys. Rev. B, 2002, 66: 100408(R).
[252] Saito H, Yuasa S, Ando K. Origin of the tunnel anisotropic magnetoresistance in Ga1-xMnxAs/ZnSe/Ga1-xMnxAs magnetic tunnel junctions of II–VI/III–V heterostructures. Phys. Rev. Lett., 2005, 95: 086604.
[253] Tsymbal E Y, Belashchenko K D, Velev J P et al. Interface effects in spin-dependent tunneling. Prog. Mater. Sci., 2005, 50: 401-420.
[254] Tiusan C, Faure-Vincent J, Bellouard C, et al. Interfacial resonance state probed by spin-polarized tunneling in epitaxial Fe/MgO/Fe tunnel junctions. Phys. Rev. Lett., 2004, 93: 106602.
[255] Colis S, Gieres G, Dimopoulos T, et al. Large magnetoresistance at high bias voltage in double magnetic tunnel junctions. IEEE trans. Magn. 2004, 40(4): 2287-2289.
[256] Ghosh K, Ogale S B, Pai S P, et al. Positive giant magnetoresistance in a Fe3O4/SrTiO3/La0.7Sr0.3MnO3 heterostructure. Appl. Phys. Lett., 1998, 73: 689-691.
[257] May S J, Phillips P J, Wessels B W. Negative magnetoresistance in metal/oxide/InMnAs tunnel junctions. J. Appl. Phys., 2006, 100: 053912.
[258] Zenger M, Moser J, Wegscheider W, et al. High-field magnetoresistance of Fe/GaAs/Fe tunnel junctions. J. Appl. Phys., 2004, 96: 2400-2402.
[259] Risbud A S, Spaldin N A, Chen Z Q, et al. Magnetism in polycrystalline cobalt-substituted zinc oxide. Phys. Rev. B, 2003, 68: 205202.
[260] Montaigne F, Nassar J, Vaurès A, et al. Enhanced tunnel magnetoresistance at high bias voltage double-barrier planar junctions. Appl. Phys. Lett., 1998, 73: 2829-2831.
[261] Ding H F, Wulfhekel W, Henk J, et al. Absence of zero-bias anomaly in spin-polarized vacuum tunneling in Co(0001). Phys. Rev. Lett., 2003, 90: 116603.
[262] Nagahama T, Santos T S, Moodera J S. Enhanced magnetotransport at high bias in quasimagnetic tunnel junctions with EuS spin-filter barriers. Phys. Rev. Lett., 2007, 99: 016602.
[263] Dias Cabral E, Boselli M A, da Cunha Lima A T, et al. On the nature of the spin-polarized hole states in a quasi-two-dimensional GaMnAs ferromagnetic layer. Appl. Phys. Lett., 2007, 90: 142118.
[264] Rodrigues S C P, Scolfaro L M R, Leite J R, et al. Charge and spin distribution in Ga1-xMnxAs/GaAs ferromagnetic multilayers. Phys. Rev. B, 2004, 70: 165308.
[265] Das Sarma S, Hwang E H, Kaminski A. Temperature-dependent magnetization in diluted magnetic semiconductors. Phys. Rev. B, 2003, 67: 155201.
[266] Yang Y C, Song C, Wang X H, et al. Cr-substitution-induced ferroelectric and improved piezoelectric properties of Zn1-xCrxO films. J. Appl. Phys., 2008, 103: 074107.
[267] Spaldin N A. Physics of ferroelectrics: A modern perspective, Topics Appl. Physics, edited byRabe K, Ahn C H, Triscone J M. Berlin Heidelberg: Springer-Verlag, 2007.
[268] Scott J F. Ferroelectrics go bananas. J. Phys.: Condens. Matter, 2008, 20: 021001.
[269] Blom P W M, Wolf R M, Cillessen J F M, et al. Ferroelectric Schottky diode. Phys. Rev. Lett., 1994, 73: 2107-2110.
[270] Dhananjay, Nagaraju J, Krupanidhi S B. Effect of Li substitution on dielectric and ferroelectric properties of ZnO films grown by pulsed-laser ablation. J. Appl. Phys., 2006, 99: 034105.
[271] Watanabe Y. Electrical transport through Pb(Zr,Ti)O3 p-n and p-p heterostructures modulated by bound charges at a ferroelectric surface: Ferroelectric p-n diode. Phys. Rev. B, 2006, 73: 245427.
[2] Zutic I, Fabian J, Das Sarma S. Spintronics: Fundamentals and application. Rev. Mod. Phys., 2004, 76(2): 323-410.
[3] Baibich M N, Brote J M, Fert A, et al. Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices. Phys. Rev. Lett., 1988, 61(21): 2472-2475.
[4] Binasch G, Grünberg P, Saurenbach F, et al. Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange. Phys. Rev. B, 1988, 39 (7): 4828-4830.
[5] Prinz G A. Magnetoelectronics. Science, 1998, 282: 1660-1663.
[6] Levy P M, Zhang S, Fert A. Electrical conductivity of magnetic multilayered structures. Phys. Rev. Lett., 1990, 65 (13): 1643-1646.
[7] Dieny B, Speriosu V S, Parkin S S P, et al. Giant magnetoresistive in soft ferromagnetic multilayers. Phys. Rev. B, 1991, 43 (1): 1297-1300.
[8] Helmolt R V, Wecker J, Holzapfel B, et al. Giant negative magnetoresistance in perovskitelike La2/3Ba1/3MnOx ferromagnetic films. Phys. Rev. Lett., 1993, 71 (14):2331-2333.
[9] Moodera J S, Kinder L R, Wong T M, et al. Large magnetoresistance at room temperature in ferromagnetic thin film tunnel junctions. Phys. Rev. Lett., 1995, 74: 3273-3276.
[10] Julliere M. Tunneling between ferromagnetic films. Phys. Lett., 1975, 54A (3): 225-226.
[11] De Teresa J M, Barthélémy A, Fert A, et al. Role of metal-oxide interface in determing the spin polarization of magnetic tunnel junctions. Science, 1999, 286: 507-509.
[12] Yuasa S, Nagahama T, Fukushima A, et al. Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions. Nat. Mater., 2004, 3: 868-871.
[13] Parkin S S P, Kaiser C, Panchula A, et al. Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers. Nat. Mater., 2004, 3: 862-867.
[14] Das Sarma S, Fabian J, Hu X, et al. Spin electronics and spin computation. Solid State Commun., 2001, 119: 207-215.
[15] Ohno Y, Young D K, Beschoten B, et al. Electrical spin injection in a ferromagnetic semiconductor. Nature, 1999, 402: 790-792.
[16] Ohno H, Shen A, Matsukura F. (Ga,Mn)As: A new diluted magnetic semiconductor based on GaAs. Appl. Phys. Lett., 1996, 69(3): 363-365.
[17] Fiederling R, Keim M, Reuscher G, et al. Injection and detection of a spin-polarized current in a light-emitting diode. Nature,1999,402: 787-789.
[18] Pan F, Song C, Liu X J, et al. Ferromagnetism and possible application in spintronics of transition-metal-doped ZnO films. Mater. Sci. Eng. R., 2008, 62: 1-35.
[19] Pearton S J, Abernathy C R, Norton D P, et al. Advances in wide bandgap materials for semiconductor spintronics. Mater. Sci. Eng. R., 2003, 40: 137-168.
[20] Jedema F J, Filip A T, Wees B J van, Electrical spin injection and accumulation at room temperature in an all-metal mesoscopic spin valve. Nature, 2001, 410: 345-348.
[21] Ohno H, Chiba D, Matsukura F, et al. Electric-field control of ferromagnetism. Nature, 2000, 408: 944-946.
[22] Allwood D A, Xiong G, Cooke M D, et al. Submicrometer ferromagnetic NOT gate and shife register. Science, 2002, 296: 2003-2006.
[23] Filip A T, LeClair P, Smits C J P, et al. Spin-injection device based on EuS magnetic tunnel barriers. Appl. Phys. Lett., 2002, 81(10): 1815-1817.
[24] Schmidt G, Ferrand D, Molenkamp L W, et al. Fundamental obstacle for electrical spin injection from a ferromagnetic metal into a diffusive semiconductor. Phys. Rev. B, 2000, 62: R4790-R4793.
[25] Awschalom D D, FlattéM E. Challenges for semiconductor spintronics. Nat. Phys., 2007, 3: 153-159.
[26] Fukumura T, Jin Z W, Ohtomo A, et al. An oxide-diluted magnetic semiconductor: Mn-doped ZnO. Appl. Phys. Lett., 1999, 75: 3366-3368.
[27] Fukumura T, et al. Magnetic properties of Mn-doped ZnO. Appl. Phys. Lett., 2001, 78: 958-960.
[28] Jin Z W, Murakami M, Fukumura T, et al. Combinatorial laser MBE synthesis of 3d ion doped epitaxial ZnO thin films. J. Cryst. Growth, 2000, 214/215: 55-58.
[29] Ando, K. et al. Magneto-optical properties of ZnO-based diluted magnetic semiconductors. J. Appl. Phys., 2001, 89: 7284.
[30] Ando K, Satio H, Jin Z W, et al. Large magneto-optical effect in an oxide diluted magnetic semiconductor Zn1-xCoxO. Appl. Phys. Lett., 2001, 78(18): 2700-2702.
[31] Ueda K, Tabata H, Kawai T. Magnetic and electric properties of transition-metal-doped ZnO films. Appl. Phys. Lett., 2001, 79: 988-990.
[32] Pearton S J, Abernathy C R, Overberg M E, et al. Wide band gap ferromagnetic semiconductors and oxides. J. Appl. Phys., 2003, 93(1): 1-13.
[33] Pearton S J, Heo W H, Ivill M, et al. Dilute magnetic semiconducting oxides. Semicond. Sci. Technol., 2004, 19: R59-R74.
[34] Pearton S J, Norton D P, Ip K. Recent progress in processing and properties of ZnO. Prog. Mater. Sci., 2005, 50: 293-340.
[35] Prellier W, Fouchet A, Mercey B. Oxide-diluted magnetic semiconductors: a review of the experimental status. J. Phys.: Condens. Matter, 2003, 15: R1583-R1601.
[36] Sharma P, Gupta A, Rao K V, et al. Ferromagnetism above room temperature in bulk and transparent thin films of Mn-doped ZnO. Nat. Mater., 2003, 2: 673-677.
[37] Radovanovic P V, Gamelin D R. High-temperature ferromagnetism in Ni2+-doped ZnO aggregates prepared from colloidal diluted magnetic semiconductor quantum dots. Phys. Rev. Lett., 2003, 91: 157202.
[38] Prellier W, Fouchet A, Mercey B, et al. Laser ablation of Co:ZnO films deposited from Zn and Co metal targets on (0001) Al2O3 substrates. Appl. Phys. Lett., 2003, 82(20): 3490-3492.
[39] Tuan A C , Bryan J D, Pakhomov A B, et al. Epitaxial growth and properties of cobalt-doped ZnO onα-Al2O3 single-crystal substrates. Phys. Rev. B, 2004, 70: 054424.
[40] Janisch R, Gopal P, Spaldin N A. Transition metal-doped TiO2 and ZnO-present status of the field. J. Phys.: Condens. Matter, 2005, 17: R657-R689.
[41] Fukumura T, Toyosaki H, Yamada Y. Magnetic oxide semiconductors. Semicond. Sci. Technol., 2005, 20: S103-S111.
[42] Coey J M D, Venkatesan M, Fitzgerald C B. Donor impurity band exchange in dilute ferromagnetic oxides. Nat. Mater., 2005, 4: 173-179.
[43] Ozgürü, Alivov Ya I, Liu C, et al. A comprehensive review of ZnO materials and devices. J. Appl. Phys., 2005, 98: 041301.
[44] Chambers S A. Ferromagnetism in doped thin-film oxide and nitride semiconductors and dielectrics. Surf. Sci. Rep., 2006, 61: 345-381.
[45] Pearton S J, Norton D P, Ivill M P, et al. ZnO doped with transition metal ions. IEEE Trans. Electron Devices, 2007, 54: 1040-1048.
[46] Ney A, Ollefs K, Ye S, et al. Absence of intrinsic ferromagnetic interactions of isolated and paired Co dopant atoms in Zn1-xCoxO with high structural perfection. Phys. Rev. Lett., 2008, 100: 157201.
[47] Behan A J, Mokhtari A, Blythe H J, et al. Two magnetic regimes in doped ZnO corresponding to a dilute magnetic semiconductor and a dilute magnetic insulator. Phys. Rev. Lett., 2008, 100: 047206.
[48] Rode K, Mattana R, Anane A, et al. Magnetism of (Zn,Co)O thin films probed by x-ray absorption spectroscopies. Appl. Phys. Lett., 2008, 92: 012509.
[49] Saito H, Zayets V, Yamagata S, et al. Room-temperature ferromagnetism in a II-VI diluted magnetic semiconductor Zn1-xCrxTe. Phys. Rev. Lett., 2003, 90: 207202.
[50] Kuroda S, Nishizawa N, Takita K, et al. Origin and control of high-temperature ferromagnetism in semiconductors. Nat. Mater., 2007, 6: 440-446.
[51] Radovanovic P V. Synthesis, spectroscopy and magnetism of diluted magnetic semiconductor nanocrystal. Ph. D. Thesis, University of Washington, Seattle, Washington, 2004.
[52] Matsumoto Y, Murakami M, Shono T, et al. Room-temperature ferromagnetism in transparent transition metal-doped titanium dioxide. Science, 291: 854-856.
[53] Shinde S R, Ogale S B, Higgins J S, et al. Co-occurrence of superparamagnetism and anomalous Hall effect in highly reduced cobalt-doped rutile TiO2-δfilms. Phys. Rev. Lett., 2004, 92: 166601.
[54] Shutthanandan V, Thevuthasan S, Heald S M, et al. Room-temperature ferromagnetism in ion-implanted Co-doped TiO2(110) rutile. Appl. Phys. Lett., 2004, 84(22): 4466-4468.
[55] Kaspar T C, Heald S M, Wang C M, et al. Negligible magnetism in excellent structural quality CrxTi1-xO2 anatase: Contrast with high-TC ferromagnetism in structurally defective CrxTi1-xO2. Phys. Rev. Lett. 2005, 95: 217203.
[56] Kaspar T C, Droubay T, Shutthanandan V, et al. Ferromagnetism and structure of epitaxial Cr-doped anatase TiO2 thin films. Phys. Rev. B, 2006, 73: 155327.
[57] Macdonald A H, Schiffer P, Samarth N. Ferromagnetic semiconductors: moving beyond (Ga,Mn)As. Nat. Mater., 2005, 4: 195-202.
[58] Wu R. Mn distribution and spin polarization in Ga1-xMnxAs. Phys. Rev. Lett., 2005, 94: 207201.
[59] Stotz J H, Hey R, Santos P, et al. Coherent spin transport through dynamic quantum dots. Nat. Mater., 2005, 4: 585-588.
[60] Jungwirth T, Sinova J, Ma?ek J, et al. Theory of ferromagnetic (III,Mn)V semiconductors. Rev. Mod. Phys., 2006, 78: 809-864.
[61] Theodoropoulou N, Hebard A F, Overberg M E, et al. Unconventional carrier-mediated ferromagnetism above room temperature in ion-implanted (Ga,Mn)P:C. Phys. Rev. Lett., 2002, 89(10): 107203.
[62] Kumar D, Antifakos J, Blamire M G, et al. High Curie temperatures in ferromagnetic Cr-doped AlN thin films. Appl. Phys. Lett., 2004, 84(24): 5004-5006.
[63] Park Y D, Hanbicki A T, Erwin S C, et al. A group-IV ferromagnetic semiconductor: MnxGe1-x. Science, 2002, 295: 651-654.
[64] Zhao Y G, Shinde S R, Ogale S B, et al. Co-doped La0.5Sr0.5TiO3: Diluted magnetic oxide system with high Curie temperature. Appl. Phys. Lett., 2004, 83(11): 2199-2201.
[65] Worledge D C, Geballe T H. Spin-polarized tunneling in La0.67Sr0.33MnO3. Appl. Phys. Lett., 2004, 76(7): 4466-4468.
[66] Lee J S, Khim Z G, Park Y D, et al. Magnetic properties of Co- and Mn-implanted BaTiO3, SrTiO3 and KTaO3. Solid-State Electron., 2003, 47: 2225-2230.
[67] Jungwirth T, Wang K Y, Ma?ek J, et al. Prospects for high temperature ferromagnetism in (Ga,Mn)As semiconductors. Phys. Rev. B, 2005, 72: 165204.
[68] Dietl T, Ohno H, Matsukura F, et al. Zener model description of ferromagnetism in zinc-blende magnetic semiconductors. Science, 2000, 287: 1019-1022.
[69] Esaki L, Stiles P J, von Molnar S. Magnetointernal field emission in junctions of magnetic insulators. Phys. Rev. Lett., 1967, 19: 852-854.
[70] Munekata H, Ohno H, von Molnar S, et al. Diluted magnetic semicondutors. Phys. Rev. Lett., 1989, 63(17): 1849-1852.
[71] Dietl T, Spalek J. Effect of thermodynamic fluctuations of magnetization on the bound magnetic polaron in dilute magnetic semiconductors. Phys. Rev. B, 1983, 28(3): 1548-1563.
[72] Story T, Galazka R R, Frankel R B, et al. Carrier-concentration-induced ferromagnetism in PbSnMnTe. Phys. Rev. Lett., 1986, 56(7): 777-779.
[73] Ohno H, Munekata, Penney T. Magnetotransport properties of p-type (In,Mn)As diluted magnetic III-V semiconductors. Phys. Rev. Lett., 1992, 68(17): 2664- 2667.
[74] Sato K, Katayama-Yoshida H. Material design for transparent ferromagnets with ZnO-based magnetic semiconductors. Jpn. J. Appl. Phys., 2000, 39: L555-L558.
[75] Hong N H, Sakai J, Prellier W, et al. Room temperature ferromagnetism in laser ablated transition-metal-doped TiO2 thin films on various types of substrates. J. Phys. D: Appl. Phys., 2005, 38: 816-821.
[76] Sudakar C, Thakur J S, Lawes G, et al. Ferromagnetism induced by planar nanoscale CuO inclusions in Cu-doped ZnO thin films. Phys. Rev. B, 2007, 75: 054423.
[77] Coey J M D, Douvalis A P, Fitzgerald C B, et al. Ferromagnetism in Fe-doped SnO2 thin films. Appl. Phys. Lett., 2004, 84(8): 1332-1334.
[78] Ogale S B, Choudhary R J, Buban J P, et al. High temperature ferromagnetism with a giant magnetic moment in transparent Co-doped SnO2-δ. Phys. Rev. Lett., 2003, 91: 077205.
[79] Tiwari A, Bhosle V M, Ramachandran S, et al. Ferromagnetism in Co doped CeO2: Observation of a giant magnetic moment with a high Curie temperature. Appl. Phys. Lett., 2006, 88: 142511.
[80] Sasaki T, Sonoda S, Yamamoto Y, et al. Magnetic and transport characteristics on high Curie temperature ferromagnet of Mn-doped GaN. J. Appl. Phys., 2002, 91(10): 7911-7913.
[81] Philip J, Punnoose A, Kim B I, et al. Carrier-controlled ferromagnetism in transparent oxide semiconductors. Nat. Mater., 2006, 5: 298.
[82] Ramachandra Rao M S, Kundaliya D C, Ogaleb S B, et al. Search for ferromagnetism in undoped and cobalt-doped HfO2-δ. Appl. Phys. Lett., 2006, 88: 142505.
[83] Park J H, Kim M G, Jang H M, et al. Co-metal clustering as the origin of ferromagnetism in Co-doped ZnO thin films. Appl. Phys. Lett., 2004, 84(4): 1338-1340.
[84] Huang J C A, Hsu H S. Inspection of magnetic semiconductor and clustering structure in CoFe-doped ZnO films by bias-dependent impedance spectroscopy. Appl. Phys. Lett., 2005, 87: 132503.
[85] MacManus-Driscoll J L, Khare N, Liu Y, et al. Structural evidence for Zn interstitionals in ferromagnetic Zn1-xCoxO films. Adv. Mat., 2007, 19: 2925-2929.
[86] Kundaliya D C, Ogale S B, Lofland S E, et al. On the origin of high-temperature ferromagnetism in the low-temperature-processed Mn–Zn–O system. Nat. Mater., 2004, 3, 709-714.
[87] Dietl T, Andrearczyk T, Lipińska A, et al. Origin of ferromagnetism in Zn1-xCoxO from magnetization and spin-dependent magnetoresistance measurements. Phys. Rev. B, 2007, 76: 155312.
[88] Kuroda S, Nishizawa N, Takita K, et al. Origin and control of high-temperature ferromagnetism in semiconductors. Nat. Mater., 2007, 6, 440-446.
[89] Schwartz D A, Gamelin D R. Reversible 300 K ferromagnetic ordering in a diluted magnetic semiconductor. Adv. Mater., 2004, 16(17): 2115-2119.
[90] Yan W, Sun Z, Liu Q, et al. Structures and magnetic properties of (Mn,N)-codoped ZnO thin films. Appl. Phys. Lett., 2007, 90: 242509.
[91] Spaldin N A. Search for ferromagnetism in transition-metal-doped piezoelectric ZnO. Phys. Rev. B, 2004, 69: 125201.
[92] Venkatesan M, Fitzgerald C B, Lunney J G, et al. Anisotropic ferromagnetism in substituted zinc oxide. Phys. Rev. Lett., 2004, 93: 177206.
[93] Coey J M D, Venkatesan M, Fitzgerald C B, et al. Anisotropy of the magnetization of a dilute magnetic oxide. J. Magn. Magn. Mater. 2005, 290-291, 1405-1407.
[94] Dorneles L S, O’Mahony D, Fitzgerald C B, et al. Structural and compositional analysis of transition-metal-doped ZnO and GaN PLD thin films. Appl. Surf. Sci., 2005, 248: 406-410.
[95] Saeki H, Tabata H, Kawai T. Magnetic and electric properties of vanadium doped ZnO films. Solid Solid Commun., 2001, 120: 439-443.
[96] Hong N H, Sakai J, Hassini A. Magnetic properties of V-doped ZnO thin films. J. Appl. Phys., 2005, 97: 10D312.
[97] Hong N H, Sakai J, Huong N T, et al. Role of defects in tuning ferromagnetism in diluted magnetic oxide thin films. Phys. Rev. B, 2005, 72: 045336.
[98] Liu H, Zhang X, Li L, et al. Role of point defects in room-temperature ferromagnetism Cr-doped ZnO. Appl. Phys. Lett., 2007, 91: 072511.
[99] Roberts B K, Pakhomov A B, Voll P, et al. Surface scalling of magnetism in Cr:ZnO dilute magnetic dielectric thin films. Appl. Phys. Lett., 2008, 92: 072511.
[100] García M A, Ruiz-González M L, Quesada A, et al. Interface double-exchange ferromagnetism in the Mn-Zn-O system: New class of biphase magnetism. Phys. Rev. Lett., 2005, 94: 217206.
[101] Park S Y, Kim P J, Lee Y P, et al. Realization of room-temperature ferromagnetism and of improved carrier mobility in Mn-doped ZnO film by oxygen deficiency, introduced by hydrogen and heat treatments. Adv. Mater., 2007, 19, 3496-3500.
[102] Wei X X, Song C, Geng KW, et al. Local Fe structure and ferromagnetism in Fe-doped ZnO films. J. Phys.: Condens. Matter, 2006, 18, 7471-7479.
[103] Sluiter M H F, Kawazoe Y, Sharma P, et al. First principles based design and experimental evidence for a ZnO-based ferromagnet at room temperature. Phys. Rev. Lett., 2005, 94: 187204.
[104] Kittilstved K R, Norberg N S, Gamelin D R. Chemical manipulation of high-TC ferromagnetism in ZnO diluted magnetic semiconductors. Phys. Rev. Lett., 2005, 94: 147209.
[105] Hsu H S, Huang J C A, Huang Y H, et al. Evidence of oxygen vacancy enhanced room-temperature ferromagnetism in Co-doped ZnO. Appl. Phys. Lett., 2006, 88: 242507.
[106] Liu X, Lin F, Sun L, et al. Doping concentration dependence of room-temperature ferromagnetism for Ni-doped ZnO thin films prepared by pulsed-laser deposition. Appl. Phys. Lett., 2006, 88: 062508.
[107] Hou D L, Ye X J, Meng H J, et al. Magnetic properties of n-type Cu-doped ZnO thin films. Appl. Phys. Lett., 2007, 90: 142502.
[108] Buchholz D B, Chang R P H, Song J H, et al. Room-temperature ferromagnetism in Cu-doped ZnO thin films. Appl. Phys. Lett., 2005, 87: 082504.
[109] Lee S, Shon Y, Lee S W, et al. Improved ferromagnetism of (Zn0.93Mn0.07)O through rapid thermal annealing. Appl. Phys. Lett., 2006, 88: 212513.
[110] Lee S J, Lee H S, Kim D Y, et al. Microstructural, optical, and magnetic properties of (Zn1-xMnx)O thin films grown on (0001) Al2O3 substrates. J. Cryst. Growth, 2005, 276: 121-127.
[111] Schmidt H, Diaconu M, Hochmuth H, et al. Weak ferromagnetism in textured Zn1-x(TM)xO thin films. Superlattices Microstruct., 2006, 39: 334-339.
[112] Ramachandran S, Tiwari A, Narayan J, et al. Epitaxial growth and properties of Zn1?xVxO diluted magnetic semiconductor thin films. Appl. Phys. Lett., 2005, 87: 172502.
[113] Kaspar T C, Droubay T, Li Y, et al. Lack of ferromagnetism in n-type cobalt-doped ZnO epitaxial thin films. New J. Phys., 2008, 10: 055010.
[114] Keavney D J, Buchholz D B, Ma Q, et al. Where does the spin reside in ferromagnetic Cu-doped ZnO? Appl. Phys. Lett., 2007, 91: 012501.
[115] Diana A, Schmerber G, Pierron-Bohnes V, et al. Magnetic perpendicular anisotropy in sputtered (Zn0.75Co0.25)O dilute magnetic semiconductor. J. Magn. Magn, Mater., 2005, 286: 37-40.
[116] Ziese M, Thornton M J. Spin electronics. Berlin: Springer, 2001.
[117] Schulthess H C, Temmerman W M, Szotek Z, et al. Electronic structure and exchange coupling of Mn impurities in III-V semiconductors. Nat. Mater. 2005, 4: 838-844.
[118] Kawakami R K, Kato Y, Hanson M, et al. Ferromagnetic imprinting of nuclear spins in semiconductors. Science, 2001, 294: 131-134.
[119] Malajovich I, Berry J J, Samarth N, et al. Persistent sourcing of coherent spins for multifunctional semiconductor spintronics. Nature, 2001, 411: 770-772.
[120] Ramachandran S, Tiwari A, Narayan J. Zn0.9Co0.1O-based diluted magnetic semiconducting thin films. Appl. Phys. Lett., 2004, 84(25): 5255-5257.
[121] Xu Q, Hartmann L, Schmidt H, et al. Metal-insulator transition in Co-doped ZnO: Magnetotransport properties. Phys. Rev. B, 2006, 73: 205342.
[122] Xu Q, Hartmann L, Schmidt H, et al. Magnetoresitance effects in Zn0.9Co0.1O films. J. Appl. Phys., 2006, 100: 013904.
[123] Xu Q, Hartmann L, Schmidt H, et al. Magnetoresitance and anomalous Hall effect in magnetic ZnO films. J. Appl. Phys., 2007, 101: 063908.
[124] Xu Q, Hartmann L, Schmidt H, et al. s-d exchange interaction induced magnetoresistance in magnetic ZnO. Phys. Rev. B, 2007, 76: 134417.
[125] Shinde S R, Ogale S B, Das Sarma S, et al. Ferromagnetism in laser deposited anatase Ti1-xCoxO2-δfilms. Phys. Rev. B, 2003, 67: 115211.
[126] Xu Q, Schmidt H, Zhou S, et al. Room temperature ferromagnetism in ZnO films due to defects. Appl. Phys. Lett. 2008, 92: 082508.
[127] Cheng X M, Chien C L. Magnetic properties of epitaxial Mn-doped ZnO thin films. J. Appl. Phys., 2003, 93(10): 7876-7878.
[128] Lin Y B, Xu J P, Zou W Q, et al. Effects of annealing and hydrogenation on the properties of ZnMnO polycrystalline films synthesized by plasma enhanced chemical vapour deposition. J. Phys. D: Appl. Phys. 40 (2007) 3674.-3677.
[129] Norton D P, Pearton S J, Hebard A F, et al. Ferromagnetism in Mn-implanted ZnO:Sn single crystals. Appl. Phys. Lett., 2003,82(2) 239-241.
[130] Potzger K, Zhou S, Reuther H, et al. Fe implanted ferromagnetic ZnO. Appl. Phys. Lett., 2006, 88, 052508.
[131] Lee H J, Jeong S Y, Cho C R, et al. Study of diluted magnetic semiconductor: Co-doped ZnO. Appl. Phys. Lett., 2002, 81(21): 4020-4022.
[132] Griffin K A, Pakhomov A B, Wang C M, et al. Intrinsic ferromagnetism in insulating cobalt doped anatase TiO2. Phys. Rev. Lett., 2005, 94: 157204.
[133] Belghazi Y, Schmerber G, Colis S, et al. Extrinsic origin of ferromagnetism in ZnO and Zn0.9Co0.1O magnetic semiconductor films prepared by sol-gel technique. Appl. Phys. Lett., 2006, 89: 122504.
[134] Che Mofor A, EI-Shaer A, Bakin A, et al. Magnetic property investigations on Mn-doped ZnO layers on sapphire. Appl. Phys. Lett., 2005, 87: 062501.
[135] Coey J M D. Dilute magnetic oxides. Curr. Opin. Solid State Mater. Sci., 2006, 10, 83-92.
[136] Kim J H, Kim H, Kim D, et al. Magnetic properties of epitaxially grown semiconducting Zn1-xCoxO thin filmsby pulsed laser deposition. J. Appl. Phys., 2002, 92(10): 6066-6071.
[137] Jung S W, An S J, Yi G C, et al. Ferromagentic properties of Zn1-xMnxO epitaxial thin films. Appl. Phys. Lett., 2002, 80(24): 4561-4563.
[138] Yin Z, Chen N, Chai C, et al. Structural and magnetic properties of insulating Zn1-xCoxO thin films. J. Appl. Phys., 2004, 96(9): 5093-5096.
[139] Cho Y M, Choo W K, Kim H, et al. Effects of rapid thermal annealing on the ferromagnetic properties of sputtered Zn1-x(Co0.5Fe0.5)xO thin films. Appl. Phys. Lett., 2002, 80(18): 3358-3360.
[140] Tay M, Wu Y, Han G C, et al. Ferromagnetism in inhomogeneous Zn1-xCoxO thin films. J. Appl. Phys., 2006, 100: 063910.
[141] Krishnamurthy S, McGuinness C, Dorneles L S, et al. Soft-x-ray spectroscopic investigation of ferromagnetic Co-doped ZnO. J. Appl. Phys., 2006, 99: 08M111
[142] Biegger E, Fonin M, Rüdiger U, et al. Defect induced low temperature ferromagnetism in Zn1-xCoxO films. J. Appl. Phys., 2007, 101: 073904.
[143] Ando K. Seeking room-temperature ferromagnetic semiconductors. Science, 2006, 312, 1883-1885.
[144] Kobayashi M, Ishida Y, Hwang J l, et al. Characterization of magnetic components in the diluted magnetic semiconductor Zn1-xCoxO by x-ray magnetic circular dichroism. Phys. Rev. B, 2005, 72: 201201(R).
[145] Neal J R, Behan A J, Ibrahim R M, et al. Room-temperature magneto-optics of ferromagnetic transition-metal-doped ZnO thin films. Phys. Rev. Lett., 2006, 96: 197608.
[146] Kim J Y, Park J H, Park B G, et al. Ferromagnetism induced by clustered Co in Co-doped anatase TiO2 thin films. Phys. Rev. Lett., 2003, 90: 017401.
[147] Diaconu M, Schmidt H, P?ppl A, et al. EPR study on magnetic Zn1-xMnxO. Superlattices Microstruct., 2005, 38: 413-420.
[148] Ahn G Y, Park S I, Shim I B, et al. M?ssbauer studies of ferromagnetism in Fe-doped ZnO magnetic semiconductor. J. Magn. Magn. Mater., 2004, 282: 166-169.
[149] Chattopadhyay A, Das Sarma S, Millis A J. Transition temperature of ferromagnetic semiconductors: A dynamical mean field study. Phys. Rev. Lett., 2001, 87: 227202.
[150] Walsh A, Da Silva J LF, Wei S H. Theoretical description of carrier mediated magnetism in cobalt doped ZnO. Phys. Rev. Lett., 2008, 100: 256401.
[151] Kaminski A, Das Sarma D. Polaron percolation in diluted magnetic semiconductors. Phys. Rev. Lett., 2002, 88: 247202.
[152] Cox P A. Transition metal oxides. Oxford: Clarendon press, 1992.
[153] Folk J A, Potoc R M, Marcus C M, et al. A gate-controlled bidirectional spin filter using quantum coherence. Science, 2003, 299: 679-682.
[154] Zhao T, Shinde S R, Ogale S B, et al. Electric field effect in diluted magnetic insulator anatase Co: TiO2. Phys. Rev. Lett., 2005, 94: 126601.
[155] Gould C, Pappert K, Schmidt G, et al. Magnetic anisotropies and (Ga,Mn)As-based spintronic devices. Adv. Mater., 2007, 19: 323-340.
[156] Chiba D, Sato Y, Kita T, et al. Current-driven magnetization reversal in a ferromagnetic semiconductor GaMnAs/GaAs/GaMnAs tunnel junction. Phys. Rev. Lett., 2004, 93(21): 216602.
[157] Tanaka M, Higo Y. Large tunneling magnetoresistance in GaMnAs/AlAs/ GaMnAs ferromagnetic semiconductor tunnel junctions. Phys. Rev. Lett., 2001, 87(2): 026602.
[158] Mattana R, George J M, Jaffrès H, et al. Electrical detection of spin accumulation in a p-type GaAs quantum well. Phys. Rev. Lett., 2003, 90: 166601.
[159] Herranz G, Ranchal R, Bibes M, et al. Co-doped (La, Sr)TiO3-δ: A high Curie temperaute diluted magnetic system with large spin polarization. Phys. Rev. Lett., 2006, 96: 027207.
[160] Toyosaki H, Fukumura T, Ueno K, et al. A ferromagnetic oxide semiconductor as spin injection electrode in magnetic tunnel junctions. Jpn. J. Appl. Phys., Part 2, 2005, 44: L896-L898.
[161] Toyosaki H, Fukumura T, Ueno K, et al. Ti1-xCoxO2-δ/AlOx/Fe0.1Co0.9 magentic tunnel junctions with varied AlOx thinckness. J. Appl. Phys., 2006, 99: 08M102.
[162] Wang W G, Ni C, Moriyama T, et al. Spin-polarized transport in hybrid (Zn,Cr)Te/Al2O3/Co magnetic tunnel junctions. Appl. Phys. Lett., 2006, 88: 202501.
[163] Nozaki T, Hirohata A, Tezuka N, et al. Bias voltage effect on tunnel magnetoresistance in fully epitaxial MgO double-barrier magnetic tunnel junctions. Appl. Phys. Lett., 2005, 86:082501.
[164] Ladak S, Hicken R J. Origin of large magnetocurrent in three-terminal double-barrier magnetic tunnel junctions. J. Appl. Phys., 2005, 97: 104512.
[165] Wang J, Neaton J B, Zheng H, et al. Epitaxial BiFeO3 multiferroic thin film heterostructures. Science, 2003, 299: 1719-1722.
[166] Béa H, Bibes M, Barthélémy A, et al. Influence of parasitic phases on the properties of BiFeO3 epitaxial thin films. Appl. Phys. Lett., 2005, 87: 072508.
[167] Lim S H, Murakami M, Sarney W L, et al. The effects of multiphase formation on strain relaxation and magnetization in multiferroic BiFeO3 thin films. Adv. Funct. Mater., 2007, 17: 2594-2599.
[168] Song C, Geng K W, Zeng F, et al. Giant magnetic moment in an anomalous ferromagnetic insulator: Co-doped ZnO. Phys. Rev. B, 2006, 73: 024405.
[169] Song C, Zeng F, Geng K W, et al. The magnetic properties of Co-doped ZnO diluted magnetic insulator films prepared by direct current reactive magnetron co-sputtering. J. Magn. Magn. Mater., 2007, 309: 25-30.
[170] Song C, Zeng F, Geng K W, et al. Substrate-dependent magnetization in Co-doped ZnO insulating films. Phys. Rev. B, 2007, 76: 045215.
[171] Song C, Liu X J, Geng K W, et al. Transition from diluted magnetic insulator to semiconductor in Co-doped ZnO transparent oxide. J. Appl. Phys., 2007, 101: 103903.
[172] Song C, Pan S N, Liu X J, et al. Evidence of structural defects enhanced room temperature ferromagnetism in Co-doped ZnO. J. Phys.: Condens. Matter, 2007, 19: 176229.
[173] Song C, Liu X J, Zeng F, et al. Epitaxial (Zn,Co)O/ZnO/(Zn,Co)O junction and its tunnel magnetoresistance. Appl. Phys. Lett., 2007, 91: 042106.
[174] Song C, Yang Y C, Li X W, et al. Anomalous voltage dependence of tunnel magnetoresistance in (Zn,Co)O-based junction with double-barrier. Appl. Phys. Lett., 2007, 91: 172109.
[175] Song C, Zeng F, Shen Y X, et al. Local Co structure and ferromagnetism in ion-implanted Co-doped LiNbO3. Phys. Rev. B, 2006, 73: 172412.
[176] Song C, Wang C Z, Yang Y C, et al. Room temperature ferromagnetism and ferroelectricity in cobalt-doped LiNbO3 films. Appl. Phys. Lett., 2008, 92: 262901.
[177] Song C, Wang C Z, Liu X J, et al. Room temperature ferromagnetism in single-crystal cobalt-doped LiNbO3 films. Cryst. Growth Des., in press.
[178] Ohkubo Y, Murakami T, Saito T, et al. Mechanism of the ferroelectric phase transitions in LiNbO3 and LiTaO3. Phys. Rev. B, 2002, 65: 052107.
[179] Prieto C, Zaldo C. Determination of the lattice site of Fe in photorefractive LiNbO3. Solid State Commun., 1992, 83: 819-821.
[180] Prieto C, Zaldo C, Fessler P, et al. Lattice position of Hf and Ta in LiNbO3: An extended x-ray-absorpt on fine-structure study. Phys. Rev. B, 1991, 43: 2594.
[181] Chen J J, Zeng F, Gao Y, et al. The effect of oxygen partial pressures on the microstructure,electrical and mechanical properties of high resistivity ZnO films. Appl. Surf. Sci., 2004, 223: 318-329.
[182] Ankudinov A L, Ravel B, Rehr J J, et al. Real-space multiple-scattering calculation and interpretation of x-ray-absorption near-edge structure. Phys. Rev. B, 1998, 58: 7565-7576.
[183] Rehr J J, Albers R C. Theoretical approaches to x-ray absorption fine structure. Rev. Mod. Phys., 2000, 72(3): 621-654.
[184] Kikkawa J M, Awschalom D D. Lateral drag of spin coherence in gallium arsenide. Nature, 1999, 397: 139-141.
[185] Paillard M, Marie X, Renucci P, et al. Spin relaxation quenching in semiconductor quantum dots. Phys. Rev. Lett., 2001, 86: 1634-1637.
[186] Moulder J F, Stickle W F, Sobol P E, et al. Hand-book of X-ray photoelectron spectroscopy. Eden Prairie: Perkin-Elmer, 1992.
[187] Fitzgerald C B, Venkatesan M, Lunney J G, et al. Cobalt-doped ZnO–a room temperature dilute magnetic semiconductor. Appl. Surf. Sci., 2005, 247: 493-496.
[188] Xu X H, Blythe H J, Ziese M, et al. Carrier-induced ferromagnetism in n-type ZnMnAlO and ZnCoAlO thin films at room temperature. New J. Phys., 2006, 8: 135.
[189] Theodoropoulou N, Misra V, Philip J, et al. High-temperature ferromagnetism in Zn1-xMnxO semiconductor thin films. J. Magn. Magn, Mater., 2006, 300: 407-411.
[190] Yang Z, Liu J L, Biasini M, et al. Electron concentration dependent magnetization and magnetic anisotropy in ZnO:Mn thin films. Appl. Phys. Lett., 2008, 92: 042111.
[191] Hong N H, Sakai J, Prellier W, et al. Transparent Cr-doped SnO2 thin films: ferromagnetism beyond room temperature with a giant magnetic moment. J. Phys.: Condens. Matter, 2005, 17: 1697-1702.
[192] Hong N H, Sakai J, Hassini A. Ferromagnetism at room temperature with a large magnetic moment in anatase V-doped TiO2 thin films. Appl. Phys. Lett., 2004, 84(14): 2602-2604.
[193] Sati P, Hayn R, Kuzian R, et al. Magnetic anisotropy of Co2+ as signature of intrinsic ferromagnetism in ZnO:Co. Phys. Rev. Lett., 2006, 96: 017203.
[194] Shang D S, Wang Q, Chen L D, et al. Effect of carrier trapping on the hysteresis current-voltage characteristics in Ag/La0.7Ca0.3MnO3/Pt heterostrucutes. Phys. Rev. B, 2006, 73: 245427.
[195] Edmonds K W, Binns C, Baker S H, et al. Doubling of the orbital magnetic moment in nanoscale Fe clusters. Phys. Rev. B, 1999, 60(1): 472-476.
[196] Kittel C. Introduction to solid state physics. New York: John Wiley & Sons, 1996.
[197] Wang X, Xu J, Zhang B, et al. Signature of intrinsic high-temperature ferromagnetism in cobalt-doped zinc oxide nanocrystals. Adv. Mater. 2006, 18: 2476-2480.
[198] Samanta K, Bhattacharya P, Katiyar R S, et al. Raman scattering studies in dilute magnetic semiconductor Zn1-xCoxO. Phys. Rev. B, 2006, 73: 245213.
[199] Liu X J, Song C, Yang P Y, et al. Substrate orientation-induced distinct ferromagnetic moment in Co:ZnO films. Appl. Surf. Sci., 2008, 254: 3167-3174.
[200] Rode K, Anane A, Mattana R, et al. Magnetic semiconductors based on cobalt substituted ZnO. J. Appl. Phys., 2003, 93: 7676-7678.
[201] Rode K, Mattana R, Anane A, et al. Magnetism of (Zn,Co)O thin films probed by x-ray absorption spectrocopies. Appl. Phys. Lett., 2008, 92: 012509.
[202] Ramachandran S, Narayan J, Prater J T. Effect of oxygen annealing on Mn doped ZnO diluted magnetic semiconductors. Appl. Phys. Lett., 2006, 88: 242503.
[203] Nielsen K, Bauer S, Lübbe M, et al. Ferromagnetism in epitaxial Zn0.95Co0.05O films grown on ZnO and Al2O3. Phys. Stat. Sol. A, 2006, 203: 3581-3596.
[204] Zhang Y B, Liu Q, Sritharan T, et al. Pulsed laser ablation of preferentially orientated ZnO:Co diluted magnetic semiconducting thin films on Si substrates. Appl. Phys. Lett., 2006, 89: 042510.
[205] Liu X J, Song C, Zeng F, et al. Enhancement of electrical and ferromagnetic properties by additional Al doping in Co:ZnO thin films. J. Phys.: Condens. Matter, 2007, 19: 296208.
[206] Liu X, Lin F, Sun L, et al. Doping concentration dependence of room-temperature ferromagnetism for Ni-doped ZnO thin films prepared by pulsed-laser depostion. Appl. Phys. Lett., 2006, 88: 062508.
[207] Harima H. Raman studies on spintronics materials based on wide bandgap semiconductors. J. Phys.: Condens. Matter, 2004, 16: S5653-S5660.
[208] Herng T S, Lau S P, Yu S F, et al. Zn-interstitial-enhanced ferromagnetism in Cu-doped ZnO films. J. Magn. Magn. Mater., 2007, 315: 107-110.
[209] Chakraborti D, Trichy G R, Prater J T, et al. The effect of oxygen annealing on ZnO:Cu and ZnO: (Cu, A l) diluted magnetic semiconductors. J. Phys. D: Appl. Phys., 2007, 40: 7606-7613.
[210] Verna A, Ottaviano L, Passacantando M, et al. Ferromagnetism in ion implanted amorphous and nanocrystalline MnxGe1-x. Phys. Rev. B, 2006, 74: 085204.
[211] Li X L, Wang Z L, Qin X F, et al. Enhancement of magnetic moment of Co-doped ZnO films by postannealing in vacuum. J. Appl. Phys., 2008, 103: 023911.
[212] Khare N, Kappers M J, Wei M, et al. Defect-induced ferromagnetism in Co-doped ZnO. Adv. Mater., 2006, 18: 1449-1452.
[213] Lin Y H, Ying M, Li M, et al. Room-temperature ferromagnetic and ferroelectric behavior in polycrystalline ZnO-based thin films. Appl. Phys. Lett., 2007, 90: 222110.
[214] Yang S G, Pakhomov A B, Hung S T, et al. Room temperature magnetism in sputtered (Zn,Co)O films. IEEE Trans. Magn., 2002, 38: 2877-2879.
[215] Zheng Y, Boulliard J C, Demaille D, et al. Study of ZnO crystals and Zn1-xMxO (M=Co, Mn) epilayers grown by pulsed laser deposition on ZnO ( 00 .1) substrate. J. Crystal Growth, 2005, 274: 156-166.
[216] Guo H, Burgess J, Street S, et al. Growth of epitaxial thin films of the ordered double perovskite La2NiMnO6 on different substrates. Appl. Phys. Lett., 2006, 89: 022509.
[217] Sakurai K, Kanehiro M, Nakahara K, et al. Effects of substrate offset angles on MBE growth of ZnO. J. Cryst. Growth, 2000, 214/215: 92-94.
[218] Mei Z X, Wang Y, Du X L, et al. Growth of In2O3 single-crystalline film on sapphire (0001) substrate by molecular beam epitaxy. J. Cryst. Growth, 2006, 289: 686-689.
[219] Ramesh R, Spaldin N A. Multiferroics: progress and prospects in thin films. Nat. Mater., 2007, 6: 21-29.
[220] Zheng H, Wang J, Lofland S E, et al. Multiferroic CoFe2O4-BaTiO3 nanostructures. Science, 2004, 303: 661-663.
[221] Duan C G, Jaswal S S, Tsymbal E Y. Predicted magnetoelectric effect in Fe/BaTiO3 multilayers: Ferroelectric control of magnetism. Phys. Rev. Lett., 2006, 97: 047201.
[222] Cheng Z, Wang X, Kannan C V, et al. Enhanced electrical polarization and ferromagnetic moment in a multiferroic BiFeO3/Bi3.25Sm0.75Ti2.98V0.02O12 double-layered thin film. Appl. Phys. Lett., 2006, 88: 132909.
[223] Zhou J P, He H C, Shi Z, et al. Magnetoelectric CoFe2O4/Pb(Zr0.52Ti0.48)O3 double-layer thin film prepared by pulsed-laser deposition. Appl. Phys. Lett., 2006, 88: 013111.
[224] Eerenstein W, Wiora M, Prieto J L, et al. Giant sharp and persistent converse magnetoelectric effects in multiferroic epitaxial heterostructures. Nat. Mater., 2007, 6: 348-351.
[225] Kim N, Kim H, Kim J W, et al. Modulation of the Curie temperature in ferromagentic/ferroelectric hybrid double quamtum wells. Phys. Rev. B, 2006, 73: 033318.
[226] Lee E C, Chang K J. Ferromagnetic versus antiferromagnetic interaction in Co-doped ZnO. Phys. Rev. B, 2004, 69: 085205.
[227] Zhang W, Wang X, Elliott M, et al. Stress effect and enhanced magnetoresistance in La0.67Sr0.33MnO3-δfilms. Phys. Rev. B, 1998, 58: 14143.
[228] Lee S, Lee H S, Hwang S J, et al. Effects of oxygen partial pressure during sputtering growth on physical properties of Zn0.93Mn0.07O thin films. J. Crystal growth, 2006, 286: 223-227.
[229] Droubay T, Heald S M, Shutthanandan V, et al. Cr-doped TiO2 anatase: A ferromagnetic insulator. J. Appl. Phys., 2005, 97: 046103.
[230] Toyosaki H, Fukumura T, Yamada Y, et al. Anomalous Hall effect governed by electron doping in a room-temperature transparent ferromagnetic semiconductor. Nat. Mater., 2004, 3: 221-224.
[231] Sakai K, Kakeno T, Ikari T, et al. Defect centers and optical absorption edge of degenerated semiconductor ZnO thin films grown by a reactive plasma deposition by means of piezoelectric photothermal spectroscopy. J. Appl. Phys., 2006, 99: 043508.
[232] Venkataraj S, Ohashi N, Sakaguchi I, et al. Structural and magnetic properties of Mn-ion implanted ZnO films. J. Appl. Phys., 2007, 102: 014905.
[233] Vaithianathan V, Lee B T, Chang C H, et al. Characterization of As-doped, p-type ZnO by x-ray absorption near-edge structure spectroscopy. Appl. Phys. Lett., 2006, 88: 112103.
[234] Ungureanu M, Schmidt H, von Wenckstern H, et al. A comparison between ZnO films doped with 3d and 4f magnetic ions. Thin Solid Films, 2007, 515: 8761-8763.
[235] Liu X J, Song C, Zeng F, et al. Influence of annealing on microstructure and magnetic properties of co-sputtered Co doped ZnO thin films. J. Phys. D: Appl. Phys., 2007, 40: 1608-1613.
[236] Kittilstved K R, Schwartz D A, Tuan A C, et al. Direct kinetic correlation of carriers and ferromagnetism in Co2+: ZnO. Phys. Rev. Lett., 2006, 97: 037203.
[237] Matsumura T, Okuyama D, Niioka S, et al. X-ray anomalous scattering of diluted magnetic oxide semiconductors: Possible evidence of lattice deformation for high temperature ferromagnetism. Phys. Rev. B, 2007, 76 : 115320.
[238] Chakraborti D, Ramachandran S, Trichy G, et al. Magnetic, electrical, and microstructural characterization of ZnO thin films codoped with Co and Cu. J. Appl. Phys., 2007, 101: 053918.
[239] Tiwari A, Snure M, Kumar D, et al. Ferromagnetism in Cu-doped ZnO films: Role of charge carriers. Appl. Phys. Lett., 2008, 92: 062509.
[240] Liu X C, Shi E W, Chen Z Z, et al. High-temperature ferromagnetism in (Co,Al)-codoped ZnO powders. Appl. Phys. Lett., 2006, 88: 252503.
[241] Ivill M, Pearton S J, Norton D P, et al. Magnetization dependence on electron density in epitaxial ZnO thin films doped with Mn and Sn. J. Appl. Phys., 2005, 97: 053904.
[242] Jayakumar O D, Gopalakrishnan I K, Kulshreshtha S K. Surfactant-assisted synthesis of Co- and Li-doped ZnO nanocrystalline samples showing room-temperature ferromagnetism. Adv. Mater., 2006, 18: 1857-1860.
[243] Tietze T, Gacic M, Schütz, et al. XMCD studies on Co and Li doped ZnO magnetic semiconductors. New J. Phys., 2008, 10: 055009.
[244] Liu X J, Song C, Zeng F, et al. Donor defects enhanced ferromagnetism in Co: ZnO films. Thin Solid Films, 2008, 516: 8757-8761.
[245] Xu H Y, Liu Y C, Xu C S, et al. Room-temperature ferromagnetism in (Mn,N)-codoped ZnO thin films prepared by reactive magnetron cosputtering. Appl. Phys. Lett., 2006, 88: 242502.
[246] Gu Z B, Lu M H, Wang J, et al. Structure, optical, and magnetic properties of sputtered manganese and nitrogen-codoped ZnO films. Appl. Phys. Lett., 2006, 88: 082111.
[247] Ivill M, Pearton S J, Heo Y W, et al. Magnetization dependence on carrier doping in epitaxial ZnO thin films doped with Mn and P. J. Appl. Phys., 2007, 101: 123909.
[248] Hong N H, BrizéV, Sakai J. Mn-doped ZnO and (Mn,Cu)-doped ZnO thin films: Does the Cu doping indeed play a key role in tuning the ferromagnetism. Appl. Phys. Lett., 2005, 86: 082505.
[249] Han S J, Song J W, Yang C H, et al. Key to room-temperature ferromagnetism in Fe-doped ZnO: Cu. Appl. Phys. Lett., 2002, 81: 4212-4214.
[250] Mokhtari A, Behan A J, Score D S, et al. Transport and magnetism studies of doped ZnO films. New J. Phys., submitted.
[251] Chun S H, Potashnik S J, Ku K C, et al. Spin-polarized tunneling in hybrid metal-semiconductor magnetic tunnel junctions. Phys. Rev. B, 2002, 66: 100408(R).
[252] Saito H, Yuasa S, Ando K. Origin of the tunnel anisotropic magnetoresistance in Ga1-xMnxAs/ZnSe/Ga1-xMnxAs magnetic tunnel junctions of II–VI/III–V heterostructures. Phys. Rev. Lett., 2005, 95: 086604.
[253] Tsymbal E Y, Belashchenko K D, Velev J P et al. Interface effects in spin-dependent tunneling. Prog. Mater. Sci., 2005, 50: 401-420.
[254] Tiusan C, Faure-Vincent J, Bellouard C, et al. Interfacial resonance state probed by spin-polarized tunneling in epitaxial Fe/MgO/Fe tunnel junctions. Phys. Rev. Lett., 2004, 93: 106602.
[255] Colis S, Gieres G, Dimopoulos T, et al. Large magnetoresistance at high bias voltage in double magnetic tunnel junctions. IEEE trans. Magn. 2004, 40(4): 2287-2289.
[256] Ghosh K, Ogale S B, Pai S P, et al. Positive giant magnetoresistance in a Fe3O4/SrTiO3/La0.7Sr0.3MnO3 heterostructure. Appl. Phys. Lett., 1998, 73: 689-691.
[257] May S J, Phillips P J, Wessels B W. Negative magnetoresistance in metal/oxide/InMnAs tunnel junctions. J. Appl. Phys., 2006, 100: 053912.
[258] Zenger M, Moser J, Wegscheider W, et al. High-field magnetoresistance of Fe/GaAs/Fe tunnel junctions. J. Appl. Phys., 2004, 96: 2400-2402.
[259] Risbud A S, Spaldin N A, Chen Z Q, et al. Magnetism in polycrystalline cobalt-substituted zinc oxide. Phys. Rev. B, 2003, 68: 205202.
[260] Montaigne F, Nassar J, Vaurès A, et al. Enhanced tunnel magnetoresistance at high bias voltage double-barrier planar junctions. Appl. Phys. Lett., 1998, 73: 2829-2831.
[261] Ding H F, Wulfhekel W, Henk J, et al. Absence of zero-bias anomaly in spin-polarized vacuum tunneling in Co(0001). Phys. Rev. Lett., 2003, 90: 116603.
[262] Nagahama T, Santos T S, Moodera J S. Enhanced magnetotransport at high bias in quasimagnetic tunnel junctions with EuS spin-filter barriers. Phys. Rev. Lett., 2007, 99: 016602.
[263] Dias Cabral E, Boselli M A, da Cunha Lima A T, et al. On the nature of the spin-polarized hole states in a quasi-two-dimensional GaMnAs ferromagnetic layer. Appl. Phys. Lett., 2007, 90: 142118.
[264] Rodrigues S C P, Scolfaro L M R, Leite J R, et al. Charge and spin distribution in Ga1-xMnxAs/GaAs ferromagnetic multilayers. Phys. Rev. B, 2004, 70: 165308.
[265] Das Sarma S, Hwang E H, Kaminski A. Temperature-dependent magnetization in diluted magnetic semiconductors. Phys. Rev. B, 2003, 67: 155201.
[266] Yang Y C, Song C, Wang X H, et al. Cr-substitution-induced ferroelectric and improved piezoelectric properties of Zn1-xCrxO films. J. Appl. Phys., 2008, 103: 074107.
[267] Spaldin N A. Physics of ferroelectrics: A modern perspective, Topics Appl. Physics, edited byRabe K, Ahn C H, Triscone J M. Berlin Heidelberg: Springer-Verlag, 2007.
[268] Scott J F. Ferroelectrics go bananas. J. Phys.: Condens. Matter, 2008, 20: 021001.
[269] Blom P W M, Wolf R M, Cillessen J F M, et al. Ferroelectric Schottky diode. Phys. Rev. Lett., 1994, 73: 2107-2110.
[270] Dhananjay, Nagaraju J, Krupanidhi S B. Effect of Li substitution on dielectric and ferroelectric properties of ZnO films grown by pulsed-laser ablation. J. Appl. Phys., 2006, 99: 034105.
[271] Watanabe Y. Electrical transport through Pb(Zr,Ti)O3 p-n and p-p heterostructures modulated by bound charges at a ferroelectric surface: Ferroelectric p-n diode. Phys. Rev. B, 2006, 73: 245427.