复合钙钛矿锰氧化物的制备与磁电特性的研究
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摘要
近年来,在形如R1-xAxMnO3(R是稀土元素,A是二价阳离子)的锰基钙钛矿多晶材料中的颗粒边界效应引起人们极大的研究兴趣。早期人们在这类材料中发现庞磁电阻效应(CMR),但CMR仅仅出现在居里温度(Tc)附近狭窄的温度范围,而且需要几个特斯拉的高磁场才可以实现,因而限制了它的应用。最近,人们发现在锰基钙钛矿多晶材料中颗粒边界效应强烈地影响其物理性能,最吸引人的特征就是在较低的磁场下就可以获得很高的磁电阻,而且低场磁电阻(LFMR)出现在整个绝缘体金属转变温度(Tp)以下宽的温度范围。一般认为,这种低场磁电阻是由于载流子通过颗粒边界的能量势垒发生自旋极化隧穿而引起的。颗粒边界的无序结构是载流子能量势垒的主要原因,因此对颗粒边界进行优化处理可以改善这类磁电阻,最有效的方法就是引入第二相形成锰基钙钛矿颗粒复合材料。本论文主要以钙钛矿锰氧化物La_(0.67)Sr_(0.33)MnO_3 (LSMO)颗粒体系为研究对象,通过在其颗粒边界引入不同性质的第二相材料对颗粒边界进行改性,并对复合体系的电、磁输运行为进行研究,从而为提高低场磁电阻效应提供实验和理论基础。主要研究结果包括如下几方面:
1.用溶胶凝胶法制备出单相的La_(0.67)Sr_(0.33)MnO_3、Pr0.67Ca0.33MnO3(PCMO)、Sm_(0.67)Ca_(0.33)MnO_3(SCMO),研究了它们的结构、磁性能及电输运。
2.将单相的La_(0.67)Sr_(0.33)MnO_3、Pr0.67Ca0.33MnO3按一定的比例混合、研磨、压片,在合适的温度下进行烧结,得到两相共存的复合锰氧化物(1-x)La_(0.67)Sr_(0.33)MnO_3 /xPr0.67Ca0.33MnO3(LSMO/PCMO)。随着PCMO含量增加,LSMO/PCMO复合样品的磁化强度显著降低,在PCMO电荷有序附近及其以下温区存在较强的磁耦合;复合体系的导电性下降,电阻率增大,电阻率峰值ρTp向低温移动,金属绝缘体的转变峰宽变窄;在低温下样品的低场磁电阻有所提高、高场磁电阻增大很多;由于颗粒间的隧穿效应样品存在低温电阻率极小值现象。
3.按同样的方法得到两相共存的复合锰氧化物(1-x)La_(0.67)Sr_(0.33)MnO_3 /xSm67Ca0.33MnO3(LSMO/SCMO)。LSMO/SCMO复合样品存在两个磁转变温度,随着SCMO含量增加,样品的磁性降低,复合样品LSMO与SCMO颗粒间存在磁耦合;LSMO颗粒周围的SCMO颗粒增多,使其相邻间的交换作用减弱,复合体系的导电性下降,电阻率增大,电阻率峰值ρTp向低温移动,金属绝缘体的转变峰宽变窄。
Recently, growing attention has been paid on the grain boundary effect in polycrystalline R1-xAxMnO3 (R is rare earth, A is divalent cation) perovskite manganites. In the early years, colossal magnetoresistance (CMR) effect was observed in this kind of materials. However, the intrinsic CMR effect in the perovskite manganites is only triggered at high magnetic fields of several tesla, which restrains its use for practical applications. Recently, growing attention is being paid to polycrystalline manganites in which the grain boundary effects dramatically modify their physical properties. An attractive feature for the polycrystalline manganites is a large magnetoresistance (MR) at very low magnetic field over wide temperature range below Tp. The low field magnetoresistance in polycrystalline manganites is usually thought to be a result of the spin polarized tunneling through energy barriers at grain boundaries. The structural disordered interfaces play a role of the energy barrier for carriers. The magnetoresistance can be enhanced through controlling the grain boundary effect by forming composites of the CMR oxides with secondary phase. In this paper, based on the polycrystalline manganese oxide of La_(0.67)Sr_(0.33)MnO_3 (LSMO), we modified the grain boundaries in these manganites by introducing the secondary phase with different properties. The electrical and magnetic properties of the composites have been investigated, which provides experimental and theoretical basis for the enhancement of low-field magnetoresistance. The main results are shown as following:
1. The polycrystalline samples of La_(0.67)Sr_(0.33)MnO_3, Pr0.67Ca0.33MnO3(PCMO) and Sm_(0.67)Ca_(0.33)MnO_3(SCMO) were synthesized by sol-gel method and the structure, magnetic and electrical transport properties were studied.
2. After mixed the manganese oxides of La_(0.67)Sr_(0.33)MnO_3 and Pr0.67Ca0.33MnO3 in a certain proportion, we ground, pressed, and sintered the samples at a certain temperature, and got the two-phase coexistence of complex manganese oxides (1-x)La_(0.67)Sr_(0.33)MnO_3 /xPr0.67Ca0.33MnO3(LSMO/PCMO) composites finally. We found that with increasing the content of PCMO, the magnetization of the LSMO/PCMO composite reduces significantly. The experimental results indicate that there is a strong magnetic coupling around and under PCMO’s charge ordering temperature. The experimental results show that with the increase of PCMO content, the conductivity of composite systems decreases, the electrical resistivity increases, the resistivity peak ofρTpmoves to lower temperature, and the metal-insulator transition peak width becomes narrower. At low temperature, the low-field magnetoresistance increases a bit, while the high-field magnetoresistance increases a lot. There is a minimum in resistivity at low-temperature because of the tunneling effect between particles.
3. The two-phase coexistence of complex manganese oxides for (1-x)La_(0.67)Sr_(0.33)MnO_3 /xSm67Ca0.33MnO3 (LSMO/SCMO) were prepared using the similar method. There are two magnetic transitions in the composite samples. The magnetization of the LSMO/PCMO composite samples reduces with increasing the content of SCMO. The exchange coupling between adjacent composite particles weakens with the increase of SCMO content. The conductivity of composite systems decreases, the electrical resistivity increases, the resistivity peak ofρTpmoves to lower temperature, and the metal-insulator transition peak width becomes narrower with increasing the content of SCMO.
1.用溶胶凝胶法制备出单相的La_(0.67)Sr_(0.33)MnO_3、Pr0.67Ca0.33MnO3(PCMO)、Sm_(0.67)Ca_(0.33)MnO_3(SCMO),研究了它们的结构、磁性能及电输运。
2.将单相的La_(0.67)Sr_(0.33)MnO_3、Pr0.67Ca0.33MnO3按一定的比例混合、研磨、压片,在合适的温度下进行烧结,得到两相共存的复合锰氧化物(1-x)La_(0.67)Sr_(0.33)MnO_3 /xPr0.67Ca0.33MnO3(LSMO/PCMO)。随着PCMO含量增加,LSMO/PCMO复合样品的磁化强度显著降低,在PCMO电荷有序附近及其以下温区存在较强的磁耦合;复合体系的导电性下降,电阻率增大,电阻率峰值ρTp向低温移动,金属绝缘体的转变峰宽变窄;在低温下样品的低场磁电阻有所提高、高场磁电阻增大很多;由于颗粒间的隧穿效应样品存在低温电阻率极小值现象。
3.按同样的方法得到两相共存的复合锰氧化物(1-x)La_(0.67)Sr_(0.33)MnO_3 /xSm67Ca0.33MnO3(LSMO/SCMO)。LSMO/SCMO复合样品存在两个磁转变温度,随着SCMO含量增加,样品的磁性降低,复合样品LSMO与SCMO颗粒间存在磁耦合;LSMO颗粒周围的SCMO颗粒增多,使其相邻间的交换作用减弱,复合体系的导电性下降,电阻率增大,电阻率峰值ρTp向低温移动,金属绝缘体的转变峰宽变窄。
Recently, growing attention has been paid on the grain boundary effect in polycrystalline R1-xAxMnO3 (R is rare earth, A is divalent cation) perovskite manganites. In the early years, colossal magnetoresistance (CMR) effect was observed in this kind of materials. However, the intrinsic CMR effect in the perovskite manganites is only triggered at high magnetic fields of several tesla, which restrains its use for practical applications. Recently, growing attention is being paid to polycrystalline manganites in which the grain boundary effects dramatically modify their physical properties. An attractive feature for the polycrystalline manganites is a large magnetoresistance (MR) at very low magnetic field over wide temperature range below Tp. The low field magnetoresistance in polycrystalline manganites is usually thought to be a result of the spin polarized tunneling through energy barriers at grain boundaries. The structural disordered interfaces play a role of the energy barrier for carriers. The magnetoresistance can be enhanced through controlling the grain boundary effect by forming composites of the CMR oxides with secondary phase. In this paper, based on the polycrystalline manganese oxide of La_(0.67)Sr_(0.33)MnO_3 (LSMO), we modified the grain boundaries in these manganites by introducing the secondary phase with different properties. The electrical and magnetic properties of the composites have been investigated, which provides experimental and theoretical basis for the enhancement of low-field magnetoresistance. The main results are shown as following:
1. The polycrystalline samples of La_(0.67)Sr_(0.33)MnO_3, Pr0.67Ca0.33MnO3(PCMO) and Sm_(0.67)Ca_(0.33)MnO_3(SCMO) were synthesized by sol-gel method and the structure, magnetic and electrical transport properties were studied.
2. After mixed the manganese oxides of La_(0.67)Sr_(0.33)MnO_3 and Pr0.67Ca0.33MnO3 in a certain proportion, we ground, pressed, and sintered the samples at a certain temperature, and got the two-phase coexistence of complex manganese oxides (1-x)La_(0.67)Sr_(0.33)MnO_3 /xPr0.67Ca0.33MnO3(LSMO/PCMO) composites finally. We found that with increasing the content of PCMO, the magnetization of the LSMO/PCMO composite reduces significantly. The experimental results indicate that there is a strong magnetic coupling around and under PCMO’s charge ordering temperature. The experimental results show that with the increase of PCMO content, the conductivity of composite systems decreases, the electrical resistivity increases, the resistivity peak ofρTpmoves to lower temperature, and the metal-insulator transition peak width becomes narrower. At low temperature, the low-field magnetoresistance increases a bit, while the high-field magnetoresistance increases a lot. There is a minimum in resistivity at low-temperature because of the tunneling effect between particles.
3. The two-phase coexistence of complex manganese oxides for (1-x)La_(0.67)Sr_(0.33)MnO_3 /xSm67Ca0.33MnO3 (LSMO/SCMO) were prepared using the similar method. There are two magnetic transitions in the composite samples. The magnetization of the LSMO/PCMO composite samples reduces with increasing the content of SCMO. The exchange coupling between adjacent composite particles weakens with the increase of SCMO content. The conductivity of composite systems decreases, the electrical resistivity increases, the resistivity peak ofρTpmoves to lower temperature, and the metal-insulator transition peak width becomes narrower with increasing the content of SCMO.
引文
[1] Hwang H Y, Cheong S W, Ong N P, et al. Spin-Polarized Intergrain Tunneling in La2/3Sr1/3MnO3 [J]. Phys Rev Lett,1996,77(10):2041-2044.
[2] Baibich M.N, Broto J M, Fert A,et al. Giant Magnetoresistance of (001) Fe/(001) Cr Magnetic Superlattices[J]. Phys Rev Lett ,1988,61(21):2472-2475.
[3] Helmolt R Von, Wecker J, Holzapfel B, et al. Giant Negative Magnetoresistance in Perovskitelike La2/3Bal/3MnOx Ferromagnetic Films[J]. Phys Rev Lett ,1993,71(14): 2331-2333.
[4] Chen L.H,Jin S,Tiefel T.H,et al. Large Magnetoresistance in La-Ca-Mn-0 Films[J]. IEEE Trans On Magn,1995,31(6):3912-3914.
[5] Julliere M. Tunneling between ferromagnetic films[J].Phys Lett A,1975,54:225-226.
[6] Miyazaki T, Tezuka N. Giant magnetic tunneling effect in Fe/Al2O3/Fe junction[J]. J Magn.Magn.Mater, 1995,139:231-235.
[7] LuYu, Li X W, Gong G Q, et al. Large magnetotunneling effect at low magnetic fields in micrometer-scale epitaxial La 0.67Sr 0.33MnO3 tunnel junctions[J]. Phys Rev B,1996,54: 8357-8360.
[8] Rao G H, Sun J R, Liang J K, et al. Giant magnetoresistance effect in bulk La1/3Nd1/3Ca1/3MnO3 at low field[J]. Appl Phys Lett,1996,69:424-426.
[9] Van Elst H C. The anisotropy in the magneto-resistance of some nickel alloys[J]. Physica,1959,25:708-720.
[10] Mc Guire.T, Potter R.Anisotropic magnetoresistance in ferromagnetic 3d alloys[J]. IEEE Trans On Magn.1975,11:1018-1038.
[11] Grunberg P, Schreiber R, Pang Y, et al. Layered Magnetic Structures: Evidence for Antiferromagnetic Coupling of Fe Layers across Cr Interlayers[J]. Phys Rev Lett,1986, 57,2442-2445.
[12] Lee S, Hwang H Y, Shraiman Boris I, et al. Intergrain Magnetoresistance via Second-Order Tunneling in Perovskite Manganites[J]. Phys Rev Lett ,1999,82:4508-4511.
[13] Berkowitz A E, Mitchell J R, Carey M.J, et al. Giant Magnetoresistance in Heterogeneous Cu-Co Alloys[J]. Phys Rev Lett ,1992,68:3745-3748.
[14] Xiao John.Q,Jiang J.Samuel,Chien C.L.Giant Magnetoresistance in Nonmultilayer Magnetic Systems[J]. Phys Rev Lett ,1992,68:3749-3752.
[15] Yuan S L, Zhao Z Y, Xia Z C, et al. Magnetic and transport properties in polycrystalline La2/3Ca1/3MnO3[J]. Solid State Communications,2003,125:653-657.
[16] Slonczewski J C. Conductance and exchange coupling of two ferromagnets separated by a tunneling barrier[J]. Phys Rev B,1989,39:6995-7002.
[17] Tedrow P M, Meservey R. Spin-Dependent Tunneling into Ferromagnetic Nickel[J]. Phys Rev Lett ,1971,26(4):192-195.
[18] Fujimori H, Mitani S, Ohnuma S.Tunnel-type GMR in metal-nonmetal granular alloy thin films[J].Mater Sci Eng B,1995,31:219.
[19] Inomata K, Okuno S N, Saito Y, et al. Oscillatory interlayer couplings as functions of a ferromagnetic metal layer and a semiconducting spacer in magnetic superlattices[J].J Magn Magn Mater,1996,156:219-223.
[20] Mitani S, Fujimori H, Ohnuma S. Spin-dependent tunneling phenomena in insulating granular systems[J]. J Magn Magn Mater,1997,165:141-148.
[21] Volger J. Further experimental investigations on some ferromagnetic oxidic compounds of manganese with perovskite structure[J].Physica,1954,20:49.
[22]Sun J R. Manganate Trilayer Junctions:Spin-Dependent Transport and Low-Field Magnetoresistance[M].Gordon and Breach Science Publishers,2000,331-334.
[23] Gupta A, Gong G Q, Xiao Gang, et al. Grain-boundary effects on the magnetoresistance properties of perovskite manganite films[J]. Phys Rev B,1996,54:R15629-15632.
[24] Balcells L, Fontcuberta J, Mart B, et al. High-field magnetoresistance at interfaces in manganese perovskites[J]. Phys Rev B,1998,58:R14697-R14700.
[25] Li X.W,Gupta A,Xiao G,et al. Low-field magnetoresistive properties of polycrystalline and epitaxial perovskite manganite films[J]. Appl Phys Lett,1997,71:1124.
[26] Mahesh, Mahendiran R, Raychaudhuri A K, et al. Effect of particle size on the giant magnetoresistance of La0.7Ca0.3MnO3[J].1996,68:2291-2293.
[27] Mathur N D, Burnell G, Isaac S P, et al. Effect of particle size on the giant magnetoresistance of LaCaMnO[J].Nature,1997,387:266-268.
[28] Hueso L E, Rivas J, Rivadulla F, et al. Tuning of colossal magnetoresistance via grainsize change in LaCaMnO[J].J Appl Phys,1999,86(7):3881-3884.
[29] Sa′nchez R D, Rivas J, Va′zquez-Va′zquez C. et al. Giant magnetoresistance in fine particle of La0.67Ca0.33MnO3 synthesized at low temperatures[J]. Appl Phys Lett,1996,68 (1): 134-136.
[30] Siwach P K, Goutam U K, Srivastava P, et al. Colossal magnetoresistance study in nanophasic La0.7Ca0.3MnO3 manganite[J].J Phys D:Appl.Phys,2006,39:14-20.
[31] Dey P, Nath T K. Enhanced grain surface effect on the temperature-dependent behavior of spin-polarized tunneling magnetoresistance of nanometric manganites[J].Appl Phys Lett, 2005,87(16):162501 1-3.
[32] Wang X L, Dou S X, Liu H.K, et al. Large low-field magnetoresistance over a wide temperature range induced by weak-link grain boundaries in La0.7Ca0.3MnO3[J]. Appl Phys Lett,1998,73(3):396-398.
[33] Peng H B,Zhao B R,Xie Z,et al. Surface pattern and large low-field magnetoresistance in La0.5Ca0.5MnO3 films[J]. Appl Phys Lett,1999,74(11):1606-1608.
[34] Bibes M, Hrabovsky D, Martinez B, et al. Magneto-optical kerr effect in laser-patterned La2/3Sr1/3MnO3 epitaxial thin films[J].J Appl Phys,2001,89(11):6958-6960.
[35] Balcells L, Carrillo A E, Martínez B, et al. Enhanced field sensitivity close to percolation in magnetoresiative La2/3Sr1/3MnO3/CeO2 composites[J].Appl Phys Lett, 1999,74(26): 4014-4016.
[36] Petrov D K, Elbaun L, Sun J Z, et al. Enhanced magnetoresistance in sintered granular manganite/insulator systems[J].Appl Phys Lett,1999,75(7):995-997.
[37] Yuan S L, X Z C , Liu S, et al. Electrical transport and low-field magnetoresistance in La2/3Ca1/3MnO3/YSZ composites[J].Chin Phys Lett,2002,19(8): 1168-1171
[38] Huang Y H, Yan C H, Luo F, et al. Large enhancement in room-temperature magnetoresistance and dramatic decrease in resistivity in La0.7Ca0.3MnO3–Ag composites[J]. Appl PhysLett,2002,81(1):76-78.
[39] Yan C H, Xu Z G, Zhu T, et al. A large low field colossal magnetoresistance in the La0.7Sr0.3MnO3 and CoFe2O4 combined system[J].J Appl Phys,2000,87(9):5588-5590.
[40] Xia Z C, Yuan S L, Zhang G H, et al. Effect of low Fe3O4 doping in La0.67Ca0.33MnO3[J].J Phys D,Appl Phys,2003,36:217-222.
[41] Huang Q, Li J, Huang X J, Ong C K. Effect of magnetic coupling on the magnetoresistive properties in La0.67Sr0.33MnO3/BaFe11.3(ZnSn)0.7O19 composites[J]. J Appl Phys,2001,90(6):2924-2929.
[42] Liu J M, Yuan G L, Sang H, et al. Low-field magnetoresistance in nanosized La0.7Sr0.3MnO3/Pr0.5Sr0.5MnO3 composites[J].Appl Phys Lett,2001,78(8): 1110-1112.
[43] Liu J M, Huang Q, Li J, et al. Low-field magnetoresistance property of partically crystallized La0.5Sr0.5MnO3 thin films by pulsed laser deposition[J].J Appl Phys, 2000,88(5): 2791-2798.
[44] Liu J M, Li J, Huang Q, et al. Partically crystallized La0.5Sr0.5MnO3 thin films by laser ablation and their enhanced low-field magnetoresistance[J].Appl Phys Lett, 2000,76(16): 2286-2288.
[45] Liu J M, Yuan G L, Chen X Y, et al.Spin-polarized inter-grain tunneling as the probable mechanism for low-field magnetoresistance in partically crystallized La0.5Sr0.5MnO3 thin films[J].Appl Phys A,2001,73(5):625-630.
[46] Yuan S L, Zhang G Q, Peng G,et al.Electrical transport and low-field magnetoresistance in the series of mixed polycrystals (1-m)La2/3Ca1/3MnO3+ mLa2/3Sr1/3MnO3 [J].J Phys Condens Matter,2001,13:5691-5697.
[47] Hong C S, Kim W S, Hur N H.Wide colossal magnetoresistance around room temperature in La0.7Ca0.3MnO3/La0.7Sr0.3MnO3 composites[J].Solid State Commu, 2002,121:657-660.
[48] Yua C, Lee S F, Tsai J L, et al.Study of domain wall magnetoresistance by submicron patterned magnetic structure[J].J Appl Phys,2003,93(10):8761-8763.
[49] Loskjkowi W, Fecht H J. The structure of intercrystalline interfaces[J].Progress in Materials Science,2000,45:339~568.
[50] Urushibara A, Moritomo Y, Arima T, et al. Insulator-metal transition and giant magnetoresistance in La1-xSrxMnO3[J]. Phys Rev B,1995,51(20):14103-14109.
[51]席力,刘杰,田航等.纳米多晶La0.7Sr0.3MnO3-δ的输运性质[J].兰州大学学报,2008,44(3):134-137。
[52]Ding W P, Zhong W, Xing D Y, et al. Tunnel-type giant magnetoresistance in the granularperovskite La0.85Sr0.15MnO3[J]. Phys Rev B,1997,56(13):8138-8142.
[53] Radaelli P G, Iannone G, Marezio M, et al. Structural effects on the magnetic and transport properties of perovskite A 1-x A`x8MnO3 (x=0.25, 0.30)[J]. Phys Rev B,1997,56(13):8265-8276.
[54] Hazama H. Ultrasonic study of orbital and charge fluctuation in Pr1-xCaxMnO3[J]. Physica B,2002,(312-314):757-759.
[55] Deac G, Mitchell J F, Schiffer P. Phase Separation and the Low-Field Bulk Magnetic Properties of Pr0.7Ca0.3MnO3 [J]. Phys Rev B, 2001,63(17):172408.
[56]项阳. Pr0.1Ca0.9MnO3体系磁性及输运性质的研究[D].哈尔滨工业大学2007年7月.
[57] Tomioka Y, Asamitsu A, Kuwahara H, et al. Magnetic-field-induced metal-insulator phenomena in Pr1-xCaxMnO3 with controlled charge-ordering instability[J]. Phys Rev B, 1996,53(4):R1689-R1692.
[58]Balcells L, Fontcuberta J, Martinez B, et al. Magnetic surface effects and low-tempersture magnetoresistance in manganese perovskites[J].J Phys:Condens Matter, 1998,10(8): 1886-1890.
[59] Tong P, Kim B, Kwon D, et al. Griffiths phase and thermomagnetic irreversibility behavior in slightly electron-doped manganites Sm1-xMnxO3 (0.80≤x≤0.92)[J]. Phys Rev B, 2008, 77(18):184432 1-7.
[60] Martin C, Maignan A, Hervieu M, et al. Magnetic phase diagrams of L1-xAxMnO3 manganites (L=Pr, Sm;A=Ca,Sr)[J]. Phys Rev B,1999,60(17):12191-12199.
[2] Baibich M.N, Broto J M, Fert A,et al. Giant Magnetoresistance of (001) Fe/(001) Cr Magnetic Superlattices[J]. Phys Rev Lett ,1988,61(21):2472-2475.
[3] Helmolt R Von, Wecker J, Holzapfel B, et al. Giant Negative Magnetoresistance in Perovskitelike La2/3Bal/3MnOx Ferromagnetic Films[J]. Phys Rev Lett ,1993,71(14): 2331-2333.
[4] Chen L.H,Jin S,Tiefel T.H,et al. Large Magnetoresistance in La-Ca-Mn-0 Films[J]. IEEE Trans On Magn,1995,31(6):3912-3914.
[5] Julliere M. Tunneling between ferromagnetic films[J].Phys Lett A,1975,54:225-226.
[6] Miyazaki T, Tezuka N. Giant magnetic tunneling effect in Fe/Al2O3/Fe junction[J]. J Magn.Magn.Mater, 1995,139:231-235.
[7] LuYu, Li X W, Gong G Q, et al. Large magnetotunneling effect at low magnetic fields in micrometer-scale epitaxial La 0.67Sr 0.33MnO3 tunnel junctions[J]. Phys Rev B,1996,54: 8357-8360.
[8] Rao G H, Sun J R, Liang J K, et al. Giant magnetoresistance effect in bulk La1/3Nd1/3Ca1/3MnO3 at low field[J]. Appl Phys Lett,1996,69:424-426.
[9] Van Elst H C. The anisotropy in the magneto-resistance of some nickel alloys[J]. Physica,1959,25:708-720.
[10] Mc Guire.T, Potter R.Anisotropic magnetoresistance in ferromagnetic 3d alloys[J]. IEEE Trans On Magn.1975,11:1018-1038.
[11] Grunberg P, Schreiber R, Pang Y, et al. Layered Magnetic Structures: Evidence for Antiferromagnetic Coupling of Fe Layers across Cr Interlayers[J]. Phys Rev Lett,1986, 57,2442-2445.
[12] Lee S, Hwang H Y, Shraiman Boris I, et al. Intergrain Magnetoresistance via Second-Order Tunneling in Perovskite Manganites[J]. Phys Rev Lett ,1999,82:4508-4511.
[13] Berkowitz A E, Mitchell J R, Carey M.J, et al. Giant Magnetoresistance in Heterogeneous Cu-Co Alloys[J]. Phys Rev Lett ,1992,68:3745-3748.
[14] Xiao John.Q,Jiang J.Samuel,Chien C.L.Giant Magnetoresistance in Nonmultilayer Magnetic Systems[J]. Phys Rev Lett ,1992,68:3749-3752.
[15] Yuan S L, Zhao Z Y, Xia Z C, et al. Magnetic and transport properties in polycrystalline La2/3Ca1/3MnO3[J]. Solid State Communications,2003,125:653-657.
[16] Slonczewski J C. Conductance and exchange coupling of two ferromagnets separated by a tunneling barrier[J]. Phys Rev B,1989,39:6995-7002.
[17] Tedrow P M, Meservey R. Spin-Dependent Tunneling into Ferromagnetic Nickel[J]. Phys Rev Lett ,1971,26(4):192-195.
[18] Fujimori H, Mitani S, Ohnuma S.Tunnel-type GMR in metal-nonmetal granular alloy thin films[J].Mater Sci Eng B,1995,31:219.
[19] Inomata K, Okuno S N, Saito Y, et al. Oscillatory interlayer couplings as functions of a ferromagnetic metal layer and a semiconducting spacer in magnetic superlattices[J].J Magn Magn Mater,1996,156:219-223.
[20] Mitani S, Fujimori H, Ohnuma S. Spin-dependent tunneling phenomena in insulating granular systems[J]. J Magn Magn Mater,1997,165:141-148.
[21] Volger J. Further experimental investigations on some ferromagnetic oxidic compounds of manganese with perovskite structure[J].Physica,1954,20:49.
[22]Sun J R. Manganate Trilayer Junctions:Spin-Dependent Transport and Low-Field Magnetoresistance[M].Gordon and Breach Science Publishers,2000,331-334.
[23] Gupta A, Gong G Q, Xiao Gang, et al. Grain-boundary effects on the magnetoresistance properties of perovskite manganite films[J]. Phys Rev B,1996,54:R15629-15632.
[24] Balcells L, Fontcuberta J, Mart B, et al. High-field magnetoresistance at interfaces in manganese perovskites[J]. Phys Rev B,1998,58:R14697-R14700.
[25] Li X.W,Gupta A,Xiao G,et al. Low-field magnetoresistive properties of polycrystalline and epitaxial perovskite manganite films[J]. Appl Phys Lett,1997,71:1124.
[26] Mahesh, Mahendiran R, Raychaudhuri A K, et al. Effect of particle size on the giant magnetoresistance of La0.7Ca0.3MnO3[J].1996,68:2291-2293.
[27] Mathur N D, Burnell G, Isaac S P, et al. Effect of particle size on the giant magnetoresistance of LaCaMnO[J].Nature,1997,387:266-268.
[28] Hueso L E, Rivas J, Rivadulla F, et al. Tuning of colossal magnetoresistance via grainsize change in LaCaMnO[J].J Appl Phys,1999,86(7):3881-3884.
[29] Sa′nchez R D, Rivas J, Va′zquez-Va′zquez C. et al. Giant magnetoresistance in fine particle of La0.67Ca0.33MnO3 synthesized at low temperatures[J]. Appl Phys Lett,1996,68 (1): 134-136.
[30] Siwach P K, Goutam U K, Srivastava P, et al. Colossal magnetoresistance study in nanophasic La0.7Ca0.3MnO3 manganite[J].J Phys D:Appl.Phys,2006,39:14-20.
[31] Dey P, Nath T K. Enhanced grain surface effect on the temperature-dependent behavior of spin-polarized tunneling magnetoresistance of nanometric manganites[J].Appl Phys Lett, 2005,87(16):162501 1-3.
[32] Wang X L, Dou S X, Liu H.K, et al. Large low-field magnetoresistance over a wide temperature range induced by weak-link grain boundaries in La0.7Ca0.3MnO3[J]. Appl Phys Lett,1998,73(3):396-398.
[33] Peng H B,Zhao B R,Xie Z,et al. Surface pattern and large low-field magnetoresistance in La0.5Ca0.5MnO3 films[J]. Appl Phys Lett,1999,74(11):1606-1608.
[34] Bibes M, Hrabovsky D, Martinez B, et al. Magneto-optical kerr effect in laser-patterned La2/3Sr1/3MnO3 epitaxial thin films[J].J Appl Phys,2001,89(11):6958-6960.
[35] Balcells L, Carrillo A E, Martínez B, et al. Enhanced field sensitivity close to percolation in magnetoresiative La2/3Sr1/3MnO3/CeO2 composites[J].Appl Phys Lett, 1999,74(26): 4014-4016.
[36] Petrov D K, Elbaun L, Sun J Z, et al. Enhanced magnetoresistance in sintered granular manganite/insulator systems[J].Appl Phys Lett,1999,75(7):995-997.
[37] Yuan S L, X Z C , Liu S, et al. Electrical transport and low-field magnetoresistance in La2/3Ca1/3MnO3/YSZ composites[J].Chin Phys Lett,2002,19(8): 1168-1171
[38] Huang Y H, Yan C H, Luo F, et al. Large enhancement in room-temperature magnetoresistance and dramatic decrease in resistivity in La0.7Ca0.3MnO3–Ag composites[J]. Appl PhysLett,2002,81(1):76-78.
[39] Yan C H, Xu Z G, Zhu T, et al. A large low field colossal magnetoresistance in the La0.7Sr0.3MnO3 and CoFe2O4 combined system[J].J Appl Phys,2000,87(9):5588-5590.
[40] Xia Z C, Yuan S L, Zhang G H, et al. Effect of low Fe3O4 doping in La0.67Ca0.33MnO3[J].J Phys D,Appl Phys,2003,36:217-222.
[41] Huang Q, Li J, Huang X J, Ong C K. Effect of magnetic coupling on the magnetoresistive properties in La0.67Sr0.33MnO3/BaFe11.3(ZnSn)0.7O19 composites[J]. J Appl Phys,2001,90(6):2924-2929.
[42] Liu J M, Yuan G L, Sang H, et al. Low-field magnetoresistance in nanosized La0.7Sr0.3MnO3/Pr0.5Sr0.5MnO3 composites[J].Appl Phys Lett,2001,78(8): 1110-1112.
[43] Liu J M, Huang Q, Li J, et al. Low-field magnetoresistance property of partically crystallized La0.5Sr0.5MnO3 thin films by pulsed laser deposition[J].J Appl Phys, 2000,88(5): 2791-2798.
[44] Liu J M, Li J, Huang Q, et al. Partically crystallized La0.5Sr0.5MnO3 thin films by laser ablation and their enhanced low-field magnetoresistance[J].Appl Phys Lett, 2000,76(16): 2286-2288.
[45] Liu J M, Yuan G L, Chen X Y, et al.Spin-polarized inter-grain tunneling as the probable mechanism for low-field magnetoresistance in partically crystallized La0.5Sr0.5MnO3 thin films[J].Appl Phys A,2001,73(5):625-630.
[46] Yuan S L, Zhang G Q, Peng G,et al.Electrical transport and low-field magnetoresistance in the series of mixed polycrystals (1-m)La2/3Ca1/3MnO3+ mLa2/3Sr1/3MnO3 [J].J Phys Condens Matter,2001,13:5691-5697.
[47] Hong C S, Kim W S, Hur N H.Wide colossal magnetoresistance around room temperature in La0.7Ca0.3MnO3/La0.7Sr0.3MnO3 composites[J].Solid State Commu, 2002,121:657-660.
[48] Yua C, Lee S F, Tsai J L, et al.Study of domain wall magnetoresistance by submicron patterned magnetic structure[J].J Appl Phys,2003,93(10):8761-8763.
[49] Loskjkowi W, Fecht H J. The structure of intercrystalline interfaces[J].Progress in Materials Science,2000,45:339~568.
[50] Urushibara A, Moritomo Y, Arima T, et al. Insulator-metal transition and giant magnetoresistance in La1-xSrxMnO3[J]. Phys Rev B,1995,51(20):14103-14109.
[51]席力,刘杰,田航等.纳米多晶La0.7Sr0.3MnO3-δ的输运性质[J].兰州大学学报,2008,44(3):134-137。
[52]Ding W P, Zhong W, Xing D Y, et al. Tunnel-type giant magnetoresistance in the granularperovskite La0.85Sr0.15MnO3[J]. Phys Rev B,1997,56(13):8138-8142.
[53] Radaelli P G, Iannone G, Marezio M, et al. Structural effects on the magnetic and transport properties of perovskite A 1-x A`x8MnO3 (x=0.25, 0.30)[J]. Phys Rev B,1997,56(13):8265-8276.
[54] Hazama H. Ultrasonic study of orbital and charge fluctuation in Pr1-xCaxMnO3[J]. Physica B,2002,(312-314):757-759.
[55] Deac G, Mitchell J F, Schiffer P. Phase Separation and the Low-Field Bulk Magnetic Properties of Pr0.7Ca0.3MnO3 [J]. Phys Rev B, 2001,63(17):172408.
[56]项阳. Pr0.1Ca0.9MnO3体系磁性及输运性质的研究[D].哈尔滨工业大学2007年7月.
[57] Tomioka Y, Asamitsu A, Kuwahara H, et al. Magnetic-field-induced metal-insulator phenomena in Pr1-xCaxMnO3 with controlled charge-ordering instability[J]. Phys Rev B, 1996,53(4):R1689-R1692.
[58]Balcells L, Fontcuberta J, Martinez B, et al. Magnetic surface effects and low-tempersture magnetoresistance in manganese perovskites[J].J Phys:Condens Matter, 1998,10(8): 1886-1890.
[59] Tong P, Kim B, Kwon D, et al. Griffiths phase and thermomagnetic irreversibility behavior in slightly electron-doped manganites Sm1-xMnxO3 (0.80≤x≤0.92)[J]. Phys Rev B, 2008, 77(18):184432 1-7.
[60] Martin C, Maignan A, Hervieu M, et al. Magnetic phase diagrams of L1-xAxMnO3 manganites (L=Pr, Sm;A=Ca,Sr)[J]. Phys Rev B,1999,60(17):12191-12199.