离子替代对双层钙钛矿锰氧化物的结构及电磁特性的影响
|
摘要
本论文系统研究了双层钙钛矿结构锰氧化物La_(1.4)Sr_(1.6)Mn_2O_7中Sr位Ca~(2+)、Mg~(2+)和K+离子的替代效应,研究了不同半径离子的替代对材料的结构、磁、磁熵变以及磁电阻的影响。主要工作可以概括为:
1.研究了名义组分La_(1.4)Sr_(1.6-x)Ca_xMn_2O_7(x=0.0- 1.6)系列样品的结构、磁和磁热效应。0≤x≤0.8的样品均为Sr3Ti2O7型四方晶系的钙钛矿结构,空间群为I4/mmm,而1.0≤x≤1.6样品为Pbnm空间群正交的ABO3型钙钛矿锰氧化物与少量CaO的混合物,晶体结构相变发生在0.8≤x≤1.0的掺杂范围。对于x=0.2- 0.8的样品,随着Ca~(2+)离子含量的增加,三维铁磁有序转变温度逐渐降低直至消失,而二维铁磁短程有序仍然存在,在x=0.4样品中甚至增大。表明Ca~(2+)的替代抑制了三维的交换相互作用,而eg电子轨道的变化造成了MnO6八面体的Jahn–Teller扭曲,是x = 0.4样品中二维铁磁短程有序增强的主要驱动力。在1T外加磁场下,名义组分La1.4Sr1.6-xCaxMn2O(7x= 1.6)样品在居里温度215K附近得到了2.28J kg-1K-1的磁熵变,由此可知该材料可以作为亚室温磁制冷材料的候选者。
2.研究了离子半径比Ca~(2+)更小的Mg~(2+)离子对钙钛矿结构锰氧化物La_(1.4)Sr_(1.6)Mn_2O_7中Sr位的替代效应,发现Mg~(2+)离子实际进入了钙钛矿结构的Mn位,形成了La1.4Sr1.6Mn2-2yMg2yO7/La0.67Sr0.33Mn1-yMgyO3(327/113)复合材料。并且随着Mg~(2+)离子含量的增加,327相的百分含量逐渐降低,113相的百分含量逐渐增加,x=0.4样品精修后得到其实际分子式为La0.6Sr0.4Mn0.83Mg0.17O3。说明在离子替代过程中,离子半径起到了至关重要的作用(Mn离子半径与Mg更接近)。Mn位Mg~(2+)离子的替代抑制了复合材料中两相的铁磁性和导电性,对于轻掺杂样品,材料在低温处的奈尔温度和高温处的居里温度均随Mg~(2+)含量的增加而降低;而对于重掺杂的样品,其磁化强度曲线表现出了自旋玻璃的行为,导致样品中的电阻率比轻掺杂样品增长了近4个数量级,电阻率表现为绝缘性。同时发现在低温和高温两个温区,Mg~(2+)的掺杂均使复合材料低场磁电阻有很大的增加,5K时x=0.1,0.2样品1T下的磁电阻分别为40%和39%,200K时分别为8%和11%,从而扩大了材料低场磁电阻的使用温区,有利于其应用。
3.系统研究了La_(1.4)Sr_(1.6)Mn_2O_7/La0.67Sr0.33MnO3复合材料的制备方法,分别合成了两相与三相的系列复合材料(1-x)La_(1.4)Sr_(1.6)Mn_2O_7/xLa0.67Sr0.33MnO3与(1-x′-y)La_(1.4)Sr_(1.6)Mn_2O_7/x′La0.67Sr0.33MnO3/yLa2O3。在对复合材料(1-x)La_(1.4)Sr_(1.6)Mn_2O_7/xLa0.67Sr0.33MnO3的磁性研究中发现,由于两相含量的变化和两相之间的反铁磁耦合,在高温和低温处出现了两个磁相变温度(TC1和TC2),并且在TC1与TC2之间,磁化强度形成了一个平台。随着掺杂量x的增加,平台处的磁化强度逐渐增大。随x逐渐增加,x≤0.67样品的电阻率逐渐变低,金属-绝缘转变温度虽然存在,但开始变得更加的平缓和宽化。当x增加到x=0.93和1.0,材料中电阻率进一步降低,在整个测量的温区内表现为金属性。而三相系列样品中La2O3的掺入,对113相的居里温度(360K)之上的顺磁态的磁化强度和电阻率影响最小,对327相的居里温度(90K)之下的铁磁-反铁磁共存态的磁化强度与电阻率影响最大,分别达到8%和30%。同时在x′=0.465样品中发现了有利于应用的宽温区、低场磁熵变,其在90K温度附近,1、2以及7T下的最大磁熵变分别达到0.45,0.9和1.55J kg-1K-1。
The structural, magnetic, magnetocaloric and magnetoresistance properties have been investigated in bilayered manganites La_(1.4)Sr_(1.6)Mn_2O_7 doping with Ca~(2+), Mg~(2+) and K+ at Sr site. The main results are as follows:
1. The structure, magnetic and magnetiocaloric properties of the nominal compositions La_(1.4)Sr_(1.6-x)Ca_xMn_2O_7 (x=0.0-1.6) have been investigated. The samples are tetragonal bilayered perovskite with space group I4/mmm in the 0≤x≤0.8 dopant regimes, while they are composed of a major phase of ABO3-type perovskite structure with space group Pbnm and a slight calcium oxide in the 1.0≤x≤1.6 dopant regimes. The structural transition takes place in the range of 0.8≤x≤1.0. For the x=0.2-0.8 samples, 3D FM ordering temperature decreases at first and then disappears with the increase of Ca~(2+)-doping level, while the 2D FM short-range ordering remains and even increases in the x = 0.4 sample. This result implies that the exchange interaction of 3D (Jc) is depressed with increasing Ca~(2+) content. The enhancement of 2D FM short-range ordering in the x=0.4 sample is mainly derived from a sufficiently large Jahn–Teller distortion of MnO6 octahedra triggered by a variation in the nature of the orbital state of the eg electrons. A large magnetic entropy change of 2.28 J kg-1 K-1 is obtained in the nominal composition La1.4Sr1.6?xCaxMn2O7 (x = 1.6) upon 1 T applied magnetic field near its Tc=215 K. It indicates that this compound could be used as a magnetic refrigerant in sub-room temperature magnetic refrigerator.
2. The doping effect of Mg~(2+) ions at Sr site in bilayered manganite La_(1.4)Sr_(1.6)Mn_2O_7 has been investigated. The Mg~(2+) ions occupy Mn sites in the perovskite structure actually, and formed La1.4Sr1.6Mn2-2yMg2yO7/La0.67Sr0.33Mn1-yMgyO3 (327/113) composites. The content of 327 phase decreases and the fraction of 113 phase increases gradually with increasing the content of Mg~(2+) ions. The practical molecular formula at x=0.4 sample is La0.6Sr0.4Mn0.83Mg0.17O3 using the Rietveld method. FM ordering and conductivity of the two phases in the composites are depressed by Mg~(2+) ions doping at Mn site. For lightly doped samples, the Neel and Curie temperature decreases with increasing the content of Mg~(2+) ions. For heavily doped samples, the magnetization exhibits the spin-glass behaveior, which may cause a insulating behavior. The resistivity in heavily doped samples is as large as four orders of that in lightly doped samples. At lower and higher temperature, the low-field magnetoresistance have been increased by doping Mg~(2+) at Mn site. For x=0.1, 0.2 samples, the MR values are as large as 40% and 39%, respectively, at 5K and 1T, and 8% and 11%, respectively, at 200 K and 1T.
3. The two and three phases composites of (1-x)La_(1.4)Sr_(1.6)Mn_2O_7/xLa0.67Sr0.33MnO3 and (1-x′-y)La_(1.4)Sr_(1.6)Mn_2O_7/x′La0.67Sr0.33MnO3/yLa2O3 have been synthesized. Two magnetic transition temperatures (TC1 and TC2) at low and high temperature are observed in (1-x)La_(1.4)Sr_(1.6)Mn_2O_7/xLa0.67Sr0.33MnO3 composites because the variation of the phase content and anti-ferromagnetic coupling between two phases. The magnetization formes a plateau between TC1 and TC2, and the magnitude of magnetization increases with increasing x when TC1 >T >TC2. For the x≤0.67 samples, the magnitude of resistivity decreases gradually with increasing x, and the peak of metal-insulator transition becomes smoother and broader. For the x=0.93 and 1.0 samples, the resistivity further decreases and shows metallic behavior in the measuring temperature range. In three-phase system, the influence of La2O3 on magnetization and resistivity is quite slight above the Curie temperature of 113 phase (360K), while it is significant under the Curie temperature of 327 phase (90K). At the same time, the large magnetic entropy change of 0.45, 0.9 and 1.55J kg-1K-1 in 1, 2, and 7T is obtained in the x′=0.465 sample at 90K.
1.研究了名义组分La_(1.4)Sr_(1.6-x)Ca_xMn_2O_7(x=0.0- 1.6)系列样品的结构、磁和磁热效应。0≤x≤0.8的样品均为Sr3Ti2O7型四方晶系的钙钛矿结构,空间群为I4/mmm,而1.0≤x≤1.6样品为Pbnm空间群正交的ABO3型钙钛矿锰氧化物与少量CaO的混合物,晶体结构相变发生在0.8≤x≤1.0的掺杂范围。对于x=0.2- 0.8的样品,随着Ca~(2+)离子含量的增加,三维铁磁有序转变温度逐渐降低直至消失,而二维铁磁短程有序仍然存在,在x=0.4样品中甚至增大。表明Ca~(2+)的替代抑制了三维的交换相互作用,而eg电子轨道的变化造成了MnO6八面体的Jahn–Teller扭曲,是x = 0.4样品中二维铁磁短程有序增强的主要驱动力。在1T外加磁场下,名义组分La1.4Sr1.6-xCaxMn2O(7x= 1.6)样品在居里温度215K附近得到了2.28J kg-1K-1的磁熵变,由此可知该材料可以作为亚室温磁制冷材料的候选者。
2.研究了离子半径比Ca~(2+)更小的Mg~(2+)离子对钙钛矿结构锰氧化物La_(1.4)Sr_(1.6)Mn_2O_7中Sr位的替代效应,发现Mg~(2+)离子实际进入了钙钛矿结构的Mn位,形成了La1.4Sr1.6Mn2-2yMg2yO7/La0.67Sr0.33Mn1-yMgyO3(327/113)复合材料。并且随着Mg~(2+)离子含量的增加,327相的百分含量逐渐降低,113相的百分含量逐渐增加,x=0.4样品精修后得到其实际分子式为La0.6Sr0.4Mn0.83Mg0.17O3。说明在离子替代过程中,离子半径起到了至关重要的作用(Mn离子半径与Mg更接近)。Mn位Mg~(2+)离子的替代抑制了复合材料中两相的铁磁性和导电性,对于轻掺杂样品,材料在低温处的奈尔温度和高温处的居里温度均随Mg~(2+)含量的增加而降低;而对于重掺杂的样品,其磁化强度曲线表现出了自旋玻璃的行为,导致样品中的电阻率比轻掺杂样品增长了近4个数量级,电阻率表现为绝缘性。同时发现在低温和高温两个温区,Mg~(2+)的掺杂均使复合材料低场磁电阻有很大的增加,5K时x=0.1,0.2样品1T下的磁电阻分别为40%和39%,200K时分别为8%和11%,从而扩大了材料低场磁电阻的使用温区,有利于其应用。
3.系统研究了La_(1.4)Sr_(1.6)Mn_2O_7/La0.67Sr0.33MnO3复合材料的制备方法,分别合成了两相与三相的系列复合材料(1-x)La_(1.4)Sr_(1.6)Mn_2O_7/xLa0.67Sr0.33MnO3与(1-x′-y)La_(1.4)Sr_(1.6)Mn_2O_7/x′La0.67Sr0.33MnO3/yLa2O3。在对复合材料(1-x)La_(1.4)Sr_(1.6)Mn_2O_7/xLa0.67Sr0.33MnO3的磁性研究中发现,由于两相含量的变化和两相之间的反铁磁耦合,在高温和低温处出现了两个磁相变温度(TC1和TC2),并且在TC1与TC2之间,磁化强度形成了一个平台。随着掺杂量x的增加,平台处的磁化强度逐渐增大。随x逐渐增加,x≤0.67样品的电阻率逐渐变低,金属-绝缘转变温度虽然存在,但开始变得更加的平缓和宽化。当x增加到x=0.93和1.0,材料中电阻率进一步降低,在整个测量的温区内表现为金属性。而三相系列样品中La2O3的掺入,对113相的居里温度(360K)之上的顺磁态的磁化强度和电阻率影响最小,对327相的居里温度(90K)之下的铁磁-反铁磁共存态的磁化强度与电阻率影响最大,分别达到8%和30%。同时在x′=0.465样品中发现了有利于应用的宽温区、低场磁熵变,其在90K温度附近,1、2以及7T下的最大磁熵变分别达到0.45,0.9和1.55J kg-1K-1。
The structural, magnetic, magnetocaloric and magnetoresistance properties have been investigated in bilayered manganites La_(1.4)Sr_(1.6)Mn_2O_7 doping with Ca~(2+), Mg~(2+) and K+ at Sr site. The main results are as follows:
1. The structure, magnetic and magnetiocaloric properties of the nominal compositions La_(1.4)Sr_(1.6-x)Ca_xMn_2O_7 (x=0.0-1.6) have been investigated. The samples are tetragonal bilayered perovskite with space group I4/mmm in the 0≤x≤0.8 dopant regimes, while they are composed of a major phase of ABO3-type perovskite structure with space group Pbnm and a slight calcium oxide in the 1.0≤x≤1.6 dopant regimes. The structural transition takes place in the range of 0.8≤x≤1.0. For the x=0.2-0.8 samples, 3D FM ordering temperature decreases at first and then disappears with the increase of Ca~(2+)-doping level, while the 2D FM short-range ordering remains and even increases in the x = 0.4 sample. This result implies that the exchange interaction of 3D (Jc) is depressed with increasing Ca~(2+) content. The enhancement of 2D FM short-range ordering in the x=0.4 sample is mainly derived from a sufficiently large Jahn–Teller distortion of MnO6 octahedra triggered by a variation in the nature of the orbital state of the eg electrons. A large magnetic entropy change of 2.28 J kg-1 K-1 is obtained in the nominal composition La1.4Sr1.6?xCaxMn2O7 (x = 1.6) upon 1 T applied magnetic field near its Tc=215 K. It indicates that this compound could be used as a magnetic refrigerant in sub-room temperature magnetic refrigerator.
2. The doping effect of Mg~(2+) ions at Sr site in bilayered manganite La_(1.4)Sr_(1.6)Mn_2O_7 has been investigated. The Mg~(2+) ions occupy Mn sites in the perovskite structure actually, and formed La1.4Sr1.6Mn2-2yMg2yO7/La0.67Sr0.33Mn1-yMgyO3 (327/113) composites. The content of 327 phase decreases and the fraction of 113 phase increases gradually with increasing the content of Mg~(2+) ions. The practical molecular formula at x=0.4 sample is La0.6Sr0.4Mn0.83Mg0.17O3 using the Rietveld method. FM ordering and conductivity of the two phases in the composites are depressed by Mg~(2+) ions doping at Mn site. For lightly doped samples, the Neel and Curie temperature decreases with increasing the content of Mg~(2+) ions. For heavily doped samples, the magnetization exhibits the spin-glass behaveior, which may cause a insulating behavior. The resistivity in heavily doped samples is as large as four orders of that in lightly doped samples. At lower and higher temperature, the low-field magnetoresistance have been increased by doping Mg~(2+) at Mn site. For x=0.1, 0.2 samples, the MR values are as large as 40% and 39%, respectively, at 5K and 1T, and 8% and 11%, respectively, at 200 K and 1T.
3. The two and three phases composites of (1-x)La_(1.4)Sr_(1.6)Mn_2O_7/xLa0.67Sr0.33MnO3 and (1-x′-y)La_(1.4)Sr_(1.6)Mn_2O_7/x′La0.67Sr0.33MnO3/yLa2O3 have been synthesized. Two magnetic transition temperatures (TC1 and TC2) at low and high temperature are observed in (1-x)La_(1.4)Sr_(1.6)Mn_2O_7/xLa0.67Sr0.33MnO3 composites because the variation of the phase content and anti-ferromagnetic coupling between two phases. The magnetization formes a plateau between TC1 and TC2, and the magnitude of magnetization increases with increasing x when TC1 >T >TC2. For the x≤0.67 samples, the magnitude of resistivity decreases gradually with increasing x, and the peak of metal-insulator transition becomes smoother and broader. For the x=0.93 and 1.0 samples, the resistivity further decreases and shows metallic behavior in the measuring temperature range. In three-phase system, the influence of La2O3 on magnetization and resistivity is quite slight above the Curie temperature of 113 phase (360K), while it is significant under the Curie temperature of 327 phase (90K). At the same time, the large magnetic entropy change of 0.45, 0.9 and 1.55J kg-1K-1 in 1, 2, and 7T is obtained in the x′=0.465 sample at 90K.
引文
[1] Kuwahara H, Tomioka Y, Asamitsu A, et al. A First-Order Phase Transition Induced by a Magnetic Field[J]. Science, 1995, 270: 961-963.
[2] Uehara M, Mori S, Chen C H, et al. Percolative phase separation underlies colossal magnetoresistance in mixed-valent manganites[J]. Nature, 1999, 399: 560-563.
[3] Zhang L W, Israel C, Biswas A, et al. Direct observation of percolation in a manganite thin film[J]. Science, 2002, 298: 805-807.
[4] Moreo A, Yunokie S, Dagotto E. Phase separation Scenario for manganese oxides and related materials[J]. Science, 1999, 283: 2034-2040.
[5] De Teresa J M, Ibarra M R, Algarabel P A, et al. Evidence for magnetic polarons in the magnetoresistive perovskites[J]. Nature, 1997, 386: 256-259.
[6] Fiebig M, Miyano K, Tomioka Y, et al. Visualization of the Local Insulator–Metal Transition in Pr0.7Ca0.3MnO3[J]. Science, 1998, 280: 1925-1928.
[7] Guo Z B, Du Y W, Zhu J S, et al. Large Magnetic Entropy Change in Perovskite-Type Manganese Oxides[J]. Phys. Rev. Lett., 1997, 78: 1142-1145.
[8] Dagotto E, Hotta T, Moreo A. Colossal magnetoresistant materials: The key role of phase separation[J]. Phys. Rep., 2001, 344: 1-153.
[9] Satpathy S, Popovi Z S, and Vukajlovi F R. Electronic Structure of the Perovskite Oxides: La1-xCaxMnO3[J]. Phys. Rev. Lett., 1996, 76: 960-962.
[10] Tokura Y, Tomioka Y. Colossal magnetoresistive manganites[J]. J. Magn. Magn. Mater., 1999, 200: 1-23.
[11] Ruddlesden S N, Popper P. The Compound Sr3Ti2O7 and Its Structure[J]. Acta Crystallogr, 1958, 11: 54-59.
[12] Jonker G H, Santen Van. J H. Ferromagnetic compounds of manganese with perovskite structure[J]. Physica, 1950. 16: 337-349.
[13] Wollan E O, Koenhler W C. Neutron Diffraction Study of the Magnetic properties of the series of perovskite-type compounds [(1-x)La, xCa]MnO3[J]. Phys. Rev., 1955, 100:545-563.
[14] Goodenough J B. Theory of the role of covalence in the perovskite-type manganites [La, M(Ⅱ)]MnO3[J]. Phys. Rev., 1955, 100: 564-573.
[15] Urushibara A, Moritomo Y, Arima T, et al. Insulator-metal transition and giant magnetoresistance in La1-xSrxMnO3[J]. Phys. Rev. B, 1995, 51: 14103-14109.
[16] Kawano H, Kajimoto R, Kubota M, et al. Canted antiferromagnetism in an insulating lightly doped La1-xSrxMnO3 with x≤0.17[J]. Phys. Rev. B, 1996, 53: 2202-2205.
[17] Xiong X, Dabrowski B, Chmaissem O, et. al. Correlation between coherent Jahn-Teller distortion and magnetic spin orientation in La1-xSrxMnO3[J]. Phys. Rev. B, 1999, 60: 10186-10192.
[18] Zener C. Interaction between the d Shells in the Transition Metals[J]. Phys. Rev., 1951, 81: 440-446.
[19] Argyiou D N, Mitchell J F, Radaelli P G, et al. Lattice Effects and Magnetic Structure in the Layered Colossal Magnetoresistance Manganite La2-2xSr1+2xMn2O7[J]. Phys. Rev. B, 1999, 59(13): 8695-8702.
[20] Battle P D, Cox D E, Green A M, et al. Sr1.8Nd1.2Mn2O7: Synthesis, Crystal Structure, and Physics Properties[J]. Chem. Mater., 1997, 9: 3215-3221.
[21] Mitchell J F, Millbum J E, Medarade M, et al. Layered Manganites: Magnetic Structure at Extreme Doping Levels[J]. J Appl. Phys., 1999, 85 (8): 4352-4354.
[22] Kuboat M, Fujioka H, Hirota K, et al. Relation between Crystal and Magnetic Structures of Layered Manganite La2-2xCa1+2xMn2O7(0.30≤x≤0.50) [J]. J Phys. Soc. Jpn., 2000, 69(6): 1606-1609.
[23] Hur N H, Kim J T, Kim K H, et al. Effect of Lanthanide Ions on the Magnetotransport Properties in Layered Sr1.6R1.4Mn2O7(R= La, Pr, Nd, Gd) [J]. Phys. Rev. B, 1998, 57(17): 10740-10744.
[24] Kimura T, Tomioka Y, Kuwahara H, et al. Interplane Tunneling Magnetoresistance in a Layered Manganite Crystal[J]. Science, 1996, 274: 1698-1701.
[25] Kimura T, Asamitsu A, Tomioka Y, et al., Pressure-Enhanced Interplane Tunneling Magnetoresistance in a Layered Manganite Crystal[J]. Phys. Rev. Lett., 1997, 79:3720-3723.
[26] Hirota K, Moritomo Y, Fujioka H, et al. Neutron-Diffraction Studies on the Magnetic Ordering Process in the Layered Mn Perovskite La2-2xSr1+2xMn2O7 (x=0.40,0.45 and 0.48) [J]. J. Phys. Soc. Jpn., 1998, 67: 3380-3383.
[27] Li J Q, Matsui Y, Kimura T, et al. Structural properties and charge-ordering transition in LaSr2Mn2O7[J]. Phys. Rev. B, 1998, 57: R3205-3208.
[28] Kimura T, Kumai R, Tokura Y, et al. Successive structural transitions coupled with magnetotransport properties in LaSr2Mn2O7[J]. Phys. Rev. B, 1998, 58: 11081-11084.
[29] Hayashi T, Miura N, Tokunaga M, et al. Magnetic properties and CMR effect in layer type manganite LaSr2Mn2O7 under high magnetic fields[J]. J. Phys.: Condens. Matter, 1998, 10: 11525-11529.
[30] Suryanarayanan R, Dhalenne G, Revcolevschi A, et al. Colossal magnetoresistance and re-entrant charge ordering in single crystalline two layer Mn perovskite LaSr2Mn2O7[J]. Solid State Commun., 2000, 113: 267-271.
[31] Kubota M, Fujioka H, Ohoyama K, et al. Neutron scattering studies on magnetic structure of the double-layered manganite La2-2xSr1+2xMn2O7 (0.30≤x≤0.50) [J]. J. Phys. Chem. Solids, 1999, 60: 1161-1164.
[32] Perring T G, Aeppli G, Moritomo Y, et al. Antiferromagnetic Short Range Order in a Two-Dimensional Manganite Exhibiting Giant Magnetoresistance[J]. Phys. Rev. Lett., 1997, 78: 3197-3200.
[33] Maezono R, Nagaosa N. Spin and orbital ordering in double-layered manganites[J]. Phys. Rev. B, 2000, 61: 1825-1830.
[34] Osborn R, Rosenkranz S, Argyriou D N, et al. Neutron Scattering Investigation of Magnetic Bilayer Correlations in La1.2Sr1.8Mn2O7: Evidence of Canting above TC[J]. Phys. Rev. Lett., 1998, 81: 3964-3967.
[35] Chatterji T, Mclntyre G J, Suryanarayanan R, et al. Spin correlations in the bilayer manganite La1.2Sr1.8Mn2O7[J]. Solid State Comnnmications, 1999, 112: 235-239.
[36] Chatterji T, McIntyre G J, Caliebe W. Reentrant behavior of the charge and orbital ordering and antiferromagnetism in LaSr2Mn2O7[J]. Phys. Rev. B, 2000, 61: 570-574.
[37] Ling C D, Millburn J E, Mitchell J F, et al. Interplay of spin and orbital ordering in the layered colossal magnetoresistance manganite La2-2xSr1+2xMn2O7(0.5≤x≤1.0) [J]. Phys. Rev. B, 2000, 62: 15096-15111.
[38] Kanamori J. Crystal distortion in magnetic compounds[J]. J. Appl. Phys., 1960, 31: 14S-23S.
[39] Tokura Y, Urushibara A, Moritomo Y,et al. Giant Magnetotransport Phenomena in Filling-Controlled Kondo Lattice System: La1-xSrxMnO3[J]. J. Phys. Soc. Jpn., 1994, 63: 3931-3935.
[40] Furukawa N. Transport Properties of the Kondo Lattice Model in the Limit S=∞and D=∞[J]. J. Phys. Soc. Jpn., 1994, 63: 3214-3217.
[41] Hundley M F, Hawley M, Heffner R H, et al. Transport‐magnetism correlations in the ferromagnetic oxide La0.7Ca0.3MnO3[J]. Appl. Phys. Lett., 1995, 67: 860-862.
[42] Millis A J, Littlewood P B, Shraiman B I. Double Exchange Alone Does Not Explain the Resistivity of La1-XSrxMnO3[J]. Phys. Rev.Lett., 1995, 74: 5144-5147.
[43] Millis A J, Mueller R, Shraiman B I. Fermi-liquid-to-polaron crossover. II. Double exchange and the physics of colossal magnetoresistance[J]. Phys. Rev. B., 1996, 54: 5405-5417.
[44] Roder H, Zang J, Bishop A R. Lattice Effects in the Colossal-Magnetoresistance Manganites[J]. Phys. Rev. Lett., 1996, 76:1356-1359.
[45] Dai P, Zhang J, Mook H A, et al. Experimental evidence for the dynamic Jahn-Teller effect in La0.65Ca0.35MnO3[J]. Phys. Rev. B., 1996, 54: R3694-R3697.
[46] Radaelli P G, Cox D E, Marezio M, et al. Simultaneous Structural, Magnetic, and Electronic Transitions in La1-xCaxMnO3 with x=0.25 and 0.50[J]. Phys. Rev. Lett., 1995, 75: 4488-4491.
[47] Varma C M. Electronic and magnetic states in the giant magnetoresistive compounds[J]. Phys. Rev. B., 1996, 54: 7328-7333.
[48] Kataoka M. Theory of the giant magnetoresistance in La1? x A x MnO3[J]. Chechoslovak J. Phys., 1996, 46:1857-1858.
[49] Kataoka M, Tachiki M. Giant spin fluctuation as a possible origin of the giantmagnetoresistance in La1-xAxMnO3[J]. Phys. B., 1997, 237: 24-25.
[50] Sternlieb B J, Hill J P, Wildgruber U C, et al. Charge and Magnetic Order in La0.5Sr1.5MnO4[J]. Phys. Rev. Lett., 1996, 76: 2169-2172.
[51] Moritomo Y, Tomioka Y, Asamitsu A, et al. Magnetic and electronic properties in hole-doped manganese oxides with layered structures: La1-xSr1+xMnO4[J]. Phys. Rev. B., 1995, 51: 3297-3300.
[52] Qing A L, Gray K E, Mitchell J F. Spin-independent and spin-dependent conductance anisotropy in layered colossal-magnetoresistive manganite single crystals[J]. Phys. Rev. B., 1999, 59: 9357-9361.
[53] Perring T G, Aeppli G, Kimura T, et al. Ordered stack of spin valves in a layered magnetoresistive perovskite[J]. Phys. Rev. B, 1998, 58: R14693- R14696.
[54] Kimura T, Tomioka Y, Asamitsu A, et al. Anisotropic Magnetoelastic Phenomena in Layered Manganite Crystals: Implication of Change in Orbital State[J]. Phys. Rev. Lett., 1998, 81: 5920-5923.
[55] Moritomo Y, Asamitsu A, Kuwahara H, et al. Giant Magnetoresistance in Layered Structure of Manganese Oxides[J]. Nature, 1996, 380: 141-144.
[56] 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: 2041-2044.
[57] Balcells Li, Carrillo A E , Mart?′nez B, et al. Enhanced field sensitivity close to percolation in magnetoresistive La2/3Sr1/3MnO3/CeO2 composites[J]. Appl. Phys. Lett., 1999, 74: 4014-4016.
[58] Petrov D K, Krusin-Elbaum L , Sun J Z , et al. Enhanced magnetoresistance in sintered granular manganite/insulator systems[J]. Appl. Phys. Lett., 1999, 75: 995-997.
[59] Subhrangsu T, Karmakar S, Chatterjee S, et al. Ferro-antiferromagnetic coupling and unusual transport properties of ferro-antiferromagnetic (100?x)La0.7Pb0.3MnO3 + xPr0.63Ca0.37MnO3 (x = 0–85 ?wt ? %) composites[J]. J. Appl. Phys., 2006, 99: 073703-073708.
[60] 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: 5588-5590.
[61] Zhu T, Yan C H, Wang Z M, et al. Low-field magnetoresistance in La2/3Sr1/3MnO3 granular composites by a sol–gel coating process[J]. Solid State Communications, 2001, 117: 471-475.
[62] Yao L D, E P, Zhang J S, et al. Magnetic and magnetotransport properties of La2/3Ca1/3MnO3/Se2FeMoO6 nano-crystalline composites synthesized under high pressure[J]. Phys. B., 2008, 403: 2241-2245.
[63]任光明,袁松柳,缪菊红等. La0.67Ca0.33MnO3/MgO复合体系中的电输运和磁电阻效应.无机材料学报, 2007, 22(4): 715-719.
[64] 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: 1110-1112.
[65] 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. Phys. Lett., 2002, 81: 76-78.
[66] Warburg E, Magnetische Untersuchungen. I. U“bereinige Wirkungen der Coe”rcitivkraft[J]. Ann. Phys., 1881, 13: 141-64.
[67] Gschneidner K A, Pecharsky V K, Tsokol A O. Recent developments in magnetocaloric materials[J]. Rep. Prog. Phys., 2005, 68: 1479-1539.
[68] Bruck E. Developments in magnetocaloric refrigeration[J]. J. Phys. D: Appl. Phys., 2005, 38: R381-R390.
[69] Giauque W F, MacDougall D P. Attainment of Temperatures Below 1°Absolute by Demagnetization of Gd2(SO4)3·8H2O[J]. Phys. Rev., 1933, 43: 768-768.
[70] Pecharsky V K, Gschneidner K A. Giant Magnetocaloric Effect in Gd5(Si2Ge2) [J]. Phys. Rev. Lett., 1997, 78: 4494-4497.
[71] Hu F X, Shen B G, Sun J R, et al. Large magnetic entropy change in a Heusler alloy Ni52.6Mn23.1Ga24.3 single crystal[J]. Phys. Rev. B., 2001, 64: 132412-132415.
[72] Wada H, Tanabe Y. Giant magnetocaloric effect of MnAs1?xSbx[J]. Appl. Phys. Lett., 2001, 79: 3302-3304.
[73] Fujieda S, Fujita A, Fukamichi K. Large magnetocaloric effect in La(FexSi1?x)13 itinerant-electron metamagnetic compounds[J]. Appl. Phys. Lett., 2002, 81: 1276-1278.
[74] Tegus O, Bruck E, Buschow K H J, et al. Transition-metal-based magnetic refrigerants for room-temperature applications[J]. Nature, 2002, 415:150-152.
[75] Phan M H, Yu S C, Hur N H. Excellent magnetocaloric properties of La0.7Ca0.3?xSrxMnO3(0.05≤x≤0.25) single crystals[J]. Appl. Phys. Lett., 2005, 86: 072504-072506.
[76] Szewczyk A, Szymczak H, Wisniewski A, et al. Magnetocaloric effect in La1?xSrxMnO3 for x = 0.13 and 0.16[J]. Appl. Phys. Lett., 2000, 77:1026-1028.
[77] Phan M H, Tian S B, Hoang D Q, et al. Large magnetic-entropy change above 300 K in CMR materials[J]. J. Magn. Magn. Mater., 2003, 258-259: 309-311.
[78] Sun Y, Salamon M B, Chun S H. Magnetocaloric effect and temperature coefficient of resistance of La2/3(Ca,Pb)1/3MnO3[J]. J. Appl. Phys., 2002, 92: 3235-3238.
[79] Biernacki S W, Schulz H J. Adiabatic temperature change in perovskite manganites[J]. Phys. Rev. B., 2004, 70: 092405-092408.
[80] Terashita H, Myer B, Neumeier J J. Influence of a first-order structural transition on magnetocaloric effects in manganese oxides[J]. Phys. Rev. B., 2005, 72: 132415-132417.
[81] Xiong C M, Sun J R, Chen Y F, et al. Relation between magnetic entropy and resistivity in La0.67Ca0.33MnO3[J]. IEEE Trans. Magn., 2005, 41:122-124.
[82] Gschneidner K A, Pecharsky V K. Magnetocaloric materials[J]. Annu. Rev. Mater. Sci., 2000, 30: 387-429.
[83] Szewczyk A, Gutowska M, Piotrowski K,et al. Direct and specific heat study of magnetocaloric effect in La0.845Sr0.155MnO3[J]. J. Appl.Phys., 2003, 94: 1873-1876.
[84] Szewczyk A, Gutowska M, Dabrowski B, et al. Specific heat anomalies in La1?xSrxMnO3 (0.12perovskite manganites[J]. J. Magn. Magn. Mater., 2002, 242-245: 698-700.
[88] Guo Z B, Zhang J R, Huang H, et al. Large magnetic entropy change in La0.75Ca0.25MnO3[J]. Appl.Phys.Lett., 1996, 70: 904-905.
[89] Zhang X X, Tejada J, Xin Y, et al. Magnetocaloric effect in La0.67Ca0.33MnOδand La0.60Y0.07Ca0.33MnOδbulk materials[J]. Appl. Phys. Lett., 1996, 69: 3596-3598.
[90] Lin G C, Wei Q, Zhang J X. Direct measurement of the magnetocaloric effect in La0.67Ca0.33MnO3[J]. J. Magn. Magn. Mater., 2006, 300: 392-396.
[91] Sun Y, Xu X, Zhang Y H, Large magnetic entropy change in the colossal magnetoresistance material La2/3Ca1/3MnO3[J]. J. Magn. Magn. Mater., 2000, 219: 183-185.
[92] Zhou T J, Yu Z, Zhong W, et al. Larger magnetocaloric effect in two-layered La1.6Ca1.4Mn2O7 polycrystal[J]. J. Appl. Phys., 1999, 85: 7975-7977.
[93] Zhu H, Song H, Zhang Y H. Magnetocaloric effect in layered perovskite manganese oxide La1.4Ca1.6Mn2O7[J]. Appl. Phys. Lett., 2002, 81:3416-3418.
[94] Zhong W, Chen W, Jiang H Y, et al. Preparation, magnetoresistance and magnetocaloric effect of two-layered perovskite La2.5-xK0.5+x Mn2O7+δ[J]. Eur. Phys. J. B , 2002, 30: 331-337.
[95] Seshadri R, Hervieu M, Martin C, et al. Study of the Layered Magnetoresistive Perovskite La1.2Sr1.8Mn2O7 by High-Resolution Electron Microscopy and Synchrotron X-ray Powder Diffraction[J]. Chem. Mater., 1997, 9: 1778-1787.
[96] Mohanram R A, Ganapathi L, Rao C N R, et al. Magnetic properties of quasi-two-dimensional La1?xSr1+xMnO4 and the evolution of itinerant electron ferromagnetism in the SrO·(La1?xSrxMnO3)n system[J]. J. Solid State Chem., 1987, 70: 82–87.
[97] Mahesh R, Mahendiran R, Raychaudhuri A K, et al. Effect of Dimensionality on the Giant Magnetoresistance of the Manganates:A Study of the (La, Sr)n+1MnnO3n+1Family[J]. J. Solid State Chem., 1996, 122: 448–450.
[98] Battle P D, Green M A, Laskey N S,et al. Layered Ruddlesden?Popper Manganese Oxides: Synthesis and Cation Ordering[J]. Chem. Mater., 1997, 9: 552–559.
[99] Asano H, Hayakawa J, Matsui M. Giant magnetoresistance of a two-dimensionalferromagnet La2?2xCa1+2xMn2O7[J]. Appl. Phys. Lett., 1996, 68: 3638–3640.
[100] Ganguly R, Siruguri V, Gopalakrishnan I K, et al. Comment on“Giant magnetoresistance of a two-dimensional ferromagnet La2?2xCa1+2xMn2O7”[Appl. Phys. Lett. 68, 3638 (1996)][J]. Appl. Phys. Lett., 2000, 76: 1956–1957.
[101] Fawcett I D, Kim E, Greenblatt M, et al. Properties of the electron-doped layered manganates La2-2xCa1+2xMn2O7 (0.6<~x<~1.0)[J]. Phys. Rev. B., 2000, 62: 6485–6495.
[102] Yu R C, Zhu J L, Li S Y, et al. TEM studies on La2-2xCa1+2xMn2O7 (x=0.5 and 0.25) [J]. Mater. Sci. Eng. A , 2003, 345: 344–349.
[103] Malavasi L, Tullio E D, Rundlof H, et al. High-temperature neutron diffraction study of the bilayered manganite La_(1.4)Sr_(1.6)Mn_2O_7[J]. Phys. Rev. B., 2005, 72: 054115-054119.
[104] Chi E O, Hong K P, Kwon Y U, et al. Neutron diffraction studies on a ferromagnetic layered manganite La2-2xSr1+2xMn2O7 (x=0.3) prepared by a ceramic method[J]. Phys. Rev. B., 1999, 60: 12867–12873.
[105] Battle P D,Millburn J E,Rosseinsky M J,et al. Neutron Diffraction Study of the Structural and Electronic Properties of Sr2HoMn2O7 and Sr2YMn2O7[J]. Chem.Mater., 1997, 9: 3136–3143.
[106] Sloan J, Battle P D, Green M A, et al., A HRTEM Study of the Ruddlesden–Popper Compositions Sr2LnMn2O7(Ln=Y, La, Nd, Eu, Ho) [J]. J. Solid State Chem., 1998, 138: 135–140.
[107] Tian S B, Phan M H, Yu S C, et al. Magnetocaloric effect in a La0.7Ca0.3MnO3 single crystal[J]. Phys. B., 2003, 327: 221–224.
[108] Dinesen A R, Linderoth S, M?rup S. Direct and indirect measurement of the magnetocaloric effect in La0.67Ca0.33?xSrxMnO3±δ(x∈[0:0.33])[J]. J. Phys. Condens. Matter, 2005, 17: 6257–6269.
[109] Bejar M, Dhahri R, Halouani F El, et al. Magnetocaloric effect at room temperature in powder of La0.5(CaSr)0.5MnO3[J]. J. Alloys Compd., 2006, 41: 431–35.
[110] Raveau B, Martin C, Maignan A. What about the role of B elements in the CMR properties of ABO3 perovskites?[J]. J Alloys and Comps, 1998, 275-277: 461-467.
[111]Ogale S B, Shreekala R, Bathe R, et al. Transport properties, magnetic ordering, andhyperfine interactions in Fe-doped La0.75Ca0.25MnO3: Localization-delocalizationtransition[J]. Phys Rev B, 1998, 57: 7841-7845.
[112] Hirot K, Ishihar S, Fujiol H, et al. Spin dynamical properties and orbital states of thelayered perovskite La2-2xSr1+2xMn2O7(0.3<~x<0.5)[J]. Phys. Rev. B, 2002, 65: 064414(1-10).
[113] Zhang J, Wang F W, Zhang P L, et al. Effect of Fe doping on magnetic properties andmagnetoresistance in La1.2Sr1.8Mn2O7[J]. J. Appl. Phys., 1999, 86: 1604-1606.
[114] Rodriguez-Carvajal J.‘‘FullProf.2000’’, Computer program, Version 2.40-May2003-LLB JRC.
[115] Brindley G W. The effect of grain or particle size on X-ray reflections from mixedpowders and alloys, considered in relation to the quantitative determination of crystallinesubstances by X-ray methods[J]. Philos. Mag., 1945, 36: 347-349.
[116]Fan J Y, Pi L, Tong W, et al. Percolative conductivity in the La0.67Sr0.33Mn1-xMgxO3system[J]. Phys. Rev. B, 2003, 68: 092407 (1-4).
[2] Uehara M, Mori S, Chen C H, et al. Percolative phase separation underlies colossal magnetoresistance in mixed-valent manganites[J]. Nature, 1999, 399: 560-563.
[3] Zhang L W, Israel C, Biswas A, et al. Direct observation of percolation in a manganite thin film[J]. Science, 2002, 298: 805-807.
[4] Moreo A, Yunokie S, Dagotto E. Phase separation Scenario for manganese oxides and related materials[J]. Science, 1999, 283: 2034-2040.
[5] De Teresa J M, Ibarra M R, Algarabel P A, et al. Evidence for magnetic polarons in the magnetoresistive perovskites[J]. Nature, 1997, 386: 256-259.
[6] Fiebig M, Miyano K, Tomioka Y, et al. Visualization of the Local Insulator–Metal Transition in Pr0.7Ca0.3MnO3[J]. Science, 1998, 280: 1925-1928.
[7] Guo Z B, Du Y W, Zhu J S, et al. Large Magnetic Entropy Change in Perovskite-Type Manganese Oxides[J]. Phys. Rev. Lett., 1997, 78: 1142-1145.
[8] Dagotto E, Hotta T, Moreo A. Colossal magnetoresistant materials: The key role of phase separation[J]. Phys. Rep., 2001, 344: 1-153.
[9] Satpathy S, Popovi Z S, and Vukajlovi F R. Electronic Structure of the Perovskite Oxides: La1-xCaxMnO3[J]. Phys. Rev. Lett., 1996, 76: 960-962.
[10] Tokura Y, Tomioka Y. Colossal magnetoresistive manganites[J]. J. Magn. Magn. Mater., 1999, 200: 1-23.
[11] Ruddlesden S N, Popper P. The Compound Sr3Ti2O7 and Its Structure[J]. Acta Crystallogr, 1958, 11: 54-59.
[12] Jonker G H, Santen Van. J H. Ferromagnetic compounds of manganese with perovskite structure[J]. Physica, 1950. 16: 337-349.
[13] Wollan E O, Koenhler W C. Neutron Diffraction Study of the Magnetic properties of the series of perovskite-type compounds [(1-x)La, xCa]MnO3[J]. Phys. Rev., 1955, 100:545-563.
[14] Goodenough J B. Theory of the role of covalence in the perovskite-type manganites [La, M(Ⅱ)]MnO3[J]. Phys. Rev., 1955, 100: 564-573.
[15] Urushibara A, Moritomo Y, Arima T, et al. Insulator-metal transition and giant magnetoresistance in La1-xSrxMnO3[J]. Phys. Rev. B, 1995, 51: 14103-14109.
[16] Kawano H, Kajimoto R, Kubota M, et al. Canted antiferromagnetism in an insulating lightly doped La1-xSrxMnO3 with x≤0.17[J]. Phys. Rev. B, 1996, 53: 2202-2205.
[17] Xiong X, Dabrowski B, Chmaissem O, et. al. Correlation between coherent Jahn-Teller distortion and magnetic spin orientation in La1-xSrxMnO3[J]. Phys. Rev. B, 1999, 60: 10186-10192.
[18] Zener C. Interaction between the d Shells in the Transition Metals[J]. Phys. Rev., 1951, 81: 440-446.
[19] Argyiou D N, Mitchell J F, Radaelli P G, et al. Lattice Effects and Magnetic Structure in the Layered Colossal Magnetoresistance Manganite La2-2xSr1+2xMn2O7[J]. Phys. Rev. B, 1999, 59(13): 8695-8702.
[20] Battle P D, Cox D E, Green A M, et al. Sr1.8Nd1.2Mn2O7: Synthesis, Crystal Structure, and Physics Properties[J]. Chem. Mater., 1997, 9: 3215-3221.
[21] Mitchell J F, Millbum J E, Medarade M, et al. Layered Manganites: Magnetic Structure at Extreme Doping Levels[J]. J Appl. Phys., 1999, 85 (8): 4352-4354.
[22] Kuboat M, Fujioka H, Hirota K, et al. Relation between Crystal and Magnetic Structures of Layered Manganite La2-2xCa1+2xMn2O7(0.30≤x≤0.50) [J]. J Phys. Soc. Jpn., 2000, 69(6): 1606-1609.
[23] Hur N H, Kim J T, Kim K H, et al. Effect of Lanthanide Ions on the Magnetotransport Properties in Layered Sr1.6R1.4Mn2O7(R= La, Pr, Nd, Gd) [J]. Phys. Rev. B, 1998, 57(17): 10740-10744.
[24] Kimura T, Tomioka Y, Kuwahara H, et al. Interplane Tunneling Magnetoresistance in a Layered Manganite Crystal[J]. Science, 1996, 274: 1698-1701.
[25] Kimura T, Asamitsu A, Tomioka Y, et al., Pressure-Enhanced Interplane Tunneling Magnetoresistance in a Layered Manganite Crystal[J]. Phys. Rev. Lett., 1997, 79:3720-3723.
[26] Hirota K, Moritomo Y, Fujioka H, et al. Neutron-Diffraction Studies on the Magnetic Ordering Process in the Layered Mn Perovskite La2-2xSr1+2xMn2O7 (x=0.40,0.45 and 0.48) [J]. J. Phys. Soc. Jpn., 1998, 67: 3380-3383.
[27] Li J Q, Matsui Y, Kimura T, et al. Structural properties and charge-ordering transition in LaSr2Mn2O7[J]. Phys. Rev. B, 1998, 57: R3205-3208.
[28] Kimura T, Kumai R, Tokura Y, et al. Successive structural transitions coupled with magnetotransport properties in LaSr2Mn2O7[J]. Phys. Rev. B, 1998, 58: 11081-11084.
[29] Hayashi T, Miura N, Tokunaga M, et al. Magnetic properties and CMR effect in layer type manganite LaSr2Mn2O7 under high magnetic fields[J]. J. Phys.: Condens. Matter, 1998, 10: 11525-11529.
[30] Suryanarayanan R, Dhalenne G, Revcolevschi A, et al. Colossal magnetoresistance and re-entrant charge ordering in single crystalline two layer Mn perovskite LaSr2Mn2O7[J]. Solid State Commun., 2000, 113: 267-271.
[31] Kubota M, Fujioka H, Ohoyama K, et al. Neutron scattering studies on magnetic structure of the double-layered manganite La2-2xSr1+2xMn2O7 (0.30≤x≤0.50) [J]. J. Phys. Chem. Solids, 1999, 60: 1161-1164.
[32] Perring T G, Aeppli G, Moritomo Y, et al. Antiferromagnetic Short Range Order in a Two-Dimensional Manganite Exhibiting Giant Magnetoresistance[J]. Phys. Rev. Lett., 1997, 78: 3197-3200.
[33] Maezono R, Nagaosa N. Spin and orbital ordering in double-layered manganites[J]. Phys. Rev. B, 2000, 61: 1825-1830.
[34] Osborn R, Rosenkranz S, Argyriou D N, et al. Neutron Scattering Investigation of Magnetic Bilayer Correlations in La1.2Sr1.8Mn2O7: Evidence of Canting above TC[J]. Phys. Rev. Lett., 1998, 81: 3964-3967.
[35] Chatterji T, Mclntyre G J, Suryanarayanan R, et al. Spin correlations in the bilayer manganite La1.2Sr1.8Mn2O7[J]. Solid State Comnnmications, 1999, 112: 235-239.
[36] Chatterji T, McIntyre G J, Caliebe W. Reentrant behavior of the charge and orbital ordering and antiferromagnetism in LaSr2Mn2O7[J]. Phys. Rev. B, 2000, 61: 570-574.
[37] Ling C D, Millburn J E, Mitchell J F, et al. Interplay of spin and orbital ordering in the layered colossal magnetoresistance manganite La2-2xSr1+2xMn2O7(0.5≤x≤1.0) [J]. Phys. Rev. B, 2000, 62: 15096-15111.
[38] Kanamori J. Crystal distortion in magnetic compounds[J]. J. Appl. Phys., 1960, 31: 14S-23S.
[39] Tokura Y, Urushibara A, Moritomo Y,et al. Giant Magnetotransport Phenomena in Filling-Controlled Kondo Lattice System: La1-xSrxMnO3[J]. J. Phys. Soc. Jpn., 1994, 63: 3931-3935.
[40] Furukawa N. Transport Properties of the Kondo Lattice Model in the Limit S=∞and D=∞[J]. J. Phys. Soc. Jpn., 1994, 63: 3214-3217.
[41] Hundley M F, Hawley M, Heffner R H, et al. Transport‐magnetism correlations in the ferromagnetic oxide La0.7Ca0.3MnO3[J]. Appl. Phys. Lett., 1995, 67: 860-862.
[42] Millis A J, Littlewood P B, Shraiman B I. Double Exchange Alone Does Not Explain the Resistivity of La1-XSrxMnO3[J]. Phys. Rev.Lett., 1995, 74: 5144-5147.
[43] Millis A J, Mueller R, Shraiman B I. Fermi-liquid-to-polaron crossover. II. Double exchange and the physics of colossal magnetoresistance[J]. Phys. Rev. B., 1996, 54: 5405-5417.
[44] Roder H, Zang J, Bishop A R. Lattice Effects in the Colossal-Magnetoresistance Manganites[J]. Phys. Rev. Lett., 1996, 76:1356-1359.
[45] Dai P, Zhang J, Mook H A, et al. Experimental evidence for the dynamic Jahn-Teller effect in La0.65Ca0.35MnO3[J]. Phys. Rev. B., 1996, 54: R3694-R3697.
[46] Radaelli P G, Cox D E, Marezio M, et al. Simultaneous Structural, Magnetic, and Electronic Transitions in La1-xCaxMnO3 with x=0.25 and 0.50[J]. Phys. Rev. Lett., 1995, 75: 4488-4491.
[47] Varma C M. Electronic and magnetic states in the giant magnetoresistive compounds[J]. Phys. Rev. B., 1996, 54: 7328-7333.
[48] Kataoka M. Theory of the giant magnetoresistance in La1? x A x MnO3[J]. Chechoslovak J. Phys., 1996, 46:1857-1858.
[49] Kataoka M, Tachiki M. Giant spin fluctuation as a possible origin of the giantmagnetoresistance in La1-xAxMnO3[J]. Phys. B., 1997, 237: 24-25.
[50] Sternlieb B J, Hill J P, Wildgruber U C, et al. Charge and Magnetic Order in La0.5Sr1.5MnO4[J]. Phys. Rev. Lett., 1996, 76: 2169-2172.
[51] Moritomo Y, Tomioka Y, Asamitsu A, et al. Magnetic and electronic properties in hole-doped manganese oxides with layered structures: La1-xSr1+xMnO4[J]. Phys. Rev. B., 1995, 51: 3297-3300.
[52] Qing A L, Gray K E, Mitchell J F. Spin-independent and spin-dependent conductance anisotropy in layered colossal-magnetoresistive manganite single crystals[J]. Phys. Rev. B., 1999, 59: 9357-9361.
[53] Perring T G, Aeppli G, Kimura T, et al. Ordered stack of spin valves in a layered magnetoresistive perovskite[J]. Phys. Rev. B, 1998, 58: R14693- R14696.
[54] Kimura T, Tomioka Y, Asamitsu A, et al. Anisotropic Magnetoelastic Phenomena in Layered Manganite Crystals: Implication of Change in Orbital State[J]. Phys. Rev. Lett., 1998, 81: 5920-5923.
[55] Moritomo Y, Asamitsu A, Kuwahara H, et al. Giant Magnetoresistance in Layered Structure of Manganese Oxides[J]. Nature, 1996, 380: 141-144.
[56] 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: 2041-2044.
[57] Balcells Li, Carrillo A E , Mart?′nez B, et al. Enhanced field sensitivity close to percolation in magnetoresistive La2/3Sr1/3MnO3/CeO2 composites[J]. Appl. Phys. Lett., 1999, 74: 4014-4016.
[58] Petrov D K, Krusin-Elbaum L , Sun J Z , et al. Enhanced magnetoresistance in sintered granular manganite/insulator systems[J]. Appl. Phys. Lett., 1999, 75: 995-997.
[59] Subhrangsu T, Karmakar S, Chatterjee S, et al. Ferro-antiferromagnetic coupling and unusual transport properties of ferro-antiferromagnetic (100?x)La0.7Pb0.3MnO3 + xPr0.63Ca0.37MnO3 (x = 0–85 ?wt ? %) composites[J]. J. Appl. Phys., 2006, 99: 073703-073708.
[60] 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: 5588-5590.
[61] Zhu T, Yan C H, Wang Z M, et al. Low-field magnetoresistance in La2/3Sr1/3MnO3 granular composites by a sol–gel coating process[J]. Solid State Communications, 2001, 117: 471-475.
[62] Yao L D, E P, Zhang J S, et al. Magnetic and magnetotransport properties of La2/3Ca1/3MnO3/Se2FeMoO6 nano-crystalline composites synthesized under high pressure[J]. Phys. B., 2008, 403: 2241-2245.
[63]任光明,袁松柳,缪菊红等. La0.67Ca0.33MnO3/MgO复合体系中的电输运和磁电阻效应.无机材料学报, 2007, 22(4): 715-719.
[64] 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: 1110-1112.
[65] 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. Phys. Lett., 2002, 81: 76-78.
[66] Warburg E, Magnetische Untersuchungen. I. U“bereinige Wirkungen der Coe”rcitivkraft[J]. Ann. Phys., 1881, 13: 141-64.
[67] Gschneidner K A, Pecharsky V K, Tsokol A O. Recent developments in magnetocaloric materials[J]. Rep. Prog. Phys., 2005, 68: 1479-1539.
[68] Bruck E. Developments in magnetocaloric refrigeration[J]. J. Phys. D: Appl. Phys., 2005, 38: R381-R390.
[69] Giauque W F, MacDougall D P. Attainment of Temperatures Below 1°Absolute by Demagnetization of Gd2(SO4)3·8H2O[J]. Phys. Rev., 1933, 43: 768-768.
[70] Pecharsky V K, Gschneidner K A. Giant Magnetocaloric Effect in Gd5(Si2Ge2) [J]. Phys. Rev. Lett., 1997, 78: 4494-4497.
[71] Hu F X, Shen B G, Sun J R, et al. Large magnetic entropy change in a Heusler alloy Ni52.6Mn23.1Ga24.3 single crystal[J]. Phys. Rev. B., 2001, 64: 132412-132415.
[72] Wada H, Tanabe Y. Giant magnetocaloric effect of MnAs1?xSbx[J]. Appl. Phys. Lett., 2001, 79: 3302-3304.
[73] Fujieda S, Fujita A, Fukamichi K. Large magnetocaloric effect in La(FexSi1?x)13 itinerant-electron metamagnetic compounds[J]. Appl. Phys. Lett., 2002, 81: 1276-1278.
[74] Tegus O, Bruck E, Buschow K H J, et al. Transition-metal-based magnetic refrigerants for room-temperature applications[J]. Nature, 2002, 415:150-152.
[75] Phan M H, Yu S C, Hur N H. Excellent magnetocaloric properties of La0.7Ca0.3?xSrxMnO3(0.05≤x≤0.25) single crystals[J]. Appl. Phys. Lett., 2005, 86: 072504-072506.
[76] Szewczyk A, Szymczak H, Wisniewski A, et al. Magnetocaloric effect in La1?xSrxMnO3 for x = 0.13 and 0.16[J]. Appl. Phys. Lett., 2000, 77:1026-1028.
[77] Phan M H, Tian S B, Hoang D Q, et al. Large magnetic-entropy change above 300 K in CMR materials[J]. J. Magn. Magn. Mater., 2003, 258-259: 309-311.
[78] Sun Y, Salamon M B, Chun S H. Magnetocaloric effect and temperature coefficient of resistance of La2/3(Ca,Pb)1/3MnO3[J]. J. Appl. Phys., 2002, 92: 3235-3238.
[79] Biernacki S W, Schulz H J. Adiabatic temperature change in perovskite manganites[J]. Phys. Rev. B., 2004, 70: 092405-092408.
[80] Terashita H, Myer B, Neumeier J J. Influence of a first-order structural transition on magnetocaloric effects in manganese oxides[J]. Phys. Rev. B., 2005, 72: 132415-132417.
[81] Xiong C M, Sun J R, Chen Y F, et al. Relation between magnetic entropy and resistivity in La0.67Ca0.33MnO3[J]. IEEE Trans. Magn., 2005, 41:122-124.
[82] Gschneidner K A, Pecharsky V K. Magnetocaloric materials[J]. Annu. Rev. Mater. Sci., 2000, 30: 387-429.
[83] Szewczyk A, Gutowska M, Piotrowski K,et al. Direct and specific heat study of magnetocaloric effect in La0.845Sr0.155MnO3[J]. J. Appl.Phys., 2003, 94: 1873-1876.
[84] Szewczyk A, Gutowska M, Dabrowski B, et al. Specific heat anomalies in La1?xSrxMnO3 (0.12perovskite manganites[J]. J. Magn. Magn. Mater., 2002, 242-245: 698-700.
[88] Guo Z B, Zhang J R, Huang H, et al. Large magnetic entropy change in La0.75Ca0.25MnO3[J]. Appl.Phys.Lett., 1996, 70: 904-905.
[89] Zhang X X, Tejada J, Xin Y, et al. Magnetocaloric effect in La0.67Ca0.33MnOδand La0.60Y0.07Ca0.33MnOδbulk materials[J]. Appl. Phys. Lett., 1996, 69: 3596-3598.
[90] Lin G C, Wei Q, Zhang J X. Direct measurement of the magnetocaloric effect in La0.67Ca0.33MnO3[J]. J. Magn. Magn. Mater., 2006, 300: 392-396.
[91] Sun Y, Xu X, Zhang Y H, Large magnetic entropy change in the colossal magnetoresistance material La2/3Ca1/3MnO3[J]. J. Magn. Magn. Mater., 2000, 219: 183-185.
[92] Zhou T J, Yu Z, Zhong W, et al. Larger magnetocaloric effect in two-layered La1.6Ca1.4Mn2O7 polycrystal[J]. J. Appl. Phys., 1999, 85: 7975-7977.
[93] Zhu H, Song H, Zhang Y H. Magnetocaloric effect in layered perovskite manganese oxide La1.4Ca1.6Mn2O7[J]. Appl. Phys. Lett., 2002, 81:3416-3418.
[94] Zhong W, Chen W, Jiang H Y, et al. Preparation, magnetoresistance and magnetocaloric effect of two-layered perovskite La2.5-xK0.5+x Mn2O7+δ[J]. Eur. Phys. J. B , 2002, 30: 331-337.
[95] Seshadri R, Hervieu M, Martin C, et al. Study of the Layered Magnetoresistive Perovskite La1.2Sr1.8Mn2O7 by High-Resolution Electron Microscopy and Synchrotron X-ray Powder Diffraction[J]. Chem. Mater., 1997, 9: 1778-1787.
[96] Mohanram R A, Ganapathi L, Rao C N R, et al. Magnetic properties of quasi-two-dimensional La1?xSr1+xMnO4 and the evolution of itinerant electron ferromagnetism in the SrO·(La1?xSrxMnO3)n system[J]. J. Solid State Chem., 1987, 70: 82–87.
[97] Mahesh R, Mahendiran R, Raychaudhuri A K, et al. Effect of Dimensionality on the Giant Magnetoresistance of the Manganates:A Study of the (La, Sr)n+1MnnO3n+1Family[J]. J. Solid State Chem., 1996, 122: 448–450.
[98] Battle P D, Green M A, Laskey N S,et al. Layered Ruddlesden?Popper Manganese Oxides: Synthesis and Cation Ordering[J]. Chem. Mater., 1997, 9: 552–559.
[99] Asano H, Hayakawa J, Matsui M. Giant magnetoresistance of a two-dimensionalferromagnet La2?2xCa1+2xMn2O7[J]. Appl. Phys. Lett., 1996, 68: 3638–3640.
[100] Ganguly R, Siruguri V, Gopalakrishnan I K, et al. Comment on“Giant magnetoresistance of a two-dimensional ferromagnet La2?2xCa1+2xMn2O7”[Appl. Phys. Lett. 68, 3638 (1996)][J]. Appl. Phys. Lett., 2000, 76: 1956–1957.
[101] Fawcett I D, Kim E, Greenblatt M, et al. Properties of the electron-doped layered manganates La2-2xCa1+2xMn2O7 (0.6<~x<~1.0)[J]. Phys. Rev. B., 2000, 62: 6485–6495.
[102] Yu R C, Zhu J L, Li S Y, et al. TEM studies on La2-2xCa1+2xMn2O7 (x=0.5 and 0.25) [J]. Mater. Sci. Eng. A , 2003, 345: 344–349.
[103] Malavasi L, Tullio E D, Rundlof H, et al. High-temperature neutron diffraction study of the bilayered manganite La_(1.4)Sr_(1.6)Mn_2O_7[J]. Phys. Rev. B., 2005, 72: 054115-054119.
[104] Chi E O, Hong K P, Kwon Y U, et al. Neutron diffraction studies on a ferromagnetic layered manganite La2-2xSr1+2xMn2O7 (x=0.3) prepared by a ceramic method[J]. Phys. Rev. B., 1999, 60: 12867–12873.
[105] Battle P D,Millburn J E,Rosseinsky M J,et al. Neutron Diffraction Study of the Structural and Electronic Properties of Sr2HoMn2O7 and Sr2YMn2O7[J]. Chem.Mater., 1997, 9: 3136–3143.
[106] Sloan J, Battle P D, Green M A, et al., A HRTEM Study of the Ruddlesden–Popper Compositions Sr2LnMn2O7(Ln=Y, La, Nd, Eu, Ho) [J]. J. Solid State Chem., 1998, 138: 135–140.
[107] Tian S B, Phan M H, Yu S C, et al. Magnetocaloric effect in a La0.7Ca0.3MnO3 single crystal[J]. Phys. B., 2003, 327: 221–224.
[108] Dinesen A R, Linderoth S, M?rup S. Direct and indirect measurement of the magnetocaloric effect in La0.67Ca0.33?xSrxMnO3±δ(x∈[0:0.33])[J]. J. Phys. Condens. Matter, 2005, 17: 6257–6269.
[109] Bejar M, Dhahri R, Halouani F El, et al. Magnetocaloric effect at room temperature in powder of La0.5(CaSr)0.5MnO3[J]. J. Alloys Compd., 2006, 41: 431–35.
[110] Raveau B, Martin C, Maignan A. What about the role of B elements in the CMR properties of ABO3 perovskites?[J]. J Alloys and Comps, 1998, 275-277: 461-467.
[111]Ogale S B, Shreekala R, Bathe R, et al. Transport properties, magnetic ordering, andhyperfine interactions in Fe-doped La0.75Ca0.25MnO3: Localization-delocalizationtransition[J]. Phys Rev B, 1998, 57: 7841-7845.
[112] Hirot K, Ishihar S, Fujiol H, et al. Spin dynamical properties and orbital states of thelayered perovskite La2-2xSr1+2xMn2O7(0.3<~x<0.5)[J]. Phys. Rev. B, 2002, 65: 064414(1-10).
[113] Zhang J, Wang F W, Zhang P L, et al. Effect of Fe doping on magnetic properties andmagnetoresistance in La1.2Sr1.8Mn2O7[J]. J. Appl. Phys., 1999, 86: 1604-1606.
[114] Rodriguez-Carvajal J.‘‘FullProf.2000’’, Computer program, Version 2.40-May2003-LLB JRC.
[115] Brindley G W. The effect of grain or particle size on X-ray reflections from mixedpowders and alloys, considered in relation to the quantitative determination of crystallinesubstances by X-ray methods[J]. Philos. Mag., 1945, 36: 347-349.
[116]Fan J Y, Pi L, Tong W, et al. Percolative conductivity in the La0.67Sr0.33Mn1-xMgxO3system[J]. Phys. Rev. B, 2003, 68: 092407 (1-4).