La_（2/3）Ca_（1/3）MnO_3颗粒系统第二相引入对其电性质的影响
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摘要
在本论文中,我们用溶胶-凝胶法制备了小尺寸的La_(2/3)Ca_(1/3)MnO_3颗粒,随后分别采用物理的和化学的方法在La_(2/3)Ca_(1/3)MnO_3颗粒系统中引入了Cu相关的顺磁性相和Sb_2O_5绝缘体相。我们从实验角度探讨了第二相的引入对复合颗粒系统的电磁输运行为和磁电阻的影响,实验测量表明:
1、较之纯La_(2/3)Ca_(1/3)MnO_3颗粒系统,零场下电阻温度关系测量表明,少量的Cu相关顺磁性物质的引入使得复合颗粒系统的电阻率大幅度降低;随着引入的Cu相关顺磁性物质的量的增加,磁测量表明,复合颗粒系统展现出新的磁相,且对外磁场的响应加强,外场下电阻温度关系测量表明,复合颗粒系统表现出明显增强的磁阻效应。
2、在La_(2/3)Ca_(1/3)MnO_3颗粒系统中引入Sb2O5绝缘体相,零场下电阻温度关系测量表明,对x<3%范围,随Sb_2O_5含量增加,复合颗粒系统的电阻率增大,绝缘体-金属转变温度降低;而对x>3%范围,随Sb_2O_5含量增加,复合颗粒系统的电阻率减小,绝缘体-金属转变温度提高。磁电阻测量表明,少量Sb_2O_5的引入可明显增强磁电阻效应。
基于La_(2/3)Ca_(1/3)MnO_3颗粒周围包覆有第二相薄层的考虑,我们对上述两种磁电阻变化行为提出了一可能的解释。
In our work, we prepared nominal La_(2/3)Ca_(1/3)MnO_3 grains with sol-gel method, then we introduced the Cu dependent material and the Sb_2O_5 material respectively to the La_(2/3)Ca_(1/3)MnO_3 grains system with physical and chemical method. We discuss the effect of the second phase in these compounds, experimental results indicated that:
1. When the second phase is the Cu dependent material, the study of temperature dependence of resistivity at zero field shows that, the resistivity of the composites decreases prodigiously with small addition level. With the addition level decreases, the composites becomes sensitively to the magnetic field, the measurement for temperature dependence of magnetoresistance (MR) indicates that MR effect can be largely enhanced in the composites with the second phase addition.
2. When the second phase is the Sb_2O_5 material, the study of temperature dependence of resistivity at zero field shows that, the metal-insulator transition temperature (Tp) and the resistivity of the composites are dependent on Sb_2O_5 addition level x. When x<3%, Tp shifts towards low temperature and resistivity increases with the increase of x. But Tp shifts towards high temperature and resistivity decreases with further increasing of x. The measurement for temperature dependence of magnetoresistance (MR) indicates that MR effect can be largely enhanced in the composites with small Sb_2O_5 addition.
Based on the structure that the La_(2/3)Ca_(1/3)MnO_3 grains are surrounded by the the second phase, just like the sandwich structure, we give a possible interpretation to the enhanced magnetoresistance (MR) effect observed in these composites.
1、较之纯La_(2/3)Ca_(1/3)MnO_3颗粒系统,零场下电阻温度关系测量表明,少量的Cu相关顺磁性物质的引入使得复合颗粒系统的电阻率大幅度降低;随着引入的Cu相关顺磁性物质的量的增加,磁测量表明,复合颗粒系统展现出新的磁相,且对外磁场的响应加强,外场下电阻温度关系测量表明,复合颗粒系统表现出明显增强的磁阻效应。
2、在La_(2/3)Ca_(1/3)MnO_3颗粒系统中引入Sb2O5绝缘体相,零场下电阻温度关系测量表明,对x<3%范围,随Sb_2O_5含量增加,复合颗粒系统的电阻率增大,绝缘体-金属转变温度降低;而对x>3%范围,随Sb_2O_5含量增加,复合颗粒系统的电阻率减小,绝缘体-金属转变温度提高。磁电阻测量表明,少量Sb_2O_5的引入可明显增强磁电阻效应。
基于La_(2/3)Ca_(1/3)MnO_3颗粒周围包覆有第二相薄层的考虑,我们对上述两种磁电阻变化行为提出了一可能的解释。
In our work, we prepared nominal La_(2/3)Ca_(1/3)MnO_3 grains with sol-gel method, then we introduced the Cu dependent material and the Sb_2O_5 material respectively to the La_(2/3)Ca_(1/3)MnO_3 grains system with physical and chemical method. We discuss the effect of the second phase in these compounds, experimental results indicated that:
1. When the second phase is the Cu dependent material, the study of temperature dependence of resistivity at zero field shows that, the resistivity of the composites decreases prodigiously with small addition level. With the addition level decreases, the composites becomes sensitively to the magnetic field, the measurement for temperature dependence of magnetoresistance (MR) indicates that MR effect can be largely enhanced in the composites with the second phase addition.
2. When the second phase is the Sb_2O_5 material, the study of temperature dependence of resistivity at zero field shows that, the metal-insulator transition temperature (Tp) and the resistivity of the composites are dependent on Sb_2O_5 addition level x. When x<3%, Tp shifts towards low temperature and resistivity increases with the increase of x. But Tp shifts towards high temperature and resistivity decreases with further increasing of x. The measurement for temperature dependence of magnetoresistance (MR) indicates that MR effect can be largely enhanced in the composites with small Sb_2O_5 addition.
Based on the structure that the La_(2/3)Ca_(1/3)MnO_3 grains are surrounded by the the second phase, just like the sandwich structure, we give a possible interpretation to the enhanced magnetoresistance (MR) effect observed in these composites.
引文
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[2] G.A.Prinz. Phys.Today , 1995,45:58
[3] E. Dagotto, T. Hotta, A. Moreo. Phys. Rep., 2001,344:1
[4] M. Ziese Rep. Prog. Phys., 2002,65:143.
[5] C. LDennis et al. The defining length scales of mesomagnetism: a review. J. Phys.: Condens. Matter, 2002,14 :1175.
[6] W. Thompson. On the electrodynamic qualities of metal: effect of magnetization on the electric conductivity of nickel and iron. Proc. R. Soc., 1857, 8 : 546.
[7] P. W. Anderson, H. Hasegawa. Considerations on double exchange. Phys. Rev. 1995, 100 : 675-681.
[8] G. Jonker, J. van Santen. Physica, 1950, 16 : 599.
[9] P.-G. de Gennes. Effects of double exchange in magnetic crystals. Phys. Rev., 1960, 118 : 141-154.
[10] G. Jonner, J. Van Santen. Physica, 1950, 16 : 337.
[11] H. Y. Hwang, S-W. Cheong, P. G. Radaelli et al. Lattice Effects on the Magnetoresistance in Doped LaMnO_3. Phys. Rev. Lett., 1995,75: 914-917.
[12] R. von Helmolt, J. Wecker, B. Holzapfel et al. Giant negative magnetoresistance in perovskitelike La_(2/3)Ba_(1/3)MnOx ferromagnetic films. Phys. Rev. Lett., 1993, 71 : 2331-2333.
[13] S. Jin, T. H. Tiefel, M. McCormack, et al. Thousandfold charge in resistivity in magnetoresistive La-Ca-Mn-O films. Science, 1994, 264 : 413-415.
[14] H. Y. Hwang, S-W. Cheong, N. P. Ong et al. Spin-Polarized Intergrain Tunneling in La_(2/3)Sr_(1/3)MnO_3. Phys. Rev. Lett., 1996, 77 : 2041-2044.
[15] J. -H. Park, E. Vescovo, H.-J. Kim et al. Magnetic properties at surfaceboundary of a half-metallic ferromagnet La0.7Sr0.3MnO_3. Phys. Rev. Lett, 1998, 81: 1953-1956.
[16] J. B. Goodenough et al. Magnetic and Other Properties of Oxides and Related Compounds, Landolt-Bornstein, New Series, Group III, Vol.4, Pt. a Springer, Berlin, 1970.
[17] Y.Moritomo,H.Kuwahara, and Y.Tomioka. Pressure effects on charge-ordering transitions in Perovskite manganites. Phys.Rev B. 1997, 55:7549
[18] A-M Haghiri-Gosnet, J-P Renard.CMR manganites: physics, thin films and devices. J. Phys. D: Appl. Phys., 2003, 36 : R127.
[19] A. J. Millis, P. B. Littlewood, B. I. Shraiman. Double Exchange Alone Does Not Explain the Resistivity of La1-xSrxMnO_3. Phys. Rev. Lett., 1995, 74 : 5144–5147.
[20] Clarence Zener. Interaction between the d-shell in the transition metal. II. ferromagnetic compounds of manganese with pervoskite structure. Phys. Rev. 1951, 82 : 403–405.
[21] E. O. Wollan, W. C. Koehler. Neutron diffraction study of the magnetic properties of the series of perovskite-type compounds [(1-x) La, xCa]MnO_3. Phys. Rev. 1955, 100 : 545-563.
[22] S-W. Cheong, H.Y, Hwang, Y. Tokura(Ed.). Contribution to Colossal Magnetoresistance Oxides. Monographs in Condensed Matter Science Gordon & Breach, London, 1999.
[23] Zaibing Guo, Jiangrong Zhang. Electrical properties of La_(0.7-x)Pr_xSr_(0.3)MnO_3 pervoskites. Appl. Phys. Lett., 1997, 70 :1997-2002.
[24] G. R. Wu. Carrier generation/reombination processes and polaron effect in pervoskite manganite thin film. Physics B, 2000, 284 : 1912-1915.
[25] M. F. Hundly, M. Awaly, R. H. Heffner. Transport-magnetism correlation in the ferromagnetic oxide La_(0.7)Ca_(0.3)MnO_3. Appl. Phys. Lett., 1995, 67 : 860-862.
[26] Clarence Zener. Interaction between the d-shell in the transition metal. II. ferromagnetic compounds of manganese with pervoskite structure. Phys. Rev. 1951, 82 : 403–405.
[27] J. M. D. Coey, M. Viret, S. von Molnar. Mixed-valence manganites. Adv. Phys., 1999, 48 : 167-293.
[28] Clarence Zener. Interaction between the d-shell in the transition metal. II. ferromagnetic compounds of manganese with pervoskite structure. Phys. Rev. 1951, 82 : 403–405.
[29] S. L. Yuan, Y. P. Yang, Z. C. Xia, et al. Unusual hysteresis and giant low-field magnetoresistance in polycrystalline sample with nominal composition of La_(2/3)Ca_(1/3)Mn0.955Cu0.045O3. Phys. Rew. B, 2002, 66 : 172402
[30] F. C. Schwerer, J. Silcox. Electrical Resistivity of Nickel at Low Temperatures. Phys. Rev. Lett., 1968, 20 : 101-103
[31] C. L. Dennis, R. P. Borges, L. D. Buda, et al.The defining length scales of mesomagnetism. J. Phys.: Condens. Matter, 2002, 14 : R1175
[32] Fert A.et al. Ultrathin Magnetic Structure ed. by Heinrich B,Bland JAC.Berlin Heidelberg.Spring Verlag, 1994, 45-49
[33] John Q. Xiao, J. Samuel, C. L. Chien. Giant magnetoresistance in nonmultilayer magnetic systems. Phys. Rev. Lett., 1992, 68 : 3749-3752.
[34] A. E. Berkowitz, J. R. Mitchell, M. J. Carey et al. Giant magnetoresistance in heterogeneous Cu-Co Alloys. Phys. Rev. Lett., 1992, 68 : 3745-3748.
[35] Fujimori H, Mitani S, Ohnuma S. Tunnel-type GMR in metal-nonmetal granular alloy thin films. Mater. Sci. Eng. B, 1995, 81 : 219-223.
[36] Fujimori H, Mitani S, Ohnuma S. Tunnel-type GMR in CoAlO insulated granular system - Its oxygen-concentration dependence. J. Magn. Magn Mater., 1996, 156,Issue: 1-3 , 311-314.
[37] K. -I. Kobayashi, T. Kimura, H. Sawada et al. Room-temperature magnetoresistance in an oxide material with an ordered double-perovskite structure. Nature, 1998, 395 : 677-680.
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