Electrical transport, magnetism, and magnetoresistance in ferromagnetic oxides with mixed exchange interactions: A study of the La0.7Ca0.3Mn1-xCoxO3 system

被引:230
作者
Gayathri, N [1 ]
Raychaudhuri, AK [1 ]
Tiwary, SK [1 ]
Gundakaram, R [1 ]
Arulraj, A [1 ]
Rao, CNR [1 ]
机构
[1] INDIAN INST SCI,SOLID STATE & STRUCT CHEM UNIT,BANGALORE 560012,KARNATAKA,INDIA
来源
PHYSICAL REVIEW B | 1997年 / 56卷 / 03期
关键词
D O I
10.1103/PhysRevB.56.1345
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
In this paper we report the results of an extensive investigation of the La0.7Ca0.3Mn1-xCoxO3 system. Substitution of Mn by Co dilutes the double-exchange (DE) mechanism and changes the long range ferromagnetic order of La0.7Ca0.3MnO3 to a cluster glass-type ferromagnetic (FM) order similar to that observed in La0.7Ca0.3CoO3. This happens even for the lowest Co substitution of x = 0.05 and persists over the entire composition range studied (0.05 less than or equal to x less than or equal to 0.5). The Co substitution also destroys the metallic state and the resistivity increases by orders of magnitude even with a very small extent of Co substitution. The charge localization due to Co substitution is likely to have its origin in polaronic lattice distortion. The Co substitution also suppresses the colossal magnetoresistance (CMR) of the pure manganate (x = 0) over the entire temperature and composition range and it becomes very small for x greater than or equal to 0.2. We conclude that the DE interaction and the resulting metallic state is very ''fragile'' and hence even a small amount of Co substitution can destroy the FM order, the metallic state, and the CMR.
引用
收藏
页码:1345 / 1353
页数:9
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