Effects of high vacancy concentrations on the magnetic properties of La1-xMn1-yO3 (0.02≤x, y≤0.13)

被引:44
作者
de Silva, PSIPN
Richards, FM
Cohen, LF
Alonso, JA
Martinez-Lope, MJ
Casais, MT
Thomas, KA
MacManus-Driscoll, JL
机构
[1] Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London SW7 2BZ, England
[2] CSIC, Inst Ciencia Mat Madrid, E-28049 Madrid, Spain
[3] Univ London Imperial Coll Sci Technol & Med, Dept Mat, London SW7 2BZ, England
关键词
D O I
10.1063/1.366653
中图分类号
O59 [应用物理学];
学科分类号
摘要
It has been found that the synthesis conditions and subsequent annealing treatments can significantly change the magnetic and transport behavior of the colossal magnetoresistive materials of the general formula La(1-z)A(z)MnO(3), where A is a divalent ion. In order to clarify the role of vacancies within this structure, resistivity and magnetization measurements have been carried out on a series of samples derived from the parent compound LaMnO3, with La and Mn vacancies introduced by systematically varying the oxygen annealing conditions. Previous studies have shown that for a given carrier concentration, the Curie temperature of the paramagnetic to ferromagnetic transition (T-c) increases as the tolerance factor of the perovskite structure increases and then begins to decrease slowly for even higher tolerance factors. Generally, T-c also increases with the Mn4+ content, consistent with a double exchange mechanism responsible for ferromagnetism. In this study T-c was found to decrease as the vacancy concentration (and therefore the Mn4+ concentration) and tolerance factor both increase. The magnetic and transport data are discussed in the light of structural information obtained from neutron diffraction studies. In the present study it is found that La and Mn vacancies play a significant role in determining the physical properties of these materials: for high vacancy concentrations (x,y greater than or equal to 0.080) the magnetic properties are analogous to those of spin glasses associated with disorder and frustration. Semiconductorlike resistivity was observed for all samples at all temperatures. (C) 1998 American Institute of Physics.
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页码:394 / 399
页数:6
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