Abstract
A study is reported of the dc and 9.2-GHz electrical and magnetoresistance (ρ0, MR 0, ρmw, and MR mw ) in La1−x CaxMnO3 polycrystals (x=0–0.3) in the 77–300 K temperature interval. The microwave magnetoresistance exhibits a sharp peak within a narrow interval near the Curie temperature T C , while MR mw ≈0 is far from T C . The microwave absorption in low magnetic fields is shown to be due to a variation of the microwave magnetic, rather than electrical losses. The peaks of ρ0, ρmw, MR 0, and MR mw do not coincide in temperature. The specific features in the behavior of ρ0, MR 0, ρmw, and MR mw are explained as being due to an inhomogeneity of the grains, which generates in the grain close to the interface a magnetic-field-dependent contact potential difference. The origin of the inhomogeneities can either be traced to the formation on a grain of a surface layer with properties differing from those in the grain bulk, or understood in terms of the model postulating grain separation into a conducting and a nonconducting phase.
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Translated from Fizika Tverdogo Tela, Vol. 42, No. 5, 2000, pp. 899–904.
Original Russian Text Copyright © 2000 by Solin, Naumov, Samokhvalov.
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Solin, N.I., Naumov, S.V. & Samokhvalov, A.A. Interface phenomena and microwave magnetoresistance in polycrystalline La1−x CaxMnO3 lanthanum manganites. Phys. Solid State 42, 925–930 (2000). https://doi.org/10.1134/1.1131313
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DOI: https://doi.org/10.1134/1.1131313