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Evidence for small or intermediate-size polarons in the ferromagnetic state of manganites

Guo-meng Zhao·D. J. Kang·W. Prellier·M. Rajeswari·H. Keller·T. Venkatesan·R. L. Greene
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Abstract

Oxygen-isotope effects on the intrinsic resistivity have been studied in high-quality epitaxial thin films of La_{0.75}Ca_{0.25}MnO_{3} and Nd_{0.7}Sr_{0.3}MnO_{3}. We found that the residual resistivity ρ_{o} increases by about 15(3)% upon replacing ^{16}O by ^{18}O. This provides strong evidence for the presence of small or intermediate-size polarons in the metallic ferromagnetic state. Furthermore, the temperature dependent part of the resistivity at low temperatures consists of an AT^{4.5} term contributed from 2-magnon scattering, and a Bω_{s}/\sinh^{2}(\hbarω_{s}/2k_{B}T) term which arises from scattering by a soft optical phonon mode. The absolute magnitudes of the coefficient A and the phonon frequency \hbarω_{s} for both isotope samples are in quantitative agreement with theoretical predictions.

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Guo-meng Zhao, D. J. Kang, W. Prellier, M. Rajeswari, H. Keller, T. Venkatesan, R. L. Greene. 2000-08-02. Evidence for small or intermediate-size polarons in the ferromagnetic state of manganites. https://arxiv.org/abs/cond-mat/0008029

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