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Anomalous temperature behavior of resistivity in lightly doped manganites around a metal-insulator phase transition

S. Sergeenkov·M. Ausloos·H. Bougrine·A. Rulmont·R. Cloots
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Abstract

An unusual temperature and concentration behavior of resistivity in $La_{0.7}Ca_{0.3}Mn_{1-x}Cu_xO_3$ has been observed at slight $Cu$ doping ($0\leq x \leq 0.05$). Namely, introduction of copper results in a splitting of the resistivity maximum around a metal-insulator transition temperature $T_0(x)$ into two differently evolving peaks. Unlike the original $Cu$-free maximum which steadily increases with doping, the second (satellite) peak remains virtually unchanged for $x<x_c$, increases for $x\ge x_c$ and finally disappears at $x_m\simeq 2x_c$ with $x_c\simeq 0.03$. The observed phenomenon is thought to arise from competition between substitution induced strengthening of potential barriers (which hamper the charge hopping between neighboring $Mn$ sites) and weakening of carrier's kinetic energy. The data are well fitted assuming a nonthermal tunneling conductivity theory with randomly distributed hopping sites.

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S. Sergeenkov, M. Ausloos, H. Bougrine, A. Rulmont, R. Cloots. 1999-09-14. Anomalous temperature behavior of resistivity in lightly doped manganites around a metal-insulator phase transition. https://doi.org/10.1134/1.568200

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