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

Abstract

An unusual temperature and concentration behavior of resistivity in $L{a}_{0.7}C{a}_{0.3}M{n}_{1-x}C{u}_x{O}_3$ has been observed at slight $Cu$ doping ($0\le x\le 0.05$). 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.

10 REVTEX pages, 2 PostScript figures (epsf.sty); to be published in JETP Letters

References in corpus (3)

• Metal-insulator transition induced by 16O -18O oxygen isotope exchange in colossal negative magnetoresistance manganites
• Influence of Cu on spin-polaron tunneling in the ferromagnetic state of La(2/3)Ca(1/3)Mn(1-x)Cu(x)O(3) from the resistivity data
• Negative magnetoresistance in La(0.6)Y(0.1)Ca(0.3)MnO(3): Evidence for charge localization governed by the Curie-Weiss law

Cited by in corpus (2)

• Influence of Zeeman splitting and thermally excited polaron states on magneto-electrical and magneto-thermal properties of magnetoresistive polycrystalline manganite La_{0.8}Sr_{0.2}MnO_3
• On the origin of unusual transport properties observed in densely packed polycrystalline CaAl_{2}