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Evidence of magnetization-dependent polaron formation in La$_{1-x}A_x$MnO$_3$, $A$=Ca, Pb

C. H. Booth·F. Bridges·G. J. Snyder·T. Geballe
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Abstract

X-ray-absorption fine-structure measurements at the Mn $K$-edge as a function of temperature were performed on samples of La$_{1-x}$Ca$_x$MnO$_3$ and La$_{0.67}$Pb$_{0.33}$MnO$_3$. All samples have a metal-insulator (MI) transition near the ferromagnetic transition, except the Ca$_{0.5}$ sample, which does not have a MI transition. Near $T_c$ for the MI samples, the Debye-Waller $σ^2$ for the Mn-O atom-pair increases rapidly with temperature. This non-thermal disorder is mostly along the direction of the neighboring oxygens. These results strongly suggest small polarons which are delocalized by a finite magnetization.

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C. H. Booth, F. Bridges, G. J. Snyder, T. Geballe. 1996-07-28. Evidence of magnetization-dependent polaron formation in La$_{1-x}A_x$MnO$_3$, $A$=Ca, Pb. https://doi.org/10.1103/physrevb.54.r15606

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