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

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 ${\sigma }^2$ 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.

11 pages REVTeX and 4 PostScript figures, submitted to PRL

References in corpus (3)

• Double Exchange Alone Does Not Explain the Resistivity of $L{a}_{1-x}S{r}_{x}Mn{O}_3$
• Dynamic Jahn-Teller Effect and Colossal Magnetoresistance in $L{a}_{1-x}{A}_{x}Mn{O}_3$
• Magnetoresistance of the Double-Exchange Model in Infinite Dimension

Cited by in corpus (3)

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• Local structural changes in paramagnetic and charge ordered phases of Sm0.2Pr0.3Sr0.5MnO3: An EXAFS Study