Evidence of Magnetization-dependent Polaron Formation in Typeset Using Revt E X
نویسندگان
چکیده
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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