We report Mn K-edge extended x-ray absorption fine structure spectra on La0.75Ca0.25MnO3 up to high momentum transfer across the metal-insulator (M-I) transition. The data show compelling evidence for (i) large, or intermediate Jahn-Teller polarons (IJTP), characterized by an anomalous longer Mn-O bond (Delta R = 0.09 Angstrom) in the metallic phase (T < 170 K), and (ii) appearance of small JT polarons (SJTP) at T > 170 K, characterized by a longer Mn-O bond (Delta R = 0.21 Angstrom), which coexist with the IJTP above the M-I transition and has equal probability in the temperature range of colossal magnetoresistance.
Cross-over from Large to small polarons across the metal-insulator transition in manganites / A., Lanzara; Saini, Naurang Lal; M., Brunelli; F., Natali; Bianconi, Antonio; P. G., Radaelli; S. W., Cheong. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - STAMPA. - 81:(1998), pp. 878-881. [10.1103/PhysRevLett.81.878]
Cross-over from Large to small polarons across the metal-insulator transition in manganites
SAINI, Naurang Lal;BIANCONI, Antonio;
1998
Abstract
We report Mn K-edge extended x-ray absorption fine structure spectra on La0.75Ca0.25MnO3 up to high momentum transfer across the metal-insulator (M-I) transition. The data show compelling evidence for (i) large, or intermediate Jahn-Teller polarons (IJTP), characterized by an anomalous longer Mn-O bond (Delta R = 0.09 Angstrom) in the metallic phase (T < 170 K), and (ii) appearance of small JT polarons (SJTP) at T > 170 K, characterized by a longer Mn-O bond (Delta R = 0.21 Angstrom), which coexist with the IJTP above the M-I transition and has equal probability in the temperature range of colossal magnetoresistance.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
