Phys. Rev. Lett. 81, 878–881 (1998)Crossover from Large to Small Polarons across the Metal-Insulator Transition in ManganitesReceived 8 October 1997; published in the issue dated 27 July 1998 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 (ΔR = 0.09Å) in the metallic phase (T<170K), and (ii) appearance of small JT polarons (SJTP) at T>170K, characterized by a longer Mn-O bond (ΔR = 0.21Å), which coexist with the IJTP above the M-I transition and has equal probability in the temperature range of colossal magnetoresistance. © 1998 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.81.878
DOI:
10.1103/PhysRevLett.81.878
PACS:
71.38.+i, 64.70.Kb, 71.30.+h, 75.30.Mb
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