Lattice dynamics in colossal magnetoresistance manganites

Abstract

Based on the Hamiltonian of small polarons with strong electron-phonon interaction, we have investigated anomalous behaviors of the sound velocity in colossal magnetoresistance (CMR) manganese oxides. In the low-doping metallic regime, the sound velocity has been found to be hardened below the ferromagnetic transition temperature T-c due to T-dependent electron screening coming from the double exchange (DE) interaction. On the contrary, in the high-doping regime (x > 0.5), the charge ordering (CO) interaction rather than the DE induces the hardening of the sound velocity by the ordering of localized polarons around the CO transition temperature T-co. (C) 1998 Elsevier Science B.V. All rights reserved.