Structural phase transition in Pr0.55Ca0.45MnO3 and Nd0.5Sr0.5MnO3 associated with charge ordering transition

We have investigated the microstructure formed in association with charge ordering transition in perovskite manganites Pr0.55Ca0.45MnO3 (PCMO) and Nd0.5Sr0.5MnO3 (NSMO). By optical microscope observation, surface relief is observed below the charge ordering transition temperature T-CO (CO represents charge ordering phase) for both of the specimens. Two surface trace analysis and Lane back reflection technique has been revealed that microstructures are composed of twinned variants which have {01}(CO) and {112}(CO) twinning planes for PCMO and NSMO, respectively. We have also investigated the magnetic field dependence of T-CO by magnetization measurements and found that the T-CO decreases parabolically with increasing magnetic field. This magnetic field dependence of T-CO in PCMO is in good agreement with the calculated one based on the Clausius-Clapeyron equation. (c) 2007 Elsevier B.V. All rights reserved.