Large positive entropy change in several charge-ordering perovskites

The Nd0.5Sr0.5Mn1-xCuxO3 (x = 0.00; 0.02; 0.10) and Nd0.25Pr0.25Sr0.5MnO3 perovskites have been prepared by solid reaction technology. The manganites are of single phase with orthorhombic structure. The FC and ZFC measurements show an evident existence of charge-ordering effect at low temperatures. At the charge-ordering temperature the magnetic entropy change, DeltaS, is positive and the \DeltaS(max)\ is larger than that determined at ferromagnetic-paramagnetic phase transition temperature. (C) 2003 Elsevier B.V. All rights reserved.