Magnetic field-induced entropy change in phase-separated manganites

Magnetic field-induced entropy change has been experimentally studied for phase-separated manganites Eu0.55Sr0.45MnO3 and La0.27Nd0.40Ca0.33 MnO3. The entropy derived from the measured heat capacity exhibits a significant decrease under applied field in a broad temperature range below Curie temperature, and the maximum change is similar to 8 J/kg K for Eu0.55Sr0.45MnO3 and is similar to 4.2 J/kg K for La0.27Nd0.40Ca0.33MnO3 for a field change of 0-5 T. In comparison with the calorimetric technique, Maxwell relation fails to give a proper description for the entropy change. It underestimates the entropy reduction in the low temperature range and even anticipates an entropy increase for Eu0.55Sr0.45MnO3. Failures of the Maxwell relation could be ascribed to the coexistence of two phases in the compound and to the variation of the proportion of each phase with applied field. (c) 2006 American Institute of Physics.