Anomalies and synergy in the caloric effects of magnetoelectrics

Abstract

We determine isothermal entropy changes (Delta S) associated with electrocaloric, magnetocaloric, and the corresponding multicaloric effects in a model type-I multiferroic system using Landau-Devonshire thermodynamic analysis. We show that (a) the magnetocaloric effect exhibits an unexpected anomaly at the ferroelectric transition occurring at a high temperature, even in the absence of magnetic ordering, and (b) the synergy between electro- and magnetocaloric effects leads to a significantly enhanced multicaloric effect (vertical bar Delta S-MultiCE vertical bar > vertical bar Delta S-ECE vertical bar + vertical bar Delta S-MCE vertical bar) over a wide temperature range when the difference in temperatures of magnetic and ferroelectric ordering (vertical bar Delta T-C vertical bar = vertical bar T-C(E) - T-C(M)vertical bar) is small. This result originate from the coupled thermal fluctuations of magnetic and electric order parameters. While the former is useful in detecting multiferroic materials from the measurements covering higher temperature transition alone, the latter augurs well for caloric applications of multiferroics.