Anomalies and synergy in the caloric effects of magnetoelectrics

We determine isothermal entropy changes (ΔS) 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 (∣ΔS_MultiCE∣>∣ΔS_ECE∣+∣ΔS_MCE∣) over a wide temperature range when the difference in temperatures of magnetic and ferroelectric ordering (∣ΔT_C∣=∣T_C^E−T_C^M∣) 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. (paper)