Electrocaloric effects in ferroelectrics and multiferroics from first principles

The electrocaloric (EC) effect characterizes the change in temperature or entropy of a material under the application of an external electric field. Ferroelectric and multiferroic materials have attracted considerable interest due to their potential for efficient solid-state refrigeration in a broad range of applications. In this review, we present recent applications of first-principles-based effective Hamiltonian, second-principles method, and spin Heisenberg model to study the EC effect in ferroelectrics, relaxor ferroelectrics, and multiferroic materials. Specifically, these methods are used to investigate the EC effect in perovskite ferroelectrics Pb(Zr_0.4Ti_0.6)O₃, (Ba_0.5Sr_0.5)TiO₃, PbTiO₃, BaTiO₃ and PbTiO₃/SrTiO₃ superlattices, relaxor ferroelectrics Ba(Zr, Ti)O₃ and Pb(Mg, Nb)O₃, as well as rare-earth-substituted BiFeO₃, BiCoO₃ and BiFeO₃ multiferroics, and Nd-substituted BiFeO₃ antiferroelectric solid solutions. Large electrocaloric responses are predicted in some of these compounds. In addition, we review the phenomenological models that can be used to analyze and understand these EC effect results.