Electrocaloric effects in multiferroics

TL;DR

This paper investigates the electrocaloric effects in multiferroic materials, specifically rare-earth substituted BiFeO3, using atomistic simulations and a phenomenological model to understand and optimize their electrocaloric response.

Contribution

It introduces a combined atomistic and phenomenological approach to analyze and interpret electrocaloric effects in multiferroics, highlighting the roles of electric and magnetic couplings.

Findings

EC coefficient peaks at the ferroelectric Curie temperature.

EC response exhibits a peak at the Néel temperature due to magnetoelectric coupling.

The model helps in optimizing electrocaloric effects in multiferroics.

Abstract

An atomistic effective Hamiltonian is used to compute electrocaloric (EC) effects in rare-earth substituted BiFeO$_{3}$ multiferroics. A phenomenological model is then developed to interpret these computations, with this model indicating that the EC coefficient is the sum of two terms, that involve electric quantities (polarization, dielectric response), the antiferromagnetic order parameter, and the coupling between polarization and antiferromagnetic order. The first one depends on the polarization and dielectric susceptibility, has the analytical form previously demonstrated for ferroelectrics, and is thus enhanced at the ferroelectric Curie temperature. The second one explicitly involves the dielectric response, the magnetic order parameter and a specific magnetoelectric coupling, and generates a peak of the EC response at the N\'eel temperature. These atomistic results and phenomenological model may be put in use to optimize EC coefficients.