Thermodynamics of multicaloric effects in multiferroics

We provide a general thermodynamic framework to study multicaloric effects in multiferroic materials. This is applied to the case of a magnetoelectric multiferroic such as BiFeO3, which is described by means of a Landau free energy with a biquadratic coupling between polarization and magnetization. We obtain a phase diagram, the isothermal entropy change and the adiabatic temperature change across different continuous and first-order phase transitions as the applied electric and magnetic fields are varied. The multicaloric effects are suitably decomposed into the corresponding electrocaloric and magnetocaloric contributions.