Multicaloric effect in multiferroic EuTiO₃ thin films

A modified Landau–Ginzburg–Devonshire phenomenological thermodynamic theory is used to investigate both the influence of biaxial compressive misfit strain between film and the substrate and the mechanical stress on the multicaloric response in epitaxial EuTiO₃ thin films. The complicated compressive misfit strain–temperature phase diagram in the low-temperature region is developed. The excellent electrocaloric and elastocaloric effect can be achieved: \( \Delta T(T_{\text{C}} ) = 3.66\,{\text{K}} \), while \( \Delta E = 100\,{\text{kV/cm}},u_{\text{m}} = - \,4.0{\%} \); \( \Delta T \) = 5.31 K at 200 MPa. Besides, the maximal adiabatic temperature change \( \Delta T(T_{\text{M}} ) = 17.3\,{\text{K}} \), while \( \Delta H = 5\,{\text{T}},u_{\text{m}} = - \,4.0{\%} \), in the low-temperature region, which is comparable with the experimental result. Both the misfit strain and the external mechanical stress play a crucial role in the multicaloric response in EuTiO₃ films. It may open more opportunities for practical application in refrigeration devices, especially for low-temperature solid-state multicaloric cooling.