Electrocaloric effect in BaTiO3 thin films.

The modified transverse Ising model taking into account the four-spin exchange interaction and quantum fluctuation, as well as the mechanical constraint of the substrate, is constructed and applied to investigate the electrocaloric effect (ECE) in BaTiO3 thin films. It is found that the temperature dependence of ECE strongly depends on both the four-spin exchange interaction and quantum fluctuation. Most importantly, we achieve the adiabatic temperature change ΔT=11.78 K at Tm=490 K, which can be comparable with that observed experimentally in PbZr0.95Ti0.05O3 thin films and ferroelectric polymers. Furthermore, the internal stresses resulting from the clamping effect of the substrate play a crucial role in the ECE of ferroelectric films. Control of the misfit stress by appropriate choice of substrate provides an effective means to improve the adiabatic temperature change for use in cooling or thermodielectric power conversion devices. [ABSTRACT FROM AUTHOR]