Giant caloric effects enhanced by the helix polarization at the 180° domain wall in tetragonal BaTiO₃

The electrocaloric and elastocaloric properties at the 180° domain wall in the tetragonal BaTiO₃ are studied using the Landau-Ginzburg-Devonshire model as a function of the domain wall rotation angle α. The Ising-Bloch character is predicted at the 180° domain wall in tetragonal BaTiO₃ under the flexoelectric effect. The electric field-induced adiabatic temperature change (ΔT _E) which is induced by the Bloch-type polarization component depends on α, and a giant positive ΔT _E appears at α  =  (π  +  12n)/24 where n is an integer. The asymmetry of ΔT _E is found around the Bloch-type domain wall. The Bloch-type polarization component has a little contribution to the stress-induced adiabatic temperature change. This calculation indicates a contribution of helix polarization at the domain wall on the caloric effects (CEs) in the ferroelectric materials.