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Abstract

The electrocaloric effect (ECE) is the adiabatic temperature change that occurs in polar materials in a varying electric field. Maximal responses are observed near the diffusionless structural phase transitions of ferroelectrics. Unlike its magnetic counterpart, the magnetocaloric effect, it is strongly tunable by the field directions. [1,2,3] However, research so far focused mainly on the high symmetric field directions, i.e. <100>, <110>, and <111>, and the general behavior of the ECE in low symmetric field direction is unclear. In this work, we study the field-direction-dependency of the ECE of the prototypical ferroelectric material BaTiO3, using a coarse-grained molecular dynamics simulator[4] based on a first-principles-derived effective Hamiltonian parameterized by DFT calculations. We sample the ECE in all potential field directions over a wide temperature range using the direct method. We find that the maximal responses are in the high symmetric <100> direction. Close to this direction, the phase stability and the ECE are particularly field-direction sensitive. We believe this finding can provide general insights into the anisotropic nature of the ECE not only for single- but also for poly-crystalline ferroelectric perovskites.

References:
[1] A. Grünebohm et al., Energy Technol. 6, 1491-1511 (2018)
[2] H. H. Wu and R. E. Cohen., J. Phys.: Condens. Matter 29, 485704 (2017)
[3] M. Marathe et al., Phys. Rev. B 96, 014102 (2017)
[4] T. Nishimatsu et al., Phys. Rev. B 78, 104104 (2008)