Regensburg 2016 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 29: Topical session: Caloric effects in ferroic materials III - Electrocalorics
MM 29.3: Vortrag
Mittwoch, 9. März 2016, 10:45–11:00, H39
Electric field direction dependence of the electrocaloric effect in BaTiO3: a first principles effective Hamiltonian approach — •Madhura Marathe1, Damian Renggli1, Anna Grünebohm2, and Claude Ederer1 — 1Materials Theory, ETH Zürich, Switzerland — 2Faculty of Physics and CENIDE, University of Duisburg-Essen, Germany
The electrocaloric (EC) effect describes heating/cooling of a material on adiabatically applying/removing an external electric field. Currently, extensive work in this area is motivated by its huge potential for solid-state cooling devices.
We have performed molecular dynamics simulations for a first principles-based effective Hamiltonian to study the EC effect. In bulk BaTiO3, there are three phase transitions – one paraelectric (PE) to ferroelectric (FE) and two FE to FE – with different polarization direction in each FE phase. The EC effect has been mainly studied at the PE to FE phase transition. We calculate the EC temperature change Δ T also at the two FE-FE transitions observed in the bulk. In particular, we consider the effect of the direction of the applied field on Δ T at each transition. The largest Δ T is observed at the PE-FE transition, however a smaller, but finite effect is also observed at the other two transitions. This is very interesting for applications because one of the FE-FE transitions occurs near room temperature. Further, we observe an “inverse” EC effect, that is, heating on field removal, when the applied field is not along the polarization direction of the ferroelectric phase of the system.