Electrocaloric effect in BaTiO$_3$: a first-principles-based study on the effect of misfit strain

TL;DR

This study uses first-principles-based simulations to explore how substrate-induced misfit strain influences the electrocaloric effect in BaTiO$_3$ thin films, revealing strain-induced enhancements and shifts in temperature response.

Contribution

It provides a detailed analysis of the impact of misfit strain on the electrocaloric effect in BaTiO$_3$ using molecular dynamics and effective Hamiltonian methods, highlighting strain as a tuning parameter.

Findings

Substrate clamping reduces maximum electrocaloric temperature change.

Compressive misfit strain significantly increases $t$ and shifts peak effect to higher temperatures.

Small compressive strain of -0.75% surpasses bulk electrocaloric response.

Abstract

We address the question of how the electrocaloric effect in epitaxial thin films of the prototypical ferroelectric BaTiO$_3$ is affected by the clamping to the substrate and by substrate-induced misfit strain. We use molecular dynamics simulations and a first-principles-based effective Hamiltonian to calculate the adiabatic temperature change $\Delta T$ under different epitaxial constraints. Our results demonstrate that, consistent with phenomenological theory, clamping by the substrate reduces the maximum $\Delta T$ compared to bulk BaTiO$_3$. On the other hand, compressive misfit-strain leads to a strong increase of $\Delta T$ and shifts the maximum of the electrocaloric effect to higher temperatures. A rather small compressive strain of $-0.75$% is sufficient to obtain a $\Delta T$ that is larger than the corresponding bulk value.