Controlling the cation distribution and electric polarization with epitaxial strain in Aurivillius-phase Bi$_5$FeTi$_3$O$_{15}$

TL;DR

This study demonstrates how epitaxial strain can be used to manipulate cation distribution and electric polarization in Bi$_5$FeTi$_3$O$_{15}$, offering a pathway to control magnetic and electric properties in this layered material.

Contribution

It provides first-principles insights into strain-induced control of cation site preference and polarization in Aurivillius-phase Bi$_5$FeTi$_3$O$_{15}$, a novel approach for tuning functional properties.

Findings

Tensile strain favors Fe$^{3+}$ at inner sites; compressive favors outer sites.

Electric polarization increases with tensile strain and decreases with compressive strain.

Bi$^{3+}$ and Ti$^{4+}$ exhibit strongly anomalous Born effective charges.

Abstract

This work explores the impact of in-plane bi-axial (epitaxial) strain on the cation distribution and electric polarization of the Aurivillius-phase compound Bi$_5$FeTi$_3$O$_{15}$ using first-principles electronic structure calculations. Our calculations indicate that the site preference of the Fe$^{3+}$ cation can be controlled via epitaxial strain. Tensile strain enhances the preference for the inner sites within the perovskite-like layers of the Aurivillius-phase structure, whereas compressive strain favors occupation of the outer sites within the perovskite-layers, i.e., the sites close to the Bi$_2$O$_2$ layer. Controlling the distribution of the magnetic cations offers the possibility to control magnetic order in this magnetically dilute system. Furthermore, the magnitude of the electric polarization is strongly strain-dependent, increasing under tensile strain and decreasing under compressive strain. Analysis of the Born effective charges reveals strongly anomalous charges, both of the Bi$^{3+}$ cations and the Ti$^{4+}$ cations.