Interplay between ferroic orders at the FeRh/BaTiO$_3$ interfaces

TL;DR

This study uses density functional theory to analyze the atomic structure and electron screening at FeRh/BaTiO$_3$ interfaces, revealing how magnetic states influence ferroelectric stability and enabling electric control of magnetic order.

Contribution

It provides detailed atomic-level insights into the interface, linking magnetic states to screening and ferroelectric stability, advancing understanding of electric-magnetic coupling in heterostructures.

Findings

Different screening capabilities for AFM and FM states of FeRh.

Magnetic order influences ferroelectric stability in thin BaTiO$_3$ films.

Reciprocal control of ferroelectricity and magnetism at the interface.

Abstract

It has been recently demonstrated that the magnetic state of FeRh can be controlled by electric fields in FeRh/BaTiO$_{\text{3}}$ heterostructures [R.O. Cherifi et al. Nature Mater. 13, 345 (2014)]. Voltage-controlled changes in the ferroelastic domain structure of BaTiO$_3$ appeared to drive this effect, with charge accumulation and depletion due to ferroelectricity playing a more elusive role. To make this electric-field control of magnetic order non-volatile, the contribution of ferroelectric field-effect must be further enhanced, which requires understanding the details of the interface between FeRh and BaTiO$_3$. Here we report on the atomic structure and electron screening at this interface through density functional theory simulations. We relate different screening capabilities for the antiferromagnetic and ferromagnetic states of FeRh to different density of states at the Fermi level of corresponding bulk structures. We predict that the stability of the ferroelectric state in adjacent very thin BaTiO$_3$ films will be affected by magnetic order in FeRh. This control of ferroelectricity by magnetism can be viewed as the reciprocal effect of the voltage-controlled magnetic order previously found for this system.