# Magnetoelectric effect in band insulator-ferromagnet heterostructures

## TL;DR

This paper theoretically investigates a disorder-immune magnetoelectric effect in band insulator-ferromagnet heterostructures, revealing how electric fields can induce magnetization with potential applications in spintronics.

## Contribution

It introduces a novel mechanism for magnetoelectric effects based on virtual interband transitions, distinct from metallic effects like Edelstein, and explores its frequency-dependent behavior.

## Key findings

- Magnetoelectric effect varies with magnetic moment orientation.
- Optical frequencies can significantly enhance the effect.
- Estimated effect magnitude in hybrid halide perovskites is promising.

## Abstract

We theoretically study magnetoelectric effects in a heterostructure of a generic band insulator and a ferromagnet. In contrast to the kinetic magnetoelectric effect in metals, referred to as the Edelstein effect or the inverse spin galvanic effect, our mechanism relies on virtual interband transitions between the valence and conduction bands and therefore immune to disorder or impurity scattering. By calculating electric field-induced magnetization by the linear response theory, we reveal that the magnetoelectric effect shows up without specific parameter choices. The magnetoelectric effect qualitatively varies by changing the direction of the magnetic moment in the ferromagnet: the response is diagonal for the out-of-plane moment, whereas it is off-diagonal for the inplane moment. We also find out that in optical frequencies, the magnetoelectric signal can be drastically enhanced via interband resonant excitations. Finally, we estimate the magnitude of the magnetoelectric effect for a hybrid halide perovskite semiconductor as an example of the band insulator and compare it with other magnetoelectric materials. We underscore that our mechanism is quite general and widely expectable, only requiring the Rashba spin-orbit coupling and exchange coupling. Our result could potentially offer a promising method of Joule heating-free electric manipulation of magnetic moments in spintronic devices.