Electrostatically Controlled Magnetization Rotation in Ferromagnet-Topological Insulator Planar Structures

TL;DR

This paper proposes a method to electrically control 90-degree magnetization rotation in topological insulator and ferromagnetic insulator structures, enabling low-energy nonvolatile memory applications.

Contribution

It introduces a novel approach to manipulate magnetization orientation via electrostatic tuning of surface electron density in TI-FMI hybrid structures.

Findings

Magnetization can be rotated from in-plane to out-of-plane within 1.7-2.7 ns.

Electrical control of uniaxial magnetic anisotropy is demonstrated.

Potential for low-energy nonvolatile memory devices is shown.

Abstract

An approach to the electrostatic control of $90^{\circ}$ magnetization rotation in the hybrid structures composed of topological insulators (TIs) and adjacent ferromagnetic insulators (FMI) is proposed and studied. The concept is based on TI electron energy variation with in-plane to put-of plane FMI magnetization turn. The calculations explicitly expose the effect of free energy variability in the form of the electrically controlled uniaxial magnetic anisotropy, which depends on proximate exchange interaction and TI surface electron density. Combining with inherent anisotropy, the magnetization rotation from in-plane to out-of-plane direction is shown to be realizable for 1.7~2.7 ns under the electrical variation of TI chemical potential in the range $\pm$ 100 meV around Dirac point. When bias is withdrawn a small signal current can target the out-of-plane magnetization instable state to the desirable direction of in-plane easy axis, thus the structure can lay the foundation for low energy nonvolatile memory prototype.