Device Applications of Heterogeneously Integrated Strain-Switched Ferrimagnets/Topological Insulator/Piezoelectric Stacks

TL;DR

This paper explores how strain-modulated ferrimagnets integrated with topological insulators and piezoelectrics can control surface currents, enabling applications like transconductance amplifiers and neuromorphic synapses.

Contribution

It introduces a novel device concept utilizing strain-controlled magnetic anisotropy in ferrimagnets on topological insulators for electronic modulation.

Findings

Strain alters magnetic anisotropy in ferrimagnets.

Interfacial exchange coupling modulates surface currents.

Potential for neuromorphic and amplifier applications.

Abstract

A family of ferrimagnets (CoV2O4, GdCo, TbCo) exhibits out-of-plane magnetic anisotropy when strained compressively and in-plane magnetic anisotropy when strained expansively (or vice versa). If such a ferrimagnetic thin film is placed on top of a topological insulator (TI) thin film and its magnetic anisotropy is modulated with strain, then interfacial exchange coupling between the ferrimagnet (FM) and the underlying TI will modulate the surface current flowing through the latter. If the strain is varied continuously, the current will also vary continuously and if the strain alternates in time, the current will also alternate with the frequency of the strain modulation, as long as the frequency is not so high that the period is smaller than the switching time of the FM. If the strain is generated with a gate voltage by integrating a piezoelectric underneath the FM/TI stack, then that can implement a transconductance amplifier or a synapse for neuromorphic computation.