Piezo-control of magnetic anisotropy in GaMnAs: Reversible manipulation of magnetization orientation and irreversible magnetization switching

TL;DR

This study demonstrates reversible and irreversible control of magnetic anisotropy and magnetization orientation in GaMnAs using piezoelectric stress, enabling voltage-driven magnetic switching for potential nonvolatile memory applications.

Contribution

It introduces a method to electrically manipulate magnetic anisotropy and magnetization orientation in GaMnAs via piezoelectric stress, including irreversible switching for memory devices.

Findings

Magnetic easy axis can be inverted by applied voltage.

Magnetization orientation can be tuned by about 70 degrees with voltage.

Piezo-voltage induced irreversible switching demonstrates nonvolatile memory potential.

Abstract

We have investigated the magnetic properties of a piezoelectric actuator/ferromagnetic semiconductor hybrid structure. Using a GaMnAs epilayer as the ferromagnetic semiconductor and applying the piezo-stress along its [110] direction, we quantify the magnetic anisotropy as a function of the voltage V_p applied to the piezoelectric actuator using anisotropic magnetoresistance techniques. We find that the easy axis of the strain-induced uniaxial magnetic anisotropy contribution can be inverted from the [110] to the [1-10] direction via the application of appropriate voltages V_p. At T=5K the magnetoelastic term is a minor contribution to the magnetic anisotropy. Nevertheless, we show that the switching fields of rho(H) loops are shifted as a function of V_p at this temperature. At 50K - where the magnetoelastic term dominates the magnetic anisotropy - we are able to tune the magnetization orientation by about 70 degree solely by means of the electrical voltage V_p applied. Furthermore, we derive the magnetostrictive constant lambda_111 as a function of temperature and find values consistent with earlier results. We argue that the piezo-voltage control of magnetization orientation is directly transferable to other ferromagnetic/piezoelectric hybrid structures, paving the way to innovative multifunctional device concepts. As an example, we demonstrate piezo-voltage induced irreversible magnetization switching at T=40K, which constitutes the basic principle of a nonvolatile memory element.