Ga1−xMnxAs/piezoelectric actuator hybrids: A model system for magnetoelastic magnetization manipulation

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. As the magnetic anisotropy in GaMnAs substantially changes as a function of temperature $T$, the ratio of the magnetoelastic and the magnetocrystalline anistropies can be tuned from approximately 1/4 to 4. Thus, GaMnAs/piezoelectric actuator hybrids are an ideal model system for the investigation of different piezoelastic magnetization control regimes. At $T=5\text{ }\text{K}$ the magnetoelastic term is a minor contribution to the magnetic anisotropy. Nevertheless, we show that the switching fields of $\ensuremath{\rho}({\ensuremath{\mu}}_{0}H)$ loops are shifted as a function of ${V}_{p}$ at this temperature. At 50 K---where the magnetoelastic term dominates the magnetic anisotropy---we are able to tune the magnetization orientation by about $70\ifmmode^\circ\else\textdegree\fi{}$ solely by means of the electrical voltage ${V}_{p}$ applied. Furthermore, we derive the magnetostrictive constant ${\ensuremath{\lambda}}_{111}$ 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 $T=40\text{ }\text{K}$, which constitutes the basic principle of a nonvolatile memory element.