Evolution of the magnetic anisotropy with carrier density in hydrogenated (Ga,Mn)As

TL;DR

This study investigates how magnetic anisotropy in hydrogenated (Ga,Mn)As thin films evolves with carrier density, revealing easy axis reversals and confirming mean-field theory predictions through comprehensive magnetometry and transport measurements.

Contribution

It demonstrates controlled modulation of hole density via hydrogenation and correlates it with magnetic anisotropy changes, providing new insights into magnetic behavior in (Ga,Mn)As.

Findings

Magnetic easy axes flip from out-of-plane to in-plane with increasing hole density.

Magnetocrystalline anisotropy constants vary systematically with temperature.

Results align with mean-field theory predictions of easy axis reversals.

Abstract

The magnetic properties of (Ga,Mn)As thin films depend on both the Mn doping level and the carrier concentration. Using a post growth hydrogenation process we show that it is possible to decrease the hole density from 1.1021 cm-3 to <1017 cm-3 while maintaining the manganese concentration constant. For such a series of films we have investigated the variation of the magnetization, the easy and hard axes of magnetization, the critical temperatures, the coercive fields and the magnetocrystalline anisotropy constants as a function of temperature using magnetometry, ferromagnetic resonance and magneto-transport measurements. In particular, we evidenced that magnetic easy axes flipped from out-of-plane [001] to in-plane [100] axis, followed by the <110> axes, with increasing hole density and temperature. Our study concluded on a general agreement with mean-field theory predictions of the expected easy axis reversals, and of the weight of uniaxial and cubic anisotropies in this material.