Evolution of the magnetic anisotropy with carrier density in hydrogenatedGa1−xMnxAs

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.