Ferromagnetic resonance study of free hole contribution to magnetization and magnetic anisotropy in modulation-doped Ga$_{1 - x}$Mn$_{x}$As/Ga$_{1 - y}$Al$_{y}$As:Be

TL;DR

This study uses ferromagnetic resonance to analyze how free holes influence magnetization and magnetic anisotropy in modulation-doped GaMnAs/GaAlAs heterostructures, revealing doping-dependent changes in anisotropy fields and effective g-factor.

Contribution

It provides direct measurements of magnetic anisotropy fields and the free hole contribution to magnetization in doped GaMnAs, highlighting doping effects on magnetic properties.

Findings

Uniaxial anisotropy field increases with doping.

Effective g-factor is strongly affected by doping.

Free hole magnetization contribution is quantified.

Abstract

Ferromagnetic resonance (FMR) is used to study magnetic anisotropy of GaMnAs in a series of Ga$_{1 - x}$Mn$_{x}$As/Ga$_{1 - y}$Al$_{y}$As heterostructures modulation-doped by Be. The FMR experiments provide a direct measure of cubic and uniaxial magnetic anisotropy fields, and their dependence on the doping level. It is found that the increase in doping -- in addition to rising the Curie temperature of the Ga$_{1 - x}$Mn$_{x}$As layers -- also leads to a very significant increase of their uniaxial anisotropy field. The FMR measurements further show that the effective $g$-factor of Ga$_{1 - x}$Mn$_{x}$As is also strongly affected by the doping. This in turn provides a direct measure of the contribution from the free hole magnetization to the magnetization of Ga$_{1 - x}$Mn$_{x}$As system as a whole.