Perpendicular magnetization reversal, magnetic anisotropy, multi-step spin switching, and domain nucleation and expansion in Ga1-xMnxAs films

TL;DR

This study investigates the complex magnetic reversal processes in Ga1-xMnxAs thin films, revealing multi-step spin switching, domain nucleation, and anisotropy effects through combined resonance and transport measurements.

Contribution

It introduces a comprehensive model explaining multi-step spin switching and double hysteresis loops in Ga1-xMnxAs, linking anisotropy and domain processes with experimental data.

Findings

Identification of the role of cubic and uniaxial anisotropy in reversal

Observation of double hysteresis loops in low Mn concentration samples

Development of a model linking domain nucleation to magnetization reversal

Abstract

We present a comprehensive study of the reversal process of perpendicular magnetization in thin layers of the ferromagnetic semiconductor Ga1-xMnxAs. For this investigation we have purposely chosen Ga1-xMnxAs with a low Mn concentration (x ~ 0.02), since in such specimens contributions of cubic and uniaxial anisotropy parameters are comparable, allowing us to identify the role of both types of anisotropy in the magnetic reversal process. As a first step we have systematically mapped out the angular dependence of ferromagnetic resonance in thin Ga1-xMnxAs layers, which is a highly effective tool for obtaining the magnetic anisotropy parameters of the material. The process of perpendicular magnetization reversal was then studied by magneto-transport (i.e., Hall effect and planar Hall effect measurements). These measurements enable us to observe coherent spin rotation and non-coherent spin switching between the (100) and (010) planes. A model is proposed to explain the observed multi-step spin switching. The agreement of the model with experiment indicates that it can be reliably used for determining magnetic anisotropy parameters from magneto-transport data. An interesting characteristic of perpendicular magnetization reversal in Ga1-xMnxAs with low x is the appearance of a double hysteresis loops in the magnetization data. This double-loop behavior can be understood by generalizing the proposed model to include the processes of domain nucleation and expansion.