Establishing micromagnetic parameters of ferromagnetic semiconductor (Ga,Mn)As

TL;DR

This study precisely characterizes the micromagnetic parameters of (Ga,Mn)As, a key ferromagnetic semiconductor, by optimized synthesis and magneto-optical measurements, establishing its suitability for spintronics applications.

Contribution

It provides a systematic and optimized methodology to determine fundamental micromagnetic parameters of (Ga,Mn)As across various doping levels.

Findings

Magnetization, carrier density, and Curie temperature increase with doping.

Damping constant ranges from ~0.1 to 0.01, indicating controlled magnetic damping.

Spin stiffness is approximately 2-3 meVnm^2.

Abstract

(Ga,Mn)As is at the forefront of research exploring the synergy of magnetism with the physics and technology of semiconductors, and has led to discoveries of new spin-dependent phenomena and functionalities applicable to a wide range of material systems. Its recognition and utility as an ideal model material for spintronics research has been undermined by the large scatter in reported semiconducting doping trends and micromagnetic parameters. In this paper we establish these basic material characteristics by individually optimizing the highly non-equilibrium synthesis for each Mn-doping level and by simultaneously determining all micromagnetic parameters from one set of magneto-optical pump-and-probe measurements. Our (Ga,Mn)As thin-film epilayers, spannig the wide range of accessible dopings, have sharp thermodynamic Curie point singularities typical of uniform magnetic systems. The materials show systematic trends of increasing magnetization, carrier density, and Curie temperature (reaching 188 K) with increasing doping, and monotonous doping dependence of the Gilbert damping constant of ~0.1-0.01 and the spin stiffness of ~2-3 meVnm^2. These results render (Ga,Mn)As well controlled degenerate semiconductor with basic magnetic characteristics comparable to common band ferromagnets.