Magnetic Anisotropy, Spin Pinning and Exchange Constants of (Ga,Mn)As films

TL;DR

This study investigates the magnetic anisotropy, spin pinning, and exchange constants in GaMnAs films, revealing how Mn concentration and growth conditions influence magnetic properties and spin wave behaviors.

Contribution

It provides detailed analysis of spin wave modes and establishes exchange stiffness constants, linking magnetic anisotropy to Mn concentration and sample growth conditions.

Findings

Magnetic anisotropy depends on Mn concentration and growth conditions.

Spin wave resonance modes are well-resolved and consistent with the Portis model.

Exchange stiffness constants are quantitatively determined for GaMnAs films.

Abstract

We present a detailed investigation of exchange-dominated nonpropagating spin-wave modes in a series of 100 nm Ga$_{1 - x}$Mn$_{x}$As films with Mn concentrations $x$ ranging from 0.02 to 0.08. The angular and Mn concentration dependences of spin wave resonance modes have been studied for both as-grown and annealed samples. Our results indicate that the magnetic anisotropy terms of Ga$_{1 - x}$Mn$_{x}$As depend on the Mn concentration $x$, but are also strongly affected by sample growth conditions; moreover, the magnetic anisotropy of Ga$_{1 - x}$Mn$_{x}$As films is found to be clearly linked to the Curie temperature. The spin wave resonance spectra consist of a series of well resolved standing spin-wave modes. The observed mode patterns are consistent with the Portis volume-inhomogeneity model, in which a spatially nonuniform anisotropy field acts on the Mn spins. The analysis of these exchange-dominated spin wave modes, including their angular dependences, allows us to establish the exchange stiffness constants for Ga$_{1 - x}$Mn$_{x}$As films.