Damping and magnetic anisotropy of ferromagnetic GaMnAs thin films

TL;DR

This study investigates the magnetic damping and anisotropy in GaMnAs thin films under stress using ferromagnetic resonance spectroscopy, revealing anisotropic damping behavior and its dependence on temperature and substrate-induced strain.

Contribution

It provides the first detailed analysis of the Gilbert damping factor and magnetic anisotropy in annealed GaMnAs films under different stress conditions using FMR spectroscopy.

Findings

Minimum damping factor of 0.003 in compressively stressed layer at 4K

Damping factor varies with magnetic field orientation and temperature

Inhomogeneous linewidths differ significantly between substrates

Abstract

The magnetic properties of annealed, epitaxial Ga0.93Mn0.07As layers under tensile and compressive stress have been investigated by X-band (9GHz) and Q-band (35GHz) ferromagnetic resonance (FMR) spectroscopy. From the analysis of the linewidths of the uniform mode spectra the FMR Gilbert damping factor "alpha" has been determined. At T=4K we obtain a minimum damping factor of "alpha" = 0.003 for the compressively stressed layer. Its value is not isotropic. It has a minimum value for the easy axes orientations of the magnetic field and increases with the measuring temperature. Its average value is for both type of films of the order of 0.01 in spite of strong differences in the inhomogeneous linewidth which vary between 20 Oe and 600 Oe for the layers grown on GaAs and GaInAs substrates respectively.