Dependence of Magnetic Anisotropies and Critical Temperatures on the Hole Concentration in Ferromagnetic GaMnAs Thin Films

The magnetic anisotropy constants and critical temperatures of a series of epitaxial GaMnAs thin films on GaAs with 7% Mn concentration in which the free hole concentration is progressively modified by hydrogen passivation is investigated by ferromagnetic resonance (FMR) spectroscopy. Ferromagnetism (FM) is lost for fully passivated films. In the FM films with the lowest hole concentration, the easy axis of magnetization is oriented perpendicular to the film plane and switches to in-plane [100] for higher hole concentrations. Temperature-dependent switching is equally observed. The numerical values of the uniaxial and cubic anisotropy constants are determined as a function of temperature and T
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