Magnetization reversal and anomalous dependence of the coercive field with temperature in MnAs epilayers grown on GaAs

The magnetic properties of MnAs epilayers have been investigated for two different substrate orientations GaAs(100) and GaAs(111). We have analyzed the magnetization reversal under magnetic field at low temperatures, determining the anisotropy of the films. The results, based on the shape of the magnetization loops, suggest a domain movement mechanism for both types of samples. The temperature dependence of the coercivity of the films has been also examined, displaying a generic anomalous reentrant behavior at T>2000.3em0exK. This feature is independent of the substrate orientation and films thickness and may be associated to the appearance of pinning centers due to the nucleation of the β phase at high temperatures.