We investigated the thermal evolution of the magnetic properties of MnAs epitaxial films grown on GaAs(001) during the coexistence of hexagonal/orthorhombic phases using polarized resonant (magnetic) soft x-ray scattering and magnetic force microscopy. The results of the diffuse satellite x-ray peaks were compared to those obtained by magnetic force microscopy and suggest a reorientation of ferromagnetic terraces as temperature rises. By measuring hysteresis loops at these peaks we show that this reorientation is common to all ferromagnetic terraces. The reorientation is explained by a simple model based on the shape anisotropy energy. Demagnetizing factors were calculated for different configurations suggested by the magnetic images. We noted that the magnetic moments flip from an in-plane monodomain orientation at lower temperatures to a three-domain out-of-plane configuration at higher temperatures. The transition was observed when the ferromagnetic stripe width L is equal to 2.9 times the film thickness d. This is in good agreement with the expected theoretical value of L=2.6d.
Bibliographical noteFunding Information:
The authors thank M. Kästner and C. Herrmann (Paul Drude Institute) for sample growth. C. Grazioli and S. Rinaldi (Circular Polarisation Beamline) and the personnel of Sincrotrone Trieste helped the authors during the x-ray experiments. This research was supported by CNPq, FAPESP, FAPEMIG, and a bilateral CNPq-CNRS agreement.