Temperature evolution of self-organized stripe domains in ultrathin Fe films on MnAs/GaAs(001)

A detailed investigation of the magnetic behavior of an ultrathin Fe film epitaxially grown onto MnAs/GaAs(001) is performed by means of both ferromagnetic resonance (FMR) and magneto-optical Kerr-effect (MOKE) experiments, as a function of temperature. When the MnAs underlayer is fully in the hexagonal ferromagnetic alpha phase (at low temperature) or in the orthorhombic non magnetic beta one (at high temperature), the magnetic behavior of the Fe film is found to be nearly the same and independent of the substrate. In contrast, at intermediate temperatures, when the MnAs underlayer presents a self-organized phase consisting of alpha-MnAs and beta-MnAs striped domains, the Fe film is strongly influenced by the dipolar (stray) fields arising from the substrate. As a consequence, the Fe film breaks in two distinct families of striped domains. Theoretical analysis of the FMR data in the whole investigated temperature range is performed using a free-energy density model which provides an accurate determination of the temperature-dependent magnetic parameters. Furthermore, the mechanism of magnetization reversal has been analyzed as a function of temperature by MOKE. The evolution of the magnetization curves can be satisfactory interpreted starting from the main achievements of the theoretical analysis of FMR data.