Galvanomagnetic properties and magnetic domain structure of epitaxial MnAs films on GaAs(001)

Epitaxial MnAs films on GaAs(001) in the thickness range 20–200 nm were studied. Using ordinary and extraordinary Hall effect data to determine the field required for perpendicular saturation and saturation magnetizations reported elsewhere, we determined the shape anisotropy constant in the basal plane of the hexagonal structure to be 3.7(0.6)×105 erg/cm3 and the surface anisotropy constant to be −1.3(0.4) erg/cm2. The negative sign indicates thin enough films will be perpendicularly magnetized. By magnetic force microscopy of a 100 nm film we found stripe domains with 180° Bloch walls, thereby avoiding the hard c axis. The widths of the domains and the walls are 4.0(0.3) μm and 95(6) nm, respectively. In magnetoresistance, we observed behavior similar to other ferromagnets, namely peaks centered around the positive and negative coercive fields, and at fields beyond the coercive field a linear dependence on magnetic field. The electrical resistance showed rapid increase with temperature beginning about 5...