Magnetic and microstructural properties type-B MnAs grains grown on GaAs substrate

We grew grains of type-B ferromagnetic MnAs films on undoped GaAs (001) substrates and investigated the magnetic and structural properties of MnAs films grown by molecular beam epitaxy (MBE) at different thickness (10-250 nm). The type-B MnAs grains with different size and eccentricity are grown by controling of growth condition with fast growth rate, optimization of beam equivalent pressure (BEP) ratio and thickness. The size and eccentricity of MnAs grains are increased with increasing thickness. The values of coercive field (Hc) are increased from 240 Oe at 10 nm to 630 Oe at 90 nm and then decreased from 618 Oe at 180 nm to 177 Oe at 250 nm. The in-plane magnetic anisotropy with increasing of thickness is decreased due to decrease in the magnetic anisotropy, induced by an increase in eccentricity of the MnAs grains. Consequently, we can control the magnetic properties of type-B MnAs thin films by controlling of grain size and morphology.