Thickness dependence of magnetic domains of MnAs films

We systematically investigated thickness and magnetization variations of the domain structures of MnAs films on GaAs(0 0 1) using magnetic force microscopy (MFM) at room temperature. The observed thickness range is from 5 to 500 nm. The magnetic domain structures drastically change with increasing thickness because of the existence of the thickness-dependent periodic ridge-groove structure. The domain structures also depend on the magnetization histories. The MnAs films with the thickness of less than 50 nm have no groove structure and the single magnetic domain is realized at the remanent state. In the thickness more than 100 nm, on the other hand, the groove structures of paramagnetic β-MnAs appear. The complex magnetic domain structures of MnAs films result from the paramagnetic groove structures, the uniaxial anisotropy and weak perpendicular anisotropy.