Magnetic domain structure and domain wall analysis of ferromagnetic MnAs nanodisks selectively-grown on Si (111) substrates for spintronic applications

Abstract

We report on the experimental and analytic results on magnetic domain and domain wall structures of MnAs nanodisks on AlGaAs nanopillar buffers selectively grown on Si (111) substrates partially covered with dielectric SiO2 thin film mask patterns using selective-area metal-organic vapor phase epitaxy. The results on the size dependence of the magnetic domain structure in MnAs nanodisks investigated by magnetic force microscopy show that a single domain is predominant in the MnAs nanodisks with an area of approximately 3 × 104 nm2 or less. It is also indicated that in the nanodisks with an area of approximately 6 × 104 nm2 or more, multiple domains, in particular, two magnetic domain structures with a 180° domain wall, are predominant. In addition, in the case of nanodisks with multiple domains, not only Néel walls but also Bloch walls are possibly formed, according to the detailed analyses of the magnetic force microscope images obtained. These results suggest that the magnetic domains and domain walls can be tuned by the control of the MnAs nanodisk size making them interesting nanostructures for spintronic applications.