Effect of the cluster magnetization on the magnetotransport at low temperatures in ordered arrays of MnAs nanoclusters on (111)B GaAs

The angle-dependent behavior of the magnetoresistance of ordered arrays of nanoclusters is studied. The arrays consist of single elongated MnAs nanoclusters, which were deposited on the (111) B GaAs substrate by selective-area metal-organic vapor phase epitaxy, which yields control of the position on the substrate as well as of the shape of the nanoclusters. Ferromagnetic resonance measurements were carried out in order to investigate the magnetic anisotropy of the nanoclusters, which is strongly determined by the cluster shape. Angle-dependent magnetotransport measurements were performed at T = 15 K. The magnetic field was rotated in three different geometries, one parallel and two perpendicular to the sample surface. At low magnetic fields the nanoclusters show nearly no influence on the transport through the matrix. However, at high magnetic fields the magnetization orientation of the nanoclusters affects the transport behavior of the sample due to the influence of the clusters' dipolar field on the electronic states in the matrix. The experimental results obtained can be understood qualitatively by considering not only the transport properties of the GaAs matrix but also an average magnetization of the MnAs nanoclusters, whose orientation is determined by the magnetic anisotropy.