Ferromagnetic resonance studies of (Ga,Mn)As with MnAs clusters

We report on the temperature and angular dependence of ferromagnetic resonances originating from MnAs clusters embedded in a Ga1-xMnxAs host matrix with x approximate to 0.1%. The MnAs Clusters were formed in situ during metal-organic vapour-phase epitaxy of (Ga,Mn)As on (0 0 1) and (1 1 1) GaAs substrates. The samples exhibit Curie temperatures of T-C approximate to 330 K which are above room temperature and about 10 K higher than in bulk MnAs and MnAs thin films. From. the angular dependence of the ferromagnetic resonances it can be concluded that the crystallographic orientation of the clusters with respect to the matrix is the same for both substrates, i.e. MnAs [0 0 0 1] \\ GaAs [1 1 1]. We observe only one orientation of the clusters for (1 1 1) and four different orientations for (0 0 1) substrates. The easy axis of magnetisation is perpendicular to the c-axis of the clusters. Only in the case of the (1 1 1) sample, all magnetic moments of the Clusters can align parallel to an applied in-plane magnetic field at small fields. (C) 2002 Elsevier Science B.V. All rights reserved.