Annealing-induced transition from a $(311)A$-oriented $Ga0.98Mn0.02As$ alloy to a $GaMnAs/MnAs$ hybrid structure studied by angle-dependent magnetotransport

The angle-dependent behavior of the magneto-resistance of a series of low-temperature molecular beam epitaxy grown $Ga0.98Mn0.02As$ samples on $(311)A$-GaAs-substrates is studied. The samples are annealed at different temperatures in a range from $300°C$ to $500°C$⁠, which leads to a redistribution of the manganese in the sample and finally to the formation of MnAs clusters. As a consequence, the angle-dependence of the magneto-resistance changes with increasing annealing temperature and vanishes finally at an annealing temperature of $400°C$⁠. The observed anisotropy of the magneto-resistance can be correlated with the magnetic anisotropy of the magnetization. The parameters describing this magnetic anisotropy and their changes due to annealing are extracted from the experimental magneto-resistance data by a fitting procedure. The magnetocrystalline anisotropy of the samples can be described by the sum of cubic and uniaxial contributions. The former are not affected by the annealing whereas the latter change considerably.