Planar Hall effect in a single GaMnAs film grown on Si substrate

We carried out systematic planar Hall effect (PHE) measurements on a layer of GaMnAs grown on a Si substrate. The field scans of the planar Hall resistance (PHR) data obtained at 4 K show a transition behavior, which is similar to the magnetization reorientation process often observed in GaMnAs film grown on a GaAs substrate that has both anisotropies along the <100> and the <110> directions. The dependence of the PHR on the applied field direction revealed the presence of an asymmetry between the <100> and the <110> directions in the magnetic energy of the film. The directions of the magnetic easy axes determined by the PHR value at zero field were about 91 away from the <110> directions. The PHR further shows the absence of the difference in the anisotropy between the <110< directions, indicating no preference of magnetic anisotropy for either the [110] or the [1̄10]direction in the GaMnAs grown on a Si substrate.