The effect of carrier density on magnetic anisotropy of the ferromagnetic semiconductor (Ga, Mn)As

Planar Hall effect (PHE) measurements are used to investigate magnetic anisotropy in two (Ga, Mn)As samples which differ by the hole concentration, but are otherwise identical. The difference in the hole density is controlled via modulation doping by Be. Angular dependence of PHE measured at 13 K reveals that the uniaxial easy axis in the sample with a lower hole concentration lies along the [110] direction, and along [1̄10] in the sample with higher doping. This difference in the orientation of uniaxial easy axes in the two samples demonstrates that the magnetization of GaMnAs can be manipulated just by varying the carrier density.