Magnetic anisotropy of GaMnAs film and its application in multi-valued memory devices

The magnetic anisotropy of GaMnAs ferromagnetic semiconductor film was investigated by magneto-transport measurements. Values of cubic and uniaxial anisotropies were obtained by analyzing the angular dependences of Hall effects based on magnetic free energy. The presence of strong cubic anisotropy gave four magnetic easy axes in the film's plane, resulting in two-step switching behavior in field scans of the planar Hall effect. Asymmetric loops containing four resistance plateaus were observed in minor scans of the planar Hall effect owing to the formation of stable multi-domain structures during magnetization reversal. Four-valued memory function based on the four observed Hall resistance states was demonstrated by using appropriate sequences of magnetic field pulses.