Tunable quaternary states in ferromagnetic semiconductor GaMnAs single layer for memory devices

The authors show that staggered asymmetric planar Hall resistance (PHR) loops observed in GaMnAs ferromagnetic semiconductor films with biaxial in-plane magnetic anisotropy result in four stable resistance states at zero magnetic field owing to the formation of a stable multidomain structure during magnetization reversal. The values of PHR can be systematically controlled by changing the direction and the scanning range of the applied magnetic field. The possibility of a quaternary memory device based on the observed four PHR states is demonstrated by obtaining consistent results in the writing process using appropriate sequences of magnetic field pulses. (c) 2007 American Institute of Physics.