Electrical Transport Across an Individual Magnetic Domain Wall in (Ga,Mn)As Microdevices

Recent studies demonstrate that an individual magnetic domain wall (DW) can be trapped and reproducibly positioned within multiterminal (Ga,Mn)As microdevices. The electrical resistance obtained from such measurements is found to be measurably altered by the presence of this single entity. To elucidate these observations we develop a simple model for the electrical potential distribution along a multiterminal device in the presence of a single DW. This is employed to calculate the effect of a single DW upon the longitudinal and transverse resistance. The model provides very good agreement with experimental observations, and serves to highlight important deviations from simple theory. We show that measurements of transverse resistance along the channel permits establishing the position and the shape of the DW contained within it. An experimental scheme is developed that enables unambiguous extraction of the intrinsic DW resistivity. This permits the intrinsic contribution to be differentiated from resistivities originating from the bulk and from magnetic anisotropy - effects that are generally manifested as large backgrounds in the experiments.