Sub-micron scale relief structures of GMR materials fabricated by half-milling control

We have investigated the magneto-transport properties of a GMR material consisting of CoPt(10 nm)/Cu(10 nm)/NiFe(6 nm) in which only the top NiFe layer is patterned by the half-milling technique. The top NiFe film was structured into a two-dimensional particle array with lateral dimensions of w = 0.2 μm and aspect ratio L/w = 1, 2, 4 or 8. From MR measurements, the remanent magnetization of the NiFe particle array was found to gradually decrease with L/w, which can be ascribed to the relative increase of an end domain area in the particles. The longitudinal switching field H_swt markedly decreases as L/w < 2. From the micromagnetic simulation, it was found that the decrease of H_swt was caused by the change of switching configuration from an edge reversal to a coherent rotation with decreasing L/w.