SIZE EFFECTS IN SUBMICRON NIFE AG GMR DEVICES

We have measured the magnetoresistive response of submicron NiFe/Ag gi ant magnetoresistive (GMR) devices as a Function of current density an d field angle. In addition to magnetostatic broadening, we observe lar ge jumps in the magnetoresistive response (Barkhausen jumps) due to do main switching, These effects lead to irregular device-specific magnet oresistive response curves. The large Barkhausen jumps are more pronou nced at low current density while at high current densities the respon se is smoother due to self field stabilization, The detailed structure of the Barkhausen jumps is very sensitive to the angle of the applied magnetic field. These effects are general properties of a wide class of GMR materials that rely on incoherent reversal of many small magnet ic domains. We compare the experimental data with a micromagnetic simu lation which incorporates phenomenological GMR transport model. The mo del qualitatively describes the experimental data and provides insight into the detailed micromagnetic behavior of these films.