Giant magnetoresistance in as-sputter-deposited Au/NiFe multilayer thin films

Abstract

Giant magnetoresistance with low saturation fields (Hs's) is reported in Au and permalloy (Ni0.82Fe0.18) or Co-doped permalloy multilayer thin films as-deposited on Ta-overcoated Si and grass substrates. A ΔR/R as high as 4.0% with approximately 25 Oe Hs was observed at 295 K for the film consisting of 10 layers of 24 angstroms Au/13 angstroms Ni0.82Fe0.18 deposited on a 3 angstroms Ta-overcoated glass at 50 °C. A Hs value as low as approximately 20 Oe with a 15% smaller ΔR/R has been observed for the films with a thicker (e.g., 50 angstroms) Ta underlayer. Magnetic hysteresis loops of these films indicate the presence of antiferromagnetic exchange coupling between the Ni0.82Fe0.18 layers. This exchange coupling is much smaller for the multilayer films without the Ta underlayer, resulting in a 6x smaller ΔR/R and 10x larger Hs observed for these films. Results of x-ray diffraction analysis indicate stronger (111) texturing for the multilayer films with a Ta underlayer, consistent with the stronger antiferromagnetic coupling between the the Ni0.82Fe0.18 layers in the film. The addition of 2-10 % Co moderately increases the ΔR/R value, but also increases substantially the Hs (up to approximately 200 Oe).