Effect of roughness slope on exchange biasing in NiO spin valves

Exchange biasing field H-ex and coercive field H-c of the exchange-biased NiO spin valves deposited over differently etched glass substrates and glass Si3N4 buffer layers were measured in order to investigate the effect of roughness at the NiO/NiFe interfaces. The magnetoresistive (MR) ratio, H-ex, and H-c were not influenced by etching time, even though the rms roughness R-rms increased from 4.7 to 33 Angstrom. However, the MR ratio, H-ex, and H-c increased with Si3N4 buffer thickness, even when the R-rms had almost the same values. To explain this ambiguous dependence of R-rms, we consider an effect of the average slope of roughness instead of R-rms in an atomic force microscope image. The steep slope of roughness played an important role in H-ex and H-c in NiO spin valves due to an increase in magnetostatic energy and the decrease in antiferromagnetic domain size. (C) 1998 American Institute of Physics.