Biasing materials for spin-valve read heads

In this paper, the performance of CoNiO, NiO, NiMn and IrMn as exchange biasing materials for use in spin-valve read heads is described. The significant material properties investigated were biasing fields, thermal stability, thickness effects and corrosion resistance. The oxide materials had excellent corrosion resistance, but NiO had poor exchange fields and CoNiO had a poor blocking temperature. NiMn had the best exchange field with an interfacial exchange coupling of 0.25 erg/cm ², but it required high temperature annealing in order to realize this. It also had good thermal and corrosion resistance properties. The blocking temperature of the oxides and IrMn were found to diminish with decreasing thicknesses of the antiferromagnets. This effect was determined to be consistent with a finite-size-scaling phenomenon. IrMn was found to have a good combination of the properties investigated, the weakest being its corrosion resistance, which was nevertheless better than FeMn. Spin-valves fabricated with IrMn as the pinning material showed excellent magnetic and thermal properties with MR ratios as high as 10% and good spin-valve responses up to 209°C IrMn pinned spin-valves had very good performance for narrow trackwidth elements, with MR ratios as high as 5% and pinning fields of >600 Oe for 0.5 μm trackwidth devices