Spin-valve structures with NiO pinning layers

Spin-valves comprised of Co or NiFe magnetic layers and NiO as the antiferromagnetic pinning layer have been prepared by magnetron sputtering. Their structural, magnetic and magnetotransport properties have been characterized. A dramatic enhancement of the coercivity of the magnetic layer adjacent to NiO is observed due to the onset of a very large uniaxial anisotropy. In addition, depending on the conditions of deposition, the hysteresis loop of the pinned layer can be either centered around zero field or shifted as is usually observed for exchange anisotropy. In the latter case, the field characterizing the shift of the loop decreases much faster with increasing temperature than does the coercive field. These samples have good thermal stability up to 250°C. Their response at low fields can be made reversible by applying a static biasing field transverse to the field to be measured. A detailed study of minor MR hysteresis loops has been carried out