SPIN-VALVE STRUCTURES WITH NIO PINNING LAYERS

Spin-valves comprised of Co or NiFe magnetic layers and NiO as the ant iferromagnetic pinning layer have been prepared by magnetron sputterin g. Their structural, magnetic and magnetotransport properties have bee n characterized. A dramatic enhancement of the coercivity of the magne tic layer adjacent to NiO is observed due to the onset of a very large uniaxial anisotropy. In addition, depending on the conditions of depo sition, the hysteresis loop of the pinned layer can be either centered around zero field or shifted as is usually observed for exchange anis otropy. In the latter case, the field characterizing the shift of the loop decreases much faster with increasing temperature than does the c oercive field, These samples have good thermal stability up to 250 deg rees C, Their response at low fields can be made reversible by applyin g a static biasing field transverse to the field to be measured. A det ailed study of minor MR hysteresis loops has been carried out.