A pinning layer structure is provided for a spin valve sensor of a read
head which has a reactively deposited nickel oxide first film which
underlies a reactively sputter deposited second film of iron oxide
(Fe.sub.2 O.sub.3) or (Fe.sub.3 O.sub.4). In the preferred embodiment the
pinning layer is composed of cobalt (Co) or cobalt iron (CoFe) which is
exchange coupled to the iron oxide (Fe.sub.2 O.sub.3) or (Fe.sub.3
O.sub.4) second film of the pinning layer. This structure results in an
improved magnetoresistive coefficient (dr/R) which is substantially
maintained after annealing so that the magnetic head has good thermal
stability when subjected to high temperatures in the presence of a field
that is antiparallel to the pinned orientation of the magnetic moment of
the pinned layer.
