A magnetoresistive element is provided as a spin valve having a synthetic
free layer. More specifically, the synthetic free layer includes a low
perpendicular anisotropy layer that is separated from a high
perpendicular anisotropy layer by a spacer. Thus, the high anisotropy
material introduces an out-of-plane component by exchange coupling. The
high perpendicular anisotropy material also has low spin polarization.
Further, the low anisotropy material positioned closer to the pinned
layer has a high spin polarization. As a result, the magnetization of the
low anisotropy material is re-oriented from an in-plane direction to an
out-of-plane direction. Accordingly, the overall free layer perpendicular
anisotropy can be made small as a result of the low anisotropy material
and the high anisotropy material. Adjusting the thickness of these
layers, as well as the spacer therebetween, can further lower the
anisotropy and thus further increase the sensitivity.