A GMR read element with differential spin valves in which the free layers of
the
two spin valves have magnetization directions that are parallel to each other while
the pinned layers most adjacent to the free layers have magnetization directions
that are anti-parallel to each other. This can be achieved by having one of the
spin valves be a synthetic spin valve and the other spin valve a non-synthetic
spin valve. In this case, a single annealing process can set the magnetization
directions of the pinned layers in this manner. It is also possible to use two
synthetic spin valves in which one spin valve has an odd number of pinned layers
and the other has an even number of pinned layers. The differential spin valves
can be connected together in a parallel or a series relationship. It is possible
for the differential sensor to be a two-, three-, or four-terminal device.
