Micromagnetic disorder in antiparallel biased spin valves.

The reorientation of antiferromagnetically coupled Co layers comprising the pinned layers of an antiparallel biased spin valve is reported. Initially, the lower Co layer is saturated in the growth field in the deposition chamber, but it reorients as the upper Co layer grows to be thicker than the lower one. We have investigated the nature of this reorientation by ex situ transport measurements and Lorentz microscopy, and found it highly inhomogeneous, leading to a complex in-plane domain pattern. This results in a reduction of the giant magnetoresistance of the spin valves close to the balance point, where the benefits of the antiparallel biasing are greatest. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]