Assume NiFe is the softer layer, with , and that interlayer coupling is weak enough to permit separate reversal. Starting at large negative , both magnetizations point in the same direction and . During an increasing-field sweep:
- At , NiFe reverses while Co does not: the state is antiparallel and the resistance rises to .
- At , Co also reverses: the state becomes parallel and the resistance returns to .
On decreasing from positive saturation, the high-resistance window instead lies between and . Thus the two sweep directions give displaced rectangular high-resistance windows, not a single reversible resistance peak centered on zero.
Pseudo spin-valve resistance loops, distributed switching and spacer dilution
. Original illustrative curves. Separate coercive fields create an antiparallel window on each sweep. The middle panel isolates switching-field broadening; its retained peak height is not a claim that real roughness leaves the GMR amplitude unchanged. Source. Details.If Co were the softer layer, the sequence of layer labels would be exchanged. A continuous spacer and sufficiently weak coupling are additional assumptions: negligible surface roughness alone does not guarantee independent switching at every Cu thickness.
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