INTERFACE INTERMIXING AND MAGNETORESISTANCE IN CO CU SPIN VALVES WITHUNCOUPLED CO LAYERS/

The interpretation of experiments on the effect of interface intermixi ng on the giant magnetoresistance (GMR) effect in antiferromagnetic-co upled multilayers can be complicated by the fact that interface interm ixing also changes the coupling strength; therefore, we have grown an artificially intermixed region in Co/Cu spin valves with uncoupled Co layers. The structure we used was a newly engineered spin valve compos ed of 100 Angstrom Co + 6 Angstrom Ru + 25 Angstrom Co + 40 Angstrom C u + 100 Angstrom Co. Here the Ru layer provides an antiparallel alignm ent of the Co layers and the Cu layer decouples the upper two Co layer s. An intermixed CoCu region has been grown at the Cu/Co interface and in some cases also at the Co/Cu interface by alternately sputtering 1 Angstrom Co and 1 Angstrom Cu. X-ray measurements confirm the existen ce of an intermixed region, although no reduction of magnetic moment i s observed as is reported for homogeneous sputtered Co0.5Cu0.5 alloys. This indicates the existence of Co clusters in the intermixed regions . There is no difference in GMR between an intermixed layer of thickne ss t at one Co/Cu interface or two intermixed layers of thickness t/2 at both Co/Cu interfaces. Thus, it seems that the total thickness of t he intermixed regions is decisive for the magnitude of the GMR. Becaus e G, Delta G, and Delta G/G(ap) all show a gradual decrease when the n ominal thickness of the intermixed region increases from 0 to 36 Angst rom, this indicates that there is no strong spin-dependent scattering in this region. This is in agreement with calculations on a model bila yer Co/Cu/Co with the Camley-Barnas model. (C) 1995 American Institute of Physics.