INDUCED PHASE-SHIFT IN INTERLAYER MAGNETIC EXCHANGE COUPLING - MAGNETIC LAYER DOPING

The changes in the phase of the long-period oscillatory interlayer exc hange coupling between two Co layers, separated by a Ru spacer layer, are examined as a function of small concentrations of Ag, Au, Cu, and Ru added to the magnetic Co layer. Phase changes of up to 360 degrees are observed for small concentrations of Ag (up to 8%) with minimal mo difications to the coupling period or strength. In addition, an additi ve antiferromagnetic bias is observed for small interlayer thicknesses , indicative of a superexchange contribution to the interlayer couplin g. The effects are also investigated for Cu as the nonmagnetic spacer material and phase shifts are observed similar to those in the systems with Ru as the spacer material. Band-structure calculations are prese nted that show that insertion of small amounts of Pig into the Co host leads to additional states at the bottom of the band. This lowering o f the lower band limit is interpreted as a change in the potential ste p that determines the spin-dependent reflection coefficients of the el ectrons crossing the ferromagnet/spacer layer interface. The observed phase shifts are therefore interpreted to directly result from changes in the band structure of the ferromagnetic layer. The insertion of sm all amounts of nonmagnetic material in the ferromagnetic layer thus pr ovides a mechanism with which the phase of the coupling can be shifted in a well controllable manner.