COUPLING MECHANISM IN CO RU SANDWICHES WITH THIN SPACERS/

A study of the indirect exchange coupling of Co/Ru sandwiches for smal l Ru spacer thicknesses has been performed. For critical thicknesses o f the spacer, a large curvature of the M-H loops can be observed and i ts origin lies in a competition between areas with different couplings . These areas are smaller than the magnetic coherence length of the co balt layers, and the existence of a large extrinsic biquadratic coupli ng is likely to occur. A strong interdiffusion at the interfaces seems to be determinant for the coupling mechanism.