INTERLAYER EXCHANGE COUPLING VERSUS FERROMAGNETIC LAYER THICKNESS IN ASYMMETRIC CO/RU/CO TRILAYER FILMS

A dependence of the interlayer exchange coupling coefficient A12 on the Co layer thickness has been observed in asymmetric Co(32 Å)/Ru(tRu)/Co(t2) trilayer structures for several series within which tRu is a constant. As a function of the second Co layer thickness, the amplitude of A12 varies significantly but the sign of A12 does not change within each series. In both parallel and antiparallel coupled structures, the variation length Δt2 between the maximum and the minimum coupling strength is rather large (about 10 Å) and consistent from series to series.