EXCHANGE COUPLING BETWEEN IRON LAYERS SEPARATED BY SILVER AND GOLD

The exchange couplings between bcc Fe layers separated by fee Ag and A u are calculated for Fe/Ag/Fe and Fe/Au/Fe (001) trilayer structures a s functions of the spacer thickness for several temperatures. The calc ulated couplings show a short-period oscillatory behavior in Fe/Au for all temperatures investigated. For Fe/Ag a long period prevails for t emperatures T greater than or equal to 300 K, but at T=0 a strong shor t-period contribution is present for Ag thicknesses greater than or eq ual to 30 atomic planes. These results are in very good agreement with finite-temperature experiments, but the coupling strengths as calcula ted by assuming perfect interfaces are much larger than those observed . It is shown that interplanar distance relaxation at the interfaces l eads to a rather large effective change of the coupling amplitude in F e/Au for Au thicknesses less than or equal to 20 atomic planes, but ma inly causes a phase shift in the oscillatory coupling for Fe/Ag. It is found that interfacial interdiffusion substantially reduces the ampli tude of the coupling in Fe/Au/Fe, but not much in Fe/Ag/Fe.