Oscillatory exchange coupling between iron layers separated by chromium

The exchange coupling J between Fe layers separated by nonmagnetic Cr is calculated for Fe/Cr/Fe (001) trilayer structures as a function of the spacer thickness N for several temperatures T. It is shown that for perfectly sharp interfaces J(N,T) is entirely dominated by short period oscillations for 0 K less than or equal to T less than or equal to 500 K and N varying from 5 to 50 atomic planes. At zero temperature the amplitude of J decays as N-3/2 for large values of N. This behavior is caused by the particular type of singularity in the nesting of the Cr Fermi which is responsible for one of the dominant short-period oscillations of J(N). A strong temperature dependence of the coupling strength is obtained for some values of N, in excellent agreement with experiments. The effect of interface mixing on J(N) reduces the overall coupling strength, as well as the relative importance of the short period oscillatory components, and causes a phase shift in the oscillations of J(N). [S0163-1829(99)03317-2].