Oscillatory behavior of interface exchange coupling caused by finite caps of variable thickness

The effect of non-magnetic cap-layers on the periods and the amplitudes of the oscillations of interlayer exchange coupling (IEC) is studied theoretically using an ab initio spin-polarized surface Green function technique within a tight-binding linear muffin-tin orbital method and the Lloyd formulation of the IEC. Applications are made to the free-electron like model as well as to Co/Cu/Co(0 0 1) trilayers with a cap interfacing vacuum through the dipole barrier. The results are analyzed in terms of a discrete two-dimensional Fourier transformation which confirms a pronounced oscillatory behavior of the IEC with respect to the thickness of the cap-and the spacer-layers. The results are in agreement with available experimental data as well as with predictions of the electron confinement model of the IEC. Copyright (C) 1998 Elsevier Science B.V.