  The interlayer exchange coupling (IEC) of two local moment ferromagnetic
layers separated by a non-magnetic spacer layer (M/N/M multilayer) is studied
using the modified RKKY method along with the s-f model. The IEC exhibits
oscillatory behaviour with respect to the spacer layer thickness and it
oscillates between ferro- and antiferromagnetic configurations. The
conventional RKKY method is also used to obtain the IEC and the results are
compared with those obtained from the modified RKKY method which incorporates
the electron correlation effects. We find significant correlation effects on
the IEC and in fact the correlations alter the nature and magnitude of the
magnetic coupling.
