EXCHANGE COUPLING BETWEEN 2 MAGNETIZED LAYERS IN A METAL

The exchange coupling energy for two magnetized monolayers embedded sy mmetrically in a metal and polarized in an arbitrary direction has bee n investigated in contact interaction approximation. Since the model c an be solved exactly in particular for-free-electron case, the couplin g energy contributed from both extended state electrons and bound stat e electrons is calculated rigorously. For weak interaction, it is foun d that the leading term in the power-series expansion of density of st ates can give a correct coupling energy compared with rigorous one whi le extended state electrons give a much larger coupling energy. Furthe rmore, the relevant problems such as phase shift, 90 degrees coupling and lattice effects have been discussed; an asymptotic expression of t he interlayer coupling has been derived in a different way and used to calculate the exchange energy between magnetic layers in copper with Fermi surface obtained from de Haas-van Alphen effect.