Ab initio calculation of the interlayer exchange coupling in Fe/Au multilayers: The role of impurities at the interface - art. no. 094418

The coupling strength of the interlayer exchange coupling in magnetic multi layer systems is strongly determined by the quality of the interfaces betwe en magnetic and nonmagnetic layers. Consequently, theoretical and experimen tal results differ in general by one order of magnitude. Measurements for F e/Au samples of high structural quality have been performed [Unguris et al. , Phys. Rev. Lett. 79, 2734 (1997)]. The obtained coupling strength (J appr oximate to 1 mJ/m(2)) is much higher than in previous measurements. The aim of this paper is to present ab initio calculations for Fe/Au (001) multila yers with the same sample dimensions as in the experiments. The structure i s characterized by a bcc-fcc transition. The calculations are based on dens ity functional theory using a scalar-relativistic Screened Korringa-Kohn-Ro stoker method. The results show that in the case of ideally smooth interfac es the differences of the theoretically and experimentally obtained couplin g strengths by one order of magnitude remain. It will be demonstrated that the usual explanation by means of mesoscopic roughness fails. Instead, impu rity scattering at the interface is discussed. This mechanism leads to high ly anisotropic damping rates of the quantum well states.