Direct observation of interface roughness dependence of interfacial magnetism using diffuse x-ray resonant magnetic scattering (abstract)

Abstract

Interfacial roughness plays an important role in the magnetoresistance of magnetic multilayers, yet the relationship between roughness and the magnetic properties at interfaces is not well understood. In recent years, x-ray resonant magnetic scattering (XRMS) has been developed to investigate the interaction of polarized x rays and magnetic materials. By combining XRMS in azimuthal transverse scans, the diffuse intensity scattered from the roughness of the boundary between magnetic and nonmagnetic layers can be probed to yield information on the relationship between magnetism and interfacial roughness that cannot be obtained by any other method. Using synchrotron produced circularly polarized x rays tuned to the L2 edge of Co, x-ray diffuse intensity scans for a fixed angle of incidence are made for sputter deposited Co films and Co/Cu/Co sandwiches. For smooth films, the ratio of the XRMS diffuse intensity to the XRMS specular intensity is smaller than the ratio of the average specular intensity to the average diffuse intensity. In addition, the shape of the XRMS diffuse intensity differs from the average diffuse intensity. We conclude that the roughness of the magnetic boundary between magnetic and magnetic layers is less than the interfacial roughness, and that long-wavelength roughness contributes more to magnetic scattering than does short-wavelength roughness. By depositing identical magnetic films on substrates with well characterized laterally correlated roughness, we investigate the effect of the roughness feature size on the XRMS diffuse intensity. We find that for long-wavelength laterally highly correlated roughness, the roughness of the magnetic boundary is the same as the interfacial roughness.