Temperature evolution of the Gd magnetization profile in strongly coupled Gd/Fe multilayers

The temperature evolution of the magnetization depth profile in Gd layers of a strongly coupled [Gd(50 Angstrom)/Fe(15 Angstrom)](15) multilayer is studied using x-ray resonant magnetic scattering (XRMS) and x-ray magnetic circular dichroism (XMCD) techniques. XRMS yields a spatially resolved, element-specific, magnetization depth profile, while XMCD spatially averages over this profile. The combined data inequivocally show the presence of an inhomogeneous magnetic profile within the Gd layers at all measured temperatures between 20 and 300 K. These inhomogeneous profiles, which feature enhanced magnetic ordering near the Gd/Fe interface, were refined using both a kinematic Born approximation and a recently developed distorted-wave Born approximation, both of which include the contribution of structural and magnetic interfacial roughness. Calculations of the static magnetic configuration within a mean-field approach that neglects interfacial roughness are in agreement with the measured inhomogeneous profile and its temperature evolution. The results suggest that the enhanced Gd magnetization near the interface arises from its proximity to magnetically ordered Fe.