Spin polarization and exchange coupling of Cu and Mn atoms in paramagnetic CuMn diluted alloys induced by a Co layer

Using the surface, interface, and element specificity of x-ray resonant magnetic scattering in combination with x-ray magnetic circular dichroism, we have spatially resolved the magnetic spin polarization, and the associated interface proximity effect, in a Mn-based high-susceptibility material close to a ferromagnetic Co layer. We have measured the magnetic polarization of Mn and Cu3d electrons in paramagnetic CuMn alloy layers in [Co/Cu (x) /CuMn/Cu (x)]₂₀ multilayer samples with varying copper layer thicknesses from x=0 to 25Å. The size of the Mn and Cu L_2,3 edge dichroism shows a decrease in the Mn-induced polarization for increasing copper thickness indicating the dominant interfacial nature of the Cu and Mn spin polarization. The Mn polarization is much higher than that of Cu. Evidently, the Mn moment is a useful probe of the local spin density. Mn atoms appear to be coupled antiferromagnetically with the Co layer below x=10Å and ferromagnetically coupled above. In contrast, the interfacial Cu atoms remain ferromagnetically aligned to the Co layer for all thicknesses studied.