Spin magnetic moments in the half-metallic ferromagnet—ferromagnet interface region detected by depth-resolved x-ray magnetic circular dichroism

Abstract

We study spin magnetic moments near half-metallic Co2FexMn1−xSi (CFMS)/metal interfaces using depth-resolved x-ray magnetic circular dichroism (XMCD) and analyze their robustness against thermal fluctuations. We prepare epitaxial magnetic multilayered films with CFMS/CoFe and CFMS/Ag interfaces and observe the x-ray absorption spectroscopy (XAS) and XMCD spectra for both the interfacial and inner CFMS regions. By analyzing the observed XAS and XMCD spectra, we approximately extract the Mn-related magnetic moments. The results show that the Mn spin magnetic moment at the CFMS/CoFe interface exhibits almost no reduction compared with that in the inner CFMS layer, in contrast to the significant reduction observed at the CFMS/Ag interface. This suggests that the CFMS/CoFe interface provides a larger interfacial exchange stiffness than the CFMS/Ag interface, consistent with theoretical interface exchange stiffness values obtained from first-principles calculations. Furthermore, the large exchange stiffness at the CFMS/CoFe interface leads to the high stability of local spin magnetic moments to thermal fluctuation, resulting in a weaker temperature dependence of the magnetoresistance (MR) ratio in current-perpendicular-to-plane giant MR devices with a CoFe/CFMS/Ag/CFMS/CoFe structure than in those with a CFMS/Ag/CFMS structure.