X-ray absorption spectroscopy and x-ray magnetic circular dichroism of epitaxially grown Heusler alloy Co_2MnSi ultrathin films facing a MgO barrier

摘要

We element specifically studied the electronic and magnetic states of epitaxially grown full-Heusler alloy Co_2MnSi (CMS) 1.1 nm (4 ML) thick ultrathin films facing an epitaxial MgO(001) tunnel barrier by means of x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD). In situ reflection high-energy electron-diffraction observations indicated that the CMS films grew into the L2_1 structure. The observed XAS and XMCD spectra revealed that the CMS ultrathin film was not oxidized. The ratio of Mn and Co spin magnetic moments obtained by applying the sum rules was about 2.7, close to a theoretical value of 2.8 for CMS with the L2_1 structure.