Effect of Ni concentration on quantum-well states of the alloy system Ag/Fe1-xNix: A spin- and angle-resolved photoemission study

초록

We investigate the quantum-well states (QWSs) of Ag on an Fe-Ni alloy film grown on a W(110) substrate, using spin- and angle-resolved photoemission spectroscopy (SPARPES). As the Ni content is increased, the Fe-Ni alloy undergoes a transition from a bcc (110) structure to a fcc (111) structure at a Ni concentration of 30%. In the bcc (110) region, we found that as the Ni concentration was increased, the binding energy shifted linearly toward higher binding energy in the QWSs of a thin Ag film, with a maximum shift of 0.4 eV for a Ni concentration of 30%. Our SPARPES data and phase accumulation model calculation indicate that this shift is due to electron doping resulting from inserting Ni, which has two more electrons than Fe. In the fcc (111) region, by contrast, the binding energy shift in the QWSs is barely noticeable, indicating that the potential shift caused by electron doping is insufficiently large in this region. Moreover, as the Ni concentration is increased, a decrease in the polarization of QWSs is observed, which can be attributed to the reduced exchange splitting energy.