Perpendicular magnetic anisotropy at the Fe/Au(111) interface studied by Mössbauer, x-ray absorption, and photoemission spectroscopies

The origin of the interfacial perpendicular magnetic anisotropy (PMA) induced in the ultrathin Fe layer on the Au(111) surface was examined using synchrotron-radiation-based M\"ossbauer spectroscopy (MS), x-ray magnetic circular dichroism (XMCD), and angle-resolved photoemission spectroscopy (ARPES). To probe the detailed interfacial electronic structure of orbital hybridization between the Fe $3d$ and Au $6p$ bands, we detected the interfacial proximity effect, which modulates the valence-band electronic structure of Fe, resulting in PMA. MS and XMCD measurements were used to detect the interfacial magnetic structure and anisotropy in orbital magnetic moments, respectively. In situ ARPES also confirms the initial growth of Fe on large spin-orbit coupled surface Shockley states under Au(111) modulated electronic states in the vicinity of the Fermi level. This suggests that PMA in the Fe/Au(111) interface originates from the cooperation effects among the spin, orbital magnetic moments in Fe, and large spin-orbit coupling in Au. These findings pave the way to develop interfacial PMA using $p\text{\ensuremath{-}}d$ hybridization with a large spin-orbit interaction.