Enhanced hyperfine magnetic fields for face-centered tetragonal Fe(110) ultrathin films on vicinal Pd(110)

The structure and hyperfine magnetic properties of epitaxial Fe ultrathin films on a vicinal Pd(110) surface have been investigated by means of Low Energy Electron Diffraction (LEED), Reflection High Energy Electron Diffraction (RHEED) and $^{57}$Fe Conversion Electron M\"{o}ssbauer Spectroscopy (CEMS). LEED and RHEED provide evidence for initial pseudomorphic film growth. The RHEED determination of the in-plane atomic distance versus Fe film thickness demonstrates the stabilization of the metastable fcc-like Fe structure on Pd(110). This interpretation is supported by\textit{ in-situ} $^{57}$Fe CEMS measurements which indicate an enhanced saturation hyperfine field of $\approx $ 39T for a 3 monolayers thick Fe film at 25 K. This is the highest value ever measured for Fe on a metallic substrate. Our results suggest that ultrathin fcc-like (face-centered tetragonal) Fe films on Pd(110) are in a ferromagnetic high-moment state, and show a considerably enhanced Fe magnetic moment due to electronic 3$d$-4$d$ hybridization at the Fe/Pd interface.