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 57Fe conversion electron Mössbauer 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 in situ 57Fe CEMS measurements which indicate an enhanced saturation hyperfine field of ∼39 T 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 with an enhanced hyperfine field due to electronic 3d-4d hybridization at the Fe/Pd interface. © 2005 The American Physical Society