Structure and magnetism in ultra-thin hcp Fe films on Re(0001)

We have characterized the structure and the magnetic properties of ultra-thin Fe films (1–6 atomic layers) grown on Re(0001) at different temperatures. For deposition temperatures above 475 K, low-energy electron microscopy shows a layer-by-layer growth up to the third layer, after which 3D growth is observed. The first Fe layer is pseudomorphic with the Re substrate, continuing its hcp stacking sequence. Subsequent atomic layers were found by low-energy electron diffraction (LEED) and IV-LEED to exhibit a quasi-hexagonal, or distorted bcc lattice, with this in-plane distortion progressively reducing with thickness till reaching the bulk bcc lattice at 10 Fe atomic layers. X-ray magnetic dichroism showed no contrast for the first two layers, whereas films of three or more atomic layers display in-plane ferromagnetic order.