Magnetic properties of epitaxial single crystal ultrathin Fe₃Si films on GaAs (001)

Magnetic properties of Fe₃Si films with thickness from 2 to 210 monolayers (ML) epitaxially grown on GaAs (001) were studied using a superconducting quantum interference device and alternating gradient force magnetometers. Growth of these single-crystal intermetallic compound films were carried out in a multichamber molecular beam epitaxy (MBE) system. The samples were covered in situ with Au 50 Å thick to prevent oxidation when the samples were removed from the MBE chamber. All the films are ferromagnetic even for samples as thin as 2 ML. The easy magnetization direction of the films is parallel to the film surface. The magnetic coercivity forces (H_c) of the samples increase as the film thickness decreases to 10 ML, and then decrease when the film thickness decreases further to 2 ML.