Spin and orbital moments of ultra-thin Fe films on various semiconductor surfaces

The magnetic moments of ultrathin 7 monolayer (ML) Fe films on GaAs, InAs and InGaAs were studied using the element specific X-ray magnetic circular dichroism (XMCD). The 7 ML Fe films were grown by molecular beam epitaxy (MBE) at room temperature and capped with 15 ML Cr to prevent oxidisation on removal from the vacuum system. The special substrates took the form of GaAs wafers topped with a 0.3μm epilayer of GaAs, InAs or InGaAs followed by an As capping layer. The lattice parameters of the GaAs, InAs and InGaAs epilayers were chosen for their lattice constants which, in a 2:1 relationship with Fe give mismatches of 1.56%, 5.32% and 0%, respectively. All samples revealed a reduced spin moment compared to bulk value and a marked enhancement in orbital moment. The similarity of the magnetic thin film features observed for the different substrates suggests that an unexpected degree of tolerance exists in these Fe films to surface issues such as strains induced by different lattice matches.