Surface magnetic properties of ultrathin Fe films on W(110) studied by spin-resolved appearance potential spectroscopy

The surface sensitivity of spin-resolved appearance potential spectroscopy (APS) was exploited to investigate the magnetic properties of ultrathin Fe layers on W(110). The spin asymmetry, used to monitor the magnetic moment w ithin the probing depth of APS, was studied as a function of the Fe film th ickness. The spin asymmetry data reveal a pronounced maximum at a film thic kness of approximate to 6 monolayers (ML), which is attributed to the compl ex film morphology in this thickness range. For thicker, structurally relax ed films, APS measurements with variable sampling depth show the Fe surface magnetic moments enhanced compared with the moments of the sublayers. The spin asymmetry data are analyzed within a simple model.