Magnetic moments of fcc Fe overlayers on Cu(100) and Co(100)

The magnetism of ultrathin fcc Fe overlayers on Cu(100) and Co(100) deposit ed at room temperature has been investigated at 110 K using magnetic circul ar dichroism in x-ray absorption spectroscopy (MCXD). Three regions of diff erent magnetic behavior in dependence of the Fe thickness are distinguished in the element-specific MCXD investigation in agreement with the results o f previous experiments. The Fe 3d magnetic spin and orbital moments are der ived from the MCXD spectra by use of sum rules as a function of the Fe thic knesses. Up to 4 ML Fe the Fe spin moment is 3.0 mu(B) on Co(100) and 2.8 m u(B) on Cu(100) demonstrating that the whole Fe film is in a ferromagnetica lly ordered high-spin state. We find that between 5 and 10 ML Fe the averag e Fe spin moment is 1.1 mu(B) on Co(100) and 0.8 mu(B) on Cu(100). The surf ace region of the Fe films is ferromagnetically ordered on both substrates. The larger average moment on Co(100) originates from the additional contri bution of the Fe atomic layer at the Fe-Co interface. For Fe thicknesses la rger than 10 ML the average Fe moment increases again. [S0163-1829(99)01806 -8].