Ultra-thin magnetic films with a few monolayer thickness show a variety of magnetic properties depending on thickness, growth condition, and lattice misfit at the interface. A quasi two-dimensional character of these films would cause a reduction of the Curie temperature and an enhancement of magnetic moment, which are much different from the bulk values. Here, we present the fcc Fe ultra-thin film on Co(001) surface, where the fcc Co can be epitaxially fabricated on Cu(001) surface. The appearance and disappearance of ferromagnetism could be controlled by the cooperation between the lattice and the spin polarized electronic states. However, several studies on the electronic structures of fcc Fe by photoelectron spectroscopy and band structure calculation showed controversial results. One of the reasons for their discrepancies must be yielded from the absence of spin-resolution in the photoelectron spectroscopy. Motivated by this, we have performed a spin- and angle- resolved photoelectron spectroscopy (SARPES) of the ultra-thin films of Fe/Co(001).
The experiment was performed with the recently developed SARPES spectrometer[1]. The SARPE spectra of 4ML Fe/Co(001) excited by the He I radiation (hν=21.22eV) shows that the peak structure (θ=0°) in the minority spin spectrum shifts from near EF to higher EB with increasing emission angle θ. The majority spin peak also shifts toward the higher EB with increasing θ. It is noted that these two majority and minority spin bands show the similar energy dispersion curves as denoted by the vertical bars, which can be assigned to the exchange split partners of the Fe 3d band. The estimated exchange splitting is 0.85eV, which is much smaller than the value for bcc Fe.
[1] K. Iori et al., Rev. Sci. Instrum. 77, 013101 (2006).
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