Spin-dependent surface and interface electronic states play important roles in their peculiar magnetism and electron conductivity. In this sense, clarifying spin-dependent electronic structures at the surface and interface of ferromagnetic materials could be one of the most attractive tasks.
Spin- and angle- resolved photoelectron spectroscopy (SARPES) is a powerful tool to obtain spin-resolved electronic structures of ferromagnetic materials. Recently, we have newly developed the SARPES system with a compact spin Mott detector and a hemispherical photoelectron spectrometer at Hiroshima Synchrotron Radiation Center[1].
In the present study, we have measured the spin resolved photoemission spectra for fcc cobalt thin films on Cu(001) surface excited with He@discharged lamp. At normal emission, the spin resolved spectra in minority spin channel show doublet peak structure at 0.12 eV and 0.36 eV, while only a broad structure is observed around EB = 0.7 eV in the majority spin channel. The minority spin state shifts toward higher EB with increasing θ up to 37° corresponding to X-bar point in the fcc surface Brillouin zone, and moves back to lower EB for θ > 37° Moreover, it is noted that the observed minority spin state at EB = 0.36 eV for θ = 0° is diminished upon a few contaminants. This result strongly suggests that the structure B is derived from the minority surface electronic state for fcc Co(001). Since energy gap of the bulk band structure is absent in this energy region as simulated by our tight binding calculation, this structure at 0.36 eV for θ = 0° should be assigned as the Co 3d surface resonance state in the minority spin channel.
[1] K. Iori et al., Rev. Sci. Instrum. 77, 013101 (2006).
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