We have newly developed a retarding-type Mott spin detector for spin- and angle-resolved photoelectron (SARPE) spectroscopy. Detection of scattered electrons at the Au target in an appropriate energy-loss window with a large opening angle has helped us to increase the efficiency of the spin polarimeter. The SARPE spectroscopy equipped with the developed spin detector has been applied to the study of surface and bulk electronic structures of fcc Co thin films grown on Cu(001) surface. The improved efficiency has enabled us to obtain the spin-resolved spectra while the surface is kept clean. As a result, we have successfully resolved a negatively spin-polarized surface resonance state of fcc Co/Cu(001) at Γ− of the surface Brillouin zone. It has also been clarified that the surface resonance state is markedly influenced by a spin-orbit coupling.
