Spin-Polarized Photoemission from f.c.c.-Cobalt above the Curie Temperature: Evidence of Short-Range Magnetic Order

We report on the first spin- and momentum-resolved photoemission studies on epitaxial f.c.c.-cobalt films above the Curie temperature. In order to obtain a thorough characterization of the electronic states, the photoelectrons have been excited by circularly polarized VUV synchrotron radiation and a vectorial spin analysis has been employed to determine size and spatial orientation of the photoelectron spin polarization. This novel experimental approach allows a direct comparison of the spin-resolved photoemission spectra from the ferromagnetic cobalt overlayer and the paramagnetic copper substrate. The results indicate a failure of the Stoner model in f.c.c.-Co and suggest the existence of a short-range ferromagnetic order above T C .