Valence-band photoemission spectroscopy of the giant magnetoresistive spinel compound Fe0.5Cu0.5Cr2S4 -: art. no. 144412

Electronic structures of the giant magnetoresistive Fe0.5Cu0.5Cr2S4 (FCCS) spinel compound have been investigated using photoemission spectroscopy (PES). Resonant PES measurements around the Cu, Fe, Cr 3p --> 3d absorption edges exhibit negligible resonant interference behavior for the Cu 3d valence electrons, indicating the monovalent valence state of the Cu ion in FCCS. The top of the valence band is found to be predominantly of the Cr 3d and the nearly filled Cu 3d electron character, whereas the Fe 3d electron character is distributed over the whole valence band. The measured valence-band PES spectra of FCCS yield better agreement with the LSDA + U calculation than with the local spin-density approximation (LSDA) calculation, suggesting the importance of the large Coulomb interactions U between d electrons. On the other hand, the low spectral intensity near E-F in the measured valence-band spectrum suggests an extra localization in FCCS, not explained by the large U alone.