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Applying k-resolved inverse photoemission (KRIPES) to the √3×√3 R30°-reconstructed 6H-SiC(0001) face, we have observed a sharp surface state U located at 1.10 ± 0.05 eV above the Fermi level at the centre of the surface Brillouin zone. Its bandwidth of 0.34 ± 0.05 eV is in good agreement with the 0.35 eV predicted by first-principle calculations based on a Si-adatom model. However, LDA calculations predict a half-filled Σ1 state and a metallic character for this reconstruction. Together with recent ARUPS data, our results reveal that the one-electron band Σ1 is split into two bands, giving a semiconducting surface with a reduced indirect bandgap around 2.0 eV at the K̄′ point. Many-body correlation effects may give rise, in the limit of strong localization, to this bandgap opening.

Powders consisting of ferromagnetic (FM) Fe nanoparticles, of about 7 nm in size, embedded in an antiferromagnetic (AFM) Cr2O3 matrix have been obtained by high-temperature reduction under a hydrogen atmosphere of a mixed Cr–Fe oxide. This FM–AFM system exhibits exchange bias effects, i.e. a loop shift (HE) and coercivity enhancement (ΔHC), when field-cooled through the Néel temperature, TN, of Cr2O3. The exchange bias properties were measured as a function of temperature. HE and ΔHC are found to vanish at about TN(Cr2O3), indicating a good quality AFM matrix. Hence, high-temperature reduction of mixed oxides is demonstrated to be a suitable technique to develop new types of FM–AFM exchange-biased nanoparticles, from which novel applications of this phenomenon may be developed.