Photoemission and electron-energy-loss-spectroscopy study ofBaRuO3

Core- and valence-level photoemission spectra of the hexagonal perovskite ${\mathrm{BaRuO}}_3$ are reported. Valence-region photoemission shows that ${\mathrm{BaRuO}}_3$ is a metallic material with a well-defined cutoff in the energy-distribution curve at the Fermi energy, while in electron-energy-loss spectroscopy a plasmon-loss peak is observed at 1.0 eV. Comparison with previously published data for ${\mathrm{CaRuO}}_3$ and ${\mathrm{SrRuO}}_3$ shows that electron correlation becomes progressively less important in the series ${\mathrm{CaRuO}}_3$-${\mathrm{SrRuO}}_3$-${\mathrm{BaRuO}}_3$.