Photoemission study of the ferromagnetic Kondo systemCeRh3B2

We have studied the electronic structure of ${\mathrm{CeRh}}_3$ ${\mathrm{B}}_2$, which has an anomalously high ferromagnetic ordering temperature, by photoemission and Auger-electron spectroscopy. The Ce 4f occupancy ${\mathit{n}}_{\mathit{f}}$≃0.85 evaluated from the Ce 3d core-level photoemission spectrum indicates a moderately strong valence fluctuation in the Kondo regime. Rh d–derived valence-band photoemission spectra are found to be in good agreement with the results of band-structure calculations when a strong energy dependence of the hole lifetime is taken into account. This observation and the deviation of the Rh ${\mathit{M}}_{4,5}$VV Auger spectrum from the self-convolution of the Rh d partial density of states provide evidence for electron correlation within the Rh d band of order of U=1–2 eV. We discuss a possible effect of the latter electron correlation on the ferromagnetic instability of this compound.