Soft-x-ray linear-dichroism and magnetic-circular-dichroism studies of CeRh₃B₂: Large crystal-field splitting and anomalous ferromagnetism

CeRh₃B₂ shows an anomalously high Curie temperature (T_c=115 K) for a Ce compound with nonmagnetic constituents, strong anisotropy in the magnetic susceptibility, and ferromagnetic ordering. We have studied its electronic structure by measuring linear dichroism (LD) and magnetic circular dichroism (MCD) in the Ce 4d core-level x-ray-absorption spectra. The result for LD indicates a highly anisotropic distribution of Ce 4f electrons along the hexagonal c axis, while the MCD result shows that the magnetic moment of the Ce 4f electron is dominated by the orbital moment as in the case of a small crystal field. Using the Anderson-impurity model including the axial crystal field, the strong interatomic Ce 4f–Ce 5d hybridization and the Ce 4f–Rh 4d hybridization, we show that there is a range of parameter sets for the axial crystal field and the Ce 4f–valence-band transfer integral which explains the results of the LD and MCD experiments. Using the same parameter set, we have also attempted to explain the Kondo temperature and the unusually high Curie temperature.