Magnetic anisotropy and intermediate valence in CeCo 5 ferromagnet

The intermediate valence of Ce in CeCo 5 challenges standard density functional theory (DFT) and static DFT + U approaches, which fail to capture its magnetic properties. By combining DFT + U with exact diagonalization of the Anderson impurity model for the Ce 4 f shell, we find a substantial reduction of Ce spin and orbital moments, consistent with DFT + DMFT (dynamical mean-field theory), arising from Ce 4 + − Ce 3 + valence fluctuations. The total magnetic moment of 6.70 µ B agrees with experiment, and the calculated 4 f density of states reproduces photoemission and bremsstrahlung isochromat spectra. The uniaxial magnetic anisotropy energy reaches 4.8 meV/f.u. when Coulomb correlations on both Ce 4 f and Co 3 d shells are included, in very good agreement with experimental data. These results highlight the importance of dynamical correlations and provide guidance for exploring high-performance, low-rare-earth-content permanent magnets.