Electronic correlations in potential new rare-earth permanent magnet materials

Designing new materials for permanent magnet applications is currently a very active field of research. While, at present, the best permanent magnets are based on the expensive rare-earth elements Nd, Sm or Dy (e.g. Nd₂Fe₁₄B), efforts are made to replace them with more available elements like Ce, with the hope to discover compounds with even better performance and lower production costs. Theoretical efforts to assist this quest encounter challenges related to the correlated nature of the rare-earth 4f states. In particular, in the family of potential Ce-based permanent magnet materials a key question is the localized vs. heavy-fermion behavior of the Ce-4f electrons. In this context, we investigate the role of electronic correlations in CeFe₂, CeFe₁₂ and CeFe₁₁Ti from first principles by using combined density functional and dynamical mean-field theory. We solve the corresponding quantum impurity problem by means of a continuous-time Quantum Monte Carlo solver and analyze the resulting electronic structure focusing on the degree of localization of the Ce-4f states as well as the magnetic properties of the compounds.