α-γ transition in cerium: Magnetic form factor and dynamic magnetic susceptibility in dynamical mean-field theory

The nature of the elemental cerium phases, undergoing an isostructural volume collapse transition, cannot be understood using conventional solid-state concepts. Using the combination of density functional theory and dynamical mean-field theory, we study the magnetic properties of both the α and the γ phases. We compute the magnetic form factor and show that it is very close to the free ion behavior in both the local moment γ phase as well as the more itinerant α phase, in agreement with neutron scattering experiments. In sharp contrast, the dynamic local magnetic susceptibility of the two phases is strikingly different. In the γ phase, the sharp low energy peak due to local moment formation and consequently low Kondo temperature dominates the spectra. In α phase two broad peaks can be identified, the first is due to Kondo screening and the second is due to Hund's coupling. This shows that hybridization plays a central role in the α-γ transition in cerium, and that from the point of view of magnetic properties, the 4f electrons are strongly correlated in both phases.