Conditions for magnetism in Pu-based systems

The possibility of the 5f count variations and its impact on magnetic properties are discussed on the background of known data on diluted alloys, intermetallic compounds and monopnictides and monochalcogenides. Weakly paramagnetic character of δ-Pu is preserved when Pu is doped by Am, which expands the crystal lattice. Specific-heat data show that the γ-coefficient does not increase. Such behaviour can be understood on the basis of LSDA + U calculations, which yield invariably non-magnetic Pu state due to the proximity to the 5f6 state. It is also shown that the ground-state density of states should not be directly compared with photoelectron spectra, because the spectral density obtained from Hubbard-I calculations is in the narrow band regime of Pu dramatically different than the underlying density of states. We suggest that a general condition for Pu magnetism is some degree of hybridization with states of other elements in alloys and compounds, which allows for the reduction of the 5f count.