| Abstract Scope |
Metallic state of light actinides and their compounds leads typically to delocalization of 5f electronic states. If the 5f band becomes broad due to a short inter-actinide spacings, e-e correlations are suppressed, yielding weak Pauli paramagnetism. In the system of Uranium, the Hill limit of approx. 340 pm should be exceeded to provide conditions for magnetic order. More recently it has been realized that a polar character of bonding provides a further tuning possibility. Typically, at U systems, a charge transfer towards ligands, affecting mainly the 6d states, reduces the 5f-6d hybridization, and supports thus formation of magnetic moments and their ordering. Such tendency has been studied at U hydrides and at Zintl phases (UCu2P2), the latter yielding TC values approaching room temperatures under pressure. |