MAGNETISM AND MAGNETOCRYSTALLINE ANISOTROPY OF NP2T2X (T=CO, NI, RU, RH, PD, IR, PT, X=IN, SN) COMPOUNDS DERIVED FROM DENSITY-FUNCTIONAL CALCULATIONS

Ab initio electronic structure calculations for Np2T2X intermetallic c ompounds were performed using an optimized linear combination of atomi c orbitals method based on the local density approximation. Thus, we a re aiming at a theoretical description of magnetic properties in the n ormal metallic state. The 5f-states of Np were assumed itinerant and t reated as band states. The particular composition dependent electronic structure results from the interplay between two main ingredients: fi rst, the band filling of the free electron background (s-, p- and nept unium d-electrons) and the transition metal bonding bands, and second, covalency (hybridization) between bonding predominantly d-states of T atoms and antibonding predominantly f-states of Np atoms. Spin and or bital moments were obtained from fully relativistic spin-polarised cal culations. A quantitative study of the magnetocrystalline anisotropy i s provided on the basis of calculated differences of eigenvalue sums f or different orientations of the magnetic moment. We show that the res ults of our approach agree with the observed experimental trends in th e magnetic properties of Np2T2X.