Magnetism of URhSi and URhGe:: a density functional study

Density-functional-theory calculations for URhX (X=Si, Ge) were performed using relativistic full-potential linearized augmented plane wave (LAPW), optimized linear combination of atomic orbitals (OLCAO) and augmented sphere wave (ASW) methods. The 5f-states of uranium were assumed itinerant and treated as the band Bloch states. The total density of states (DOS) and the partial densities of states (PDOS) of the nonmagnetic crystal calculated with the fully relativistic approach (OLCAO) suggest substantial hybridization between the U-5f states and Rh-4d states. In both compounds, the Fermi level is situated in a region with high U-5f DOS. The calculations with the use of the fixed-spin-moment method (ASW method) confirm the instability of the paramagnetic state of URhX found experimentally. Spin polarized relativistic calculations (LAPW) showed that the uranium magnetic moments of both URhX compounds are very similar and rather small (0.3 mu(B)) due to strong cancellation of the spin and orbital component. The calculated moments are in good agreement with experimental values. We have studied the magnetic anisotropy energy (MAE) and the relatively small MAE in the b-c plane were found for URhGe. A possible noncollinearity of the magnetic structures is discussed on the basis of the symmetry analysis. The results of the symmetry analysis are related to the available experimental information. (C) 2002 Elsevier Science B.V. All rights reserved.