Chemical bonding and magnetism in 3d-5f intermetallics

We report self-consistent energy band calculations for UFe2 and UCo2 in four approximations: both semi-relativistic and fully relativistic for the paramagnetic ground states; both spin-polarised and spin-polarised with spin-orbit coupling included self-consistently for the ferromagnetic ground state of UFe2. We compare ab initio calculated and measured lattice constants, bulk moduli, linear specific heat coefficients, pressure dependence of the magnetic moment and magnetic form factor. UCo2 is found to be an enhanced paramagnet and UFe2 an itinerant ferromagnet with a magnetic moment due mainly to the iron moments. However, the magnetism on the uranium sites is unusual in that we calculate both spin and orbital contributions to the moment that are large, antiparallel and almost equal. (author)