Electronic structure, dynamic susceptibility, and Néel temperature of the heavy-fermion magnet UCu5

A formalism for treating both spin and orbital moment effects within the linearized muffin-tin orbital method is applied to the heavy-fermion magnet UCu5. A magnetic moment of 1.1μB is found, in agreement with neutron-scattering data, which indicate a moment of 1.3μB. Moreover, the calculation finds that 70% of the density of states at EF is removed at the magnetic phase transition, in rough agreement with specific-heat data, which reveal a 60% reduction. Using a modification of the spin-fluctuation formalism of Moriya, we calculate a Néel temperature of 12 K, close to the experimental value of 15 K. Finally, a simple method for calculating the dynamic susceptibility including spin-orbit effects is introduced and used to discuss the nature of the two phase transitions observed in UCu5. We find that the renormalized dynamic susceptibility has a peak corresponding in energy to the neutron-scattering linewidth.