Electronic structure, dynamic susceptibility, and Néel temperature of the heavy-fermion magnetUCu5

A formalism for treating both spin and orbital moment effects within the linearized muffin-tin orbital method is applied to the heavy-fermion magnet ${\mathrm{UCu}}_5$. A magnetic moment of 1.1${\mu }_B$ is found, in agreement with neutron-scattering data, which indicate a moment of 1.3${\mu }_B$. Moreover, the calculation finds that 70% of the density of states at $E_F$ 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 ${\mathrm{UCu}}_5$. We find that the renormalized dynamic susceptibility has a peak corresponding in energy to the neutron-scattering linewidth.