Magnetic excitations in USn3.

Abstract

We report on inelastic-neutron-scattering studies of the paramagnetic response in polycrystalline samples of the heavy-electron compound ${\mathrm{USn}}_{3}$. The magnetic scattering function, S(Q,E), was determined over a wide range of momentum and energy transfer, 0.5Q6 \AA{} $^{\mathrm{\ensuremath{-}}1}$ and 0E200 meV, at temperatures ranging from 1.5 to 300 K. We find that S(Q,E) at E>2 meV consists of only a broad quasielastic component characteristic relaxational dynamics of the U spins. The temperature dependence of the line width of this quasielastic peak exhibits a ${\mathit{T}}^{1/2}$-type power law with a large residual width at the lowest temperature. At E2 meV, on the other hand, there is evidence of an additional narrow component with a full width at half maximum of the order of 1 meV. Within experimental precision, we find no evidence of other inelastic peaks due to crystal-field excitations. The single-site magnetic susceptibility, \ensuremath{\chi}(Q,T), obtained by a Kramers-Kronig analysis of the quasielastic spectra, is smaller than the bulk static susceptibility at low temperatures. At a given temperature, \ensuremath{\chi}(Q) exhibits a Q dependence indicative of an instability towards antiferromagnetic ordering. The experimental results are compared with the spin dynamics observed in other heavy-f-electron compounds and the implication of s-f electronic hybridization is discussed.