Spin fluctuations in the antiferromagnetic heavy-fermion systemU2Zn17

Inelastic neutron scattering from the antiferromagnetic (${\mathrm{T}}_{\mathrm{N}}$=9.7 K) heavy-fermion system ${\mathrm{U}}_2$ ${\mathrm{Zn}}_{17}$ reveals magnetic fluctuations which are highly localized in reciprocal space and broad in frequency. At higher energies, the fluctuations persist almost unchanged to temperatures well above ${\mathrm{T}}_{\mathrm{n}}$. Analysis of the neutron and bulk susceptibility data in terms of Kondo-type single-ion response functions modified by Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions between ions indicates that it is the temperature dependence—anticipated theoretically—of the effective RKKY coupling which drives the magnetic phase transition in ${\mathrm{U}}_2$ ${\mathrm{Zn}}_{17}$.