Neutron-scattering measurements of long-range antiferromagnetic order inURu2Si2

Abstract

Neutron scattering from a high-quality single crystal of the heavy-fermion superconductor ${\mathrm{URu}}_2$ ${\mathrm{Si}}_2$ has shown the onset of the small, antiferromagnetic ordered moment (0.037${\mathrm{\mu }}_{\mathit{B}}$) occurs abruptly at ${\mathit{T}}_{\mathit{N}}$, unlike the gradual onset in previously studied samples. The results are in good agreement with x-ray-resonance magnetic scattering. The magnitude of the moment and the magnetic excitation spectrum are the same as previously observed, including the anomalous damping of excitations with a component of momentum transfer along the ${\mathit{c}}^{\mathrm{*}}$ axis. This shows that these are intrinsic properties of ${\mathrm{URu}}_2$ ${\mathrm{Si}}_2$ and confirms the microscopic coexistence of antiferromagnetism and superconductivity.