Neutron-scattering measurements of long-range antiferromagnetic order in URu2Si2

Neutron scattering from a high-quality single crystal of the heavy-fermion superconductor URu2Si2 has shown the onset of the small, antiferromagnetic ordered moment (0.037μB) occurs abruptly at TN, 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 c* axis. This shows that these are intrinsic properties of URu2Si2 and confirms the microscopic coexistence of antiferromagnetism and superconductivity.