title: Inflection point in the magnetic field dependence of the ordered moment of URu2Si2 observed by neutron scattering in fields up to 17 T.
abstract: We have measured the magnetic field dependence of the ordered antiferromagnetic moment and the magnetic excitations in the heavy-fermion superconductor URu2Si2 for fields up to 17 T applied along the tetragonal c axis, using neutron scattering. The decrease of the magnetic intensity of the tiny moment with increasing field does not follow a simple power law, but shows a clear inflection point, indicating that the moment disappears first at the metamagnetic transition at approximately 40 T. This suggests that the moment m is connected to a hidden order parameter psi which belongs to the same irreducible representation breaking time-reversal symmetry. The magnetic excitation gap at the antiferromagnetic zone center Q = (1,0,0) increases continuously with increasing field, while that at Q = (1.4,0,0) is nearly constant. This field dependence is opposite to that of the gap extracted from specific-heat data.
authors.affiliation: Département de Recherche Fondamentale sur la Matière Condensée, SPSMS/MDN, CEA Grenoble, 38054 Grenoble, France.
authors.forename: F
authors.initials: F
authors.lastname: Bourdarot
authors.forename: B
authors.initials: B
authors.lastname: Fåk
authors.forename: K
authors.initials: K
authors.lastname: Habicht
authors.forename: K
authors.initials: K
authors.lastname: Prokes