Inflection point in the magnetic field dependence of the ordered moment of URu2Si2 observed by neutron scattering in fields up to 17 T

TL;DR

This study uses neutron scattering to explore how the antiferromagnetic moment and magnetic excitations in URu2Si2 change under magnetic fields up to 17 T, revealing an inflection point linked to a hidden order parameter and a metamagnetic transition.

Contribution

It provides new insights into the magnetic field dependence of the ordered moment and excitations in URu2Si2, highlighting the connection to a hidden order parameter and identifying an inflection point in the magnetic intensity.

Findings

Magnetic intensity shows an inflection point with increasing field.

The ordered moment disappears near the 40 T metamagnetic transition.

Magnetic excitation gaps behave differently at distinct wave vectors.

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 Tesla 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 ~40 T. This suggests that the moment m is connected to a hidden order parameter Phi 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.