Magnetic structure in U(Ru0.92Rh0.08)2Si2 single crystal studied by neutron diffraction in static magnetic fields up to 24 T

TL;DR

This study reveals the high-field magnetic structure of U(Ru0.92Rh0.08)2Si2, showing an uncompensated antiferromagnetic order with specific propagation vector and magnetic moments, reconstructed Fermi surface, and preserved tetragonal symmetry.

Contribution

The paper provides the first detailed neutron diffraction analysis of the high-field magnetic phase in Rh-doped URu2Si2, identifying its magnetic structure and field-induced electronic changes.

Findings

Uncompensated antiferromagnetic order with propagation vector Q2 = (2/3, 0, 0)

U moments of 1.45 μB aligned along the c axis in an up-up-down sequence

Fermi surface significantly reconstructed by the magnetic field

Abstract

We report the high-field induced magnetic phase in single crystal of U(Ru0.92Rh0.08)2Si2. Our neutron study combined with high-field magnetization, shows that the magnetic phase above the first metamagnetic transition at Hc1 = 21.6 T has an uncompensated commensurate antiferromagnetic structure with propagation vector Q2 = ( 2/3 0 0) possessing two single-Q domains. U moments of 1.45 (9) muB directed along the c axis are arranged in an up-up-down sequence propagating along the a axis, in agreement with bulk measurements. The U magnetic form factor at high fields is consistent with both the U3+ and U4+ type. The low field short-range order that emerges from the pure URu2Si2 due to Rh-doping is initially strengthened by the field but disappears in the field-induced phase. The tetragonal symmetry is preserved across the transition but the a axis lattice parameter increases already at low fields. Our results are in agreement with itinerant electron model with 5f states forming bands pinned in the vicinity of the Fermi surface that is significantly reconstructed by the applied magnetic field.