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

We report a high-field-induced magnetic phase in a 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 μ0Hc1=21.6 T has an uncompensated commensurate antiferromagnetic structure with a propagation vector Q2=2300 possessing two single-Q domains. U moments of 1.45(9)μB 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+ types. The low-field short-range order that emerges from 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 an 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