We report a high-field-induced magnetic phase in a single crystal of $\mathrm{U}{\left({\mathrm{Ru}}_{0.92}{\mathrm{Rh}}_{0.08}\right)}_2{\mathrm{Si}}_2$. Our neutron study, combined with high-field magnetization, shows that the magnetic phase above the first metamagnetic transition at ${\mu }_0{H}_{c1}=21.6$ T has an uncompensated commensurate antiferromagnetic structure with a propagation vector ${\mathit{Q}}_2=\left(\frac{2}{3}00\right)$ possessing two single-$\mathit{Q}$ domains. U moments of $1.45\left(9\right){\mu }_B$ 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 ${\mathrm{U}}^{3+}$ and ${\mathrm{U}}^{4+}$ types. The low-field short-range order that emerges from pure ${\mathrm{URu}}_2{\mathrm{Si}}_2$ 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.

• Received 23 February 2017
• Revised 15 September 2017

DOI:https://doi.org/10.1103/PhysRevB.96.121117