Study of Correlation between Charge-density-wave and Magnetism in UPt<sub>2</sub>Si<sub>2</sub> using Polarized Neutron Scattering

We examined the antiferromagnetic (AFM) structure of UPt2Si2, which develops below TN = 34 K, using polarized and unpolarized neutron diffraction techniques. Previous studies report that this system undergoes the AFM order with the propagation vector Q = 0 and magnetic moments aligned along the c-axis. Notably, our recent resonant X-ray scattering (RXS) experiments revealed that this magnetic structure is modulated by the charge-density-wave (CDW) order, which is formed in one of the Pt layers with the propagation vector qCDW = (∼0.42, 0, 0) below ∼320 K. In this neutron scattering study, we observed the magnetic scattering contributions below TN at the superlattice reflections corresponding to qCDW. Our detailed analysis confirmed the presence of the transversal magnetic modulation in the AFM phase and quantified its amplitude to be 0.72(2) μB/U. These results indicate that the CDW causes the ordered magnetic moments to tilt by up to ～20° in the AFM phase, suggesting significant hybridization between the U 5f and Pt 5d electrons in this compound.