Competing Charge and Magnetic Order in Fe_1/3NbS₂

Fe_xNbS₂ is an antiferromagnetic intercalated transition-metal dichalcogenide (TMD) that exhibits intriguing resistance-switching behavior. Recent neutron scattering studies have revealed highly tunable magnetic phases around x = 1/3 and coupled charge ordering in the x = 0.35. Of particular interest is the x = 1/3 compound, where two magnetic phases coexist. However, the role of Fe in stabilizing charge modulation and its coupling to magnetic ordering at this composition has remained unclear.In this work, we present comprehensive synchrotron X-ray measurements on Fe_1/3NbS₂ crystal. Using resonant elastic X-ray scattering (REXS) at the Fe L-edge (BL 13-3, SLAC), we investigated the stripe-type magnetic order, and with incident energy E_i = 14 keV (BL 17-2), we probed charge order in the same x= 1/3 crystal. We observe a nonmonotonic temperature dependence of the magnetic peak associated with the stripe phase: the peak develops below the Néel temperature (T_N ∼ 45K), reaches maximum intensity near 38 K, and is suppressed upon further cooling, becoming nearly undetectable at 10 K. In contrast, charge order develops at T_c ~ 30 K. The anticorrelated temperature dependence—where charge order strengthens as stripe-type magnetic order disappears—provides direct evidence of competition between charge and magnetic order in Fe_1/3NbS₂. These results highlight this material as a potential platform for exploring and manipulating coupled spin–charge phenomena.