Incommensurate Nature of the Antiferromagnetic Order in GdCu₂

A magnetic order in orthorhombic GdCu2 was investigated via a single crystal neutron diffraction with thermal neutron. Magnetic peaks were observed at incommensurate positions described by the ordering vector \(\boldsymbol{q} = (\delta ,1,0)\) with δ = 0.678 at 4.6 K. This ordering vector is close to the commensurate one with \(\boldsymbol{q}_{\text{c}} = (2/3,1,0)\) reported earlier, but clearly deviates. The incommensurate nature of the magnetic order in GdCu2 is further corroborated by the peak shift with temperature below TN.