Magnetic ground state of GdNiSn4 studied by resonant elastic X-ray scattering

GdNiSn4 is a newly synthesised lanthanide intermetallic containing distorted square nets of Gd. High symmetry lattices of Gd have been shown to host non-coplanar magnetic order which give rise to the topological Hall effect and have potential applications for spintronic devices. Here we present zero-field Gd-L2-edge resonant elastic X-ray scattering measurements on GdNiSn4. We find incommensurate magnetic order, which slides to a commensurate value when warmed. Magnetic symmetry analysis combined with azimuthal dependence restricts the magnetic structure to a moment-modulated spin density wave. We discuss connections between the observed magnetic order and physical properties at zero magnetic field and physical interpretations of the SDW sliding.