Incommensurate antiferromagnetism in GdSi

Rare earth magnets are interesting model systems to study correlated spin, orbital and lattice degrees of freedom. Here we present a study of the antiferromagnetism in single crystal GdSi, using high-resolution, x-ray magnetic diffraction techniques. Our results clearly show an incommensurate magnetic structure at 6.5 K, with a lattice distortion from orthorhombic to monoclinic accompanying the magnetic phase transition in a second order fashion. We discuss implication to the anisotropic susceptibility in lights of the detailed magnetic structure.