Helical magnetism and structural anomalies in triangular lattice α-SrCr₂O₄

α-SrCr₂O₄ has a triangular planar lattice of d³⁺Cr^{3 +} made from edge sharing CrO₆ octahedra; the plane shows a very small orthorhombic distortion from hexagonal symmetry. With a Weiss temperature of - 596K and a three-dimensional magnetic ordering temperature of 43K, the magnetic system is quasi-two-dimensional and frustrated. Neutron powder diffraction shows that the ordered state is an incommensurate helical magnet, with an in-plane propagation vector of k = (0, 0.3217(8), 0). Temperature dependent synchrotron powder diffraction characterization of the structure shows an increase in the inter-plane spacing on cooling below 100K and an inflection in the cell parameters at the magnetic ordering temperature. These anomalies indicate the presence of a moderate degree of magnetostructural coupling.