Resolving structural changes and symmetry lowering in spinel FeCr2S4

The ferrimagnetic spinel FeCr${}_{2}$S${}_{4}$ reveals fascinating properties, such as colossal magnetoresistance, half-metallicity, dynamic and static Jahn-Teller effects, strong magnetocrystalline anisotropy, topological Hall effect, multiferroicity, and unconventional magnetostructural transformations. In contrast to well characterized magnetic phases, the crystal structure in the different magnetic and orbitally ordered phases has remained an enigma over the years. Here, using high-resolution synchrotron diffraction, the authors resolve the long sought-after cubic to tetragonal transition at 65 K, reducing the lattice symmetry to $I{4}_{1}a\phantom{\rule{0}{0ex}}m\phantom{\rule{0}{0ex}}d$ with further lowering likely to $I{4}_{1}m\phantom{\rule{0}{0ex}}d$ in the multiferroic state established below 9 K.