Determining symmetry and structure of FeCr2S4

In condensed matter physics there is growing interest in correlated phenomena that arise via competing instabilities, such as those provided by systems like FeCr2S4 with its strong spin-orbital (SO) interaction that compete with Jahn-Teller (JT) distortions. In FeCr2S4 these strongly correlated phenomena are manifested as, e.g., a metal-to-insulator transition, colossal magnetoresistance and half-metallic ground state. Despite significant investigation for the last 50 years the exact space-group or even the crystal symmetry, of the low temperature phase is yet to be established. The aim of this proposal is to establish the space-group of the system below 9 K. This will be done with high-resolution X-ray scattering at ID22 to have the best chance possible to observe the subtle structural changes that is expected, before Rietveld refinements are used to determine the symmetry. Time permitting, we will also collect data of the structure across the transitions at 165 K and 60 K.