Spin ordering and orbital ordering transitions in MnV2O4

We present low-temperature x-ray diffraction, susceptibility, specific heat, and thermal conductivity results both on single crystal and polycrystalline MnV2O4. The single crystal sample exhibits two transitions: a spin ordering (ferrimagnetic) transition at TSO=56K and an orbital ordering transition at TOO=52K. The structural change and phase separation at TOO suggest that the transition is first order. With applied magnetic fields, both TSO and TOO increase and TOO disappears with H⩾0.5T. The polycrystalline sample just exhibits one transition at 55K. The difference between the single crystal and polycrystalline samples is due to the nonstoichiometric polycrystalline sample.