Crystal and Magnetic Structure of FeV$_{2}$O$_{4}$ with e$_{g}$ and t$_{2g}$ orbital degeneracies

We have performed neutron diffraction measurements on a powder and a single crystal of a spinel FeV$_{2}$O$_{4}$ that has e$_ {g}$ as well as t$_{2g}$ orbital degeneracy. Our data show that upon cooling this system undergoes three successive phase transitions: a cubic-to-tetragonal structural transition at 140 K, a tetragonal-to-orthorhombic transition at 110 K accompanied by a ferri-magnetic order and an orthorhombic-to-orthorhombic phase transition with another magnetic order at 80 K. The magnetic structures of the two magnetic phases were refined by the group theoretical analysis of our powder diffraction data. We will also discuss implication of the magnetic structures regarding to the orbital states of FeV$_{2}$O$_{4}$.