We used infrared ellipsometry to study phonons in a spinel MnV${}_2$O${}_4$ single crystal. At 300 K, the imaginary part of the complex dielectric function spectra show four phonon peaks. Below the cubic-tetragonal structural transition temperature at 58 K, small peaks appear around the cubic modes and the number of phonons becomes more than 12. The group analysis predicted 12 infrared modes for the $I{4}_1/a$ symmetry. The observed modes support the $I{4}_1/a$ or lower crystal symmetry, which reflects the antiferro ordering of V${}^{3+}$ $t_{2g}$ orbitals.

• Received 2 July 2011

DOI:https://doi.org/10.1103/PhysRevB.85.224423