The Raman spectra of single crystals of ${\text{NiFe}}_2{\text{O}}_4$ were studied in various scattering configurations in close comparison with the corresponding spectra of ${\text{Ni}}_{0.7}{\text{Zn}}_{0.3}{\text{Fe}}_2{\text{O}}_4$ and ${\text{Fe}}_3{\text{O}}_4$. The number of experimentally observed Raman modes exceeds significantly that expected for a normal spinel structure and the polarization properties of most of the Raman lines provide evidence for a microscopic symmetry lower than that given by the $Fd\overline{3}m$ space group. We argue that the experimental results can be explained by considering the short-range 1:1 ordering of ${\text{Ni}}^{2+}$ and ${\text{Fe}}^{3+}$ at the $B$ sites of inverse spinel structure, most probably of tetragonal $P{4}_{1}22/P{4}_{3}22$ symmetry.

• Received 4 May 2010

DOI:https://doi.org/10.1103/PhysRevB.82.024104