Lattice dynamics and electronic structure of cobalt–titanium spinel Co2TiO4

The results are presented on phonon excitations and the electronic structure of Co2TiO4 inverse spinel in which magnetically ordered cobalt ions Co2+ (3d7) are in equal amounts in tetrahedral and octahedral sublattices below TC = 56 K. Single crystals are studied using optical reflection and absorption in a wide spectral range, Raman scattering, and dielectric spectroscopy methods. The dynamics of infrared and Raman-active phonons are studied, and the features associated with disordering in tetrahedral sites are detected. The d–d electronic transitions recorded in the regions of 3800 and 6300 cm–1 confirm the coordination features of Co2+ ions. An increase in the permittivity in the temperature region below 130 K is detected.