Lattice dynamics and electronic structure of cobalt–titanium spinel Co2TiO4

Abstract

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 T_C = 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.