Lattice dynamics and spontaneous magnetodielectric effect in ilmenite CoTiO3

Abstract Ilmenite-type crystals find a variety of technological applications due to their intriguing physical properties. We present the results of the lattice dynamics studies of honeycomb antiferromagnetic ilmenite COTIO3 single crystal by the complementary polarized infrared, Raman, and dielectric spectroscopic techniques that are supplemented by the DFT calculations. The symmetries and frequencies of all predicted infrared and Raman active phonons were uniquely identified. Furthermore, it was found that the dielectric permittivity demonstrates distinct changes below antiferromagnetic ordering temperature in zero magnetic field due to the spontaneous magnetodielectric effect. Our results establish the solid basis for further investigations and more deep understanding of the coupling of phonons with spins and magnetic excitations, as well as their involvement in other physical phenomena in this promising material.