Magnetodielectric coupling in the ilmenitesMTiO3(M=Co, Ni)

Abstract

We report magnetodielectric coupling in rhombohedral ilmenites ${\mathrm{CoTiO}}_{3}$ and ${\mathrm{NiTiO}}_{3}$ along with heat capacity and magnetic measurements. ${\mathrm{CoTiO}}_{3}$ and ${\mathrm{NiTiO}}_{3}$ undergo antiferromagnetic ordering at $\ensuremath{\approx}$ 38 and $\ensuremath{\approx}$ 22 K, respectively. The dielectric permittivity of ${\mathrm{CoTiO}}_{3}$ decreases below its magnetic ordering temperature while the dielectric permittivity of ${\mathrm{NiTiO}}_{3}$ increases below the N\'eel temperature. The dielectric permittivity of ${\mathrm{CoTiO}}_{3}$ and ${\mathrm{NiTiO}}_{3}$ are dependent on the applied magnetic field and temperature with the strongest dependence observed close to the magnetic-ordering temperature. We analyze magnetodielectric coupling in ${\mathrm{CoTiO}}_{3}$ and ${\mathrm{NiTiO}}_{3}$ on the basis of spin-phonon coupling and suggest other possible mechanisms such as exchange coupling and magnetostrictive effects.