Magnetodielectric coupling in the ilmenites MTiO_3 (M = Co, Ni)

摘要

We report magnetodielectric coupling in rhombohedral ilmenites CoTiO_3 and NiTiO_3 along with heat capacity and magnetic measurements. CoTiO_3 and NiTiO_3 undergo antiferromagnetic ordering at ≈ 38 and ≈ 22 K, respectively. The dielectric permittivity of CoTiO_3 decreases below its magnetic ordering temperature while the dielectric permittivity of NiTiO_3 increases below the Neel temperature. The dielectric permittivity of CoTiO_3 and 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 CoTiO_3 and NiTiO_3 on the basis of spin-phonon coupling and suggest other possible mechanisms such as exchange coupling and magnetostrictive effects.