Magnetodielectric coupling in a triangular Ising lattice: Experiment and modeling

Dielectric constant measurement under magnetic field is an efficient technique to study the coupling between charges and spins in insulating materials. For magnetic oxides, the geometric frustration is known to be a key ingredient to observe such a coupling. Measurements for the triangular Ising-like cobaltite Ca3Co2O6 have been made. Single crystals of Ca3Co2O6 are found to exhibit a magnetodielectric effect below T-N=25 K with a peak in the epsilon(H) curve at the ferri to ferromagnetic transition. This relation between epsilon and magnetization has been modelized by using two order parameters in an energy expansion derived from the Landau formalism and the fluctuation-dissipation theorem. This result emphasizes the great potential of insulating transition metal oxides for the search of magnetodielectric effect.