The Origin and Coupling Mechanism of the Magnetoelectric Effect in TMCl2-4SC(NH2)2 (TM = Ni and Co)
(a) CoCl2-4SC(NH2)2. Left axis: magnetization isotherms at K for H ∣∣ ab (open circles) and H ∣∣ c (solid line). Right axis: electric polarization change at K for H ∣∣ ab and ∣∣ c. The horizontal small arrows indicate the up- and down-sweeps of the magnetic field. (b) NiCl2-4SC(NH2)2. Left axis: at K for H ∣∣ c (solid line). Right axis: at for H ∣∣ c (solid squares) and quantum Monte Carlo (QMC) calculations of the electric polarization (solid circles) .