Dielectric ordering and colossal magnetodielectricity in the antiferromagnetic insulating state ofλ−(BEDT−TSF)2FeCl4

Antiferromagnetic Insulating Ground State of Molecular π-d System Λ-(BETS)2FeCl4 (BETS = Bis(ethylenedithio)tetraselenafulvalene): A Theoretical and Experimental Review

“…A huge dielectric change by sweeping the field was observed inside the AFI phase, called 'colossal magnetodielectricity'. The magnetic field where the divergence of the dielectric constant occurs is similar to the results on the depolarization regime by Rutel et al (see Figure 1b) [12,39]. Such a sub-phase inside the AFI phase is confirmed from other studies [35,40].…”

“…We point out that the huge change of the high-frequency response within the AFI phase, the colossal magnetodielectricity, and nonlinear transport should be considered more seriously [12,38,39]. As shown in Figure 2a, we observed kink structures in the resistance below T N (MI transition).…”

“…They explained that this behavior is due to the metastable state in the π-electronic system within the AFI phase. Negishi and co-workers obtained similar results by measuring the capacitance and conductance in the AFI phase [39]. A huge dielectric change by sweeping the field was observed inside the AFI phase, called 'colossal magnetodielectricity'.…”

“…Based on the above measurements, Negishi et al proposed a charge ordering-induced polarization model [39]. Due to the exclusively large π-d super-exchange interaction between the π-orbitals at selective Se sites in BETS molecules labeled B (B') in Figure 1a and 3d-orbital via Cl, the charge as well as the spin of the π-electrons are expected to be localized at these Se sites.…”

“…This indicates that charge ordering is the primary origin of the AFI state. At low field and low temperature, the π-electrons are locked at the Se sites to keep J πd as effectively as possible, then, these π-electrons are considered to be unlocked or melted by applying the magnetic field [39].…”