Dipolar glass and magneto-electric coupling within a π-stacked organic system

Abstract

There is much interest for the search for novel materials that show magneto-electric coupling, such as that observed in multiferroics. TEA(TCNQ)2 shows promise in this area with features in the dielectric data at the magnetic transition, related to an uneven electron density across the TCNQ dimers.

A study of the dynamics and structure of the dielectric anomaly within the molecular solid TEA(TCNQ)2

“…Recently we have shown that at both the low and high temperature transitions, there are anomalies in the dielectric data. 27 At low temperatures, we were able to observe changes in the capacitance and loss that coupled with the magnetisation, presenting strong evidence for magneto-electric coupling. At the higher temperature transition, which hereafter will be referred to as the dielectric transition, we found that the capacitive response was glassy and akin to a relaxor-ferroelectric.…”

“…28 Two processes were seen which had activation energies of 1430(50) K and 750(30) K when modeled using the Vogel–Fulcher analysis and were within different frequency regimes, 27–300 kHz and 0.6–22 kHz for the high and low activation energies respectively. 27 Using a simple activated behaviour to analyse the dielectric data resulted in significantly increased values for the activation energy and attempt frequencies. Given this intriguing dielectric behaviour, it is important to revisit this dielectric transition and explore both the underlying dynamics and molecular motions to fully understand it.…”

The low energy phonon modes of the hydrogenated and deuterated π-conjugated system 7,7,8,8-tetracyanoquinodimethane: an inelastic neutron scattering study

“…order-disorder, as well as magnetic transitions 6 . The fact that there are dielectric anomalies upon going through the magnetic transitions is particularly appealing as it illustrates that the system shows magento-electric coupling, part of the recipe for multiferroic applications 20,21 . All of the above applications involve the compounds within their solid, crystalline, form where the 1D stacking of the TCNQ molecules is extremely important.…”