Ferroelectric valence transition and phase diagram of a series of charge-transfer complexes of 4,4'-dimethyltetrathiafulvalene and tetrahalo-p-benzoquinones

S Horiuchi; Y Okimoto; R Kumai; Y Tokura

doi:10.1021/ja0016654

Ferroelectric valence transition and phase diagram of a series of charge-transfer complexes of 4,4'-dimethyltetrathiafulvalene and tetrahalo-p-benzoquinones

J Am Chem Soc. 2001 Jan 31;123(4):665-70. doi: 10.1021/ja0016654.

Authors

S Horiuchi¹, Y Okimoto, R Kumai, Y Tokura

Affiliation

¹ Contribution from the Joint Research Center for Atom Technology (JRCAT), Tsukuba 305-0046, Japan.

PMID: 11456578
DOI: 10.1021/ja0016654

Abstract

Variation of the ferroelectric phase transition has been investigated for a series of isomorphous donor (D)-acceptor (A) charge-transfer complexes composed of 4,4'-dimethyltetrathiafulvalene (DMTTF) and tetrahalo-p-benzoquinones by measurements of dielectric susceptibility, X-ray diffraction, and infrared molecular vibrational spectra. The neutral-ionic phase transition of DMTTF-p-chloranil at 65 K accompanies a dielectric peak anomaly associated with the DA stack dimerization. Successive halogen replacement by bromine in the component tetrahalo-p-benzoquinone molecule expands the lattice along the DA stack of the DMTTF complex, and reduces the critical temperature steeply toward zero temperature in an analogous way to the critical behavior of quantum ferroelectrics. The 2,6-dibromo-substituted compound showing the behavior of the quantum paraelectricity is located in the immediate vicinity of the quantum critical point of this phase diagram as signified also by enhancement of the ionicity, the dielectric susceptibility, and the dynamical dimeric distortion at the lowest temperature.