Relaxor ferroelectricity induced by electron correlations in a molecular   dimer Mott insulator
  We have investigated the dielectric response in an antiferromagnetic dimer-Mott insulator beta'-(BEDT-TTF)2ICl2 with square lattice, compared to a spin liquid candidate kappa-(BEDT-TTF)2Cu2(CN)3. Temperature dependence of the dielectric constant shows a peak structure obeying Curie-Weiss law with strong frequency dependence. We found an anisotropic ferroelectricity by pyrocurrent measurements, which suggests the charge disproportionation in a dimer. The ferroelectric actual charge freezing temperature is related to the antiferromagnetic interaction, which is expected to the charge-spin coupled degrees of freedom in the system. 
S. Iguchi, S. Sasaki, N. Yoneyama, H. Taniguchi, T. Nishizaki, and T.   Sasaki
cond-mat.str-el