Antiferromagnetic Phases of One-Dimensional Quarter-Filled Organic Conductors

Abstract

The magnetic structure of antiferromagnetically ordered phases of\nquasi-one-dimensional organic conductors is studied theoretically at absolute\nzero based on the mean field approximation to the quarter-filled band with\non-site and nearest-neighbor Coulomb interaction. The differences in magnetic\nproperties between the antiferromagnetic phase of (TMTTF)$_2$X and the spin\ndensity wave phase in (TMTSF)$_2$X are seen to be due to a varying degrees of\nroles played by the on-site Coulomb interaction. The nearest-neighbor Coulomb\ninteraction introduces charge disproportionation, which has the same spatial\nperiodicity as the Wigner crystal, accompanied by a modified antiferromagnetic\nphase. This is in accordance with the results of experiments on (TMTTF)$_2$Br\nand (TMTTF)$_2$SCN. Moreover, the antiferromagnetic phase of (DI-DCNQI)$_2$Ag\nis predicted to have a similar antiferromagnetic spin structure.\n