Spin frustration, charge ordering, and enhanced antiferromagnetism in TMTTF${}_2$SbF${}_6$

Abstract

We theoretically investigate the effects of charge order and spin frustration on the spin ordering in TMTTF salts. Using first-principles band calculations, we find that a diagonal inter-chain transfer integral $t_{q1}$, which causes spin frustration between the inter-chain dimers in the dimer-Mott insulating state, strongly depends on the choice of anion. Within the numerical Lanczos exact diagonalization method, we show that the ferroelectric charge order changes the role of $t_{q1}$ from the spin frustration to the enhancement of the two-dimensionality in spin sector. The results indicate that $t_{q1}$ assists the cooperative behavior between charge order and antiferromagnetic state observed in TMTTF${}_2$SbF${}_6$.

Fig. 2 (a) and Fig. 3(a) are revised. 4 pages, 4 figures, Proceedings of ECRYS 2011