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

TL;DR

This paper explores how charge order and spin frustration influence magnetic properties in TMTTF salts, revealing that anion-dependent inter-chain interactions enhance antiferromagnetism and two-dimensional spin behavior.

Contribution

It demonstrates that the inter-chain transfer integral $t_{q1}$, affected by the anion, shifts from causing spin frustration to promoting antiferromagnetic order and two-dimensionality.

Findings

Charge order modifies the role of $t_{q1}$ from frustration to enhancing two-dimensional spin interactions.

The anion choice significantly influences the inter-chain transfer integral $t_{q1}$.

Charge order and antiferromagnetism are cooperatively enhanced 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$_6$.