Charge Order Breaks Magnetic Symmetry in Molecular Quantum Spin Chains

TL;DR

Charge order in molecular quantum spin chains influences magnetic properties by inducing non-equivalent magnetic sites and a novel interaction mechanism, revealed through electron-spin-resonance experiments.

Contribution

This study demonstrates that charge order can alter magnetic symmetry and interactions in molecular spin chains, challenging previous assumptions.

Findings

Charge order modifies magnetic properties below TCO.

Anisotropic Zeeman interaction causes doubling of rotational periodicity.

Magnetic sites become non-equivalent due to charge order.

Abstract

Charge order affects most of the electronic properties but is believed not to alter the spin arrangement since the magnetic susceptibility remains unchanged. We present electron-spin-resonance experiments on quasi-one-dimensional (TMTTF)2X salts (X= PF6, AsF6 and SbF6), which reveal that the magnetic properties are modified below TCO when electronic ferroelectricity sets in. The coupling of anions and organic molecules rotates the g-tensor out of the molecular plane creating magnetically non-equivalent sites on neighboring chains at domain walls. Due to anisotropic Zeeman interaction a novel magnetic interaction mechanism in the charge-ordered state is observed as a doubling of the rotational periodicity of Delta H.