Helimagnetism in a disordered and geometrically frustrated quantum spin chain

TL;DR

This study investigates the low-temperature magnetic order in a disordered quantum spin chain, revealing helimagnetism influenced by non-stoichiometry, with implications for understanding frustrated magnetic systems.

Contribution

It provides the first detailed neutron diffraction analysis of helimagnetic order in LiCu$_2$O$_2$, linking disorder and frustration to magnetic ground states.

Findings

Helimagnetic magnetic structure with specific propagation vector.

Estimated exchange constants indicating frustration.

Long-range order due to non-stoichiometry.

Abstract

Neutron diffraction and bulk measurements are used to determine the nature of the low-temperature ordered state in LiCu$_2$O$_2$, a $S=1/2$ spin-chain compound with competing interactions. The magnetic structure is found to be helimagnetic, with a propagation vector $(0.5,\zeta,0)$, $\zeta=0.174$. The nearest-neighbor exchange constant and frustration ratio are estimated to be $J=5.8$ meV and $J_2/J_1=0.29$, respectively. For idealized spin chains these parameter values would signify a gapped spin-liquid ground state. Long-range ordering is attributed to intrinsic non-stoichiometry.