Quantum spin correlations in an organometallic alternating sign chain

TL;DR

This study uses neutron scattering and calculations to reveal that DMACuCl3 is an $S=1/2$ alternating AFM-FM chain with nearly equal exchange interactions, showing inter-dimer spin correlations and implications for quantum entanglement.

Contribution

The paper establishes the magnetic Hamiltonian of DMACuCl3 as an $S=1/2$ alternating AFM-FM chain with nearly equal exchange strengths, supported by experimental and theoretical analysis.

Findings

DMACuCl3 is an $S=1/2$ alternating AFM-FM chain.

Evidence of inter-dimer spin correlations.

Exchange interactions are nearly equal in strength.

Abstract

High resolution inelastic neutron scattering is used to study excitations in the organometallic magnet DMACuCl$_3$. The correct magnetic Hamiltonian describing this material has been debated for many years. Combined with high field bulk magnetization and susceptibility studies, the new results imply that DMACuCl$_3$ is a realization of the $S=1/2$ alternating antiferromagnetic-ferromagnetic (AFM-FM) chain. Coupled-cluster calculations are used to derive exchange parameters, showing that the AFM and FM interactions have nearly the same strength. Analysis of the scattering intensities shows clear evidence for inter-dimer spin correlations, in contrast to existing results for conventional alternating chains. The results are discussed in the context of recent ideas concerning quantum entanglement.