Coupled dimerized alternating-bond quantum spin chains in the distorted honeycomb-lattice magnet Cu$_5$SbO$_6$

TL;DR

This study reveals that Cu$_5$SbO$_6$ hosts interacting dimerized spin chains with unique antiferromagnetic couplings, differing from previous honeycomb lattice models, supported by neutron scattering, magnetization data, and structural analysis.

Contribution

It introduces a new magnetic coupling scheme in Cu$_5$SbO$_6$, showing dominant interlayer antiferromagnetic interactions instead of intra-layer couplings, based on neutron scattering and structural refinement.

Findings

Cu$_5$SbO$_6$ has dimerized spin chains with alternating ferromagnetic-antiferromagnetic couplings.

The primary magnetic coupling occurs between layers, not within the honeycomb layers.

Refined crystal structure and stacking-fault model of Cu$_5$SbO$_6$.

Abstract

We analyze powder-averaged inelastic neutron scattering and magnetization data for the distorted honeycomb compound Cu$_5$SbO$_6$ using a first-order dimer expansion calculation and quantum Monte Carlo simulations. We show that, in contrast to the previously proposed honeycomb lattice model, Cu$_5$SbO$_6$ accommodates interacting dimerized spin chains with alternating ferromagnetic-antiferromagnetic couplings along the chain. Moreover, unlike the typical couplings observed in other Cu$^{2+}$-based distorted honeycomb magnets, the spin chains in Cu$_5$SbO$_6$ primarily couple through an antiferromagnetic coupling that arises between the honeycomb layers, rather than the expected interchain coupling in the layers. This finding reveals a different magnetic coupling scheme for Cu$_5$SbO$_6$. In addition, utilizing x-ray spectroscopy and transmission electron microscopy, we also refine the crystal structure and stacking-fault model of the compound.