The Spin Dynamics of the Spin Ladder, Dimer Chain Material Sr14Cu24O41

TL;DR

This study investigates the spin dynamics of Sr14Cu24O41 using inelastic neutron scattering, revealing detailed dispersion relations, spin gaps, and couplings in the spin ladder and dimer chain structures.

Contribution

It provides the first detailed characterization of spin excitations and couplings in Sr14Cu24O41, combining neutron scattering data with modeling of ladder and dimer chain behaviors.

Findings

Identified a spin gap of 32.5 meV and maximum excitation energy of 193.5 meV.

Determined ladder couplings J|| = 130 meV and J⊥ = 72 meV.

Described low-energy excitations with a dimer chain model with specific intra- and inter-dimer couplings.

Abstract

We have performed inelastic neutron scattering on a single crystal sample of Sr14Cu24O41 to study the spin dynamics of the Cu2O3 spin ladder layers, and CuO2 chains. Data collected with incident energies of 50 meV, 200 meV, 350 meV and 500 meV are best fitted with a dispersion with a spin gap of 32.5+/-0.1 meV and a maximum of 193.52.4 meV, consistent with a coupling along the ladders, J|| = 130 meV and a rung coupling J^=72 meV. We find that excitations with an energy transfer of approximately 11.5 meV can be described solely in terms of a dimer chain with an antiferromagnetic intra-dimer coupling, J1 = 11.2 meV, between next-nearest-neighbour Cu ions and a ferromagnetic inter-dimer coupling, J2 = -1.1 meV. The dimers are separated by two Cu ions providing a periodicity for the dimer chain of five units.