Spin Dynamics in the Magnetic Chains Arrays of Sr14Cu24O41: a Neutron Inelastic scattering Investigation

TL;DR

This study investigates the spin dynamics in Sr14Cu24O41's chain arrays using neutron scattering, revealing a 2D arrangement of interacting dimers with specific coupling strengths and magnetic correlations.

Contribution

It provides detailed experimental insights into the 2D spin arrangement and couplings in Sr14Cu24O41, highlighting the role of frustration and chain sliding effects.

Findings

Spin arrangement develops in 2D below 150 K.

Intra-dimer coupling J ≈ 10 meV.

Inter-dimer couplings J// ≈ -1.1 meV and Jperp ≈ 1.7 meV.

Abstract

Below about 150 K, the spin arrangement in the chain arrays of Sr14Cu24O41 is shown to develop in two dimensions (2D). Both the correlations and the dispersion of the observed elementary excitations agree well with a model of interacting dimers. Along the chains, the intra- and inter-dimer distances are equal to 2 and about 3 times the distance (c) between neighboring Cu ions. While the intra-dimer coupling is J about 10 meV, the inter-dimer couplings along and between the chains are of comparable strenght, J// about -1.1 meV and Jperp about 1.7 meV, respectively. This remarkable 2D arrangement satisfies the formal Cu valence of the undoped compound. Our data suggest also that it is associated with a relative sliding of one chain with respect to the next one, which, as T decreases, develops in the chain direction. A qualitative analysis shows that nearest inter-dimer spin correlations are ferromagnetic, which, in such a 2D structure, could well result from frustration effects.