Spin dynamics of edge-sharing spin chains in SrCa13Cu24O41

TL;DR

This study investigates the magnetic excitations in highly Ca-doped SrCa13Cu24O41, revealing gapless spin waves with specific dispersions, and compares these findings to similar compounds to understand doping effects on spin dynamics.

Contribution

The paper provides the first detailed inelastic neutron scattering analysis of SrCa13Cu24O41, showing a transition from gapped to gapless excitations due to hole transfer upon Ca doping.

Findings

Gapless spin-wave excitations observed along a and c axes.

Nearest-neighbour interaction Jc is 5.4 meV, interchain Ja is 4.4 meV.

Transition from gapped to gapless excitations with Ca doping.

Abstract

The low-energy magnetic excitation from the highly Ca-doped quasi-one-dimensional magnet SrCa13Cu24O41 was studied in the magnetic ordered state by using inelastic neutron scattering. We observed the gapless spin-wave excitation, dispersive along the a and c axes but nondispersive along the b axis. Such excitations are attributed to the spin wave from the spin-chain sublattice. Model fitting to the experimental data gives the nearest-neighbour interaction Jc as 5.4 meV and the interchain interaction Ja = 4.4 meV. Jc is antiferromagnetic and its value is close to the nearest-neighbour interactions of the similar edge-sharing spin-chain systems such as CuGeO3. Comparing with the hole-doped spin chains in Sr14Cu24O41, which shows a spin gap due to spin dimers formed around Zhang-Rice singlets, the chains in SrCa13Cu24O41 show a gapless excitation in this study. We ascribe such a change from gapped to gapless excitations to holes transferring away from the chain sublattice into the ladder sublattice upon Ca doping.