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.
@article{arxiv.1901.02102,
title = {Spin dynamics of edge-sharing spin chains in SrCa13Cu24O41},
author = {Guochu Deng and Dehong Yu and Richard Mole and Ekaterina Pomjakushina and Kazimierz Conder and Michel Kenzelmann and Shin-ichiro Yano and Chin-Wei Wang and Kirrily C. Rule and Jason S. Gardner and Huiqian Luo and Shiliang Li and Clemens Ulrich and Paolo Imperia and Wei Ren and Shixun Cao and Garry J. McIntyrea},
journal= {arXiv preprint arXiv:1901.02102},
year = {2019}
}