It is suggested that modes, observed in recent neutron scattering experiments by Lake {\it et al.}, on La2−xSrxCuO4 in strong magnetic fields (≈ 7 T), are due to the existence of antiferromagnetic moments associated with the cores of vortices generated by the field. These moments form one-dimensional chains along the c-axis (the vortex axis), which at finite temperatures are disordered. At temperatures higher than 10 K the correlation length gets shorter than the lattice parameter, resulting in no scattering from coherent spin-waves above that temperature. The bandwidth of the spin-waves is estimated to be ≈ 4 meV in accordance with the observations.
@article{arxiv.cond-mat/0102070,
title = {Magnetic Vortices in High Temperature Superconductors},
author = {Per Hedegard},
journal= {arXiv preprint arXiv:cond-mat/0102070},
year = {2007}
}