An ancient Hamiltonian of electrons with entangled spin and orbital degrees of freedom is re-examined as a model of magneto-electric multipoles. In the model, a magnetic charge and simple quantum rotator are tightly locked in action, some might say they are enslaved entities. It is shown that magneto-electric multipoles almost perfectly accord with those inferred from an analysis of magnetic neutron diffraction data on a ceramic superconductor (YBCO) in the pseudo-gap phase. Nigh on perfection between Stone's model and inferred magneto-electric multipoles is achieved by addition to the original model of a crystal-field potential appropriate for the magnetic space-group used in the published data analysis
@article{arxiv.1409.8582,
title = {A model of magneto-electric multipoles},
author = {S. W. Lovesey},
journal= {arXiv preprint arXiv:1409.8582},
year = {2015}
}