title: A model of magneto-electric multipoles.
abstract: A long-known Hamiltonian of electrons with entangled spin and orbital degrees of freedom is re-examined as a model of magneto-electric multipoles (MEs). 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 MEs 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 MEs 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. An impression of thermal properties of multipoles is sought from a molecular-field model.
authors.affiliation: ISIS Facility, STFC, Oxfordshire OX11 0QX, UK. Diamond Light Source Ltd, Oxfordshire OX11 0DE, UK.
authors.forename: S W
authors.initials: SW
authors.lastname: Lovesey
authors.forename: E
authors.initials: E
authors.lastname: Balcar