Themes
In the area of quantum magnetism current work includes neutron scattering experiments from the quasi-one-dimensional spin-1/2 Heisenberg insulating antiferromagnet, KCuF3. This system lies in the crossover region between a conventional three-dimensional magnet which is characterised by Néel ordering and spin-wave excitations, and a one-dimensional spin-1/2 antiferromagnet characterised by exotic multi-spinon excitations and the absence of long-range Néel order. These measurements suggest a physically appealing picture of spinons at high energies, separated from spin-waves at low energies by a novel longitudinal mode which is a manifestation of dimensional crossover.
Other work has focused on the cuprate high-temperature superconductors. Here the pairing mechanism is unknown research area. Recent experiments on Sr-doped La2CuO4 using neutron scattering to measure the changes that take place when a magnetic field is applied in the superconducting state, show that for small fields there is a large enhancement of the antiferromagnetism at temperatures within the superconducting phase. The results reveal the strong differences between cuprate and conventional superconductors and demonstrate the important role that magnetic interactions play in these systems.
