Scientific Review: Maps and Magnetism in Single Crystals

The MAPS spectrometer at ISIS is a direct geometry instrument that has been designed to measure coherent excitations in single crystals. Knowledge of the momentum, Q, and energy, _∊, dependent spectrum of excitations in a single crystal permits the most exacting tests of models for the interactions in a material. For example, the imaginary part of the generalized magnetic susceptibility, _χ'' (Q, ∊), contains the full information of the spin-spin correlation functions in a magnetic material from which the strength, range, and symmetry of the magnetic interactions can be determined. This quantity is directly measured by inelastic neutron scattering.