ABSTRACT
Experiments provide the quantitative information about materials properties on which all applications depend. They also serve to inspire and refine physical theory. The traditional image of apparatus on a laboratory bench has evolved so that some measurements are conducted at national or multinational institutes built around large-scale facilities for generating high magnetic fields, neutron beams or intense streams of UV or x-ray radiation. The foundation of magnetism in solids is the atomic-scale structure of the crystal. The electronic structure of the atoms, together with the crystal structure of the solid, determine atomic moments, exchange and dipolar interactions and crystal fields which are the ingredients of collective magnetic order. Direct imaging of individual magnetic atoms is at the extreme limit of experimental capabilities. A beam of radiation is needed whose wavelength is comparable to the inter-atomic spacing. The radiation is scattered by the atomic electrons or nuclei or, in the case of neutrons, by the magnetic moments of the electrons.
