Magnetic scattering experiments

We discuss the relative use of neutrons and X-rays as scattering tools to p robe the magnetic properties of materials. Neutron diffraction experiments continue to be the most appropriate tool to determine the magnetic structur e of bulk solids. Synchrotron X-ray experiments are and will be used to inv estigate selectively the magnetic behaviour of different chemical species a nd/or electronic shells in magnetic systems. There exist some grey areas wh ere the two probes can be used depending on the scientific problem under in vestigation. In particular, neutrons allow very accurate measurements of ma gnetic form factors, but X-rays provide a separation of the orbital momentu m contribution to magnetisation. Comparisons between X-rays and neutrons st udies of magnetism at surfaces are presented. Finally, one can anticipate t hat only inelastic neutron scattering experiments will allow the observatio n of magnetic excitations across the whole Brillouin zone. (C) 2001 Elsevie r Science B.V. All rights reserved.