Magnetism and neutron scattering

Magnetic neutron scattering is very closely connected to the fundamental magnetic quantities of magnetisation and susceptibility. This is because, to a very high degree of approximation which becomes exact at long neutron wavelengths, the interaction of the neutron magnetic dipole moment is with the local magnetic induction in the magnetic material. The strength of neutron scattering for the investigation of magnetic materials lies in this and the facility of the technique to probe Fourier components of the moment and the susceptibility with wavelengths down to atomic distances, as well as to probe susceptibility fluctuation time scales the same as those that are thermally excited. This paper provides a concise account of the formal connection between neutron scattering cross sections and more familiar bulk magnetic parameters. (author)