Neutron spectroscopy and strongly correlated electrons: a view from the inside

Neutron spectroscopy results concerning the characteristic features of electronic states in strongly correlated electron systems are reviewed. It is shown that the effects of crystal electric field, exchange interaction, and local-itinerant electron hybridization, separately or in combination, manifest themselves in the spectral features of magnetic neutron scattering. The review discusses information that can be obtained from these spectra to be used to investigate the nature of heavy-fermion, intermediate-valence, and a number of other nontrivial types of ground states occurring in this class of systems. Problems interpreting experimental results are pointed out, suggesting the need for the development of the existing models.