Neutron magnetic form factor in studies of f-electron instability

The main results obtained in measurements of neutron magnetic form factors for rare earth systems with strong electronic correlations are presented.It is shown that in some cases neutron spectroscopy methods can provide information on the valence unstable state in the f-electron system, which is unique as regards the development of adequate physical concepts.Studies of the magnetic form factor in intermediatevalence systems based on Sm (SmB 6 , SmS) and Eu (EuCu 2 Si 2 type) and their impact on the shaping of a realistic description of the physical nature of the intermediate valence state are discussed in detail.