Neutrons at the boundary of magnetic media

The behavior of a neutron as a quantum-mechanical top at the boundary of two magnetically noncollinear media is analyzed. Attention is paid to such phenomena as splitting of reflected and refracted beams, total reflection forwards, cross interference, polarization and depolarization effects. The exact formulae are obtained for the reflectivity and transmittance of neutrons with the spin precessing in the guide field. In a weak guide field approximation, they are simplified and generalized for a stratified, collinearly magnetized, medium and for oscillating guide fields. It is pointed out that reflection of neutrons can be used to study the spin superposition and to carry out the Wigner experiment on the result of a quantum mechanic measurement. Neutron spin turners including flippers can be made with mirrors on the basis of magnetically anisotropic thin films.