Neutron small angle scattering and Bloch wall thickness of FeSi(2.5%)-single-crystals with defined domain structure

Application of a mechanical selector for neutrons makes measurements with monochromatic neutrons of 4-6A wave-length possible. At these wavelengths, the scattering at the Bloch-wall disappears at exactly grazing incidence if the wall is in a position so that the neutrons very accurately have the (110) direction. Previously observed scattering patterns appear at angles of 10-20 of incidence. Exact calculations with the solution of the Pauli equation of the problem show, that with angles greater than 0.50 one can use as approximation the usual law of diffraction with the wall as a sharp boundary. This describes the observations between 0.50 and 50. The exact solution also shows that the behaviour at smaller angles is strongly dependent on the wall thickness and may allow its measurement to be made. (Auth.)