Theory of magnetic neutron small-angle scattering using the dynamical theory of diffraction instead of the Born approximation. II. The behaviour of the intensity of neutrons after transition through a helical magnetic structure

Abstract

The internal magnetic structure of Bloch walls is idealized in a model with a conical helix of uniform pitch. The solution of the Schrödinger equation in this wall and the solution in the domains divided by the wall are applied to solve the boundary value problem on the two sides of the wail. Thence the transmission and reflectivity of the wall are determined. The solution is investigated further by calculation of the behaviour of the spin direction of a neutron in the wall. The result shows that the intensities of the direct and deflected beams depend on the path of the transition of the magnetization from the direction in the first domain to that in the second domain in the interior of the wall, i.e. on the wall thickness. It also indicates the possibility of an approximate method, the results of which are compared with the results of the exact method. Both methods described give results other than the Born approximation, until now the only possible method. It appears necessary for the elements of the method described here to be applied to magnetic scattering far from Laue reflections, i.e. in small-angle scattering.