Dynamical Theory of Neutron Diffraction by Magnetic Crystals for Laue Geometry

Abstract

AbstractThe dynamical diffraction of thermal neutrons by magnetic crystals is being considered for the case of the symmetrical Laue‐geometry. It is shown that the results depend on the angle between BA, the average value of the magnetic field in the crystal, and BH, the Fourier‐transform of the magnetic field. The neutron wave function in the crystal consists of four wave‐fields, which have the form |Ψ> =[Ψ0|χ0> +ΨH|χH> · exp (i Hr)] · exp (ik′r), where |χ0> and |χH> are spin states. In the general case |X0> and |X)H> differ from each other. The ratio of the reflected to the incident intensity is derived for the incidence of neutrons polarized parallel or antiparallel to BA and for the incidence of unpolarized neutrons, for the case of pure magnetic diffraction, and for the case that BA is normal to BH. In both cases, for each of the two spin‐directions of the incident beam, there are up to two Braggpeaks. For unpolarized neutrons there are up to three peaks.