Magnon scattering of slow neutrons on a pyrrhotite single crystal

Abstract

The magnetic inelastic scattering of a monoenergetic beam of neutrons, λ0 = 1.376 Å, on a natural single crystal of pyrrhotite, Fe1—δ S, was investigated. The scattering surface connected with τ = (001) was examined by means of the Cracow neutron spectrometer installed at the TVRS reactor in Vinca. The energy analysis together with the diffraction method were applied and are described. The results are interpreted in the frame of spin wave theory. A spin wave (magnon) dispersion relation for the acoustical branch was obtained and its anisotropy discovered. Evidence for the optical branch was also found. A model is proposed which agrees with the observed phenomena when relevant calculations are performed