Scattering of Polarized Neutrons by Spin Waves in YIG

Abstract
The neutron diffraction technique has been employed to study the inelastic scattering of polarized 1.08‐Å neutrons by magnetic spin waves in yttrium iron garnet (YIG) at room temperature. Measurements were made for the case when the YIG scatterer was oriented near the position for (220) Bragg reflection. Quantitative confirmation has been obtained for the theoretical predictions of the dependence of this scattering on the incident neutron polarization. Two new methods are described for determining the parameter D appearing in the expression Dk2 for the energies of long‐wavelength acoustic magnons in usual ferromagnets and ferrimagnets. These methods require only measurements of the peak intensities of the diffuse magnetic reflections. The values D=0.25(+0.04, −0.03) eV·Å2 and D=0.26±0.02 eV·Å2 have been obtained for YIG by these procedures.