Acoustic Magnon Research Articles

The propagation and attenuation of acoustic waves in ferromagnetic metals

The physics underlying the propagation and attenuation of acoustic waves in ferromagnetic metals is discussed. The propagating modes are considered as coupled acoustic phonon-magnon-photon modes and their dispersion relation is derived for both ferromagnetic insulators and metals by treating the modes as electromagnetic waves. The damping of the coupled modes is discussed in terms of the individual damping mechanisms for the acoustic phonons, magnons and photons and their relative content as a function of frequency. Data on the attenuation of high frequency (220 MHz) sound waves at low temperatures in ferromagnetic Ni is presented and discussed.

Scattering of Polarized Neutrons by Spin Waves in YIG

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.