Spin-Wave Propagation and the Magnetoelastic Interaction in Yttrium Iron Garnet

Abstract

Excitation of spin waves by the method of nonuniform internal dc magnetic fields in disk‐shaped samples is demonstrated in two types of experiments. The first is a cw microwave absorption experiment in YIG disks. At high gain an absorption continuum is observed on the low field side of the magnetostatic mode spectrum of a disk magnetized perpendicular to its plane. This is shown to correspond to the expected absorption due to certain spin‐wave modes in terms of the field values at which it occurs, its intensity and general shape. The second type of experiment permits observation of the propagation of microwave pulses via short wavelength spin waves and coupled magnetoelastic waves. The propagation time of the pulses is analyzed in terms of the group velocity of these waves and found to be in good agreement using known values of the exchange constant and velocities of elastic waves in YIG. The magnetoelastic coupling constant b₂ in YIG is estimated from these experiments to be of the order of 10⁷ ergs/cm³ or less.