Study of Magnetoelastic Interactions by Parallel Pumping

Abstract

Magnetoelastic interactions, the coupling of spin waves with phonons, have been studied in single crystals of yttrium iron garnet using the parallel pumping technique. Observations of the coupling have been made for various temperatures and crystalline orientations at 4.75 and 11.6 kMc. An increase in the threshold field for spin‐wave excitation occurs when there is magnetoelastic coupling, and the form of the increase provides a line shape for the spin‐wave‐phonon interaction. From the magnitude, width, and location of the interaction line are found the acoustic Q, the magnetoelastic constant b₂, and the spin‐wave exchange constant. The quantities obtained (i.e., Q=2×10⁴ and b₂=4.7×10⁶ ergs/cm³ at room temperature) are in reasonable agreement with those from lower frequency measurements, assuming a f⁻¹ variation for Q. The magnetoelastic constant b₂ is found to increase with decreasing temperature. Correlation of the temperature variation of b₂ with theoretical predictions is good and, if the comparison is valid, provides an evaluation of the higher‐order magnetoelastic constant b₅.