Parallel Pumping of Magnetoelastic Waves in Ferromagnets

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Abstract
An analysis is presented of the parallel pumping of magnetoelastic waves in ferromagnets. The resulting general threshold expression has as special cases the spin wave and elastic wave limits. The analysis clarifies the nature of the instability near the spin‐wave‐elastic‐wave crossover where the normal modes are magnetoelastic. It is shown that the magnetoelastic notch in the spin‐wave threshold curve (hcrit vs Hdc) observed in yttrium iron garnet is not the expected behavior for materials with large magnetoelastic coupling constants, small elastic losses, and low saturation magnetization. Under these conditions and for frequencies above the crossover frequency it is shown that the lowest threshold may result from the elastic‐wave instability instead of the spin‐wave instability.