Nonlinear interactions of acoustic modes in ferromagnets near magnetoacoustic resonance: Effective elastic constants

The magnetoelastic contribution ΔĈ ₍₃₎ to the effective third-order elastic constants Ĉ ₍₃₎ ^ef is determined; it describes the additional elastic anharmonicity induced by nonlinear spin-spin and spin-phonon interactions in ferromagnets. In the vicinity of magnetoacoustic resonance, this anharmonicity can be manifested in three-frequency elastic wave interactions, producing magnetoacoustic mode-frequency transformation effects. It is shown that these effects are magnified in resonance as the result of a huge increase (by several orders of magnitude) in the dynamic elastic constants ΔĈ ₍₃₎. Quantitative estimates are obtained for yttrium iron garnet. Fiz. Tverd. Tela (St. Petersburg) 40, 2080–2084 (November 1998)