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

The magnetoelastic contribution Delta (C) over cap((3)) to the effective third-order elastic constants (C) over cap((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 Delta (C) over cap((3).) Quantitative estimates are obtained for yttrium iron garnet. (C) 1998 American Institute of Physics. [S1063-7834(98)02511-8].