Generation of Spin Waves in Nonuniform Magnetic Fields. III. Magnetoelastic Interaction

If a spin wave propagates through a region of nonuniform magnetic field in which the effective magnon wavenumber equals the phonon wavenumber, it is partially converted into an elastic wave. The conversion efficiency depends primarily on the field gradient (H′) at the crossover point. Theories have been developed both for the case of weak magnetoelastic coupling and strong magnetoelastic coupling. For weak coupling the magnon-phonon conversion efficiency ηmp is ηmp=H′crit/|H′| (for |H′|>>H′crit), whereas for strong coupling ηmp = 1−π2exp(−H′crit/|H′|) (for |H′|<