Spin-acoustic Wave Interaction in Time-and-spatially-varying Magnetic Fields

Theoretical and experimental investigations were conducted on the propagation of elastic, magnetoelastic, and spin waves in the presence of time-varying and time- and spatially-varying magnetic fields. The propagating media are axially biased rods of yttrium iron garnet (YIG), Ga substituted (GaYIG), Mn substituted YIG (MnYIG), and non-magnetic yttrium aluminum garnet (YAG), all much larger than the propagation wave length so that a uniform plane wave solution description is possible. The theoretical calculations and experimental results verify that a magnetoelastic wave propagating in a time-varying magnetic field experiences a change in frequency (energy) at constant wavenumber (momentum) while the same wave propagating in a spatially-varying magnetic field experiences a change in wavenumber (momentum) at constant frequency (energy). A time- and spatially-varying field yields changes in both frequency and wavenumber and results in frequency and wavenumber sweeping. The use of both time-varying and spatially-varying magnetic fields provides a number of new signal processing effects. (Author).