The theoretical transit time is derived for propagation of spin waves across a normally-magnetized disk. The exchange-free case is described first. The group velocity is obtained for magnetostatic spin waves in an infinite slab. This is combined with the inhomogeneous internal field of a disk to compute the time delay of a wave packet in the disk. The time delay obtained from a computer calculation is compared with an approximate calculation. The dispersion relation is then modified to include exchange effects and the delay time is computed for this case. Experimental observations of microwave pulse-echo behavior in disks of yttrium iron garnet are compared with these theoretical results.
Microwave pulse-echo experiments have been performed using YIG samples, and data are presented illustrating a variety of elastic, magnetoelastic, and spin wave propagation p h e nomena. Both disks and rods of YIG were used, with excitation at X-band frequencies. The spin wave mode of propagation shows very strongly dispersive behavior when the spin wavelength is comparable to one of the sample dimensions. The group velocity is obtained from the magnetostatic mode spectrum of the appropriate configuration and is combined with the spatial variation of the internal magnetic field to compute the delay time. Exchange effects are important in the case of the disk and are included in the analysis. The agreement between theoretical and experimental delay times is quite satisfactory for all configurations.
Magnetostatic surface waves are coupled to Love waves when the substrate is magnetoelastic. The coupling causes a nonreciprocal splitting of the Love wave spectrum.
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