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studies. It also allows at least semiquantitative estimates of the parameters which enter many electronic properties. Finally, it provides a basis for experimentally determining a more precise band structure in terms of the observed deviations from single-OPW behavior.In this last regard, it is worth remarking that for most purposes one does rot desire a precise description of the band structure. One more generally wishes to have a parameterized model of the structure which is simple enough to allow the calculation of a particular property, but reliable enough to include the important features of that effect.In connection with the detailed studies of zinc and cadmium, rather explicit descriptions of the Fermi surfaces of these metals emerged. The surfaces resemble those shown in Fig. 3 for valence two. The surfaces in the combined first and second bands are distorted qualitatively in the manner indicated on the right-hand side of Fig. 4, but not to the extent that the lateral ridges on the surface meet the lateral edges of the zone.The ridges are everywhere rounded oG somewhat such that the cross sections of the diagonal arms are reduced by a few percent. In zinc the cross section of the horizontal ring is narrowed down by a factor of ten midway between the lateral edges of the zone; in cadmium the ring is pinched off completely in these regions. In the combined third and fourth bands the needle-like segments along the lateral edges of the zone are narrowed down greatly in zinc and disappear in cadmium. In both cases the horizontal central disk is reduced appreciably in size, while the V-shaped segments at the lateral zone faces are rounded off, but presumably not greatly reduced in size.In addition to the applications mentioned above, a study of the anomalous skin effect in aluminum was made, although there were no suitable data on singlecrystal specimens to allow for comparison. The oscillatory magnetoacoustic eGect was also discussed brieRy in terms of the method. Finally, the generalization of the scheme to a study of alloys was outlined.Examination of the spatial configuration of the magnetostatic modes of a ferromagnetic body shows that those modes whose frequency lies between a&=p(B;H,)& and co=&(K+2sM) are surface modes. It is also found that the complete spin-wave spectrum consists of a set of surface spin waves in addition to the spinwave band usually considered. The magnetostatic mode spectrum thus merges smoothly into the spin-wave spectrum.The characteristic equation for the surface modes on a plane surface at an arbitrary angle to the applied dc field is given. The properties of the surface modes on plane surfaces and on spheroidal bodies are discussed.'HE characteristic magnetostatic modes of a ferromagnetic slab, magnetized parallel to its surface, were recently examined by the authors. ' It was found that the mode spectrum extends over the same frequency range as the magnetostatic mode spectrum of a spheroid ' namely from to=&H; to &o=p(He+27rjtrI). It was also found that the spectrum of a slab c...

The characteristic modes of a thin slab magnetized in its plane are obtained in the magnetostatic limit,and the mode spectrum and configuration are discussed. The wavelength dependence of magnetostatic mode density is determined and utilized to establish a connection to the modes obtained in the spin-wave approximation. In this geometry the modes lying above the spin-wave band are surface waves, decaying toward the interior of the slab, while volume modes occur in the same frequency range as the long-wavelength limit of the spin-wave band of an infinite medium. The mode density exhibits poles at the upper and lower frequency limits of the surface mode spectrum. The surface modes become statistically less important at shorter wavelengths because the ratio of surface mode density to volume mode density varies approximately as 1/|k|.

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.

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