Excitation of Spin Waves in a Ferromagnet by a Uniform rf Field

It is possible to excite exchange and magnetostatic spin waves in a ferromagnet by a uniform rf field, provided that spins on the surface of the specimen experience anisotropy interactions different from those acting on spins in the interior. Modes with an odd number of half-wavelengths should be excited in a flat plate. The definition of what is meant by a different anisotropy interaction is worked out and is a rather lenient condition. Experiments which would determine the exchange energy constant should be possible using sufficiently thin platelets of single crystals having parallel faces. It is perhaps not unlikely that the theory may account for the observation by Waring and Jarrett of a large number of resonance peaks in NiMn${\mathrm{O}}_3$.