New Releases by Michael Richards

A theoretical and experimental study was undertaken of harmonic generation in ferrites with emphasis on the second harmonic variation of the z-component of magnetization. The normal mode formulation, based on the Holstein-Primakoff transformation, was extended to a treatment of harmonic generation from arbitrary distributions of magnetization. Experiments were performed at a fundamental frequency of 9320 mc on polycrystalline yttrium iron garnet (YIG) samples of varying composition and gave good quantitative agreement with theory for harmonic generation in the linearized region, for which the susceptibility is independent of power levels. An extensive calculation was made of the effects of spin waves excited in a conventional ferrimagnetic resonance (Suhl instability) upon harmonic generation. Spin wave excitation in the presence of crystalline anisotropy was considered. It is shown that if the sample is magnetized along an intermediate anisotropy direction, such as the (110) for cubic symmetry, the z-directed spin waves are elliptically polarized and can contribute directly to the second harmonic component. (Author).