Theory and Application of Dipolar Ferrite Modes

Experimental verification at X and K band of theoretical calculations on the magnetodynamic resonant modes of a ferrite rod between parallel conducting sheets is reported. Critically coupled mode $Q$ 's as high as 1100 have been measured. The characteristic equation includes propagation effects and dipolar coupling between electron spins. Mode charts for the symmetric modes are displayed for biasing fields from 3 to 20 koe and for frequencies from 4 to 50 kMc for both Ferramic R-1 and polycrystalline YIG. The modes have been experimentally observed in the ranges of 10 and 20 kMc. Comparison of theoretical and experimental data is made in these bands for both R-1 and YIG. The variation of the observed loaded $Q$ with biasing magnetic field is described. The advantages that these modes possess over the magnetostatic modes for microwave engineering applications are pointed out. These include: (a) relatively high $Q$ , (b) ability to critically couple, and (c) sample size is comparable to the wavelength.