Microwave Properties of a Calcium-Vanadium-Bismuth Garnet

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Abstract
The microwave properties of single crystals of the garnet {Ca2.5Bi0.5}[Fe2](Fe1.75V1.25)O12 were measured from 4.2°K to room temperature. This garnet is of particular interest in applications since it is free of expensive rare-earth and yttrium ions which require extensive purification. The linewidth is quite small, varying from 1.5 to 9 Oe, depending on temperature and orientation. Considering the small saturation magnetization of this garnet (4πM=610 G) the magnetic anisotropy field is unusually low at 4.2°K, namely about 275 Oe along the easy axis of magnetization. The calcium-vanadium-bismuth garnets have been found to be particularly useful in isolators for traveling-wave masers. Because of the unique combinations of low anisotropy and low magnetization, operation can be obtained at lower frequencies in the frequency-magnetic field region near g=2 than for pure or substituted yttrium iron garnet. The characteristics of such an isolator operating at 1750 Mc/sec and 300 Oe are described.