Temperature Stable Microwave Hybrid Garnets

Abstract

Temperature stability of the magnetization of microwave garnet materials is very desirable provided in obtaining this stability the linewidth, g factor, and Curie temperature of the material are still suitable for microwave applications. Most rare-earth garnets possess compensation points in their magnetization vs temperature characteristics. These compensation points when suitably controlled by ionic substitutions can be used to produce microwave garnet materials whose magnetizations are quite temperature independent. The microwave properties of the following compositions have been investigated: 3[(1−X−Z)Y2O3·XGd2O3·ZDy2O3]·5[(1−W)Fe2O3·WAl2O3], for X=0 to 1.00, Z=0 to 0.1, and W=0 to 0.1. The magnetizations of these compositions have been studied from −195°C to the Curie temperatures. The compensation points of the magnetization are controlled by varying the rare-earth and aluminum content of the material. The result is a series of materials possessing magnetizations in the region of 1200 to 300 gauss which vary no more than ±10% over the temperature range of −25° to +125°C. The other associated properties of these compositions are very suitable for microwave applications. The thresholds for nonlinear effects in these materials are relatively high particularly for those compositions containing dysprosium. Many temperature stable microwave components have been developed for high-power applications using these materials.