Nickel Aluminum Gallium Ferrites for Use at High Signal Levels

Abstract

A new nickel ferrite has been developed which contains simultaneously aluminum and gallium. Compositions have been prepared according to the formula NiAlyGaxFe2−(x+y)O4. The total substitutions of gallium and aluminum have been varied from 0 to 1.2. Several ratios of aluminum to gallium have been made. The unique feature of this system is that since the gallium substitutes in the tetrahedral sites and aluminum in the octrahedral sites, the compensation point normally associated with nickel aluminum spinels can be shifted to much higher nonmagnetic ion substitutions. There exists a composition for which there is no compensation point. Measurements of saturation magnetization, Curie temperature, linewidth, and geff factor have been made. A C-band circulator-switch using one of these materials has been constructed and successfully tested at 75-kw peak power with a 0.001 duty cycle. This device was also successfully tested at a power level of 475 w cw in an ambient temperature of 85°C.