Ge-substituted ferroxplanes

We examined the formation of Ba/sub 3/Co/sub 2+x/Ge/sub x/Fe/sub 24-2x/O/sub 41/ substitutional solid solutions having the Z structure and the effects of Ge/sup 4 +/ on the major magnetic characteristics. We chose germanium for the following reasons. One anticipates that the tendency of Ge/sup 4 +/ (3d/sup 10/) to form sp/sup 3/ bonds will stabilize the ions in tetrahedral positions, which should increase the resultant magnetization. Since Ge/sup 4 +/ has a small ionic radius (0.44 A), the replacement may reduce the ionic separation and thus may strengthen the exchange interaction. We used polycrystalline ferrites made by ceramic technology and having x = 0.1 to examine how the phase composition varied with the sintering temperature by applying x-ray phase analysis to textured specimens. Specimens made at temperatures corresponding to the maximum Z phase yield were used in measuring the saturation magnetization in pulsed fields up to 4 x 10/sup 6/ A/m, while the anisotropy field was measured by the singular-point method, and the Curie temperature T/sub C/ and spin-orientation transition temperature T/sub t/ (from easy plane to easy axis) from the temperature dependence of the initial permeability.