Nonmagnetic Inclusions in Ferrites for High‐speed Switching

A technique is described for obtaining fast switching in square‐loop ferrites. Domain wall motion is inhibited by addition of nonmagnetic inclusions such as thorium oxide and palladium. The magnetization is then reversed by the faster nonuniform rotational mode of switching. Coincident current switching times as low as 0.10‐μsec were measured for samples containing inclusions. A control sample of the same composition, but without inclusions, had a switching time of 0.85μsec. This technique improved the stability of ferrite properties with respect to firing time and temperature and the presence of reactive impurities. For example, the coercive force varied by no more than ±2% within a 4‐hour range of firing times and only ±6% variation was noted for a 50°C range of firing temperatures. A similar stabilizing effect occurred when inclusions were added to a ferrite containing 0.03 at.% calcium, a reactive impurity.