Ｇｄイオン置換によるＺ型フェライトの高周波初透磁率の改善

Abstract

Ceramics made from a series of room-temperature ferrimagnetic mixed oxides, Ba3Co2GdxFe24-xO41 (x = 0-1.0), with Z-type structure, were prepared by the conventional powder metallurgy method. A series of Ba3Co2GdxFe24-xO41 samples were made with BaCO3, CoO, Gd2O3, and α-Fe2O3 as starting materials. The frequency dependence of the initial permeability of all samples was measured. The initial permeability of Ba3Co2Gd0.1Fe23.9O41 was 22.3 (at 0.1 GHz), which was the highest of all the samples. It was a remarkably high value compared with those reported for isotropic samples. The crystal structure was determined by the x-ray diffraction method; a single phase of the Z-type structure was obtained for Ba3Co2GdxFe24-xO41 (x = 0.01, 0.1). Gadolinium ions formed a solid solution of Co2Z ferrite. This is one of the reasons for the high initial permeability. The other reasons are higher densification and the change in magnetic anisotropy caused by a small quantity of Gd ions forming a solid solution of the Z-phase.