Cobalt is electro-deposited on the anodic oxide cating of aluminum in the sulfate solution with an alternating current. Cobalt metal, electro-deposited in regularly arranged columnar pores of the anodic surface of aluminum, shows strong magnetic anisotropy and can be used as a memory material for magnetic devices. The results of the present study are as follows:
(1) Electron microscopic and X-ray studies revealed that fine granular metals of α-cobalt existed in columnar micro-pores of the anodic coating.
(2) Strong magnetic anisotropy perpendicular to the surface was observed in films which were anodized in the sulfric acid, the oxalic acid and the sodium bisulfate solution. However, films anodized in the chromic acid and the sodium hydroxide solution showed weak anisotropy. Further, it was found that the anisotropy of films anodized in the phosphoric acid was stronger along the parallel direction than along the perpendicular direction.
(3) Coercive forces of anodic oxide films formed in the sulfuric acid depended on the elctrolytic voltage and varied between 1000 and 1600Oe. Residual magnetization increased with the amount of deposited metals.