Abstract: The object of the present invention is to provide titanium discs to be used as high-density read-while-write magnetic discs. Further object of the present invention is to provide said titanium discs coated with a non-magnetic plated layer.Titanium discs to be used as magnetic discs which satisfy the above object have the following structures: A titanium disc to be used as magnetic disc having the mean height of the peaks from the center line, R.sub.a, of 0.0002 .mu.m to 0.0060 .mu.m and pits on its surface of 25 .mu.m or less in diameter or 5 .mu.m or less in depth. Further, said titanium disc to be used as a magnetic disc is coated with a non-magnetic plated layer with a thickness of 0.09 .mu.m to 5 .mu.m. Moreover, a titanium disc that is most suitable to be used as a magnetic disc is the titanium disc provided with a plated layer of 30/100 or less in a knife-cut peeling test.

Abstract: A silicon single crystal manufacturing apparatus according to the CZ method which includes a partition member for dividing a quartz crucible into a single crystal growing section and a material melting section and having at least one small hole for permitting the passage of molten silicon, and a heat keeping cover for covering the partition member and the material melting section. The heat keeping cover is made of a sheet of metal selected from the group consisting of Ta, Mo and W and containing Fe 50 ppm or less and Cu 10 ppm or less. The metal sheet includes a surface layer composed of a silicon-enriched layer, and the depth of an area of the silicon-enriched layer in which the content of Si is greater than the contents of Fe and Cu at the same position therein is not less than 10 .mu.m from the surface. The content of Fe in the silicon-enriched layer is not greater than 5 ppm.

Abstract: A method of manufacturing a magnetic disk substrate made of titanium, in which chemical etching is performed on a titanium disk for magnetic disk substrate, thereby removing a surface portion thereof having a thickness of at least 2 nm, and the new surface of the titanium disk, formed by the chemical etching, is anodized, thereby forming anodized film on the titanium disk.