FERRIMAGNETIC MATERIAL FOR RECORDING READ OUT AND ERASE HEADS UTILISED IN MAGNETIC LAYER DEVICES AND MANUFACTURING PROCESS OF THIS MATERIAL

摘要

1414771 Nickel zinc ferrite THOMSONCSF 11 Dec 1972 [14 Dec 1971] 57146/72 Heading C1J A spinel structured polycrystalline ferrite of formula Ni 1-x Zn x Fe 2(1+e) O 4 where and -0À08 # e # 0À015 is prepared by dissolving zinc, nickel and iron salts (e.g. sulphates) of at least 99% purity in water, dehydrating mixture of salts thus obtained by heating at approximately 220‹ C., decomposing to the oxides at approximately 800‹ C., fabricating the powder obtained into a disc, sintering at between 400‹ C., and 1200‹ C. and at between 0À5 and 1 metric ton/cm.SP2/SP for between 15 and 300 minutes and cooling in air for 5-10 hours. In a modification powders of zinc, nickel and iron oxides (purity at least 99%) are mixed, fabricated and subsequently treated as above. In this modification the mixed powders of the oxides may be crushed in steel vessels containing steel balls in the presence of distilled water for 24 hours, dried, fired at between 900‹ C. and 1100‹ C. for at least 1 hour, again crushed in the above manner for 48 hours and again dried prior to the fabrication. Fabrication is by mixing the powder with an organic binder (e.g. polyvinyl alcohol), producing a granulate by screening or by atomizing, pressing the granulate in a cylindrical mould and heat-treating to eliminate the binder.