GB441714A - Improvements in or relating to a method of manufacturing a magnet made of metal oxide - Google Patents

Abstract

441,714. Magnets. MITSUBISHI DENKI KABUSHIKI KAISHA, 4, Nichome, Marunouchi, Kojimachi-ku, Tokio. Sept. 8, 1934, No. 25898. Convention date, June 14. Drawings to Specification. [Class 35] A permanent magnet is pressed or otherwise formed from a mixture of iron oxide with cobalt oxide and /or nickel oxide, or a mixture of iron oxide with cobalt ferrite and /or nickel ferrite, the mixture being subjected during or after the forming operation to heat treatment at temperatures ranging from 850 to 1150‹ C., and then magnetized, the magnetizing operation being commenced at a raised temperature. The Specification describes two examples, viz. : mixtures of magnetic oxide of iron and cobalt ferrite and of iron oxide and cobalt ferrite in equimolecular proportions and figures for residual magnetism and coercive force are given for different temperatures of heat treatment. The magnet is placed in an electromagnetic field at a temperature of 300-500‹ C., and allowed to cool therein. Such a field may be obtained by the use of continuous or alternating current. The Specification as open to inspection under Sect. 91 gives other examples employing (1) Fe3O4 and CoFe2O4 with or without NiFe2O4 and (2) Fe(NO3)3 with Co(NO3)3 or with Co(NO3)2 and Ni(NO3)2. This subject-matter does not appear in the Specification as accepted.