. The Bell System technical journal . —Typical structure of an age-hardening iron-cobalt-moiybdenuin alloy,containing 12 per cent cobalt and 16 per cent molybdenum, after quenching ° C. Mag. 125 X. These magnets are composed, according to the Japanese authors, inone instance of a solid solution of cobalt ferrite (CoFe204) in magneticiron oxide (FeFe204). Although the method of manufacture and exactcompositions are not completely disclosed, it appears that the prepara-tion involves the powdering of the metallic oxides, compressing in asuitable die to the desired shape, and subsequent h
. The Bell System technical journal . —Typical structure of an age-hardening iron-cobalt-moiybdenuin alloy,containing 12 per cent cobalt and 16 per cent molybdenum, after quenching ° C. Mag. 125 X. These magnets are composed, according to the Japanese authors, inone instance of a solid solution of cobalt ferrite (CoFe204) in magneticiron oxide (FeFe204). Although the method of manufacture and exactcompositions are not completely disclosed, it appears that the prepara-tion involves the powdering of the metallic oxides, compressing in asuitable die to the desired shape, and subsequent heating. Cobalt ferrite magnets, it is reported, are not easily magnetized atroom temperature; but if the temperature is raised, for example, to MAGNETIC MATERIALS IN RELATION TO STRUCTURE 39 300° C. the magnetization is readily accomplished. In this procedurethe magnet is cooled in the magnetizing field. If the magnet has oncebeen magnetized at the high temperature, succeeding magnetizationscan be carried out at room Fig. 20—The same alloy as shown in Fig. 19 after a subsequent aging treatment of5 hours at 725° C. Mag. 125 X. The mxagnetic characteristics of the material are illustrated in Fig. 21,in which a hysteresis loop for a metallic oxide magnet is compared withone for carbon steel. The coercive force of the new material is ap-proximately 600 oersteds and the residual intensity of magnetization,320 units, corresponding to a residual induction of approximately4000 gauss. The high coercive force of the oxide magnet makes possible the moreexact location of poles and permits the utilization of the material in 40 BELL SYSTEM TECHNICAL JOURNAL short magnets. Because of the lower density of the oxide comparedwith that of iron, the oxide magnets have approximately the sameinduction flux as metallic magnets on a weight basis. 1500 -1000 ^ y CARBON STEEL MAGNET 1 / j OXIDE MAC .NET-^ /// // // / /1 / 1 / / // / ^^ ^ -800 -600 -400 -200 0 200 400 MAGNETIC FIELD
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