Preparation of composite ultrastrong permanent magnet composed of hard and soft magnetic materials by MA

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The purpose of this research is to develop the ultrastrong permanent magnet composed of hard and soft magnets by MA, and we succeeded in (Sm-Co)+Fe system. The results obtained are summarized as follows : The powder annealed at comparatively low temperature in vacuum after MA was composed of fine grains whose size was 10-30 nm in diameter and showed superior magnetic properties. When the annealing temperature was raised to 1073 K, most of Fe was consumed for the growth of 2-17 phase. This consumption of Fe and the growth of 2-17 phase resulted in the decrease of the remanence and coercivity. The powder without Fe showed low remanence and its maximum energy product was very low. On the other hand, remanence enhancement was found in the powder to which Fe was added, and the remanece increased with increasing Fe concentration. Though the shape of demagnetization curve varied with Fe concentration, the maximum product of about 100 kj/m^3 was obtained for both high and low Fe concentration samples. Such superior magnetic properties seemed to be the result of exchange interaction between hard and soft phase. The specimen obtained in this experiment was magnetically isotropic. And it is under investigation how to get the Sm_2Fe_<17>N_<2x> specimen with magnetic anisotropy.