Development of High-performance Magnetic Coupling Composite-type Rare Earth Magnets

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Rare earth permanent magnets produced from intermetallic compounds with excellent magnetic property such as Sm_2Fe_<17>N_x and Nd-Fe-B HDDR materials contribute to fabricate the portable-type high-performance OA, audio players. Particularly, these materials can be molded as bonded magnets with good accuracy for the dimension control.From the above point of view, this work was made to prepare the good oxidation-resistant bonded magnets from the Sm_2Fe_<17>N_x and Nd-Fe-B HDDR powders by surface coating methods of zinc metal vapor sorption and/or Self Assemble Monolayer (SAM) coating (Zn/Nd-Fe-B and SAM/Sm_2Fe_<17>N_x). The resultant bonded magnets provide high (BH)max values of 166 and 183 kJ/m^3 for Zn/Nd-Fe-B and SAM/Sm_2Fe_<17>N_x, respectively. In addition, the high-performance magnetic coupling composite-type bonded magnets were prepared from the mixture of Nd-Fe-B HDDR and SAM/Sm_2Fe_<17>N_x powders. The (BH)max values observed were around 200 kJ/m^3 and the magnets were stable toward the oxidation by air or water.