Development of Spring-type Magnet in Nitrogen Contained Rare-earth-Fe Compounds

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Possibility of the exchange-spring magnets in Sm-Fe-(C,N) and Nd-Fe-Mo-N systems has been studied by preparing the microduplex structure consisting of a nanocrystalline soft magnetic alpha-Fe phase and a hard magnetic Sm_2Fe_<17> (C,N) _x and Nd (Fe, Mo) _<12>N_x phase. In this study, the microduplex structure was prepared by annealing the melt-spun ribbons with amorphous state. The magnetic properties of annealed Sm_yFe_<95-y>C_5 (y=5-10) ribbons after nitriding, whose Sm content was lower than the stoichiometric composition of Sm_2Fe_<17>C,were investigated in correlation with their microstructures. In as-spun state, Sm_<7-10>Fe_<85-88>C_5 (y=7-10) ribbons consist only of amorphous phase, while in the Sm_5Fe_<90>C_5 (y=5) and Sm_6Fe_<91>C_5 (y=6) ribbons an alpha-Fe phase is also observed. The alpha-Fe phase in the ribbons with y=5 and 6 can be formed by the crystallization during melt-quenching. In all cases, the amorphous phase disappears after the annealing above 600ﾟC,resulting i … More n the microduplex structure with alpha-Fe and Sm_2Fe_<17>C_x phases. Relatively high coercivities were observed in Sm_<7-10>Fe_<85-88>C_5 ribbons after annealing and subsequent nitriding. Especially, Sm_7Fe_<88>C_5 ribbon annealed at 600ﾟC for 5min and subsequently nitrided at 450ﾟC for 4h exhibits the coercivity of 269kAm^<-1> with the maximum energy product of 70.1kJm^<-3>. In Nd-Fe-Mo-N melt-spun ribbons, the crystallization temperatures of Nd (Fe, Mo) _<12> phase with ThMn12-type structure and alpha-Fe phase are at around 600ﾟC and 500ﾟC,respectively. Nd_<0.9>Fe_<11>Mo_<0.9>N_X ribbon after heat treatment at 900ﾟC for 30 min and subsequent nitriding at 550ﾟC for 4h exhibits coercivity of 240kAm^<-1>. The V addition increases coercivity and the highest coercivity of 312kAm^<-1> can be obtained with the Nd_<0.9> (Fe_<0.98>V_<0.02>) _<11>Mo_<0.9>N_X ribbon annealed at 900ﾟC for 30min and nitrided at 550ﾟC for 4h. It can be concluded that Sm-Fe-C-N and Nd_<1-delta> (Fe, Mo) _<12>N_X melt-spun ribbons show a relatively high magnetic properties. Less