| The magnetic properties of (Co,Fe)(,3n+5)R(,n+1)B(,2n )(R = Y, Ce, CeMM, Pr, and Gd) (n = 1,2) and the ternary boride of Fe-R-B, nominally Fe(,14)R(,2)B, were investigated(,.); For the (Co,Fe)(,3n+5)R(,n+1)B(,2n) homologous series (R = Y, Ce, CeMM, Pr, Sm, Gd) (n = 1,2,3), the results of previous work and the present investigation can be summarized as follows: (1) The magnetic moments and Curie temperatures decrease with increasing boron content in the compound series. (2) For Co-Sm-B and Co-Gd-B compound series the coercivity increases with increasing boron content in the compound, but this was not observed in other rare earth compound series. The coercive forces obtained without special treatment have the highest values for the compounds with Sm and Gd. (3) The moment and the Curie temperature vary according to the type of rare earth element in the compound as well as its elemental moment and its coupling in the structure. The compounds with Sm have the highest Curie temperatures. (4) The Fe-replacement for Co atoms increases both the values of magnetic moments and Curie temperatures as the Fe content increases in the structure. The presence of Fe atoms does not increase the coercivity except for compounds based on Sm and Pr. (5) The maximum inclusion of Fe in each homologue decreases systematically with increasing series index n. (6) The addition of Zr increases the coercivity of the compound series.; The properties of cobalt-free and samarium-free permanent magnet materials based on an iron-rare earth boride can be summarized as follows: (1) The magnetic phase in the Fe-Pr-B system has a primitive tetragonal lattice (a = 0.886, c = 1.224 nm). It exhibits high magnetocrystalline anisotropy with a single easy axis along 001 . The systems Fe-La-B, Fe-Ce-B, Fe-Nd-B, Fe-Sm-B, and Fe-Gd-B have the same phase and comparable properties. (2) The ideal composition of the tetragonal magnetic boride is Fe(,14)R(,2)B; its real composition may be Fe(,14)R(,2)B(,1+x) where x is a fraction. (3) The tetragonal boride does not melt congruently. The amount of primary iron phase decreases in the direction La(--->)Pr(--->)Nd. Ni does not form the tetragonal phase. (4) The addition of Co and Ni increases the Curie temperature of the boride while the addition of Mn decreases the Curie temperature. (5) We believe that a major contribution to coercivity in sintered Fe-Nd-B magnets is due to particle size and a smaller fraction to inclusions or a defect structure. |
