A single phase consisting of a ThMn.sub.12 phase can be obtained by having the composition thereof represented by a general formula R(Fe.sub.100-y-wCo.sub.wTi.sub.y).sub.xSi.sub.zA.sub.v (in the general formula, R is at least one element selected from rare earth elements (here the rare earth elements signify a concept inclusive of Y), Nd accounts for 50 mol % or more of R, and A is N and/or C) in which the molar ratios in the general formula are such that x=10 to 12.5, y=(8.3-1.7.times.z) to 12.3, z=0.1 to 2.3, v=0.1 to 3 and w=0 to 30, and the relation (Fe+Co+Ti+Si)/R>12 is satisfied.