The metallic calcium may be used in the form of granules or powder, and its average particle size is preferably 10 mm or less in order to more effectively reduce aggregation during the reduction reaction. The average particle size is determined by measuring the particle size of ten particles with a light microscope and then calculating the arithmetic average. The metallic calcium may be added in an amount that is 1.1 to 3.0 times, preferably 1.5 to 2.0 times the equivalent weight for the reaction (the stoichiometric amount required to reduce the rare earth oxide, which, if Fe is present as an oxide, includes the amount required to reduce the latter oxide).

Nitridation Step

The nitridation step includes nitriding the alloy particles obtained in the reduction step to obtain anisotropic magnetic particles. Since the particulate precipitate obtained in the precipitation step is used instead of fusing metals together, the alloy particles obtained in the reduction step are in porous bulk form. This permits the alloy particles to be directly heat treated in a nitrogen atmosphere for nitridation without being crushed. Thus, uniform nitridation can be achieved.

The heat treatment temperature in the nitridation of the alloy particles (hereinafter referred to as the nitridation temperature) is preferably set to 300 to 600° C., particularly preferably 400 to 550° C., and the atmosphere may be purged with nitrogen in this temperature range. The heat treatment duration may be selected so that the alloy particles can be sufficiently uniformly nitrided.