The precipitation step may be followed by washing and separating the resultant precipitate. The step of washing may be appropriately performed until the conductivity of the supernatant reaches 5 mS/m² or lower. The step of separating the precipitate may be performed, for example, by adding and mixing a solvent, preferably water, to the resultant precipitate, followed by filtration, decantation, or other separation methods.

Oxidation Step

The oxidation step includes calcining the precipitate formed in the precipitation step to obtain an oxide containing Sm and Fe. The precipitate may be converted into an oxide by heat treatment, for example. The heat treatment of the precipitate requires the presence of oxygen. For example, the heat treatment may be performed in an air atmosphere. Since the presence of oxygen is necessary, the precipitate preferably contains oxygen atoms as nonmetallic constituents.

The heat treatment temperature in the oxidation step (hereinafter referred to as the oxidation temperature) is not particularly limited, but it is preferably 700 to 1300° C., more preferably 900 to 1200° C. If the temperature is below 700° C., the oxidation tends to be insufficient. If the temperature exceeds 1300° C., the intended powder particle shape, average particle size, and particle size distribution of the magnetic powder tend not to be obtained. The heat treatment duration is also not particularly limited, but it is preferably one to three hours.

The resultant oxide consists of oxide particles in which Sm and Fe have been sufficiently mixed microscopically and which reflect the properties of the precipitate such as shape and particle size distribution.

Pretreatment Step