The heat treatment temperature in the orientation step is preferably, for example, 90 to 200° C., more preferably 100 to 150° C. The magnitude of the orientation field in the orientation step may be, for example, 720 kA/m. The magnitude of the magnetizing field in the magnetization step may be, for example, 1500 to 2500 kA/m.

Examples are described below. It should be noted that “%” is by mass unless otherwise specified.

Fe—Sm Sulfuric Acid Solution

FeSO₄.7H₂O (5.0 kg) was mixed and dissolved in pure water (20.0 kg). Then, Sm₂O₃ (0.49 kg) and 70% sulfuric acid (0.74 kg) were added to the mixture and completely dissolved with adequate stirring. Next, pure water was added to the resultant solution to adjust the final Fe and Sm concentrations to 0.726 mol/1 and 0.112 mol/l, respectively. The resulting solution was used as a Fe—Sm sulfuric acid solution.

Fe—Sm—La Sulfuric Acid Solution

FeSO₄.7H₂O (5.0 kg) was mixed and dissolved in pure water (20.0 kg). Then, Sm₂O₃ (0.48 kg), 31.8% LaCl₃ (0.071 kg), and 70% sulfuric acid (0.72 kg) were added to the mixture and completely dissolved with adequate stirring. Next, pure water was added to the resultant solution to adjust the final Fe, Sm, and La concentrations to 0.726 mol/1, 0.109 mol/l, and 0.0063 mol/l, respectively. The resulting solution was used as a Fe—Sm—La sulfuric acid solution.

Fe—Sm—La—Co Sulfuric Acid Solution