JPH0576521B

PURPOSE:To lessen the deterioration of magnetic characteristics as a result of cutting by injecting hard powder under pressure to the surface of a sintered magnet body consisting essentially of a specific rare earth, B and Fe to remove the surface layer and depositing a thin Al film on such surface. CONSTITUTION:The sintered permanent magnet body which consists essentially of 10-30atom% R, 2-28% B and 65-80% Fe and of which the main phase consists of a tegragonal crystal phase is molded. R is >=1 kinds among Nd, Pr, Dy, Ho and Tb and >=1 kinds among La, Ce, Sm, Gd, Er, Eu, Tm, Yb, La and Y. >=1 kinds of the hard powders such as Al2O3 powder having 20-35mum average grain size and >=5 Mohs hardness are injected together with a pressurized gas such as gaseous N2 under 1.0-6.0kg/cm pressure for 0.5-60min onto the surface of such magnet body to remove the surface layer of the magnet body. The thin Al film layer is then deposited by an ion plating method, etc. on such surface. The deterioration of the magnetic characteristics by cutting are lessened and the excellent corrosion resistance is provided to the magnet body by the above-mentioned method.