JPH0617491B

PURPOSE:To lessen the deterioration of magnet characteristics as a result of oxidation and machining by injecting hard powder under pressure to the surface of a sintered magnet body consisting essentially of a specific rare earth, B and Fe thereby removing the oxide layer and work strain layer on the 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 tetragonal 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 20-350mum 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. The oxide layer and work strain layer remaining on the surface of the magnet body are thereby removed and the deterioration of the magnet characteristics is lessened.