Patent ID: 7559996

Claim:
A method for preparing a rare earth permanent magnet from a sintered magnet body of a R 1 —Fe—B composition wherein R 1 is at least one element selected from among rare earth elements inclusive of Y and Sc, the method comprising the steps of: forming a plurality of slits in at least one surface of the magnet body, disposing a powder on the magnet body surface, the powder comprising at least one compound selected from among an oxide of R 2 , a fluoride of R 3 , and an oxyfluoride of R 4 wherein each of R 2 , R 3 , and R 4 is at least one element selected from among rare earth elements inclusive of Y and Sc, and heat treating the magnet body and the powder at a temperature equal to or below the sintering temperature of the magnet body in vacuum or in an inert gas, wherein the formation of the slits facilitates absorption of at least one of R 2 , R 3 and R 4 in the magnet body from the powder comprising at least one of the oxide of R 2 , fluoride of R 3 , and oxyfluoride of R 4 present on the magnet surface, thereby increasing a coercive force.