Rare earth permanent magnet

Details Rare earth permanent magnet Rare earth permanent magnet

2006-01-27

2009-02-10

Sheehan, John P (Department: 1742)

Metal treatment

Stock

Magnetic

C148S301000, C075S232000, C075S236000, C075S244000

Reexamination Certificate

active

07488393

ABSTRACT:
A rare earth permanent magnet is in the form of a sintered magnet body having a composition R1aR2bTcAdFeOfMgwherein F and R2are distributed such that their concentration increases on the average from the center toward the surface of the magnet body, the concentration of R2/(R1+R2) contained in grain boundaries surrounding primary phase grains of (R1,R2)2T14A tetragonal system within the sintered magnet body is on the average higher than the concentration of R2/(R1+R2) contained in the primary phase grains, and the oxyfluoride of (R1,R2) is present at grain boundaries in a grain boundary region that extends from the magnet body surface to a depth of at least 20 μm. The invention provides R—Fe—B sintered magnets which exhibit high magnet performance despite minimal amounts of Tb and Dy used.

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