FUNCTIONALLY IMPROVED RARE-EARTH PERMANENT MAGNET Russian patent published in 2009 - IPC H01F1/57 H01F1/08 

FIELD: electricity.

SUBSTANCE: proposed functionally improved rare-earth permanent magnet with low eddy-current losses, in form of a sintered magnet body with composition R_aE_bT_cA_dF_eO_fM_g, is obtained through absorption of E and fluorine atoms in a sintered magnet body based on R-Fe-B from its surface. F is distributed such that, its concentration in the middle increases from the centre to the surface of the body of the magnet. Concentration E/(R+E), on the grain boundaries of surrounding grains of the primary phase (R,E)₂T₁₄A of the tetragonal system, is on average greater than concentration E/(R+E), in the grains of the primary phase. Oxyfluoride (R,E) is present on the grain boundaries in the inter-grain region, which stretches from the surface of the body of the magnet at a depth of at least 20 mcm. Particles of oxyfluoride, with diametre of equivalent round of at least 1 mcm, are distributed in the inter-grain region with quantity of at least 2000 particles/mm². Oxyfluoride particles occupy at least 1% surface area. The body of the magnet has a surface layer, with higher electrical resistance than the inner part.

EFFECT: limited generation of eddy currents in magnetic circuit.

4 cl, 4 dwg, 2 tbl, 5 ex