Rare-earth magnet

Abstract

In a ferromagnetic material containing at least one kind of rare-earth element, a layer containing at least one kind of alkaline earth element or rare-earth element and fluorine is formed at the grain boundary or near the powder surface of the ferromagnetic material. A further layer containing at least one kind of rare-earth element, having a fluorine concentration lower than that of the layer described first and having a rare-earth element concentration higher than that of the host phase of the ferromagnetic material, or an oxide layer containing a rare-earth element is formed in adjacent with a portion of the layer described first.

1 . A rare-earth sintered magnet comprising:
 a host phase of Nd 2 Fe 14 B; and   a fluorine-compound layer containing a fluorine-compound and being formed on a surface of the host phase,   wherein the fluorine-compound is an amorphous fluorine-compound and indicated as MxFy (M represents one or more metal elements, X is 1 to 5 and Y is 1 to 10), and   wherein oxides containing rare-earth elements present near a boundary between the host phase and the fluorine-compound layer.   
     
     
         2 . The rare-earth sintered magnet according to  claim 1 ,
 wherein the fluorine-compound layer contains 10 atom % or more of fluorine.   
     
     
         3 . The rare-earth sintered magnet according to  claim 1 ,
 wherein the fluorine-compound layer contains 50 atom % or more of fluorine.   
     
     
         4 . The rare-earth sintered magnet according to  claim 1 ,
 wherein the fluorine-compound contains at least one kind of oxygen, carbon, nitrogen and boron.   
     
     
         5 . The rare-earth sintered magnet according to  claim 1 ,
 an average thickness of the fluorine-compound layer is 1 nm to 10000 nm.   
     
     
         6 . The rare-earth sintered magnet according to  claim 1 ,
 wherein the fluorine-compound is any one of BaF 2 , CaF 2 , MgF 2 , SrF 2 , LiF, LaF 3 , NdF 3 , PrF 3 , SmF 3 , EuF 3 , GdF 3 , TbF 3 , DyF 3 , CeF 3 , HoF 3 , ErF 3 , TmF 3 , YbF 3 , LuF 3 , LaF 2 , NdF 2 , PrF 2 , SmF 2 , EuF 2 , GdF 2 , TbF 2 , DyF 2 , CeF 2 , HoF 2 , ErF 2 , TmF 2 , YbF 2 , LuF 2 , YF 3 , ScF 3 , CrF 3 , MnF 2 , MnF 3 , FeF 2 , FeF 3 , CoF 2 , CoF 3 , NiF 2 , ZnF 2 , AgF, PbF 4 , AlF 3 , GaF 3 , SnF 2 , SnF 4 , InF 3 , PbF 2 , and BiF 3 .   
     
     
         7 . A rotor of an electric using the rare-earth magnet according to  claim 1 .