Rare-earth magnet

• US 20060022175A1
• Filed: 07/27/2005
• Published: 02/02/2006
• Est. Priority Date: 07/28/2004
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Komuro, Matahiro, Satsu, Yuichi, Kozono, Yuzo, Maeda, Kunihiro
• Granted Patent: US 8,119,260 B2
• Time in Patent Office: Days
• US Class Current: 252/500
• CPC Class Codes: B22F 2203/03 for feed-back
• CPC Class Codes: H01F 1/0572 with a protective layer
• CPC Class Codes: H01F 1/0577 sintered
• CPC Class Codes: H01F 41/0293 diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets
• CPC Class Codes: H02K 1/02 characterised by the magnetic material
• CPC Class Codes: Y10T 428/32 Composite [nonstructural laminate] of inorganic material having metal-compound-containing layer and having defined magnetic layer
• CPC Class Codes: Y10T 428/325 Magnetic layer next to second metal compound-containing layer

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.

Claims

1. A rare-earth magnet comprising a ferromagnetic material containing at least one kind of rare-earth element, wherein

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, and

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.

2. The rare-earth magnet according to claim 1, wherein the thickness of the layer containing at least one kind of alkaline earth element or rare-earth element and fluorine is thicker than that of the further layer which has a high rare-earth element concentration and is formed adjacent to the host phase.

3. The rare-earth magnet according to claim 1, wherein the fluorine-containing layer is formed at the grain boundary or along the powder surface of the ferromagnetic material.

4. A rotor of an electric using a rare-earth magnet according to claim 1.