Rare-earth magnet

• US 8,119,260 B2
• Filed: 07/27/2005
• Issued: 02/21/2012
• Est. Priority Date: 07/28/2004
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Komuro, Matahiro, Satsu, Yuichi, Maeda, Kunihiro, Kozono, Yuzo
• Primary Examiner(s): Ruthkosky, Mark
• Assistant Examiner(s): HARRIS, GARY D
• Application Number:
  US11/189,912
• Publication Number:
  US 20060022175A1
• Time in Patent Office: 2,400 Days
• Field of Search: 428/693.1, 428/636, 428/692.1, 428/900
• US Class Current: 428/693.1
• 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 sintered magnet comprising:

a host phase of a NdFeB series ferromagnetic material containing Nd as at least one kind of rare-earth element,

a primary coating being formed on a surface of the host phase substantially along an outer periphery of the host phase, the primary coating being constituted by a rare-earth element containing layer having rare-earth element concentration higher than that of the host phase, and

a fluorine-containing layer containing rare-earth element and fluorine having a fluorine concentration higher than that of the host phase and containing 10 atom % or more of fluorine, the fluorine-containing layer being formed on the primary coating in a continuous layer,

wherein the average thickness of the fluorine-containing layer is thicker than that of the primary coating, and which is 1 nm to 10000 nm.

2. The rare-earth sintered magnet according to claim 1, wherein the fluorine-containing layer contains 50 atom % or more of fluorine.

3. The rare-earth sintered magnet according to claim 1, wherein the host phase, the primary coating, and the fluorine-containing layer have been heat treated at a temperature of from 600°

C. to 1200°

C.

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