To provide a rare earth magnet having excellent coercive force and a production method thereof. A rare earth magnet, wherein the rare earth magnet comprises a magnetic phase containing Sm, Fe, and N, a Zn phase present around the magnetic phase, and an intermediate phase present between the magnetic phase and the Zn phase, wherein the intermediate phase contains Zn and the oxygen content of the intermediate phase is higher than the oxygen content of the Zn phase; and a method for producing a rare earth magnet, including mixing a magnetic raw material powder having an oxygen content of 1.0 mass % or less and an improving agent powder containing metallic Zn and/or a Zn alloy, and heat-treating the mixed powder.

A method for producing a magnetic powder includes the steps of: mixing neodymium oxide, boron, and iron to prepare a first mixture; adding and mixing calcium to the first mixture to prepare a second mixture; mixing an alkali metal with the second mixture to prepare a third mixture; and placing a carbon sheet on the third mixture, placing silica sand (SiO.sub.2 sand) thereon, and then heating the same to a temperature of 800° C. to 1100° C.

R—Fe—B sintered magnet has a main phase containing R.sub.2(Fe,(Co)).sub.14B intermetallic compound and a grain boundary phase. The inter-particle grain boundary includes an expanded width part that is surrounded by a narrow width part at which the inter-particle width is 10 nm or less and that has a structure distended in the inter-particle width direction as compared with the grain boundary width of the narrow width part; the inter-particle width at the expanded width part is at least 30 nm; Fe/R ratio in the expanded width part is 0.01-2.5; the main phase includes, in the surface part thereof, an HR-rich phase represented by (R′,HR).sub.2(Fe,(Co)).sub.14B (R′ represents rare-earth elements excluding Dy, Tb, and Ho, and that essentially include Nd; and HR represents Dy, Tb, and Ho); the contained amount of HR in the HR-rich phase is higher than that in the central part of the main phase.

A permanent magnet for a motor, a rotor assembly having the permanent magnet, a motor, and a compressor are disclosed. The permanent magnet has a Nd—Fe—B-based main phase. The main phase has a grain size of smaller than or equal to 4 micrometers. The mass ratio of dysprosium and/or terbium in the permanent magnet is less than or equal to 0.5%. The intrinsic coercivity Hcj of the permanent magnet at 25° C. satisfies Hcj≥1500 kA/m. The permanent magnet according to embodiments of the present disclosure can have fewer or no heavy rare-earth elements, and meanwhile exhibit excellent performance, which improves the cost performance.

A permanent magnet for a motor, a rotor assembly having the permanent magnet, a motor, and a compressor are disclosed. The permanent magnet has a Nd—Fe—B-based main phase. The main phase has a grain size of smaller than or equal to 4 micrometers. The mass ratio of dysprosium and/or terbium in the permanent magnet is less than or equal to 0.5%. The intrinsic coercivity Hcj of the permanent magnet at 25° C. satisfies Hcj≥1500 kA/m. The permanent magnet according to embodiments of the present disclosure can have fewer or no heavy rare-earth elements, and meanwhile exhibit excellent performance, which improves the cost performance.

Disclosed are a device and method for continuously performing grain boundary diffusion and heat treatment, characterized in that the alloy workpiece or the metal workpiece are arranged in a relatively independent processing box together with a diffusion source; the device comprises, in successive arrangement, a grain boundary diffusion chamber, a first cooling chamber, a heat treatment chamber, and a second cooling chamber, and a transfer system provided between various chambers for delivering the processing box; each of the first cooling chamber and the second cooling chamber uses an air cooling system, and the cooling air temperature of the first cooling chamber is above 25° C. and at least differs by 550° C. from the grain boundary diffusion temperature of the grain boundary diffusion chamber; the cooling air temperature of the second cooling chamber is above 25° C. and at least differs by 300° C. from the heat treatment temperature of the heat treatment chamber; and the cooling chamber has a pressure of 50 kPa to 100 kPa. The device provided by the present invention can increase the cooling rate and production efficiency, and improve product consistency.

Provided is a permanent magnet including a rare-earth element R, a transition metal element T, B, Zr, and Cu. The permanent magnet contains main phase grains including Nd, T, and B, and grain boundary multiple junctions, the grain boundary multiple junction is a grain boundary surrounded by three or more of the main phase grains, one of the grain boundary multiple junctions contains a ZrB.sub.2 crystal and an R—Cu-rich phase, a concentration of B in the grain boundary multiple junction containing both the ZrB.sub.2 crystal and the R—Cu-rich phase is from 5 to 20 atomic %, a concentration of Cu in the grain boundary multiple junction containing both the ZrB.sub.2 crystal and the R—Cu-rich phase is from 5 to 25 atomic %, and a surface layer part of the main phase grain includes at least one kind of heavy rare-earth element among Tb and Dy.

Provided is a permanent magnet including a rare-earth element R, a transition metal element T, B, Zr, and Cu. The permanent magnet contains main phase grains including Nd, T, and B, and grain boundary multiple junctions, the grain boundary multiple junction is a grain boundary surrounded by three or more of the main phase grains, one of the grain boundary multiple junctions contains a ZrB.sub.2 crystal and an R—Cu-rich phase, a concentration of B in the grain boundary multiple junction containing both the ZrB.sub.2 crystal and the R—Cu-rich phase is from 5 to 20 atomic %, a concentration of Cu in the grain boundary multiple junction containing both the ZrB.sub.2 crystal and the R—Cu-rich phase is from 5 to 25 atomic %, and a surface layer part of the main phase grain includes at least one kind of heavy rare-earth element among Tb and Dy.

An R-T-B-based permanent magnet which contains R that represents at least one rare earth element essentially including Tb or Dy, T that represents Fe or at least one iron-group element essentially including Fe and Co, and B that represents boron, and further contains Cu. The total content of R is 28.35 to 29.95% by mass, inclusive, the content of Cu is 0.05 to 0.40% by mass, inclusive, and the content of B is 0.93 to 1.00% by mass, inclusive. The distribution of the concentration of Tb or Dy decreases from the outside of the R-T-B-based permanent magnet toward the inside of the R-T-B-based permanent magnet.

An R-T-B-based permanent magnet which contains R that represents at least one rare earth element essentially including Tb or Dy, T that represents Fe or at least one iron-group element essentially including Fe and Co, and B that represents boron, and further contains Cu. The total content of R is 28.35 to 29.95% by mass, inclusive, the content of Cu is 0.05 to 0.40% by mass, inclusive, and the content of B is 0.93 to 1.00% by mass, inclusive. The distribution of the concentration of Tb or Dy decreases from the outside of the R-T-B-based permanent magnet toward the inside of the R-T-B-based permanent magnet.