An R-T-B based permanent magnet includes main phase grains composed of R.sub.2T.sub.14B type compound. R is a rare earth element. T is iron group element(s) essentially including Fe or Fe and Co. B is boron. An average grain size of the main phase grains is 0.8 μm to 2.8 μm. The R-T-B based permanent magnet contains at least C and Ga in addition to R, T, and B. B is contained at 0.71 mass % to 0.86 mass %. C is contained at 0.13 mass % to 0.34 mass %. Ga is contained at 0.40 mass % to 1.80 mass %. A formula (1) of 0.14≦[C]/([B]+[C])≦0.30 is satisfied, where [B] is a B content represented by atom %, and [C] is a C content represented by atom %.

An R-T-B based permanent magnet includes main phase grains composed of R.sub.2T.sub.14B type compound. R is a rare earth element. T is iron group element(s) essentially including Fe or Fe and Co. B is boron. An average grain size of the main phase grains is 0.8 μm or more and 2.8 μm or less. The R-T-B based permanent magnet contains at least C and Zr in addition to R, T, and B. B is contained at 0.75 mass % or more and 0.88 mass % or less. Zr is contained at 0.65 mass % or more and 5.00 mass % or less. A formula (1) of 5.0≦[B]+[C]−[Zr]≦5.6 is satisfied, where [B] is a B content represented by atom %, [C] is a C content represented by atom %, and [Zr] is a Zr content represented by atom %.

A method of producing a sintered magnet is disclosed herein. In some embodiments, a method of producing a sintered magnet comprises, sintering a R—Fe—B based magnetic powder to produce a sintered magnet; wherein the R is Nd, Pr, Dy, Ce or Tb, and infiltrating a eutectic alloy into the sintered magnet, wherein the eutectic alloy contains Pr, Al, Cu and Ga, and wherein infiltration the eutectic alloy includes applying the eutectic alloy to the sintered magnet and heat-treating the sintered magnet to which the eutectic alloy is applied.

A magnetic core includes a metal magnetic powder, which has a large size powder, an intermediate size powder, and a small size powder. A particle size of the large size powder is 10 μm or more and 60 μm or less. A particle size of the intermediate size powder is 2.0 μm or more and less than 10 μm. A particle size of the small size powder is 0.1 μm or more and less than 2.0 μm. The large size powder, the intermediate size powder, and the small size powder have an insulation coating. When A1 represents an average insulation coating thickness of the large size powder, A2 represents an average insulation coating thickness of the intermediate size powder, A3 represents an average insulation coating thickness of the small size powder, A3 is 30 nm or more and 100 nm or less, A3/A1≥1.3, and A3/A2≥1.0.

The present invention discloses a short process preparation technology of sintered NdFeB magnets from the NdFeB sludge, which relates to a field of recycle technology of NdFeB sludge. The present invention comprises the following steps: water bath distillation of organics in sludge, ultrasonic cleaning, calcium reduction and diffusion, ultrasonic rinsing in a magnetic field and drying, powders mixing and sintering. NdFeB sludge as raw materials was directly prepared from recycled sintered magnets with high magnetic properties. Most of the organics in the sludge could be removed by a vacuum distillation process with stepwise heating. The ultrasonic rinsing process in a magnetic field could effectively remove the remaining organics. The recycled sintered magnets exhibited good maximum energy product [(BH).sub.max] of 35.26 MGOe. The present invention has important features, such as the short processing time, efficient environmental protection, high recycling rate and effective utilization rate of rare earth metals.

Rare earth-containing alloy flakes and a sintered magnet made of the same are provided, which alloy flakes are useful in the production of sintered magnets of which Br and HcJ may be excellent and well-balanced according to the Dy and/or Tb content. The rare earth-containing alloy flakes are R-TM-A-M-type alloy flakes which have a particular composition, and a structure having a Nd.sub.2Fe.sub.14B main phase and a boundary phase, the Fe content in the boundary phase is not more than 10 mass %, and a ratio of the total content (b) of Dy and Tb in the boundary phase to the total content (a) of Dy and Tb in the main phase is higher than 1.0, and are useful as a sintered magnet material.

A step of, while a powder of an RLM alloy (where RL is Nd and/or Pr; M is one or more elements selected from among Cu, Fe, Ga, Co, Ni and Al) and a powder of an RH compound (where RH is Dy and/or Tb; and the RH compound is one, or two or more, selected from among an RH fluoride, an RH oxide, and an RH oxyfluoride) are present on the surface of a sintered R-T-B based magnet, performing a heat treatment at a sintering temperature of the sintered R-T-B based magnet or lower is included. The RLM alloy contains RL in an amount of 65 at % or more, and the melting point of the RLM alloy is equal to or less than the temperature of the heat treatment. The heat treatment is performed while the RLM alloy powder and the RH compound powder are present on the surface of the sintered R-T-B based magnet at a mass ratio of RLM alloy:RH compound=9.6:0.4 to 5:5.

The present disclosure provides a method for preparing a high-coercivity sintered NdFeB magnet. The method including the steps of: S1, Providing a NdFeB powder as a main material; S2, Vacuum coating a layer of a rare earth alloy R.sub.xH.sub.(100-x) on a surface of a metal nano-powder M to obtain an auxiliary alloy material with a core-shell structure, with R being selected from one or more of Dy, Tb, Pr, Nd, La, and Ce; H being selected from one or more of Cu, Al, and Ga; the nano-powder M being selected from one or more of Mo, W, Zr, Ti, and Nb; 0≤x≤90 wt. %; S3, Adding the auxiliary alloy material obtained by step S2 to the NdFeB powder of step S1 and mixing, then orientation pressing of the mixture to obtain a compact body; and S4, Sintering and annealing treatment of the compact body to obtain the high-coercivity sintered NdFeB magnet.

A method for manufacturing a sintered magnet according to one embodiment of the present disclosure is provided. The method includes producing an R-T-B-based magnetic powder through a reduction-diffusion method, and sintering the R-T-B-based magnetic powder, wherein R is a rare earth element, and T is a transition metal, and wherein the producing the magnetic powder includes adding a refractory metal sulfide powder to a R-T-B-based raw material.

A sintered magnet and a method for producing the same are provided. The method includes producing an R—Fe—B-based magnet powder by a reduction-diffusion method, adding a R—Al—Cu powder as a sintering agent to the R—Fe—B-based magnet powder to form a mixed powder, wherein the R—Al—Cu powder is an alloy of R, Al and Cu, and R is Nd, Pr, Dy, Tb or Ce, and sintering the mixed powder to form a sintered magnet.