This disclosure is directed to sintered bodies comprising grains and a grain boundary composition, wherein: (a) the grains comprise a composition substantially represented by a formula G.sub.2M.sub.14B, where G is Nd, Dy, Pr, Tb, or a combination thereof, and M is Co, Fe, Ni, or a combination thereof, wherein the grains are optionally doped with one or more rare earth elements; and (b) the grain boundary composition is an alloy composition substantially represented by the formula: Nd.sub.8.5-12.5Dy.sub.35-45Co.sub.32-41Cu.sub.3-6.5Fe.sub.1.5-5, wherein the subscript values are atom percent relative to the total composition of the the alloy composition. Corresponding populations of particles are also disclosed

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.

Disclosed herein is a method for manufacturing an R-T-B permanent magnet and the magnet made with the method. The method may include preparation of strip pieces by melting and casting, preparing coarse powder by hydrogen decrepitation of the strip pieces; milling the powder into fine powder; pressing the fine powder is pressed to form a compact, pre-sintering the compact in vacuum or inert gas, machining the pre-sintered block to a desired shape; and dispersing the heavy rare earth compound powder into an organic solvent to prepare a slurry and a second sintering step.

Provided is a sintered magnet that is an R-T-B based sintered magnet having a region having a concentration of at least one heavy rare earth element decreasing from the surface toward the inside, in which the at least one heavy rare earth element includes at least either of Tb or Dy, R includes Nd, T includes Fe, Co, and Cu, there is a grain boundary phase containing at least either of Tb or Dy and Nd between two main phase particles, and a value obtained by subtracting a half value width of a concentration distribution curve of Cu from a half value width of a concentration distribution curve of Tb or Dy in a part including the grain boundary phase is from 10 to 20 nm.

A method of manufacturing a rare earth magnet includes (i) manufacturing a rare earth magnet precursor using a sintered compact which is obtained by sintering magnetic powder which is a rare earth magnet material; (ii) causing a modifying alloy to diffusively penetrate into the rare earth magnet precursor so as to manufacture the rare earth magnet; and (iii) causing the modifying alloy to diffusively penetrate into the rare earth magnet precursor by adhering a sheet material, in which alloy powder of the modifying alloy is dispersed in a thermoplastic resin, to a surface of the rare earth magnet precursor and performing a heat treatment on the sheet material.

[Problem] To provide a highly efficient manufacturing method including an RH supply-diffusion process by which the number of magnets processed at a time can be increased without allowing sintered R-T-B based magnets to stick to holding members. [Solution] A method for producing a sintered R-T-B based magnet including the steps of: forming a stack of RH diffusion sources and sintered R-T-B based magnet bodies by stacking the diffusion sources and the magnet bodies alternately with a holding member having openings interposed; and carrying out an RH supply-diffusion process by loading the stack into a process vessel and creating an atmosphere with a pressure of 0.1 Pa to 50 Pa and a temperature of 800° C. to 950° C. within the process vessel.

A rare earth magnet capable of reducing an eddy current loss by virtue of a low-cost, simple configuration, when mounted in a motor, is to be provided, where the rare earth magnet comprising: a magnet body comprising a rare earth element and iron; and a resistive layer formed on at least one surface of the magnet body, the resistive layer comprising a rare earth element, iron, and oxygen and having an average volume resistivity of 10.sup.3 Ωcm or more and a thickness of from 3 to 25 μm, as is shown in FIG. 2.

Provided is a combined type RFeB-based magnet, including: a first unit magnet; a second unit magnet; and an interface material that bonds the first unit magnet and the second unit magnet, in which the first unit magnet and the second unit magnet are RFeB-based magnets containing a light rare earth element R.sup.L that is at least one element selected from the group consisting of Nd and Pr, Fe, and B, in which the interface material contains at least one compound selected from the group consisting of a carbide, a hydroxide, and an oxide of the light rare earth element R.sup.L, and in which an amount of a heavy rare earth element R.sup.H that is at least one element selected from the group consisting of Dy, Tb and Ho in the second unit magnet is more than that in the first unit magnet.

A step of, while an RLM alloy powder (where RL is Nd and/or Pr; M is one or more elements selected from among Cu, Fe, Ga, Co, Ni and Al) and an RH compound powder (where RH is Dy and/or Tb; and the RH compound is an RH fluoride and/or 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 50 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.

A method for producing a sintered R-T-B based magnet of this disclosure includes the steps of preparing a plurality of sintered R-T-B based magnet bodies (R is at least one of rare earth elements and necessarily contains Nd and/or Pr; and T is at least one of transition metals and necessarily contains Fe); preparing a plurality of alloy powder particles having a size of 90 μm or less and containing a heavy rare earth element RH (the heavy rare earth RH is Tb and/or Dy) at a content of 20 mass % or greater and 80 mass % or less; loading the plurality of sintered R-T-B based magnet bodies and the plurality of alloy powder particles of a ratio of 2% by weight or greater and 15% by weight or less with respect to the plurality of sintered R-T-B based magnet bodies into a process chamber; and heating, while rotating and/or swinging, the process chamber to move the sintered R-T-B based magnet bodies and the alloy powder particles continuously or intermittently to perform an RH supply and diffusion process.