Disclosed in the present invention is an R—Fe—B sintered magnet and grain boundary diffusion treatment method. The R—Fe—B sintered magnet is obtained by performing HR grain boundary diffusion treatment on an R—Fe—B sintered green body, wherein the green body at least comprises 28 wt %-33 wt % of R, which is at least one rare earth element including Nd; 0.83 wt %-0.96 wt % of B; and 0.3 wt %-1.2 wt % of M. A grain boundary diffusion direction is perpendicular to a magnetization direction, and in the diffusion direction, the ratio of HR contents of any two points spaced from the diffusion plane by a distance of no more than 500 μm is 0.1-1.0. Grain boundary diffusion of a diffusion source is performed in a direction perpendicular to c axis, so that local demagnetization is efficiently controlled, a diffusion effect is enhanced, a manufacturing procedure is simplified, and deformation factors are eliminated.

The invention discloses an NdFeB permanent magnet with high coercivity and high resistivity and a method for preparing the same. The method comprises the steps of: spraying powdery slurry containing heavy rare earth compounds, oxides and/or carbides on a flaky NdFeB permanent magnets blank after it is subjected to surface cleaning process; then stacking magnets on top of each other, and performing three-stage heat treatment on the stacked magnets to obtain the NdFeB permanent magnet with high coercivity and high resistivity. Heavy rare earth penetrates into interior of the flaky magnets at a high temperature, so that coercivity of the flaky magnets is improved. However, part of the heavy rare earth elements or alloy elements and carbide powder or oxide powder, which are not penetrated into the flaky magnets, form an interlayer bonding two of flaky magnets together.

To provide an alloy for an R-T-B based permanent magnet from which an R-T-B based permanent magnet having improved magnetic properties can be manufactured. The alloy for an R-T-B based permanent magnet contains R, T, and B, in which R is a rare earth element, T is a transition metal element, and B is boron. An area ratio of a non-columnar crystal structure in a cross section is 1.0% or more and 30.0% or less.

A rare earth magnet includes a main phase and a particle boundary phase and in which an overall composition is represented by a formula, (R.sup.2.sub.(1-x)R.sup.1.sub.x).sub.yFe.sub.(100-y-w-z-v)Co.sub.wB.sub.zM.sup.1.sub.v.(R.sup.3.sub.(1-p)M.sup.2.sub.p).sub.q.(R.sup.4.sub.(1-s)M.sup.3.sub.s).sub.t, where R.sup.1 is a light rare earth element, R.sup.2 and R.sup.3 are a medium rare earth element, R.sup.4 is a heavy rare earth element, M.sup.1, M.sup.2, M.sup.3 are a predetermined metal element. The main phase includes a core portion, a first shell portion, and a second shell portion. The content proportion of medium rare earth element is higher in the first shell portion than in the core portion, the content proportion of medium rare earth element is lower in the second shell portion than in the first shell portion. The second shell portion contains heavy rare earth elements.

This application provides a motor rotor, including a rotor iron core and a plurality of permanent magnets disposed on the rotor iron core. Coercive forces of at least some permanent magnets are continuously gradiently distributed or gradiently distributed in a multi-stage manner from the middle to both ends along at least one direction perpendicular to a magnetization direction. The permanent magnet with a gradient coercive force design is used in the motor rotor. A coercive force of the permanent magnet is continuously gradiently distributed or gradiently distributed in a multi-stage manner from the middle to both ends. In this way, a coercive force change of the entire permanent magnet is uniform, and stability and reliability of the motor can be maximized. In addition, this can avoid excessive anti-demagnetization performance, reduce an amount of usage of heavy rare earth elements, and minimize costs of the motor.

A Sm—Fe—N-based rare earth magnet more resistant to demagnetization than ever before, particularly at high temperatures, and a production method thereof are provided.

The present disclosure presents a production method of a rare earth magnet, including mixing a SmFeN magnetic powder and a modifier powder to obtain a mixed powder, compression-molding the mixed powder in a magnetic field to obtain a magnetic-field molded body, pressure-sintering the magnetic-field molded body to obtain a sintered body, and heat-treating the sintered body, and a rare earth magnet obtained by the method. D.sub.50 of the magnetic powder is 1.50 μm or more and 3.00 μm or less, the content ratio of the zinc component in the modifier powder is 6 mass % or more and 30 mass % or less, and the heat treatment temperature is 350° C. or more and 410° C. or less.

An R-T-B based sintered magnet containing a first heavy rare earth element, in which R includes Nd, T includes Co and Fe, the first heavy rare earth element includes Tb or Dy, the R-T-B based sintered magnet has a region in which a concentration of the first heavy rare earth element decreases from the surface toward the inside, a first grain boundary phase which contains the first heavy rare earth element and Nd but does not contain Co is present in one cross section including the region, and an area occupied by the first grain boundary phase in one cross section including the region is 1.8% or less.

A grain boundary diffusion method for a bulk rare earth permanent magnetic material includes the following steps: (1) fabricating an initial magnet by a sintering, hot pressing, or hot deformation process; (2) loading a grain boundary diffusion alloy source on a surface of the magnet through electrodeposition, chemical vapor deposition (CVD), physical vapor deposition (PVD), direct physical contact, or adhesive bonding; and (3) placing the initial magnet loaded with the grain boundary diffusion alloy source in a SPS device, and heating to obtain a final magnet. The current, plasma, and pressure in an SPS process can be controlled to significantly improve elemental diffusion coefficient and enhance the diffusion depth. The bulk rare earth permanent magnetic material undergoing grain boundary diffusion fabricated in the present disclosure has a significant increase in magnetic properties that catering to commercial demands for industrial production.

A method is provided for the heat treatment of an object comprising at least one rare-earth element with a high vapor pressure. One or more objects comprising at least one rare-earth element with a high vapor pressure are arranged in an interior of a package. An external source of the at least one rare-earth element is arranged so as to compensate for the evaporation of this same rare-earth element from the object and/or to increase the vapor pressure of the rare-earth element in the interior of the package, and the package is heat treated.

An anisotropic rare earth sintered magnet represented by the formula (R.sub.1-aZr.sub.a).sub.x(Fe.sub.1-b CO.sub.b).sub.100-x-y(M.sup.1.sub.1-cM.sup.2.sub.c).sub.y where R is at least one element selected from rare earth elements and Sm is essential; M.sup.1 is at least one of V, Cr, Mn, Ni, Cu, Zn, Ga, Al, and Si; M.sup.2 is at least one of Ti, Nb, Mo, Hf, Ta, and W; and x, y, a, b, and c each satisfy certain conditions. The anisotropic rare earth sintered magnet includes 80% by volume or more of a main phase composed of a compound of a ThMn.sub.12 type crystal, the main phase having an average crystal grain size of 1 μm or more, and containing an R-rich phase and an R(Fe,Co).sub.2 phase in a grain boundary portion. A method for producing the anisotropic rare earth sintered magnet is also described.