A rare-earth magnet is an R-T-B-based rare-earth magnet containing a rare-earth element R, a transition metal element T, and boron B. The rare-earth magnet further contains Cu and Co, while having a Cu concentration distribution with a gradient along a direction from a surface of the rare-earth magnet to the inside thereof, Cu having a higher concentration on the surface side of the rare-earth magnet than on the inside thereof, and a Co concentration distribution with a gradient along a direction from the surface of the rare-earth magnet to the inside thereof, Co having a higher concentration on the surface side of the rare-earth magnet than on the inside thereof. The rare-earth magnet is excellent in corrosion resistance.

The present invention provides an R-T-B based sintered magnet that inhibits the demagnetization rate at high temperature even when less or no heavy rare earth elements such as Dy, Tb and the like are used. The R-T-B based sintered magnet includes R.sub.2T.sub.14B crystal grains and two-grain boundary parts between the R.sub.2T.sub.14B crystal grains. Two-grain boundary parts formed by RCoCu-M-Fe phase exist, and M is at least one selected from the group consisting of Ga, Si, Sn, Ge and Bi.

The present invention provides an R-T-B based sintered magnet that inhibits the demagnetization rate at high temperature even when less or no heavy rare earth elements such as Dy, Tb and the like are used. The R-T-B based sintered magnet includes R.sub.2T.sub.14B crystal grains and two-grain boundary parts between the R.sub.2T.sub.14B crystal grains. Two-grain boundary parts formed by RCoCu-M-Fe phase exist, and M is at least one selected from the group consisting of Ga, Si, Sn, Ge and Bi.

An R-T-B based sintered magnet includes R.sub.2T.sub.14B crystal grains. A grain boundary formed by the two or more adjacent R.sub.2T.sub.14B crystal grains includes an RNOC concentrated part having higher concentrations of R, N, O, and C than those in the R.sub.2T.sub.14B crystal grains. R of the RNOC concentrated part includes Y. A ratio of Y atom to R atom in the RNOC concentrated part is 0.65 or more and 1.00 or less. A ratio of O atom to R atom in the RNOC concentrated part is more than 0 and 0.20 or less. A ratio of N atom to R atom in the RNOC concentrated part is 0.03 or more and 0.15 or less.

An R-T-B based sintered magnet includes R.sub.2T.sub.14B crystal grains. A grain boundary formed by the two or more adjacent R.sub.2T.sub.14B crystal grains includes an RNOC concentrated part having higher concentrations of R, N, O, and C than those in the R.sub.2T.sub.14B crystal grains. R of the RNOC concentrated part includes Y. A ratio of Y atom to R atom in the RNOC concentrated part is 0.65 or more and 1.00 or less. A ratio of O atom to R atom in the RNOC concentrated part is more than 0 and 0.20 or less. A ratio of N atom to R atom in the RNOC concentrated part is 0.03 or more and 0.15 or less.

The present invention provides a method for manufacturing a rare-earth magnet, the method comprising the steps of preparing a rare-earth magnet raw material powder including R, Fe and B as composition components (R is one or more elements selected from the rare earth elements including Y and Sc); packing the raw material powder into a molding die, and compacting and molding the raw material powder while applying a magnetic field, wherein, in the compacting and molding step, compacting is performed biaxially, in the directions of X and Y axes, when the magnetic field is applied in the direction of Z axis.

The present invention provides a method for manufacturing a rare-earth magnet, the method comprising the steps of preparing a rare-earth magnet raw material powder including R, Fe and B as composition components (R is one or more elements selected from the rare earth elements including Y and Sc); packing the raw material powder into a molding die, and compacting and molding the raw material powder while applying a magnetic field, wherein, in the compacting and molding step, compacting is performed biaxially, in the directions of X and Y axes, when the magnetic field is applied in the direction of Z axis.

A dynamic compaction process comprises forming first and second preforms. Forming each preform includes utilizing a container having an interior and an exterior. Filling the interior of the container with a powder material; sealing the container; subjecting the exterior of the container to an instantaneous dynamic compaction, forming a solid powder metallurgy preform encased by the container. The container gets removed from each preform. The process includes inserting the first and second preforms in another container in a predefined pattern; the predefined pattern aligns the first and second preforms creating an interface. The process includes inserting a backstop against the predefined pattern in this container; subjecting the exterior of this container to an instantaneous dynamic compaction. The process includes bonding the first preform and second preform along the interface to form a component precursor; and removing the container from the precursor. Another step includes processing the precursor into components.

The present invention relates to a method of preparing an anisotropic complex sintered magnet having MnBi, that includes: (a) preparing a non-magnetic phase MnBi-based ribbon by a rapidly solidification process (RSP); (b) heat treating the non-magnetic phase MnBi-based ribbon to convert the non-magnetic phase MnBi-based ribbon into a magnetic phase MnBi-based ribbon; (c) grinding the magnetic phase MnBi-based ribbon to form a MnBi hard magnetic phase powder; (d) mixing the MnBi hard magnetic phase powder with a rare-earth hard magnetic phase powder; (e) magnetic field molding the mixture obtained in step (d) by applying an external magnetic field to form a molded article; and (f) sintering the molded article.

The present invention relates to a method of preparing an anisotropic complex sintered magnet having MnBi, that includes: (a) preparing a non-magnetic phase MnBi-based ribbon by a rapidly solidification process (RSP); (b) heat treating the non-magnetic phase MnBi-based ribbon to convert the non-magnetic phase MnBi-based ribbon into a magnetic phase MnBi-based ribbon; (c) grinding the magnetic phase MnBi-based ribbon to form a MnBi hard magnetic phase powder; (d) mixing the MnBi hard magnetic phase powder with a rare-earth hard magnetic phase powder; (e) magnetic field molding the mixture obtained in step (d) by applying an external magnetic field to form a molded article; and (f) sintering the molded article.