The invention provides an anisotropic rare earth sintered magnet having an Nd.sub.2Fe.sub.14B-type compound crystal as a main phase and containing Ce, and exhibiting good magnetic characteristics, and a method for producing the same. The anisotropic rare earth sintered magnet has a composition of a formula R.sub.x(Fe.sub.1−aCo.sub.a).sub.100−x−y−zB.sub.yM.sub.z (where R is two or more kinds of elements selected from rare earth elements and indispensably including Nd and Ce), in which the main phase is formed of an Nd.sub.2Fe.sub.14B-type compound crystal, main phase grains such that the Ce/R′ ratio in the center part of the grains (where R′ is one or more kinds of elements selected from rare earth elements and indispensably including Nd) is lower than the Ce/R′ ratio in the outer shell part thereof exist, and a Ce-containing R′-rich phase and a Ce-containing R′(Fe,Co).sub.2 phase exist in the grain boundary part. The production method is for producing the anisotropic rare earth sintered magnet.

An R-T-B based permanent magnet includes a rare-earth element R, a transition metal element T, and B. The R-T-B based permanent magnet includes at least Nd as R. The R-T-B based permanent magnet includes at least Fe as T. The R-T-B based permanent magnet contains a plurality of main phase grains and a plurality of voids. The plurality of main phase grains includes at least R, T, and B. An area ratio of the plurality of voids in an arbitrary cross-section of the R-T-B based permanent magnet is larger than 0.2% and 2% or smaller.

A neodymium-iron-boron (NdFeB) magnet is represented by a chemical formula R1-R2-Fe-M-B, and has a composite structure of a high-coercivity region and a high-remanence region. In the formula R1 is a rare earth element comprising at least Nd, R2 is a heavy rare earth element comprising at least Dy and/or Tb, and M is a transition metal element comprising at least Co. The neodymium-iron-boron magnet can greatly improve resistance to high-temperature demagnetization and inhibit reduction of magnetic flux of a magnet by adopting a small amount of Dy/Tb. The magnet can be used in an embedded high-speed motor. The preparing method for the magnet improves the material utilization and the production efficiency, and is feasible for a large-scale production.

A rare earth permanent magnet is prepared by immersing a portion of a sintered magnet body of R.sup.1—Fe—B composition (wherein R.sup.1 is a rare earth element) in an electrodepositing bath of a powder dispersed in a solvent, the powder comprising an oxide, fluoride, oxyfluoride, hydride or rare earth alloy of a rare earth element, effecting electrodeposition for letting the powder deposit on a region of the surface of the magnet body, and heat treating the magnet body with the powder deposited thereon at a temperature below the sintering temperature in vacuum or in an inert gas.

This sintered R-T-B based rare-earth magnet includes: R.sub.2Fe.sub.14B type compound crystal grains, including a light rare-earth element RL (which includes at least one of Nd and Pr) as a major rare-earth element R, as main phases; and a heavy rare-earth element RH (which includes at least one of Dy and Tb). Before its surface region is removed, the sintered R-T-B based rare-earth magnet has no layer including the rare-earth element R at a high concentration in that surface region. The sintered R-T-B based rare-earth magnet has a portion in which coercivity decreases gradually from its surface region toward its core portion. The difference in the amount of TRE between a portion of the sintered R-T-B based rare-earth magnet that reaches a depth of 500 μm as measured from its surface region toward its core portion and the core portion of the sintered R-T-B based rare-earth magnet is 0.1 through 1.0.

A chip inductor comprises a laminate including a plurality of sheets stacked therein; a coil disposed in the laminate and including an exposed portion, in which a portion of the coil is exposed outwardly of at least one surface of the laminate; and a non-magnetic insulating layer disposed on an external surface of the laminate to cover the exposed portion of the coil.

The present invention discloses an electro-deposition process, an electro-deposition bath, and a method for preparing a rare earth permanent magnetic material through electro-deposition. The electro-deposition process is used for depositing a heavy rare earth element on the surface of a sintered R.sup.2-T-B type master alloy, and comprises Step 1: providing an electro-deposition bath, comprising a main salt containing the heavy rare earth element, an induction salt for inducing the heavy rare earth element to deposit, and an organic ionic liquid as the solvent, wherein the main salt is a tetrafluoroborate of the heavy rare earth element; and Step 2: electroplating the sintered R.sup.2-T-B type master alloy in the electro-deposition bath at a temperature of 0 to 200° C. The present invention has the following beneficial effects: deposition of the heavy rare earth element on the surface of the sintered R.sup.2-T-B type master alloy is rapid, so that the electro-deposition process time can be saved, and the production efficiency is improved. In addition, a higher plating thickness of up to 10 to 40 μm can be achieved.

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 oxide powder (where RH is Dy and/or Tb) 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 oxide powder are present on the surface of the sintered R-T-B based magnet at a mass ratio of RLM alloy:RH oxide=9.6:0.4 to 5:5.

An R-TM-B hot-pressed and deformed magnet (here, R represents a rare earth metal selected from the group consisting of Nd, Dy, Pr, Tb, Ho, Sm, Sc, Y, La, Ce, Pm, Eu, Gd, Er, Tm, Yb, Lu, and a combination thereof, and TM represents a transition metal) of the present invention comprises flat type anisotropic magnetized crystal grains and a nonmagnetic alloy distributed in a boundary surface between the crystal grains, and thus the magnet of the present invention has an excellent magnetic shielding effect as compared with an existing permanent magnet since the crystal gains can be completely enclosed in the nonmagnetic alloy, so that a hot-pressed and deformed magnet with enhanced coercive force can be manufactured through a more economical process.

A two-step diffusion method for preparing high-performance dual-main-phase sintered mischmetal-iron-boron magnet belongs to the preparing technical field of rare earth permanent magnet materials. The compositions of the two main phase alloys are RE-Fe—B (RE is Nd or Pr) and (Nd, MM)-Fe—B (MM is mischmetal), respectively. First, PrHoFe strip-casting alloy is used as a diffusion source. Next, a PrHo-rich layer is uniformly coated on the surface of (Nd, MM)-Fe—B hydrogen decrepitation powders. The higher anisotropic fields of Pr.sub.2Fe.sub.14B and Ho.sub.2Fe.sub.14B are used to improve the coercivity. Then, the ZrCu strip-casting alloy is used as a diffusion source. A Zr-rich layer is uniformly coated on the surface of the powders after the first-step diffusion, which prevents the growth of the MM-rich main phase grains during the sintering process and the inter-diffusion between the two main phases, thus obtains high coercivity.