A composite permanent magnet includes a first magnetically-hard layer formed from a compacted powder material and a magnetically-soft layer formed from a sheet material applied over the first magnetically-hard layer. The composite permanent magnet also includes a second magnetically-hard layer formed over the magnetically-soft layer. The combination of the first magnetically-hard layer, the magnetically-soft layer, and the second magnetically-hard layer defines an anisotropic layered internal structure within the composite permanent magnet.

The present invention discloses an yttrium-added rare earth permanent magnet material and a preparation method therefor. The chemical formula of the material is expressed as (Y.sub.xRe.sub.1-x).sub.aFe.sub.100-a-b-cM.sub.bB.sub.c according to the mass percentage, wherein 0.05≤x≤0.5, 20≤a≤28, 0.5≤b≤2, 0.5≤c≤1.5, Re is Nd and/or Pr, and M is Al and/or Nb. According to the present invention, the relatively surplus and inexpensive rare earths yttrium and cerium are used to replace Nd and/or Pr in NdFeB. By controlling the ratio of the rare earth elements such as yttrium, cerium and neodymium, and adding an appropriate amount of Nb and/or Al element, the rare earth elements are used in a comprehensive and balanced manner while better magnetic properties are maintained.

A method of producing a magnetic powder and a magnetic powder is provided. The method of producing a magnetic powder according to an exemplary embodiment of the present disclosure includes: producing an iron powder by a reduction reaction of iron oxide, producing a magnetic powder using a molded body obtained by press molding a mixture including the iron powder, a rare earth oxide, boron, and calcium at a pressure of 22 MPa or more, and coating a surface of the magnetic powder with ammonium fluoride.

A method of producing an oppositely magnetized magnetic structure within or on a substrate material includes: First and second numbers of cavities are generated within or on a substrate material and are filled with first and second hard magnetic materials, respectively, exhibiting first and second coercive field strengths, respectively, so as to produce first and second arrangements of hard magnetic structures, respectively, the second coercive field strength being smaller than the first coercive field strength.

The first and second arrangements of hard magnetic structures are magnetized in a first direction by a first magnetic field exhibiting a field strength which exceeds the first and second coercive field strengths.

The second arrangement of hard magnetic structures is magnetized in a second direction, which differs from the first direction, by a second magnetic field exhibiting a field strength which falls below the first coercive field strength but exceeds the second coercive field strength. Magnetizing the second arrangement of hard magnetic structures includes exposing the first and second arrangements of hard magnetic structures to the second magnetic field.

A nano magneto-rheological fluid, comprising nano-scale magnetizable magnetic particles, wherein an average particle size or a minimum size in one dimension is less than 100 nanometers; and fluids used as carrier liquids, wherein the magnetic particles are dispersively distributed in the fluids. An apparatus for making the nanometric magnetorheological fluid including a ball mill, a settling separator located downstream of the ball mill for receiving the primary magnetic particles, a magnetic separator located downstream of and connected to the settling separator for receiving the upper layer of fluid containing fine magnetic particles, and an agitator for mixing the desired secondary magnetic particles with a carrier liquid and an additive. A method for making the nano magneto-rheological fluid wherein the nano magneto-rheological fluid has performance advantages such as no remanent magnetization, non-settlement, low viscosity, low abrasive rate for components, long service life, high reliability and fast and clear response.

There is provided a method for manufacturing a rare earth sintered magnet by many times repetitively finely pulverizing a rare earth alloy on a jet mill by supplying high-pressure nitrogen gas to narrow grain size distribution to make an easy alignment in a magnetic field, and by micronizing crystal grains by using a hydrogenation-disproportionation-desorption-recombination (HDDR) process, to improve the coercivity and thermostability of the rare earth sintered magnet.

According to an embodiment, a composite permanent magnet includes a matrix of magnetically hard phase grains having an average grain size of 10 nm to 50 m; and magnetically soft phase grains embedded within the matrix, and having an average grain size of at least 50 nm, each grain having an elongated shape with an aspect ratio of at least 2:1. According to another embodiment, a composite permanent magnet includes a matrix of magnetically hard phase grains having an average grain size of 10 nm to 50 m; and magnetically soft phase grains embedded within the matrix, and having an average grain width of at least 50 nm, an average grain height of 20 to 500 nm, and an aspect ratio of at least 2:1. According to yet another embodiment, a method of forming a composite permanent magnet is also provided.

The present invention discloses a method of manufacturing, powder making device for rare earth magnet alloy powder, and a rare earth magnet. The method comprises a process of fine grinding at least one kind of rare earth magnet alloy or at least one kind of rare earth magnet alloy coarse powder in inert jet stream with an oxygen content below 1000 ppm to obtain powder that has a grain size smaller than 50 m. Low oxygen content ultra-fine powder having a grain size smaller than 1 m is not separated from the pulverizer, and the oxygen content of the atmosphere is reduced to below 1000 ppm in the pulverizer when crushing the powder. Therefore, abnormal grain growth (AGG) rarely happens in the sintering process. A low oxygen content sintered magnet is obtained and the advantages of a simplified process and reduced manufacturing cost are realized.

A method for producing a magnetic powder includes the steps of: mixing neodymium oxide, boron, and iron to prepare a first mixture; adding and mixing calcium to the first mixture to prepare a second mixture; mixing an alkali metal with the second mixture to prepare a third mixture; and placing a carbon sheet on the third mixture, placing silica sand (SiO.sub.2 sand) thereon, and then heating the same to a temperature of 800 C. to 1100 C.

A method for preparing rare earth permanent magnet material, comprising: firstly weighing powders of three raw materials, H, M and Q, according to the atomic percentage content in general formula H.sub.100-x-yM.sub.xQ.sub.y, and performing the mixing treatment and sieving treatment in a nitrogen gas or other oxygen-free environments to obtain a composite powder; then machining a sintered NdFeB magnet into a prescribed shape and size, and performing the surface cleaning and drying to obtain a NdFeB magnet to be treated; next, adhering the composite powder to the surface of the NdFeB magnet to be treated by static electricity in an oxygen-free environment; next performing a vacuum thermal treatment and tempering treatment sequentially thereby obtaining the rare earth permanent magnet material. For the above method, the efficiency is high and binding force between the heavy rare earth element attachments and the substrate magnet is strong, it is convenient for the residual powder materials to be recycled. The coercivity of the prepared NdFeB magnet can be increased by 4000-14000 Oe, the remanence is only reduced by 1-2%, and the magnet with equivalent performance can be saved 30% of the heavy rare earth usage amount.