A bi-material permanent magnet for an electric machine includes a core including a first magnetic material and a shell portion located on the core and made of a second magnetic material. The first magnetic material comprises a magnet material with an energy less than 20 Mega Gauss Oersteds (MGOe). The second magnetic material comprises a magnet material with an energy greater than 30 MGOe.

Disclosed is a surface modification technique for permanent magnetic materials. First, a sintered Nd—Fe—B magnet is immersed in a chlorine-containing solution to corrode its surface after the sintered Nd—Fe—B magnet is ground, polished and cleaned, so that atomic vacancies or gaps are produced at the grain boundaries in the surface layer of the corroded sintered Nd—Fe—B magnet; then, compound nanopowders coated on the surface of the sintered Nd—Fe—B magnet are implanted into the grain boundaries by laser shock peening to obtain a gradient nanostructure layer along the depth direction; at the same time, the surface nanocrystallization of the sintered Nd—Fe—B magnet and a residual compressive stress layer are induced by laser shock peening which remarkably improves the corrosion resistance of the sintered Nd—Fe—B magnet.

A permanent magnet may include a Fe.sub.16N.sub.2 phase constitution. In some examples, the permanent magnet may be formed by a technique that includes straining an iron wire or sheet comprising at least one iron crystal in a direction substantially parallel to a <001> crystal axis of the iron crystal; nitridizing the iron wire or sheet to form a nitridized iron wire or sheet; annealing the nitridized iron wire or sheet to form a Fe.sub.16N.sub.2 phase constitution in at least a portion of the nitridized iron wire or sheet; and pressing the nitridized iron wires and sheets to form bulk permanent magnet.

An application step of applying an adhesive agent to an application area of a surface of a sintered R-T-B based magnet work, an adhesion step of allowing a particle size-adjusted powder that is composed of a powder of an alloy or a compound of a Pr—Ga alloy which is at least one of Dy and Tb to the application area of the surface of the sintered R-T-B based magnet work, and a diffusing step of heating it at a temperature which is equal to or lower than a sintering temperature of the sintered R-T-B based magnet work to allow the Pr—Ga alloy contained in the particle size-adjusted powder to diffuse from the surface into the interior of the sintered R-T-B based magnet work are included. The particle size of the particle size-adjusted powder is set so that, when powder particles composing the particle size-adjusted powder are placed on the entire surface of the sintered R-T-B based magnet work to form a particle layer which is not less than one layer and not more than three layers, the amount of Ga contained in the particle size-adjusted powder is in a range from 0.10 to 1.0% with respect to the sintered R-T-B based magnet work by mass ratio.

A method of producing an oppositely magnetized magnetic structure within or on a substrate material includes: generating first and second numbers of cavities within or on a substrate material and filling the first and second numbers of cavities with first and second hard magnetic materials, respectively exhibiting first and second coercive field strengths, wherein the second coercive field strength is smaller than the first coercive field strength. The method further includes magnetizing, in a first direction, the first and second arrangements of magnetic structures, by a magnetic field having a field strength that exceeds the first and second coercive field strengths. The method further magnetizes the second arrangement of hard magnetic structures in a second direction, which differs from the first direction, by a second magnetic field having a field strength below the first coercive field strength but greater than the second coercive field strength.

A three-dimensional magnet structure (6) made up of a plurality of individual magnets (4), the magnet structure (6) having a thickness that forms its smallest dimension, the magnet structure (6) incorporating at least one mesh (5a) exhibiting mesh cells each one delimiting a housing (5) for a respective individual magnet (4), each housing (5) having internal dimensions just large enough to allow an individual magnet (4) to be inserted into it, the mesh cells being made from a fibre-reinforced insulating material, characterized in that a space is left between the housing (5) and the individual magnet (4), which space is filled with a fibre-reinforced resin, the magnet structure (6) comprising a non-conducting composite layer coating the individual magnets (4) and the mesh structure (5a).

A method of manufacturing a permanent magnet, including providing a powder composition, of which a first fraction includes ferromagnetic metal particles and a second fraction includes thermoplastic polymer particles; using the powder composition in a powder-bed based additive manufacturing process to form a part including ferromagnetic metal particles embedded in a fused thermoplastic polymer body; and subsequently conferring magnetism on the built part by arranging the finished part in a magnetic field.

A method of producing a compound for bonded magnets, the method including: heat-curing a thermosetting resin and a curing agent having a ratio of the number of reactive groups of the curing agent to the number of reactive groups of the thermosetting resin of at least 2 but not higher than 11 to obtain an additive for bonded magnets; and kneading the additive for bonded magnets, magnetic powder, and a thermoplastic resin to obtain a compound for bonded magnets in which a filling ratio of the magnetic powder is at least 91.5% by mass.

A method for producing a bonded magnet, comprising: (i) low-shear compounding of a thermoplastic polymer and magnetic particles to form an initial homogeneous mixture thereof; (ii) feeding the initial homogeneous mixture into a plasticator comprising a low-shear single screw rotating unidirectionally toward a die orifice and housed within a heated barrel to result in heating of the initial homogeneous mixture until the thermoplastic polymer melts and forms a further homogeneous mixture, wherein said further homogeneous mixture is transported within threads of the single screw towards the die orifice and exits the die orifice as a solid pellet; (iii) conveying the solid pellet into a mold and compression molding the pellet in the mold, to form the bonded magnet, wherein the bonded magnet possesses a magnetic particle loading of at least 80 vol % and exhibits one or more magnetic properties varying by less than 5% throughout the bonded magnet.

A preparation method of improved sintered neodymium-iron-boron (Nd—Fe—B) casting strips includes the following steps: firstly nucleation assisted alloy particles used for sintered Nd—Fe—B casting strips are prepared, all elements are weighted as follows: 26.68-28% of Pr—Nd, 70-72.5% of Fe and 0.90-1% of B, and a Pr element in two elements of Pr—Nd accounts for 0-30 wt %; the compounded materials are smelted and poured to obtain alloy strips, then the alloy strips are crushed into particles with diameter of 1-10 mm; secondly, Nd—Fe—B casting strips are prepared: the prepared intermediate materials are smelted and melted into molten steel, and then are refined; after the intermediate materials are fully melted, the nucleation assisted alloy particles are added; and after the nucleation assisted alloy particles are added, smelting is performed for 3-15 minutes pouring is performed, and final Nd—Fe—B alloy casting strips are obtained.