A synthesis process is disclosed for fabrication of mass quantities of high-purity α-MnBi magnetic powder and subsequent bulk permanent magnet. An illustrative process includes certain steps that include: multiple annealing, multiple comminuting such as multiple ball milling, forming a non-magnetic phase on and/or in the powder particles at particle grain boundaries before particle consolidation such as pressing, and magnetic annealing of a pressed compact. A reproducible and high productive synthesis process is created by combining these steps with other steps, which makes possible production of mass quantities of MnBi powder and bulk magnets with high performance.

A hybrid rotor assembly is provided. The assembly utilizes two different types of magnets within the lamination cavities of the lamination stack: sintered permanent magnets and bonded magnets.

A FeNi ordered alloy includes a plurality of particles having a L1.sub.0 type ordered structure. A size of the particles is in a range between 200 nm and 500 nm. A volume fraction of a pore in the particles with respect to a volume of the particles having an unit of vol. % is 5% or less.

A hybrid rotor assembly is provided. The assembly utilizes two different types of magnets within the lamination cavities of the lamination stack: sintered permanent magnets and bonded magnets.

A ferrite sintered magnet 100 comprises M-type ferrite crystal grains 4 and multiple-crystal grain boundaries 6b surrounded by three or more of the M-type ferrite crystal grains 4. The ferrite sintered magnet 100 contains at least Fe, Ca, B, and Si, and contains 0.005 to 0.9 mass % of B in terms of B.sub.2O.sub.3. The multiple-crystal grain boundaries 6b contain Si and Ca, and in a case where the molar ratio of Ca to Si in the multiple-crystal grain boundaries 6b is represented by (Ca/Si).sub.G, the following formula is satisfied.

0.1<(Ca/Si).sub.G<0.9

The present invention provides fine grain structures for rare earth permanent magnets (REPMs) and their production in a manner to significantly enhance flexural strength and fracture toughness of the magnets with no or little sacrifice in the hard magnetic properties. The tough REPMs can have either homogeneous or heterogeneous refined grain microstructural architectures achieved by introducing a small amount of additive particle materials into the magnet matrix, such as fine-sized, insoluble, chemically stable, and non-reactive with the magnet matrix. These additive materials can act effectively as both heterogeneous nuclei sites and grain growth inhibitors during the heat treatment processes, which in turn resulting in refined grain structures of the REPMs. Alternatively, the fine grain structures were also achieved by using magnet alloy feedstock powders with finer particle sizes. The fine grains acting as the strengthening sites can inhibit the crack nucleation and can also slow down the propagation of micro-cracks, which in turn increasing magnet's fracture toughness.

A hybrid rotor assembly is provided. The assembly utilizes two different types of magnets within the lamination cavities of the lamination stack: sintered permanent magnets and bonded magnets.

Provided is a method for producing a sintered body that forms a rare-earth permanent magnet, has a single sintered structure and an arbitrary shape, and has easy magnetization axis orientations of different directions applied to the magnet material particles in a plurality of arbitrary regions. This method forms a three-dimensional first molded article from a composite material formed by mixing a resin material and magnet material particles containing a rare-earth substance. The first molded article is then subjected to a deforming force and a second molded article is formed in which the orientation direction of the easy magnetization axis of the magnet material particles in at least the one section of the horizontal cross-section is changed to a direction which differs from the orientation direction of the first molded article. The second molded article is heated to a sintering temperature and kept at the temperature for a period of time.

A method for producing rare-earth magnets is provided in which, when a slurry 2 having a rare-earth-compound powder dispersed therein is applied to sintered magnet bodies 1 and dried to apply the powder thereto, the magnet bodies 1 are accommodated and conveyed in holding pockets 42 of a conveyance drum 4 which rotates in a state of being partially immersed in the slurry 2, and, as a result, the magnet bodies 1 are immersed in the slurry 2, withdrawn from the slurry 2, and dried to apply the powder to the sintered magnet bodies 1. According to this production method, the powder can be uniformly and efficiently applied, wastage of the rare-earth compound can be effectively suppressed, and a reduction in the surface area of equipment for performing an application step can also be achieved.

When a slurry in which a rare-earth-compound powder is dispersed is applied to sintered magnet bodies 1 and dried to apply the powder thereto, the sintered magnet bodies 1 are conveyed by a conveyer 2 and made to pass through the slurry 4 to apply the slurry to the sintered magnet bodies 1. Furthermore, a plurality of push-up members 51, which pass through insertion holes 22 provided in a conveyor belt 21, and protrude above the conveyor belt, are used to temporarily push up the sintered magnet bodies 1, and temporarily separate the conveyor belt 21 and the sintered magnet bodies 1. As a result, the slurry can be efficiently applied, even mass production can be suitably dealt with, and the slurry can be uniformly and reliably applied to the entire surface of each of the sintered magnet bodies.