RE:Rare Earth Free Motor Designs with MnBi- the MANGANESE-BISMUTH {Mn-Bi} ELEMENTAL MAGNET in the EV MOTORS LOOKS VERY PROMISING but is HIGHLY DEPENDENT on the MICROSCOPIC STUCTURE of the POWDERED PARTICLES used in MANUFACTURING of the MAGNETS
- the BEAUTY of the Mn-Bi magnets is that they have HIGH COERCIVITY {H} as the TEMPERATURES INCREASES to 225 Degrees Celsius which is an IMPORTANT PROPERTY to have in PERMANENT MAGNETS to make POWERFUL ELECTRIC MOTORS
some background: Coercivity of Neodymium Magnets
Permanent magnets radiate magnetic fields and do not require an outside source of magnetism. Their materials will take on the properties of a strong magnetic field when exposed to it. The magnet continues to emit a magnetic field after the initial field is withdrawn.
Resistance to demagnetization is one of the most useful properties for a magnetic material. A high-quality permanent magnet should emit a high magnetic field with a low mass. It should be stable against things that would demagnetize it.
Remanence and coercivity tell how much a material can resist demagnetization. A material that is still very magnetic after the magnetizing field withdraws has high remanence. Coercivity measures how much magnetic intensity is needed to demagnetize a magnet.
Neodymium (NdFeB) magnets are the most powerful permanent magnets available. The coercivity of these magnets will drop notably at higher temperatures. The low Curie point of the NdFeB phase limits their use at high temperatures. Developing high performance magnets requires understanding and managing coercivity.
Coercivity in a magnetic material is a measure of whether it is able to resist an outside magnetic field without losing magnetism. This describes the magnetic properties of a material in a useful way. Another way to understand coercivity is as the resistance of a material to demagnetization.
There are different types of coercivity. The measurement you need will depend on the threshold for demagnetization:
- Normal coercivity, Hcb, is the magnetic field required to reduce the magnetic flux to zero.
- Intrinsic coercivity, Hcj, is the magnetic field required to reduce the magnetization to zero.