Permanent magnet motor

This type of motor is used in GM's Chevrolet Bolt[1] and Volt, and the rear wheel drive of Tesla's Model 3.

It is the voltage that occurs in electric motors from the relative motion between the stator windings and the rotor’s magnetic field.

The four primary permanent magnetic materials that are found in the vast majority of industrial applications are neodymium iron boron (NdFeB), samarium cobalt (SmCo), aluminum nickel cobalt (Alnico), and strontium carbonate-iron oxide (also known as “ceramic magnet”); furthermore, significant materials science research is ongoing into the development of additional non-rare earth (NRE) permanent magnetic materials.

However, this also leads to corrosion vulnerability in NdFeB magnets along sintered grain boundaries, which requires alleviation through the addition of copper-nickel or aluminum-based metallic surface coatings.

[7][8] In addition, the high cost, rarity, and radioactive waste associated with production of the metal neodymium as an input means that NdFeB magnets are very financially and environmentally expensive.

[9] SmCo is a strong permanent magnetic material of comparable strength to NdFeB and is used across range of applications including very high-performance vehicle electric motors, NMR spectrometers, turbomachinery, and frictionless bearings.

These magnets exhibit weaker performance in comparison to NdFeB and SmCo counterparts but still maintain high coercivity and are far cheaper due to their lack of rare earth metals.

[14] Development of non-rare earth, low cost, mechanically robust, and high strength permanent magnetic materials is a vigorous and ongoing area of research.

China, the top producer of neodymium, restricted shipments to Japan in 2010 during a controversy over disputed ownership of islands.

China imposed strict export quotas on several rare earth metals, saying it wanted to control pollution and preserve resources.