Lewis and Villacorta reported in 2015 that permanent magnet development has historically been driven by the need to supply larger magnetic energy in ever smaller volumes for incorporation in an enormous variety of applications that include consumer products, transportation components, military hardware, and clean energy technologies such as wind turbine generators and hybrid vehicle regenerative motors. Since the 1960s, the so-called rare-earth ‘‘supermagnets,’’ composed of iron, cobalt, and rare-earth elements such as Nd, Pr, and Sm, have accounted for the majority of global sales of high energy–product permanent magnets for advanced applications.
In rare-earth magnets, the transition-metal components provide high magnetization, and the rare-earth components contribute a very large magnetocrystalline anisotropy that donates high resistance to demagnetization. However, at the end of 2009, geopolitical influences created a worldwide strategic shortage of rare-earth elements that may be addressed, among other actions, through the development of rare-earth-free magnetic materials harnessing sources of magnetic anisotropy other than that provided by the rare-earth components. Materials engineering at the micron scale, nanoscale, and Angstrom scales, accompanied by improvements in the understanding and characterization of nanoscale magnetic phenomena, is anticipated to result in new types of permanent magnetic materials with superior performance.
Magnetic materials play a key role in modern life and are present in advanced devices and motors of every kind. Their unique ability to (1) enable the conversion of
electrical to mechanical energy, (2) transmit and distribute electric power, (3) facilitate microwave communications, and (4) provide the basis for data storage systems
make them indispensible to modern life. In particular, advanced permanent magnets—which maintain a large magnetic flux in the absence of a magnetizing field—underlie the operation of generators, alternators, eddy current brakes, motors, and relays. Among many applications, permanent magnets are found in computers, automobiles, motor scooters, consumer electronic products, medical products, and speakers/headphones.
In particular, they are of vital importance to military applications as they add functionality to jet fighter engines, electronic countermeasure systems, missile systems, and satellite communication systems. Advanced permanent magnets are also integral parts of alternative energy technologies, such as those that harvest wind, wave, and tidal power. In this review article, a summary of the magnetism and materials science underlying historic, current, and future permanent magnets will be provided and presented in the 21st-century context of global strategic materials supply and world demand.
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