Practical Aspects of Modern and Future Permanent Magnets

Abstract

The mandate to reduce greenhouse gases will require highly efficient electric machines for both power generation and traction motor applications. Although permanent magnet electric machines utilizing Nd 2 Fe 14 B-based magnets provide obvious power-to-weight advantages over induction machines, the limited availability and high price of the rare earth (RE) metals make these machines less favorable. Of particular concern is the cost and supply criticality of Dy, a key RE element that is required to improve the high-temperature performance of Nd-based magnetic alloys for use in generators and traction motors. Alternatives to RE-based alloys do exist, but they currently lack the energy density necessary to replace Nd-based magnets. Many of these compounds have been known for decades, but serious interest in their development waned once compounds based on RE elements were discovered. In this review, intrinsic and extrinsic materials factors that impact the optimization of both existing and potential future permanent magnets for energy applications are examined in light of new insights gained from renewed examination.

Magnetic properties of(Fe1−xCox)2Balloys and the effect of doping byEdström1, Werwiński2, Iuşan3 et al. 2015Phys. Rev. B

“…For the energy product, we generally require it to be as large as possible. The energy product is a relatively complex quantity; it depends on the structure of the material (size of crystalline grains, their shape and orientation), but from the microscopic point of view it depends mainly on the saturation magnetization (M s ) and magnetocrystalline anisotropy energy (MAE), which is a measure of how difficult it is to rotate the magnetization direction by external magnetic field [2][3][4].…”

Resonant x-ray diffraction revealing chemical disorder in sputtered L10FeNi on Si(0 0 1)

“…The last years' uncertainty in both availability and prices of rare earth elements (REE), which are utilized in high performance permanent magnets, has motivated a search for possible REE free replacement materials and also for substitution materials with intermediate performance and lower prices [2,3,4,5,6]. FeNi in the L1 0 structure is a possible candidate for such an intermediate material [7,8].…”

Simulation of alnico coercivity

“…Alnico magnets-a family of nanostructured alloys consisting primarily of Fe, Al, Ni, and Co-are an exception, because their magnetic anisotropy and hysteresis originate almost entirely from magnetostatic dipole-dipole interactions [4][5][6][7]. These materials have attracted renewed attention in the context of magnetic materials that are free of rare-earth elements and do not contain other expensive elements, such as Pt [7][8][9][10][11][12][13][14]. The magnetic anisotropy of alnicos reflects their peculiar nanostructure, where highmagnetization rods with an approximate composition of FeCo (α 1 -phase) are embedded in an essentially nonmagnetic Al-Ni-rich matrix (α 2 -phase) [4][5][6][7][14][15][16][17][18].…”