A Family of New Cobalt-Base Permanent Magnet Materials

Abstract

A feasible approach for preparing remanence enhanced NdFeB based permanent magnetic compositesThe magnetocrystalline anisotropy of several intermetallic phases of the type RC06 (R= Y, Ce, Pr, Sm, Yorich and Ce-rich mischmetals) has been investigated, and it is concluded that these alloys are promising candidates for fine-particle permanent magnets. They have extremely high uniaxial anisotropy (K = 5.4 to 7.7 X 10 7 erg/cm 3 ), single easy axis, high saturation (B, = 8500 to 11 200 G) and Curie point (l c =464° to 747°C). Approximate upper limits for the possible energy product lie between 18 and 31.3 MGOe. Experimentally, coercive forces of over 8000 Oe and (BH) max = 5.1 MGOe have been observed in SmC06 merely ground at room temperature. Grinding of YCo. and (Ce-MM) C0 6 produces an increase of MHc to 2200 and 2700 Oe, respectively, followed by a decrease as particle size continues to decrease.

Rare-Earth Magnets

“…Magnetic measurements on powders of several RCo 5 and R 2 (Co,Fe)i 7 compounds 6 " 8 (R = rare earth) soon showed that several of these compounds with light rare earths had promising values of magnetization, Curie temperature, and anisotropy. So far, so good.…”

Magnetization compensation and spin reorientation transition in ferrimagnetic DyCo5 : Multiscale modeling and element-specific measurements

“…Furthermore, these compounds are known to exhibit large magnetocrystalline anisotropy energies up to several meV/f.u. [1]. Thus, compounds of the light REs, such as Y, Ce, Pr, and Sm, with ferromagnetic coupling to the Co sublattice and an easy c axis, are ideal for permanent magnet applications since they combine the aforementioned properties with a high magnetic energy density and high coercivity [1][2][3][4].…”

Prospects for nanoparticle-based permanent magnets

“…(BH) max strongly depends on the saturation magnetic polarization (J s = 4πM s or μ 0 M s , where M s is the saturation magnetization) and coercivity (H c ), which originates from the magnetic anisotropy (K 1 ) and ferromagnetic ordering in these materials [5,6]. The rare-earth-based magnets, especially SmCo 5 (K 1 = 17 MJ m −3 and J s = 10.7 kG or 1.07 T) and Nd 2 Fe 14 B (K 1 = 5 MJ m −3 and J s = 16.1 kG) are stronger magnets so far, owing to their high K 1 and J s at room temperature [7,8] and thus have an ever-increasing demand, but further improvement in their performance has been slowing in recent years [2][3][4]. L1 0 -ordered (face-centered tetragonal) FePt alloys have shown superior permanentmagnet properties with K 1 = 7 MJ m −3 and J s = 13.8 kG among the rare-earth-free alloys, but the high cost of Pt is a limiting factor.…”