Accelerated magnet development via microstructure design

CMI researchers from Ames National Laboratory conducted the activity for this highlight

Innovation
Development of rare earth free Fe-Co-B magnets through particle (grain) size and morphology control.

Achievement

  • Micromagnetic simulations find Fe-Co-B may achieve a coercivity of 2.7 kOe for a polycrystalline bulk magnet with an average grain size of 20 nm. The maximum energy product (BH)m is 26 MGOe, 2-3 times as that of the best Alnico. 
  • Fe-Co-B nanowire (a diameter 16-30 nm and a length of 200-300nm) may gain a coercivity of 10 kOe due to magnetocrystalline- and magnetic shape anisotropy. Bonded magnet with a 65% nanowire volume has a (BH)m of 18 MGOe, larger than Nd-Fe-B anisotropic bonded magnets.

Significance and Impact

  • Criticality and cost: the material has no rare earth and just 10-30 wt. percent cobalt.
  • The developed Fe-Co-B magnets may partially replace rare earth magnets such as Nd-Fe-B and high-performance Alnico.

Hub Goal Addressed 
Accelerated magnet discovery and maturation.

Fully dense polycrystalline bulk magnet (a) and nanowire bonded magnet (b) of (Fe0.7Co0.3)2B show theoretical coercivity and maximum energy product of Hci=2.7 kOe, (BH)m=26 MGOe and Hci=10 kOe, (BH)m= 18 MGOe, respectively.
Fully dense polycrystalline bulk magnet (a) and nanowire bonded magnet (b) of (Fe0.7Co0.3)2B show theoretical coercivity and maximum energy product of Hci=2.7 kOe, (BH)m=26 MGOe and Hci=10 kOe, (BH)m= 18 MGOe, respectively.