Influence of Mischmetal on the magnetic properties of B-rich Nd-Fe-B nanocrystalline ribbons

In this work, a study of the structural and magnetic properties of B-rich rare earth (RE)-Fe-B nanocomposite alloys, was carried out. The samples were produced by annealing amorphous ribbons having compositions (Nd1−xMMx)4.5Fe77B18.5 (Mischmetal (MM), x=0.0 and 0.25). For x=0.0 and 0.25, the crystalline t-(Fe, RE)3B and α-(Fe, RE) phases precipitated at temperatures above 550 °C, with typical grain sizes on the nanometric scale. Low MM addition (x=0.25) degraded the coercivity of annealed ribbons, which was found to diminish from 1.330 to below 0.035 kOe, although similar hard and soft phases with optimised volume fractions are present. These two extreme values for a few MM at% content could be attributed to changes in the magneto-crystalline anisotropy, which modify the typical nanomagnetic lengths.