High performance misch-metal (MM)-Fe-B magnets prepared by melt spinning

A series of misch-metal (MM = 28.27 wt % La, 50.46 wt % Ce, 5.22 wt % Pr, 15.66 wt % Nd)-iron-boron isotropic ribbons with atomic formula (MM)12+xFe82-x-yB6+y (x = 0, 1, 2, 3, 4, y = 0, 0.5, 1, 1.5, 2) are prepared by melt spinning technique. A large energy product (BH)max of 12 MGOe is obtained with the composition of MM13Fe81B6 at optimized processing. The ribbons with both coercivity larger than 10 kOe and (BH)max larger than 10 MGOe are achieved in a wide composition range. All the samples exhibit the tetragonal crystal structure. The magnetization and Henkel plot (δM) measurements indicate that the ribbons have a relatively homogeneous microstructure and strong exchange-coupling interactions. The average grain size of the ribbons is around 30 nm determined via Scherrer's formula. Meanwhile, the transmission electron microscope (TEM) image also verifies that the ribbons have a homogeneous nanoscale microstructure. In addition, the spin reorientation temperature Tsr is investigated by ac susceptibility χac measurement. •A large energy product (BH)max of 12 MGOe is obtained.•Coercivity larger than 10 kOe and (BH)max larger than 10 MGOe are both achieved.•The average grain size of the ribbons is around 30 nm.•The ribbons have a homogeneous nanoscale microstructure.•The spin reorientation temperature Tsr of MM13Fe80B7 is about 40 K.