The melt-spinning method combined with annealing technology was used to prepare Mn-based permanent
alloys in the paper. The influences of Fe-doping on the microstructure and magnetic performances of the MnBi
alloys were studied. According to the results of XRD pattern, the fraction of the LTP-MnBi in the as spun
MnBi ribbons increases with the doping of Fe element, a significant increase of the LTP-MnBi is due to annealing
treatment. The magnetization at the 20 kOe field of Mn55Bi40Fe5 melt-spun ribbons increases to 45 emu/g
after being annealing. With the addition of Fe, the coercivity H
cj of the annealed ribbons increases first and
then decreases. The results of δM plots show that the reduction of H
cj for the Mn55Bi40Fe5 melt-spun ribbons
can be attributed to enhanced exchange coupling interaction between MnBi LTP particles. The grain refinement
contributes directly to an enhanced exchange coupling for the addition of 5 at% Fe from TEM images.
The dependence of coercivity on temperature for the annealed MnBi alloy melt-spun ribbons is discussed.