Mn-Bi Magnetic Powders With High Coercivity and Magnetization at Room Temperature

Mn₅₅Bi₄₅+x at.% Mn ( x=0, 7 and 11) magnetic powders were prepared by low energy ball milling technique. The x-ray diffraction pattern showed that the samples mainly contain over 90% of the low temperature Mn-Bi phase for x = 0 and 7 with a very small amount of Bi phase. Microstructural analysis showed that the amount of sub-micron particles increases with milling time. The milling time dependent magnetic properties were studied for all the compositions. An intrinsic coercivity (H_ci) of 12.2 kOe, remanent magnetization (4 πM_r) of 7.1 kG, and energy product (BH)_max of 11 MGOe have been obtained for the 8 hours milled Mn₅₅Bi₄₅+7 at.% Mn sample. These Mn-Bi powders have potential use as precursor for rare earth free permanent magnets.