DEPENDENCE OF PERMANENT-MAGNET PROPERTIES OF MN55AL45 ON PARTICLE-SIZE

The magnetic properties of the alloy Mn55Al45 in its metastable ferromagnetic state have been investigated as a function of particle size in the range 1000 µm down to about 20 µm. It has been shown that the coercivity rises very rapidly as the particle size decreases but the remanence was shown to increase slowly and then to decrease rapidly due to the disorder resulting from the plastic deformation during grinding. The maximum intrinsic coercivity of 5 kOe was obtained for 63–75 µm particles while the maximum remanence of 60 e.m.u/g was obtained for 125–150 µm particles. The best potential permanent magnet properties were obtained for 125–150 µm particles viz. (BH)max = 2.2 MGOe, Br = 4.2 kG. and BHC = 2 kOe. © 1978 IEEE