Effect of milling on the structure and magnetic properties in Mn54Al46 flakes prepared by surfactant-assisted ball milling

MnAl flakes with different size were prepared using the surfactant-assisted ball-milling method. Depending on the sequence of ball milling and anneal, different microstructures and magnetic properties were obtained. [001] textured ε-phase MnAl flakes were obtained by surfactant-assisted ball-milling isotropic powders. After annealing the textured flakes, high purity τ-phase MnAl have been obtained from milled powders. Regardless of the sequence between anneal and ball milling, the coercivities of the milled powders are much higher than those of bulk ingots. The magnetic properties are dependent on the fraction of the τ-phase and ball milled time. A high coercivity of 234.9 kA/m and a saturation magnetization of 0.47 T have been obtained in milled powders. Addition of oleic acid and oleyl amine in the ball milling were found to be critical to the formation of MnAl flakes.