Synthesis of Fe-Si-B-Mn-based nanocrystalline magnetic alloys with large coercivity by high energy ball milling

Alloys of Fe-Si-B with varying compositions of Mn were prepared using high energy planetary ball mill for maximum duration of 120 h. X-ray diffraction (XRD) analysis suggests that Si gets mostly dissolved into Fe after 80 h of milling for all compositions. The residual Si was found to form an intermetallic Fe 3 Si. The dissolution was further confirmed from the field emission scanning electron microscopy/energy dispersive X-ray analysis (FE-SEM/EDX). With increased milling time, the lattice parameter and lattice strain are found to increase. However, the crystallite size decreases from micrometer (75–95 μ m) to nanometer (10–20 nm). Mössbauer spectra analysis suggests the presence of essentially ferromagnetic phases with small percentage of super paramagnetic phase in the system. The saturation magnetization ( M s ), remanance ( M r ) and coercivity ( H c ) values for Fe-0Mn sample after 120 h of milling were 96.4 Am 2 /kg, 11.5 Am 2 /kg and 12.42 k Am −1 , respectively. However, for Fe-10Mn-5Cu sample the M s , H c and M r values were found to be 101.9 Am 2 /kg, 10.98 kA/m and 12.4 Am 2 /kg, respectively. The higher value of magnetization could be attributed to the favourable coupling between Mn and Cu.