State of doped Mn in Fe–Mn soft magnetic powders fabricated by wet process and hydrogen reduction

Abstract

Novel Fe–Mn soft magnetic powders produced by the wet method and hydrogen reduction have been developed for electric motor applications. Aiming to clarify the magnetic properties and associated mechanism, the state of doped Mn in Fe–Mn soft magnetic powders was analyzed in this work. X-ray absorption fine structure spectroscopy (XAFS) was used to detect the presence of manganese as a solid solution in the body-centered cubic (BCC) iron phase of Fe–Mn powders. Although the presence of manganese in the BCC iron phase typically reduces magnetization and increases coercivity, the Fe–Mn powders exhibited coercivity values below approximately 80 A/m, and the saturation magnetization of the Fe–Mn powders was comparable to that of bulk pure iron (218 A m2/kg). Because MnO is typically resistant to reduction under hydrogen at 1373 K, the results of this study suggest that elements that are difficult to reduce using hydrogen might be doped in a metallic state by using the wet method. This method is promising to produce novel soft magnetic materials and base materials for soft magnetic composites.