Improvement of the Properties of Hard Magnetic NdFeb/Fe Nanocomposites by Minor Addition of Refractory Metals

摘要

The effect of the addition of selected refractory metals on structure and magnetic properties was studied for the nanocomposite Nd₉Fe_77−x B₁₄M _x (M=Ti, Mo, Nb) system, consisting of hard magnetic Nd₂Fe₁₄B phase, and soft magnetic phases (Fe, Fe₃B). It was found that 2-5 at % of Ti, Mo or Nb addition leads to a substantial increase of the coercivity and maximum energy product of the nanocomposite magnets maintaining the remanence unchanged. The highest properties were obtained for the alloys containing 4-5 at% of the refractory metals. The hysteresis loops for the alloys containing additional elements are smooth and characteristic of single phase alloys. The initial magnetization curve indicates the change of the coercivity mechanisms giving rise for pinning of domain walls, which is caused by the reduction of the crystallite size.