High-coercivity (NdDy)2(FeNb)14B–α–Fe nanocrystalline alloys

Abstract

High coercivity, high remanence, and high energy product (NdDy)2(FeNb)14B–α–Fe nanocrystalline alloys containing 0 to 30 wt % α–Fe have been prepared by melt spinning and subsequent annealing. The best magnetic properties of remanence (Br), coercivity (Hci), and maximum energy product [(BH)max] are 1.02 T, 702 kA/m, and 134 kJ/m3, respectively, for Nd8.16Dy1Fe85.26Nb1B4.58. The microstructure consists of a two phase nanocomposite of hard magnetic (NdDy)2(FeNb)14B and soft magnetic α–Fe with an average size of about 30 nm. These small dimensions allow effective exchange coupling between hard and soft magnetic grains and result in the simultaneous enhancement of Br, Hci, and (BH)max. A systematic study on the effect of annealing temperature and time on the microstructure and magnetic properties has been carried out.