The effect of cobalt substitution on the magnetic properties of nanostructured NdFeB based melt spun ribbons

The magnetic properties of nanostructured, directly cast melt spun alloys in the compositional series Nd-11.7(Fe1-xCox)(82.4)B-5.9 and Nd-10.0(Fe1-xCox)(84.1)B-5.9 with x varying within the range 0 to 0.24 have been studied. The low Nd, nanocomposite alloy series contained an estimated 15 vol % of alpha-(Fe,Co) phase in addition to the principal hard magnetic phase Nd-2(Fe,Co)(14)B, whilst the near stoichiometric 11.7 at % Nd series were single phase. The Curie temperature, Tc. increased with cobalt addition, typically by similar to 100 degrees C per 10 at % substitution. For the stoichiometric Nd series, the remanence Jr and energy product (BH)mas were found to increase slightly with cobalt concentration, whilst the intrinsic coercivity jHc, in contrast, decreased by similar to 30% to 700kA/m at x similar to 0.15. In the nanocomposite series, Co substitution led to slight reductions in Jr, jHc and (BH)mas. Thus, especially for the stoichiometric Nd series, a very useful increase in the Curie temperature, Tc, and thermal stability is achieved whilst still retaining the enhanced Jr and (BH)mas associated with the nanophase stucture.