A comparative study on the microstructure and magnetic properties of melt-spun RE/sub 2/Fe/sub 14/B//spl alpha/-Fe and RE/sub 2/Fe/sub 14/B/Fe/sub 3/B (RE=Nd, Pr) nanocomposites

Abstract

The microstructure and magnetic properties of melt-spun RE/sub 2/Fe/sub 14/B//spl alpha/-Fe and RE/sub 2/Fe/sub 14/B/Fe/sub 3/B nanocomposite powders were studied using Pr and Nd versions of RE/sub 9/Fe/sub 86/B/sub 5/(RE/sub 2/Fe/sub 14/B//spl alpha/-Fe) and RE/sub 9/Fe/sub 79/B/sub 12/(RE/sub 2/Fe/sub 14/B/Fe/sub 3/B) alloys. It was found that the RE/sub 9/Fe/sub 86/B/sub 5/ exhibited a finer and more uniform microstructure with an average grain size of /spl sim/10 nm, whereas a relatively coarse microstructure (grain size up to 100 nm) was observed in the RE/sub 9/Fe/sub 79/B/sub 12/. It was also found that the RE/sub 9/Fe/sub 86/B/sub 5/ yielded higher B/sub r/ and (BH)/sub max/, and a more square demagnetization loop, although the H/sub ci/ was slightly lower. The superior magnetic properties observed in the RE/sub 9/Fe/sub 86/B/sub 5/ can be attributed to the more favorable intrinsic magnetic properties of /spl alpha/-Fe (higher M/sub s/ and lower K) and the much finer microstructure, which produces a stronger intergrain exchange coupling between the RE/sub 2/Fe/sub 14/B and /spl alpha/-Fe phases. The results indicate that RE/sub 2/Fe/sub 14/B//spl alpha/-Fe nanocomposites are more desirable than RE/sub 2/Fe/sub 14/B/Fe/sub 3/B for future development of RE-Fe-B nanocomposite magnets.