The enhanced exchange coupled interaction in nanocrystalline Nd2Fe14B/Fe3B+αFe alloys with improved microstructure

The effects of additives and heat-treatment conditions on the microstructure in nanocrystalline ahoy Nd2Fe14B/Fe3B + alpha Fe were studied using H-c(T)/M-s(T) versus 2k(1)(T)/mu(0)M(s)(2)(T) plots, TEM, and Mossbauer spectroscopy in this paper. It was found that the additives I-If and Ga improve the condition of the grain shapes, but simultaneously deteriorate the grain surfaces. Magnetic field heat-treatment not only induces grain refinement but also causes a uniform distribution of the soft and hard phases in this nanocomposite alloy. The influences of Hf, Ga and magnetic field heat-treatment are weakened upon increasing the annealing temperature. Furthermore, the magnetic interaction was examined using delta M plot in this paper. It was found that the exchange coupled interaction is greatly enhanced in the sample annealed with magnetic heat-treatment, which has the highest energy product of (BH)(max) = 15.8 MG Oe. (C) 1999 Elsevier Science B.V. All rights reserved.