The effect of magnetic field treatment on enhanced exchange coupling of Nd/sub 2/Fe/sub 14/B/Fe/sub 3/B magnet

An externally applied magnetic field during heat treating the Nd/sub 2/Fe/sub 14/B/Fe/sub 3/B based spring magnet was found to enhance the exchange coupling between the hard and soft magnetic grains. More than 30% increase in M/sub r//M/sub s/ values for melt-spun Nd/sub 4/Fe/sub 73.5/Co/sub 3/(Hf/sub 1-x/Ga/sub x/)B/sub 18.5/ (x=0. 0.5, 1) alloys was resulted from a uniform distribution of Fe/sub 3/B, /spl alpha/-Fe as well as Nd/sub 2/Fe/sub 14/B, and also from the reduced grain size of those phases by 20%. The externally applied magnetic field induced the uniform distribution of fine grains. The present study also showed that there is an optimum grain size exhibiting a high coercivity (22 nm for the Nd/sub 4/Fe/sub 73.5/Co/sub 3/Hf/sub 1-x/Ga/sub x/B/sub 18.5/ alloys).