Microstructure and magnetic domain structure of boron-enriched Nd-2(FeCo)(14)B melt-spun ribbons

Heat treated melt-spun ribbons of(Nd0.95La0.05)(9.5)FebalCo5Nb2B10.5 have b een studied systematically by superconducting quantum interference device ( SQUID) magnetometry, conventional transmission electron microscopy (CTEM) a nd Lorentz transmission electron microscopy (LTEM). The sample's microstruc ture grew from an amorphous state through a partially crystallized state at 650 degrees C, and finally to a fully crystallized state at 750 degrees C. Excessive grain growth producing grains from 38 to 68 nm in diameter was o bserved when the ribbon was annealed at 850 degrees C. Soft magnetic phases such as Fe3B and alpha-Fe precipitated at the grain boundaries. These inte rgranular phases are exchange coupled with the hard phase causing a decreas e of H-c. Exchange-coupling dominant and dipolar-coupling dominant regions co-exist inside the sample. In the latter regions, snake-shaped interactive domains are frequently observed. (C) 1999 Elsevier Science B.V. All rights reserved.