THE STRUCTURE AND MAGNETIC-PROPERTIES OF RAPIDLY QUENCHED AND ANNEALED MULTIPHASE NANOCRYSTALLINE ND9FE91-XBX RIBBONS

Melt-spun and annealed Nd9Fe91-xBx ribbons with 0 less than or equal t o x less than or equal to 9 have been studied by means of X-ray diffra ction, thermomagnetic analysis and magnetic measurements. The metastab le phase diagram up to 780 degrees C has been plotted. A metastable ph ase of the TbCu7 structure has been identified in the ribbons of binar y composition and those containing up to 7 at.% B. The Curie temperatu re of this phase was found to be strongly affected by both boron conte nt and annealing temperature. The structure of exchange coupled nanocr ystallites of Nd2Fe14B, alpha-Fe and Fe3B was realized by means of sho rt-time annealing. The annealed isotropic Nd9Fe84B7 ribbons had a rema nence of 100.5 emu g(-1), an intrinsic coercivity of 4.5 kOe, and an e nergy product of about 13 MG Oe. The details of structure formation, a s well as the criteria and conditions for the effective exchange coupl ing, are discussed.