Dependence of the magnetic and magnetoelastic properties of (TbFe2)(1-x)B-x melt-spun alloys on x

Rare earth-iron alloys containing highly anisotropic rare earth ions exhibi t huge values of magnetostriction in the crystalline compounds with large v alues still maintained in the amorphous counterparts (for amorphous (TbFe2) (87)B-13 lambda(s) was found to be 620 ppm at 77 K and 1.6 T). Melt-spun ri bbons have a high potential for applications due to their softer magnetic p roperties and dimensions (similar to 25 mu m thick) allowing lower applied fields and higher operating frequencies. Melt-spun ribbons of TbFe2 contain ing between 3 and 14 at. % boron as the glass former were prepared and exhi bit an x-ray amorphous structure for x greater than or equal to 7 at. % B. Their magnetic and magnetostrictive properties are discussed in terms of th e boron concentration. For the amorphous alloys little variations in these properties are observed whereas for x<7 at. % significant changes take plac e due to a nanocrystalline structure. By applying a two-sublattice mean-fie ld model to the M(T) data, the intrasublattice and intersublattice exchange parameters have been obtained and are compared with previous results on cr ystalline TbFe2. The results are consistent with the differences in Curie t emperatures. (C) 1999 American Institute of Physics. [S0021-8979(99)41408-2 ].