THE EFFECT OF GD SUBSTITUTION ON THE MAGNETIC-PROPERTIES AND HYPERFINE FIELDS OF MELT-SPUN ND4FE77.5B18.5 ALLOYS

The hyperfine fields (HFS) and magnetic properties of amorphous and cr ystallized Gd(x)Nd4-xFe77.5B18.5 (0 less-than-or-equal-to x less-than- or-equal-to 4) alloys have been investigated by means of magnetization measurements, zero-field spin-echo nuclear magnetic resonance (NMR) a nd Mossbauer effect (ME). For comparison, the x-ray diffraction (XRD) pattern of Nd4Fe77.5B18.5 annealed at 670-degrees-C for a short time i s also presented. It is found that the Curie temperatures of amorphous alloys increase slightly on addition of Gd, but the coercive fields o f crystallized alloys decrease monotonically with increasing x. NMR, M E and XRD indicate that these samples consist of Fe3B with a body-cent red tetragonal structure (BCT Fe3B) and a small amount of alpha-Fe, wi th no Nd2Fe14B and Nd1.1Fe4B4 phases. Furthermore, the NMR results ind icate that the B-11 HFS of BCT Fe3B increase linearly from 25.3 kOe (3 4.7 MHz) for x = 0 to 26.3 kOe (36.0 MHz) for x = 4, but that of alpha -Fe does not change with increasing Gd concentration; the Mossbauer sp ectra (MSS) show that the relative intensity of the subspectrum corres ponding to Fe-57 at Fe(III)(8g) sites in BCT Fe3B is about 5% weaker t han those of the other two, implying that about 5 at.% Fe atoms in thi s site are substituted by other atoms. According to this, it may be re asonable to assume that the R atoms enter into the BCT Fe3B.