AMORPHIZATION OF TBFE3 BY NITROGEN ABSORPTION

The nitrogenation process of the TbFe3 intermetallic compound was stud ied by heat treating the alloy between 573 and 873 K in a nitrogen atm osphere. The structural and magnetic properties of the nitrogenated sa mples were characterized by x-ray diffraction (XRD), Mossbauer spectro scopy, and magnetic measurements. The magnetic moments of the nitrogen ated samples were found to be a function of the annealing temperature and showed a minimum for the sample heat treated at 673 K. The XRD pat tern of this sample (673 K) showed that the Bragg peaks of the 1-3 pha se had completely disappeared and were replaced by a broad maximum ind icating a breakdown of the TbFe3 Structure into an amorphous phase. Th e room-temperature Mossbauer spectrum of the same sample consisted alm ost entirely of a quadrupole-split doublet plus a small amount of alph a-Fe and TbFe3. This doublet split into a broad spectrum upon cooling which is typical of amorphous rare-earth-transition-metal compounds. F or samples heat treated at higher temperatures, the amount of alpha-Fe and TbN phases gradually increased. This nitrogenation process is unl ike that of R2Fe17. In this study, nitrogen atoms do not go into the i nterstitial sites. Instead, they create a ferromagnetic (T(C) almost-e qual-to 215 K) amorphous phase of Th, Fe, and N which is stable over a wide temperature range.