NMR measurements in milled RE-TM(sub 2) compounds (RE=Gd and TM=Co, Fe)

摘要

Milled samples of the Laves phase intermetallic compounds Gd Fe(sub 2) and Gd CO(sub 2) were measured by NMR at 4.2 K. The milling was made from the crystalline intermetallic compounds, inside a cylindrical tool made of hard steel, under argon atmosphere, for several different time intervals. The initial compounds were produced from high purity elements in an arc furnace, under inert atmosphere. Their X-ray diffraction patterns agreed with those of the literature. The milling of Gd Fe(sub 2) and of Gd CO(sub 2), induces amorphization. Above 1 hour the milling of Gd Fe(sub 2) leads to segregation of (alpha)-Fe and formation of a Gd-Fe phase. These results are shown in the X-ray analysis. The spin-echo pulse NMR technique was utilized to study some structural and magnetic as a function of milling time. The measurements were made in a broad band pulse NMR spectrometer. The NMR spectra of the (sup 155) Gd (sup 157) Gd isotopes in Gd Fe(sub 2) show a broadening and displacement of the NMR lines, reflecting the introduction of defects, some kind of disorder and also the formation of a new Gd-rich phase after 1 hour. This result is in agreement with the X-ray spectra. In both systems, the spectra of the amorphous samples show broader lines, and the measured hyperfine fields do not change much with milling. (author). 9 refs., 4 figs. (Atomindex citation 28:029199)