NMR measurements in milled GdCo sub(2) and GdFe sub(2) intermetallic compounds

• Published in: Journal of magnetism and magnetic materials 1999-04, Vol.195 (1), p.49-56
• Main Authors: Tribuzy, C V B, Biondo, A, Larica, C, Alves, K M B, Guimaraes, A P
• Format: Article
• Language: English
• ISSN: 0304-8853

We have used the nuclear magnetic resonance technique to study the magnetic and structural properties of the Gd-Co and Gd-Fe metallic systems, starting with the C15 Laves phase intermetallic compounds, and submitting them to a high-energy milling process. This leads to the amorphization of the samples, as determined by the X-ray diffraction spectra. For the Gd-Co system the NMR study used the super(59)Co nucleus; in the Gd-Fe system, super(155,157)Gd and super(57)Fe were used. Both systems showed segregation of the pure elements, after a few hours of milling. In the Gd-Co system, a single line, of increasing width, was observed in the super(59)Co spectrum. In the Gd-Fe system, the super(155)Gd and super(157)Gd resonances show three lines, arising from electric quadrupole interaction. With increasing milling time, the lines broaden, and extra lines appear attributed to a cubic phase of Gd; this interpretation is supported by the X-ray analysis of the samples. The super(57)Fe NMR spectrum of this system also informs on the direction of magnetization of the samples in the early stages of milling. From 1 to 7 h of milling, a spectrum of alpha -Fe was observed. The study of the NMR line intensity as a function of radio frequency (RF) power in GdCo sub(2) suggests the existence of regions of the samples with different degrees of disorder. We have observed the persistence of NMR signals from the original intermetallic compounds in the samples with up to 10 and 7 h of milling, respectively, for GdCo sub(2) and GdFe sub(2).