Gd-155,Gd-157 NMR study of Gd-Ni intermetallic compounds

The spin-echo NMR technique was used to study the magnetic properties of th e following intermetallic compounds of the Gd-Ni series: Gd2Ni17, GdNi5, Gd Ni3, GdNi2 and GdNi, with Gd-155 and Gd-157 nuclei as local probes. These c ompounds have different crystal structures and order ferri- or ferromagneti cally. The NMR measurements were performed at 4.2 and 1.5 K. The NMR spectr a were compared to computed line positions obtained from the diagonalizatio n of the complete hyperfine Hamiltonian. The RKKY contribution to the hyper fine field was computed for Gd2Ni17 and GdNi3, and differences in the value s of B-hf at the two sites of Gd, of the order, respectively, of 18 and 6 T , were thus justified. An intense quadrupole interaction was observed at th e Gd sites in the compounds GdNi5, Gd2Ni17, and in one of the sites of the compound GdNi3 ; in all these cases, the values of V-zz are of the order of 10(22) V/m(2). The NMR results in GdNi are consistent with a direction of magnetization along the b-axis for this compound. The present study present s the first systematics of hyperfine interactions in Gd-Ni compounds. (C) 2 000 Elsevier Science B.V. All rights reserved.