145Nd NMR study of Nd xY 2 − xCo 17 and Nd xY 2 − xCo 14B

Abstract

The 145Nd Nuclear magnetic resonance (NMR) spin-echo spectra of the Nd x Y 2 − x Co 17 and Nd x Y 2 - x Co 14B compounds at 4.2K are presented. Quadrupole septets are assigned to the Nd sites 4f, 4g in Nd x Y 2 − x Co 14B and 6c in Nd x Y 2 − x Co 17. A large change of the quadrupole splitting between x = 0.1 and x = 0.2 and only slight changes of the hyperfine fields is observed in Nd x Y 2 − x Co 14B. The effect is attributed to a change of the easy magnetisation direction with Nd content from the c-plane to the c-axis. For Nd x Y 2 − x Co 17 slight changes of quadrupole splitting and hyperfine field in the whole concentration region 0.1< x<2.0 are observed only, reflecting a planar anisotropy of the compounds in the whole series. From the quadrupole splittings the values of the 4f-electron- and the lattice contributions to the electric field gradient at Nd nuclei are derived. The lattice contributions are related to the crystal electric field coefficient A 2 0 at the neodymium sites. The A 2 0 values amount to 192 Ka 0 −2 for the 4g and 57 Ka 0 −2 for the 4f site in Nd x Y 2 − x Co 14B. The directions of magnetic moments at the Nd sites are also obtained.