NMR of Nd and Sm in Nd2Fe14B and Sm2 Fe14B

The spin-echo nuclear magnetic resonance (NMR) spectra of ¹⁴³ Nd, ¹⁴⁵Nd, ¹⁴⁷Sm and ¹⁴⁹Sm in polycrystalline samples of Nd₂Fe₁₄B and Sm₂ Fe₁₄B measured at 4.2 K are presented. Well resolved quadrupole subspectra are assigned to the rare earth sites 4f and 4g in the compounds. The corresponding values of the quadrupole splitting and hyperfine fields are analyzed in terms of the contributions, depending on the rare earth type, as well as local symmetry and environment of the sites. From the quadrupole splitting, the 4f and the lattice contributions to the electric field gradient at Nd and Sm nuclei are derived. On this basis, the crystal electric field coefficients A₂ ⁰ for both rare earth sites are obtained and compared to those obtained in other measurements