¹⁰⁵Pd NMR and NQR study of the cubic heavy fermion system Ce₃Pd₂₀Si₆

Abstract

We report 105Pd nuclear magnetic resonance (NMR) and nuclear quadrupolar resonance (NQR) measurements on a single crystal of Ce3Pd20Si6, where antiferroquadrupolar and antiferromagnetic orders develop at low temperature. From the analysis of NQR and NMR spectra, we have determined the electric field gradient (EFG) tensors and the anisotropic Knight shift (K) components for both inequivalent Pd sites—Pd(32f) and Pd(48h). The observed EFG values are in excellent agreement with our state-of-the-art density functional theory calculations. The principal values of the quadrupolar coupling are MHz and MHz, for the Pd(32f) and Pd(48h) sites, respectively, which is large compared to the Larmor frequency defined by the gyromagnetic constant MHz/T for 105Pd. Therefore, the complete knowledge of K and the EFG tensors is crucial to establish the correspondence between NMR spectra and crystallographic sites, which is needed for a complete analysis of the magnetic structure, static spin susceptibility, and the spin-lattice relaxation rate data and a better understanding of the groundstate of Ce3Pd20Si6.

Cascade of magnetic-field-driven quantum phase transitions in Ce3Pd20Si6

“…This compound crystallizes in the Fm3m cubic space group with two crystallographically inequivalent Ce sites at the 4a (Ce1) and 8c (Ce2) Wyckoff positions [50]. The Ce1 site is surrounded by 12 Pd atoms and 6 Si atoms, resulting in octahedral (O h ) point symmetry, whereas the Ce2 site is tetrahedrally coordinated with 16 Pd atoms (T d point symmetry) [51]. Based on recent experimental evidence from diffuse neutron scattering, it was suggested that the coherent magnetic neutron-scattering intensity is dominated by the contribution from the simple-cubic Ce2 sublattice, whereas the face-centered-cubic Ce1 sublattice is magnetically silent [47].…”