Electric quadrupole and magnetic dipole interactions at ~(181)Ta impurity in Zr_2Ni_7 intermetallic compound: Experiment and first-principles calculations

摘要

Electric quadrupole interactions at ~(181)Ta impurity in the intermetallic compound Zr_2Ni_7 have been studied by perturbed angular correlation technique. It has been found that there are two electric field gradients (EFG) at the ~(181)Ta site due to two different crystalline configurations in Zr_2Ni_7, while contradictory results were reported from previous investigations. The values of EFG at room temperature have been found to be V_(zz)=7.9 × 10~(17) V/cm~2 and 7.1 × 10~(17) V/cm~2 corresponding to present experimental values of quadrupole frequencies and asymmetry parameters for the two sites: (ωq1= 70.7(1) Mrad/s, I=0.28(1), δ=0.8(2)% (site fraction 84%) and ωq2= 63(1) Mrad/s, ν=0.35(5), S～0 (site fraction 9%). Electric field gradients and asymmetry parameters have been computed from the complementary first-principles density functional theory (DFT) to compare with present experimental results. Our calculated values of EFG are found to be in close agreement with the experimental results. No magnetic interactions in Zr_2Ni_7 have been observed at 298 and 77 K which implies that there is no ferromagnetic ordering in this material down to 77 K. This observation is corroborated by theoretical calculations, wherein no magnetic moment or hyperfine field is found at any atomic site.