Hyperfine Interactions at 181Ta in Hf2Ni7 and Zr2Ni7

Abstract

We report on a time differential perturbed angular correlations (TDPAC) study of the hyperfine interactions at 181Ta in Hf2Ni7 and Zr2Ni7. The samples were prepared by arc melting proper amounts of constituents together with a small amount of Hf containing radioactive 181Hf atoms. A further heat treatment was necessary to obtain samples of the required crystal structure (monoclinic symmetry in the C2/m space group). As known, two non-equivalent lattice sites of Hf/Zr metal exist in this structure.The PAC measurements were performed at 20 - 1123 K. Two quadrupole interactions were observed, corresponding to two possible crystallographic positions of the probe atom in the studied structure. The electric quadrupole interaction parameters at 181Ta in Hf2Ni7 are υQ1(300K) = 586.7(65) MHz with η1 = 0.79(4) and υQ2(300K) = 466.8(41) MHz with η2 = 0.20(3), and in Zr2Ni7 they are υQ1(300K) = 498.4(22) MHz with η1 = 1.0 and υQ2(300K) = 418.0(50) MHz with η2 = 0.35(3). The presence of a magnetic interaction, reported in the literature, was not confirmed.