Investigations of Zr-Ni intermetallic compounds by perturbed angular correlations

The hyperfine interactions experienced by 181Ta in ZrNi5 and Zr2Ni7 intermetallic compounds have been investigated by the perturbed angular correlation (PAC) technique. In ZrNi5, a strong electric quadrupole interaction (∼40%) with ωQ=72.0(1) Mrad/s, η=0.25(1), δ=0 at room temperature has been found due to the presence of Zr2Ni7 contaminating phase produced during sample preparation in the arc furnace. A weak quadrupole interaction of Zr2Ni7 (∼5%) with ωQ=65(1) Mrad/s, η=0.24(6), δ=0 has also been observed. The cubic component of ZrNi5 also has been observed (∼40% at room temperature) in this sample along with associated defect (15%). It is found that at 873 K, the cubic fraction increases to ∼54% at the cost of its defect fraction. No magnetic interaction in ZrNi5 has been observed which supports the earlier PAC results but rules out the result of strong magnetic ordering found from magnetization measurement. In Zr2Ni7, two regular fractions corresponding to two different crystallographic sites of Zr have been clearly identified with the parameters ωQ(1)=70.9(1) Mrad/s, η(1)=0.28(1), δ=1.3(3)% and ωQ(2)=64(1) Mrad/s, η(2)=0.34(8), δ=0 while contradictory results were reported from previous measurements.