Electric field gradients at 181Ta probe in ZrNi: Results from perturbed angular correlation and first-principles calculations

Abstract

Abstract Results of temperature dependent perturbed angular correlation (PAC) measurements in the equiatomic ZrNi alloy have been reported for the first time using 181 Hf probe. At room temperature, values of quadrupole frequency and asymmetry parameter for the major component (~80%) are found to be ω Q =26.8(4) Mrad/s, and η =0.413(7). The resulting electric field gradient comes out to be V zz =2.99 ×10 17 V/cm 2 and this corresponds to the probe nuclei occupying the regular substitutional Zr sites. In ZrNi system, no magnetic interaction is observed down to 77 K indicating absence of any magnetism in this material. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies on an inactive but similarly prepared sample confirm the dominant presence of the orthorhombic ZrNi phase in the sample. A complementary density functional theory (DFT) calculation results in V zz =−2.35×10 17 V/cm 2 , η =0.46 at the 181 Ta probe impurity site and zero magnetic moment on each atomic site, in close agreement with the experimental results. Furthermore, it is found that electric field gradient for the regular component follows a T 3/2 temperature dependence between 77 and 353 K, beyond which it varies linearly with temperature.