ELECTRIC QUADRUPOLE INTERACTION AT CD-111 AND SN-119 IN ISOSTRUCTURALNIIN AND COSN COMPOUNDS

The perturbed angular correlation technique and Mossbauer spectroscopy were applied to study the electric field gradient on Cd-111 and Sn-11 9 probe atoms in isostructural NiIn and CoSn compounds. The Cd-111 PAC measurements performed in the temperature range 80-1100 K demonstrate d the existence of two axially symmetric EFG's in each of the investig ated compounds, related to the 2(d) and 1(a) probe sites in the B35 st ructure. A 1(a)-site preference for Cd probes in CoSn compound was obs erved. The temperature dependence of the quadrupole frequencies for Cd -111 in both compounds, interpreted in terms of the empirical model pr oposed by Christiansen et al. [1], follows a T-3/2 relation with diffe rent slope parameters for each of the observed frequencies. These resu lts are combined with the data from the Mossbauer experiment. The Sn-1 19 Mossbauer spectra taken at liquid nitrogen and at room temperatures showed two quadrupole split doublets with the intensity ratio 2:1 for CoSn and 8:1 for NiIn0.99Sn0.01 sample, giving an evidence of 2(d)-si te preference for tin atoms in NiIn. The EFG values measured on Sn-119 are 2.5 to 4 times larger than those on Cd-111 nuclei, while the rati o of the respective Sternheimer antishielding factors is equal to 0.77 . Within the limits of errors no differences were observed in the magn itude and temperature dependence of Debye-Waller factors for 2(d) and 1(a) Sn-119 positions in CoSn and NiIn lattices.