PAC Studies of Ag-Hf Intermetallic Compounds

Abstract

The hyperfine quadrupole interaction of 181Ta and 111Cd probes in HfAg and HfiAg com-pounds was studied at 24 to 1100 K with the time -differential perturbed angular correlation (TDPAC) technique. The EFGs measured in HfAg on 181Ta and 111Cd are 1.388(5)x1018 Vcm-2 and 0.340(5)x1018 Vcm -2 , respectively. For both probe atoms a linear decrease of the EFG with temperature was observed with slopes 1.11(2)x10-4 K-1 and 1.73(5)x10-4 K-1 for 181Ta and 111Cd, respectively. In Hf2 Ag, 0.469(2)x1018 Vcm-2 was determined on 181Ta nuclei and 0.428(5)x1018 Vcm-2 on 111Cd. Also a linear EFG temperature dependence with the large slope of 2.39(6)x10-4 K-1 was observed for 111Cd probes in Hf2Ag, while the EFG measured on 181Ta nuclei in this compound exhibits a very weak temperature variation which can be fitted neither with a linear T nor a T 3/2 dependence. In all cases the electronic contributions to the EFG are very small indicating that these transition element systems do not obey the universal correlation between the electronic and the ionic EFG observed in numerous other systems not belonging to the transition metal series.

ZrAg and Zr2Ag phases studiedby perturbed angular correlation with 181Ta probes

“…The much lower value of the observed quadrupole frequency than in the case of ZrAg correlates with the EFG for Hf 2 Ag [10] (see Table 1) and agrees within the error bars with the value reported in [12]. Table 1 Quadrupole interaction parameters for 181 Ta in Zr -Ag and Hf -Ag [10] compounds (the room temperature value of the quadrupole frequency ν Q , the corresponding EFG (V zz ), the parameters of the V zz (T) temperature dependence and the calculated EFG at the Ta site ( theor zz V ) [13] The data obtained for the temperature interval between 24 and 1100 K are presented in Fig. 2 and compared with those for Hf 2 Ag [10].…”

“…The shape of the spectrum points to a texture of the sample similar to that observed for many Hf and Zr intermetallic compounds [2,3,5,10,11]. The value of the quadrupole frequency obtained and the corresponding EFG (see Table 1) are close to the values for the isostructural HfAg compound [10], reflecting the chemical similarity of Hf and Zr and the similar lattice constants of both compounds. The very narrow frequency distribution (δ close to zero) indicates a well-defined nearest neighbourhood of the probe atoms.…”

“…The data are consistent with a linear function and can be well fitted with Eq. (3), as is the case for the HfAg compound [10].…”

Time-differential perturbed angular correlation study of the electric field gradient in Ti2Rh MoSi2-type compound

“…This low strength of quadrupole interaction was explained as due to the unusually small value (being of the same order as the d term) of the usually dominant p orbital contribution in this structure [17]. It can be seen from Table 1 that the V zz values at 4(e) site in C11 b structure grow up when going from Cu-, through Au- [14], Ag- [3,13] and Pd-compounds [2] up to the Ti 2 Rh. Yaar et al [18] basing on EFG values for 4(e) site in MoSi 2 Hf 2 X (X = Pd, Ag, Cd) compounds found the strong correlation between the V zz value at the Hf site and the distance to the nn Hf atom.…”

“…The 181 Ta and 111 Cd quadrupole interaction in the MoSi 2 -type compounds Hf 2 Pd, Hf 2 Ag and Zr 2 Pd were measured in the past as a function of temperature, using TDPAC technique [2,3]. In most metal systems, the temperature dependence of the P. Wodniecki (B) · A. Kulińska · B. Wodniecka IFJ PAN, Radzikowskiego 152, 31-342, Kraków, Poland e-mail: pawel.wodniecki@ifj.edu.pl Fig.…”