The effect of orthogonalization on the conduction electron electric field gradient in noncubic metals

By orthogonalizing the conduction electron states of model potential theory to the core electron states, the local conduction electron electric field gradient (EFG) is expressed by a model wave function EFG enhanced by a factor correlated with the Sternheimer antishielding factor.     

Temperature dependence of electric field gradient in TbCoO3

The temperature dependence of the electric field gradient (efg) in TbCoO₃ perovskite was measured by perturbed angular correlation (PAC) technique using ¹¹¹Cd and¹⁸¹Ta nuclear probes. The radioactive parent nuclei ¹¹¹In and ¹⁸¹Hf were introduced into the compound through a chemical process during sample preparation. The electric quadrupole interactions at ¹¹¹Cd show two different sites, assigned to probe substituting Tb and Co atoms. The temperature dependence of quadrupole frequencies show sharp discontinuities which have been interpreted as thermally activated spin state transitions from low-spin ground state configuration to the intermediate-spin state and from intermediate-spin to high-spin state of Co^3?+? ion. For ¹⁸¹Ta only one interaction was observed, which was assigned to probe at Co site. Indication of a Jahn–Teller distortion, which stabilizes the intermediate-spin state with orbital ordering, is also pointed out. No magnetic order was observed till 77 K.     

Temperature dependence of the electric field gradient in Er metal

The method of perturbed angular distributions was used to measure the temperature dependence of the electric field gradient in Er single crystal for 98 KT156 K. The I=11^– isomer in Er¹⁵⁴) was used as a probe. ₀ increases monotonically for 98 KT259 K and then decreases. A possible cause for this effect may be short range interactions between the f electrons above the Neel point.Visitor from the Weizmann Institute, Rehovoth, Israel.     

Temperature dependence studies of the electric field gradient at cadmium impurities in heavy rare earth metals

Several of the rare earth metals (Gd, Tb, Dy, Ho and Er) containing¹¹¹Cd impurities have been studied by the method of time differential perturbed angular correlations (TDPAC) to study electric field gradients. Experiments have been made over a temperature range in which no magnetic interactions are expected. We have observed general correlation patterns whose shapes are temperature dependent. We suggest this provides evidence of a reversible temperature dependent strain or distortion near the impurity atom.Supported in part by the US Energy and Research Development Administration under grant #E(11-1)-2184.     

Temperature dependence of the electric field gradient of Hg in Bi

The temperature dependence of the nuclear quadrupole interaction of the¹⁸⁸Hg(12⁺) isomer in a Bi host has been measured by the TDPAD technique. Assuming that the T^3/2 law is valid for this system a fit at the high temperature region yields _Q(T=0)=132(6) MHz and B=7.2(6)×10^–5K^–3/2. The EFG of HgBi and the temperature dependence strength follow the general trend of other probes in Bi.Supported in part by the MINERVA Foundation, Munich, Germany and the Israeli Academy of Science, Jerusalem, Israel.Incumbent of the Arye Dissentshik Career Development Chair.Incumbent of the Ruth Epstein Recu Career Development Chair.     

Temperature dependence of the electric field gradient of Cd in Hg

We have measured the quadrupole interaction of ¹⁰⁷Cd$\text{Hg}$ as a function of temperature. The relatively large temperature variation observed is consistent with the assumption of lattice vibrations as the main source for the temperature dependence of the electric field gradient.     

Temperature dependence of the surface electric field gradient for indium metal

The electric field gradient at indium surfaces was studied with¹¹¹In PAC-probes as a function of temperature. The surface field gradient was determined to be temperature independent up to 100 K and the fraction of¹¹¹In surface sites shows a pronounced annealing behaviour between 150 K and 250 K.     

Temperature dependence of the electric field gradient for111Cd in antimony

For the temperature dependence of the electric field gradient of¹¹¹Cd in the semimetal antimony the well knownT ^3/2 relationship is valid over a wide temperature range. The slope parameterB differs from that for^{121, 123}Sb in antimony by a factor of about 2.3.     

Temperature dependence of the electric field gradient in CdSe and HfO2

The time differential perturbed angular correlation technique was applied to study the electric field gradient in the semiconductor CdSe and the insulator HfO₂ at different temperatures. Whereas the semiconductor CdSe shows an increasing quadrupole coupling constant with increasing temperature, the insulator HfO₂ exhibits no temperature dependence of the electric field gradient over the whole temperature range investigated.     

Temperature dependence of the electric field gradient in AgIn2 intermetallic compound

The temperature dependence of the electric field gradient in the AgIn₂ intermetallic compound was measured using the TDPAC technique. From 80 K up to 415 K a linear dependence was found. Below 80 K a change in this behaviour was observed. This and previous results are interpreted as related to optical-phonon modes in intermetallic compounds.     

Pressure dependence of the electric field gradient at Cd-impurities in the heavy rare-earth metals

The pressure dependence of the electric field gradient at Cd impurities in Gd, Tb, Dy, Ho and Er have been measured at room temperature.The average isotropic volume dependence is dlneq/dlnV –4.4 and no systematic trend within the RE series is observed. The rather large volume dependence can be explained if the screening charge distribution of the host ions is considered.On leave from Panjab University, Chandigarh, India     

Temperature dependence of the electric field gradient in the AgIn2 intermetallic compound

The temperature dependence of the electric field gradient in the AgIn₂ intermetallic compound was measured using the TDPA correlation technique. From 80 K up to 415 K the electric field gradient follows a linear temperature dependence. Below 80 K a change in this behaviour is observed.Work supported in part by FINEP and CNPq.     

Temperature dependence of the electric field gradient of204Pb in hexagonal Tl

The temperature dependence of the nuclear quadrupole interaction of²⁰⁴Pb(4⁺) isomer in hexagonal Tl host has been investigated by the TDPAD technique. It is the first reported EFG which does not respect the T^3/2 law fors-p metals. The chosen approach is the independent treatment of the ionic contribution and of the electronic contribution in the approximation of the additivity of the two contributions, avoiding any assumption of a direct temperature dependence for the total EFG.     

Temperature dependence of the electric field gradient at Ta nuclei in hafnium pyrovanadate

The electric field gradient EFG in hafnium pyrovanadate has been measured at Hf sites at different temperatures with the time-differential perturbed angular correlation method. The results obtained show the existence of a phase transition around 110°C.