Quadrupole interaction at111Cd in rare-earth intermetallics

Quadrupole interactions at¹¹¹Cd in various rare-earth intermetallics have been investigated. The enhancement in the efg due to the electronic configurations is found to be small in contrast to pure metals.The authors thank K. Raghunathan for helpful discussions.     

Hyperfine interaction at111Cd in manganese

The hyperfine interaction is studied in two different crystal lografic forms of Mn. In the -Mn no magnetic, but a distinct electric quadrupole interaction is found. Effects of heat treatment are discussed. For the -Mn two magnetic field sites are found. Their temperature dependence and dependence on the In concentration are discussed.     

Quadrupole interaction at111Cd in RRh3B2 compounds (R=Ce to Gd) and absence of transferred hyperfine field at111Cd in GdRh3B2

The quadrupole interaction at¹¹¹Cd in RRh₃B₂ compounds studied by the TDPAC technique supports the prediction that Ce in CeRh₃B₂ is not trivalent. The highly anisotropic EFG indicates that¹¹¹Cd in GdRh₃B₂ cannot occupy the rare earth site. The transferred magnetic hyperfine field at¹¹¹Cd is nearly zero which supports the conjecture that the impurity probe nuclei are at the 3g(Rh) site.     

Quadrupole interaction at181Ta in tellurium

The quandrupole interaction at¹⁸¹Ta in tellurium measured at various temperatures revealed two unique sites with an axially symmetric electric field gradient. These are interpreted as a near substitutional site with almost octahedral symmetry and a pure interstitial site in the tellurium lattice. The temperature dependence observed for QI frequencies corresponding to these sites supports this conclusion.     

Quadrupole interaction at181Ta in selenium

The nuclear quadrupole interaction of Ta-181 in selenium was measured using perturbed angular correlation technique. The electric field gradient at room temperature is 4.56(32) × 10¹⁷ V/cm². The temperature dependence of EFG follows the usual T^3/2 behaviour.     

Magnetic and quadrupole interaction studies at 111Cd in GdMn2 and TbMn2

The temperature dependence of the electric quadrupole interaction and the magnetic hyperfine field at ¹¹¹Cd probe sites in RMn₂ (R=Gd, Tb) has been studied by TDPAC method. In the paramagnetic region the quadrupole interaction frequency ν_Q in both compounds varies linearly with temperature. Below the Neel temperature, we find an abrupt decrease in the magnitude of ν_Q which is consistent with an expansion of the unit cell. As an important feature, the data near T_N shows the coexistence of localized and itinerant magnetism of Mn atoms. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hyperfine interaction of111Cd in antiferromagnetic cobalt oxide

The temperature dependence of the hyperfine field of substitutional¹¹¹Cd in antiferromagnetic CoO has been measured by means of the perturbed angular correlation technique. The Larmor frequency ω_L is found to obey a power law ω_L(t=ω₀ t ^β) up tot _max=0.4 wheret=1−T/T _N is the reduced temperature withT _N=291.2(3) K and β=0.393 (5) the critical exponent. The results are discussed and compared with PAC experiments on¹¹¹Cd in NiO and Ni and with results obtained by other methods.     

Hyperfine interaction of111Cd in In-Pd intermetallic compounds

Perturbed - angular correlation (PAC) spectroscopy was applied to study the hyperfine parameters for¹¹¹In probes in In-Pd intermetallic compounds. The PAC spectra measured in In₃Pd, In₃Pd₂ and InPd₂ compounds reflect the number, population and symmetry of nonequivalent indium probe sites predicted by the crystallographic data. The temperature dependence of the observed electric field gradients was measured in the temperature range 80–873 K.     

Quadrupole interaction at57Fe in zirconium metal

The nuclear quadrupole interaction at⁵⁷Fe nuclei in hcp -zirconium metal is measured in the temperature range 4.2 to 560 K using Mössbauer spectroscopy of⁵⁷Fe. The quadrupole splitting at room temperature is measured to be 0.660(8) mm/sec which corresponds to an electric field gradient of |eq|=3.17×10¹⁷ V/cm² at the⁵⁷Fe nucleus in a -Zr host. As has been observed in many other systems, the results show significant electronic contributions. The temperature variation of the quadrupole interaction is much stronger than is expected from the lattice contributions and is found to follow theT ^3/2 dependence approximately.⁵⁷FeZr does not follow the universal correlation betweeneq _ion andeq _el observed in most of the normal metal hosts but follows the trends recently observed by Krusch and Forker for the transition metal hosts. Our results are compared with the predictions of the conduction electron charge shift model recently proposed by Bodenstedt and Perscheid.     

Quadrupole interaction at181Ta in BaHfO3

BaHfO₃ is prepared by sintering a mixture of BaCO₃ and HfO₂ giving the same heat treatments as for YBa₂Cu₃O_7– (YBCO). X-ray diffraction analysis confirms the formation of cubic BaHfO₃ along with some unreacted HfO₂. A¹⁸¹Ta TDPAC study of the sample, prepared using neutron-irradiated HfO₂ and BaCO₃, shows a relaxation process to be present in the sample. The value of the relaxation constant0.26 ns is unusually large and temperature independent.     

Electric quadrupole interaction at 111Cd and 119Sn in isostructural NiIn and CoSn compounds

The perturbed angular correlation technique and Mössbauer spectroscopy were applied to study the electric field gradient on ¹¹¹Cd and ¹¹⁹Sn probe atoms in isostructural NiIn and CoSn compounds. The ¹¹¹Cd PAC measurements performed in the temperature range 80--1100 K demonstrated the existence of two axially symmetric EFG's in each of the investigated compounds, related to the 2(d) and 1(a) probe sites in the B35 structure. A 1(a)-site preference for Cd probes in CoSn compound was observed. The temperature dependence of the quadrupole frequencies for ¹¹¹Cd in both compounds, interpreted in terms of the empirical model proposed by Christiansen et al.[1], follows a T^3/2 relation with different slope parameters for each of the observed frequencies. These results are combined with the data from the Mössbauer experiment. The ¹¹⁹Sn Mössbauer 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 NiIn_0.99Sn_0.01sample, giving an evidence of 2(d)-site preference for tin atoms in NiIn. The EFG values measured on ¹¹⁹Sn are 2.5 to 4 times larger than those on ¹¹¹Cd nuclei, while the ratio of the respective Sternheimer antishielding factors is equal to 0.77. Within the limits of errors no differences were observed in the magnitude and temperature dependence of Debye--Waller factors for 2(d) and 1(a) ¹¹⁹Sn positions in CoSn and NiIn lattices.     

EFG Studies at 111Cd in InBi Systems

TDPAC study of InBi_1−x Te _x with x=0.0, 0.01, 0.05, 0.1 and 0.2 as a function of temperature is done. Both pure and Te-doped samples show a semi-metallic character up to around room temperature. Above room temperature a steep transition to semiconducting state was observed, which is independent of the doping concentrations. Hence Te may be in the interstitial sites. Conductivity measurement of the above samples showed the same trend as observed in the EFG studies. Thus the importance of the conduction electron density is prominently seen in these systems. This revised version was published online in September 2006 with corrections to the Cover Date.     

Quadrupole interaction at169Tm in orthorhombic TmF3

Quadrupole interaction data recorded by Triplett et al for the C_1hTm site in TmF₃ are analysed via semi-empirical procedures, one of which employs rank 2 CF parameters derived from the¹⁵⁵Gd: GdF₃ Mössbauer results of Katila et al. The fitted crystal field interactions are compared with available optical spectroscopy results.     

TDPAC measurement of quadrupole interaction at111Cd in the nearly heavy fermion system USn2.9

Quadrupole interaction at¹¹¹Cd probe has been studied in the nearly heavy fermion system USn_3– using the TDPAC method. We observe a large quadrupole interaction frequency withv _Q =89.9(10) MHz at 300 K which is much higher than the earlier reported result. The observed frequency shows a linear temperature dependence in the range 25–300 K.     

Fluctuating Electric Field Gradients at 111Cd in Ice

¹¹¹Cd–PAC measurements have been made using the high specific activity of ¹¹¹In in the methanol–water mixtures of various concentrations at the room temperature. These experiments revealed that the perturbation factors 〈A ₂ G ₂〉 (integrated over two mean lives τ_N) do not follow the dependence of the macroscopic viscosity η. The observed dynamic character of the PAC spectra in ice is explained by the mobility of orientational and ionic defects. The activation energy for the diffusion process was determined to be E _a =0.35(1) eV. This revised version was published online in September 2006 with corrections to the Cover Date.