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1.
Nanocrystalline indium (nano-In) was prepared with different particle sizes by electrochemical deposition. The temperature
dependence of the local electric field gradient (EFG) of nano-In was investigated in a temperature range of 20–300 K using
the probe 111In for perturbed γγ angular correlation (PAC) experiments. The temperature dependence of the EFG of nano-In can be described
by a (1−BT
3/2) dependence as in bulk-In. It is shown that the low temperature value of the EFG and the proportionality constant B vary
systematically with particle size. 相似文献
2.
A strong electric field gradient (EFG) has been observed at181 Ta in Pd and Zn metals using DPAC technique. The value of the EFG in Pd is found to be 12.5(8)×1017 V/cm2 with an asymmetry parameter () of 0.33(2). The value of the EFG in Zn has the same value as in the Pd metal, but the asymmetry parameter has the value 0.36(3). The variation of EFG in Pd with temperature has shown a weak dependence. The results are interpreted in terms of oxygen trapping at Hf atoms during the sample preparation. 相似文献
3.
The electric quadrupole coupling constant of the210Po(6+) isomer in a Bi single crystal was measured as a function of the temperature using the time-differential perturbed angular
correlations technique. The electric field gradient (EFG) for Po in Bi is found to be temperature independent in the range
77–477 K. Using a calculated value of the nuclear quadrupole moment, the magnitude of the EFG is derived, and in turn serves
to re-examine the systematics of quadrupole moments of λh
9
2/2
configurations in the lead region. 相似文献
4.
The electric field gradients (EFG) for ruthenium in scandium and yttrium metal were determined by TDPAC measurements to be 19(4) × 1017 V/cm2 and 5.5(12) × 1017 V/cm2 respectively at room temperature. The EFG for Ru in Sc was found to vary considerably in the temperature range from 14 to 700 K, whereas for Ru in Y only an extremely small temperature dependence of the EFG was observed. 相似文献
5.
Electric field gradient (EFG) in scandium metal has been evaluated at temperatures 11 K and 293 K using band wave functions
determined in the temperature dependent model potentials. The results of net EFG obtained are −3.756×1013 esu/cm3 and −8.009×1013esu/cm3 at 11 K and 293 K respectively. The agreement with available experimental result is reasonably good. 相似文献
6.
The 6.2-keV Mössbauer transition of181Ta was used to study both the Isomer-Shift (IS) and the quadrupole interaction in Re-single crystal host in the temperature range of 77 K to 517 K. Spectra were obtained for the181W diffused into Re-single crystal source using a single line Ta-metal absorber. The temperature change for the IS, δS/δT, is 55(1)×10?4 mm/s·deg, which is of the order of ?24 times the second-order Doppler shift. The temperature change of the electric field gradient follows the T3/2 relation. The relative smaller change of the EFG with respect to the IS change with temperature, reflects the strong role of the change of the s-electron density (s-d electron transfer) with temperature over other parameters. 相似文献
7.
J. N. Rimbert F. Adnet C. Lafargue F. Dumas C. Wolf G. Bereziat 《Hyperfine Interactions》1990,61(1-4):1227-1230
TDPAC measurements of the 150–247 keV gamma-ray cascade in111Cd have been performed at room temperature on Calmodulin (CaM) and Parvalbumin (Pa) labelled with radioactive111mCd. The anisotropy of the coincidence counting rate shows a time-dependent behaviour, typical of two different nuclear quadrupole
interactions (NQI) in CaM. The NQI parameters indicate the presence of two distinct metal-binding sites, presenting non-equivalent
local electric charge structure. In Pa samples, only one NQI is observed and the measured electric field gradient (EFG) value
agrees well with the large one obtained in CaM. 相似文献
8.
We have performed self-consistent full potential LAPW calculations of Cu2O. Since the new results agree well with a previous muffin-tin calculation, it can be concluded that non-muffin-tin effects
are relatively small in Cu2O. By using the present self-consistent charge density, we, obtain the electric field gradient (EFG) at the Cu site without
further approximations. Our theory yields a value of −0.85 e/au3, in good agreement with experiment but in contrast to a previous cluster calculation in which a positive sign of the EFG
was obtained. The origin of the EFG and the discrepancies between our band structure and the cluster calculation is analyzed. 相似文献
9.
10.
The metal-insulator (M-I) transition in vanadium sesquioxide V2O3 has been investigated by time differential perturbed angular correlation measurements of the electric fieldgradient (EFG) and the magnetic hyperfine field at dilute111Cd impurities. The EFG undergoes a first-order change at the M-I transition at Tt=160 K, but does not reflect the high temperature resistivity anomaly. The increase of the EFG with temperature in the metallic phase can be attributed to thermal variations of the oxygen sublattice. The temperature dependence of the magnetic hyperfine field in the insulating phase follows a Brioullin function with a saturation value of Hhf(O)=15 KOe and an extrapolated Neel temperature, which, depending on the impurity concentration, varies between 188 and 230 K. 相似文献
11.
Shengyun Zhu Shennan Zheng Anli Li Hangchen Huang Hongshan Du Honglin Din Donghong Li 《Hyperfine Interactions》1990,62(3):213-218
HighT
c superconductivity in the YBaCuO superconductor has been investigated through the quadrupole interaction of the probe nuclei99Tc. The quadrupole interactions were measured by the TDPAC method from 77 to 296 K. The probe nuclei99Tc were introduced into the YBaCuO superconducting specimen by diffusion. The derived electric quadrupole interaction parameters
show that the probe nuclei are subject to a unique EFG interaction and occupy a substitutional lattice site in the YBaCuO
superconductor. A strong EFG of 1019 V/cm2 was observed. The temperature dependence of the EFG exhibits a linear decrease with temperature increase. Anomalies of both
EFG and ν were found in the superconducting transition temperature region. The role of the oxygen vacancies in the Cu−O chains
is discussed. 相似文献
12.
Corrections to results of electric field gradient (EFG) already published [Pramana — J. Phys.41, 443 (1993)] are reported. The corrected net EFG is:q=−8.01×1013 esu/cm3 against the published valueq=16.06×1013 esu/cm3. The present result agrees reasonably well with the experimental result, |q
expt|=13×1013 esu/cm3.
Recently, a computational error is detected, which modifies the results of EFG, we have already published [1]. The error was
committed mainly in the part that evaluated thep-p contribution [1] to EFG by the conduction electrons. The corrected results are summarized in table 1 which must replace the
table 1 of the published work [1].
In addition, the lattice parameters as well as the temperature were also misquoted in the previous work [1]. The right parameters
are:a=6.25311 au andc=9.96509 au. The temperature at which EFG’s are calculated is 293 K instead of 11 K as reported before [1].
The discussions and conclusions made in the published work [1] remain almost unchanged except that they now refer to the corrected
numbers. Although the corrected net EFG suffers a sign reversal from the one already published [1], the agreement with experiment
is still considered reasonably good because the sign of experimental EFG is not determined. The computational error however
does not affect the introduction and theory section of the published work [1]. 相似文献
13.
K. Venugopalan K. C. Sebastian S. S. Sharma S. N. A. Jaffrey D. R. S. Somayajulu J. Verma 《Hyperfine Interactions》1987,34(1-4):239-242
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 T3/2 behaviour. 相似文献
14.
H. -R. Blank M. Frank M. Geiger R. Joyce M. Kaltenhäuser R. Kapp U. Lossen R. Sporer B. Zapf 《Zeitschrift für Physik B Condensed Matter》1995,97(4):493-497
Using the111Cd-TDPAC (time differential perturbated angular correlation) method, the pressure dependence of the electric field gradient (EFG) in Sb and Sb1–x
M
x
(M=ln, Zn, Ge, Pb, Cd, Sn) was investigated. The application of a phenomenological ansatz for the parametrisation of the pressure and temperature dependence of the EFG made it possible to combine temperature data gained in former studies [1], [2] with the pressure dependent data presented in this paper. The resulting pressure dependence of –2±0.2 MHz/kbar is shown to be independent of concentration and element of admixture. Results for the volume and explicit temperature dependence agree with existing information on the mixed system Sb1–x
M
x
(M=ln, Zn, Ge, Pb, Cd, Sn); the investigation of the EFG in Sb1–x–y
M
x
Pb
y
showed that the resulting EFG may be interpreted as the weighted sum of the individual contributions of the two metals.This paper is dedicated to Prof. Dr. W. Kreische on the occasion of his 60th aniversary on 02.02.1995 相似文献
15.
The internal electric fieldgradient (EFG) at the Zr-site in antiferroelectric polycristalline PbZrO3 has been investigated as a function of temperature by time differential angular correlation measurements. For the application of this technique PbZrO3 was doped with small amounts of radioactive181Hf. In the antiferroelectric phase of PbZrO3 the EFG decreases continously with increasing temperature and exhibits a sharp discontinuity at 230 °C, the Curie point of the compound. In the cubic phase a small remaining EFG is observed which is probably caused by lattice imperfections in the source. The antiferroelectric distortion of the lattice decreases slightly when the temperature approaches the Curie point, as shown by the temperature dependence of the asymmetry parameter of the EFG. The measured EFG at room temperature is compared with the result of a lattice sum calculation. 相似文献
16.
For optoelectronic devices semiconductors with large band gap doped with rare earth are used. Doping is generally performed during growth but for more structured doping the ion implantation technique is preferable. The perturbed γγ-angular correlation technique is an ideal tool to study the behavior of semiconductors after implantation. An adequate rare earth isotope for such investigations of semiconductors is 172Yb. The temperature dependence of the hyperfine fields for 172Lu(172Yb) in GaN has been analysed. The total electric field gradient (EFG) at the site of this probe is a superposition of the lattice EFG due to the GaN wurtzite structure and the EFG due to the 4f shell of the rare earth probe itself. The latter is strongly temperature dependent and opposed to the lattice EFG which in contrast is nearly constant since the lattice parameters change only negligibly with temperature. At elevated temperatures the sublevels of the 4f shell, split by the crystal electric field, are equally populated. But at low temperatures the lowest level is occupied preferentially. Sign and magnitude of the EFG caused by the 4f shell can be calculated (Tomala et al, J Magn Magn Mater 89(1–2):143, 1990) and the result compared to the experimental data. 相似文献
17.
O.J. Zogal A.H. Vuorimäki E.E. Ylinen 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(2):201-207
2H NMR spectra and spin-lattice relaxation rates, R1 are measured as functions of temperature (4.2-310 K) for YD1.99 and YD1.99+0.04. In YD1.99 the measured temperature dependence of R1 is explained by the interaction of deuteron spins with conduction electrons and the value s-1 K-1 is obtained for the inverse Korringa product . Most of the spectral features in the “rigid” lattice regime are described by the dipolar interaction. No evidence of the
deuterium self-diffusion was observed in the measured temperature range. The low-temperature spectra in YD1.99+0.04 consisted of two components: a central line and a doublet characteristic for the quadrupole interaction. The central line
corresponds to zero electric field gradients (EFG) at the sites of the deuterons which have a surrounding with cubic symmetry
like in YD1.99. The doublet indicates a non-zero EFG which can be explained in terms of the presence of short-range ordered domains of the
hypothetical YD2.25 stoichiometry. Other possible interpretations of the spectra are also discussed. In the vicinity of 250 K both spectra and
R1 reflect the onset of the rapid motion of deuterium atoms. The linear dependence of R1 at low temperatures yields s-1 K-1.
Received 8 September 1998 相似文献
18.
A. G. Smol’nikov V. V. Ogloblichev A. F. Sadykov Yu. V. Piskunov A. P. Gerashchenko S. V. Verkhovskii A. Yu. Yakubovskii S. N. Barilo G. L. Bychkov S. V. Shiryaev 《Journal of Experimental and Theoretical Physics》2011,112(6):1020-1025
The NMR spectra and the decay of a spin echo signal from 51V nuclei in Kagome-staircase Co3V2O8 (CVO) and Ni3V2O8 (NVO) single crystals are measured in the temperature range 30–300 K and a magnetic field H
0 = 20 kOe. The orientation dependences of the 51V NMR line shape are used to determine the electric field gradient (EFG) parameters, namely, quadrupole frequency ν
Q
and asymmetry parameter η. These parameters for NVO and CVO are ν
Q
= 180(10) kHz, η = 0.5(1) and ν
Q
= 130(10) kHz, η = 0.6(1), respectively. A comparison of the results of calculating EFG tensors with a point charge model
and the NMR data indicates that the crystallographically equivalent vanadium atoms in the Ni3V2O8 and Co3V2O8 compounds differ in the EFG axis orientation. M3V2O8 crystals are found to have vanadium positions (V1, V2) with different orientations of the z axis, which specifies the direction of the principal value of EFG (V
zz
): these orientations lie in the bc plane and make an angle of either +51(5)° (V1) or −51(5)° (V2) with axis c. In the temperature range 30–300 K, the EFG tensor components and the local symmetry of the charge surrounding of the vanadium
positions in NVO and CVO oxides are found to change insignificantly. 相似文献
19.
MgB2 was successfully fabricated through diffusion-controlled three-layered (B-Mg-B) technique under high pressure. Due to melting temperature of Mg, the material was pre-heat treated at 600 °C between 1 and 48 h. Optimum pre-heat treatment condition was found to be 600 °C for 48 h. Then, the compacted material was grinded and pelletized under pressure of 2 ton. The pellets were heat treated at 600-900 °C for 1-48 h. Optimum heat treatment condition was determined to be 800 °C for 1 h for formation of almost pure MgB2. Diffusion coefficient was determined with Fick's law and EDX data. Diffusion coefficient value for B in Mg matrix and Mg in B matrix was determined to be 1.66×10−7 and 3.14×10−8 cm2/sn, respectively. Best Tc value (39.4 K) was obtained for material heat treated at 800 °C for 1 h. A symmetric hysteresis was obtained for the best MgB2 material and magnetization decreased with increase in the temperature and the applied magnetic field. 相似文献
20.
W. -G. Thies H. Appel R. Heidinger Proffessor Dr. G. M. Then 《Hyperfine Interactions》1986,30(2):153-165
The hyperfine quadrupole interaction in HfF4.HF.2H2O was studied using the time differential perturbed angular correlation (TDPAC) technique. The electric field gradient (EFG)
and the corresponding asymmetry parameter were measured in the temperature range from 9 to 350 K. The EFG is characterized
by a rather strong increase with temperature, whereas the asymmetry parameter reaches its maximum value (η≈1) at aboutT=160 K. At 420 K, the complex is dehydrated and looses HF: The quadrupole parameters determined from subsequent TDPAC measurements
are charateristic for HfF4. 相似文献