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1.
The Knight shift of a short lived β-emitting nucleus 12B (I = 1, T 1/2 = 20 ms) implanted into Pt has been measured as a function of temperature (140?600 K) by means of the β-NMR method. The relation between the Knight shift and the susceptibility for Pt was deduced, which shows the similar tendency to that for the case of 12B in Pd.  相似文献   

2.
The rapid decrease of the isothermal magnetic susceptibility χ of single phase PdHn with n ( = atomic ratio H/Pd) above the critical temperature Tc = 564 differs from that of the magnetically similar single phase system Pd1−xAgx (x: silver mole fraction) at the same temperature and at equal valence electron concentrations (n = x), i.e. χ (PdHn)−χ(Pd1−xAgx) <0. By use of a semiphenomenological susceptibility ansatz related to the nonideal solution behaviour of H (Ag) in Pd the susceptibility difference is interpreted as an electronic excess effect.The analysis of the steep descent of the magnetic susceptibility also applies to the Pd-rich side of PdHn in the subcritical temperature region (so-called α-phase) and can be supported by 105Pd Knight shift data at 348 K.  相似文献   

3.
In order to investigate the electronic structure of the rapidly quenched Ni100-XPX metallic glass system (18 ≦ x ≦ 22), NMR and magnetic susceptibility measurements have been carried out for temperatures 4.2 °KT ≦ 295 °K and magnetic fields H ≦ 20 kOe. The 31P Knight shift and relaxation rate behavior demonstrate a metalloid concentration dependence which is consistent with earlier work on the ternary NiPdP and NiPtP metallic glass systems. A consideration of the trends in the magnetic susceptibility indicates that, relative to the Fermi energy, the d-states associated with Ni are higher (the number of d-holes are greater) than those for Pd or Pt.  相似文献   

4.
Angular dependences of 9Be NMR (±1/2) and (±1/2 ? ±3/20 transition frequencies are measured in a single-crystal beryllium metal plate in a field of 7.04T. The isotropic K iso and anisotropic K aniso components of the Knight shift are determined. The measured values of K iso and T 1 are considered in terms of the contact, polarization, and orbital contributions.  相似文献   

5.
Nuclear pure quadrupole resonance has been observed in single crystal gallium as a function of hydrostatic pressure up to 7 kbar at temperatures of 77, 198 and 273 K. The resonance frequency vQ increases linearly with pressure and the slope (δvOδP)T is 13.7, 15.5 and 16.3 Hz/bar at 77, 198 and 273 K respectively. The asymmetry parameter decreases nonlinearly with pressure. Using compressibility and thermal expansion data, the volume dependence of the major principle component of the electric field gradient was deduced. The principal components Kx, Ky and Kz of the Knight shift tensor have been measured as a function of pressure to 6 kbar at 77 K. The isotropic and anisotropic components of the Knight shift were deduced as a function of pressure, and Kiso is found to vary with volume as V4.95 ± 0.80.  相似文献   

6.
The temperature dependence of the Knight shift of Ag in palladium has been observed between 80 K and 1000 K and is proportional to that of the susceptibility of Pd. The shift at 80 K is K = -1.4(3)%. The measurements were performed by observing the perturbed angular distribution of γ-rays following a nuclear reaction (DPAD).  相似文献   

7.
Inclusive K0-production has been measured in e+e- annihilation at a center of mass energy of about W = 30 GeV. The ratio of K0 + K0 production to μ+μ- production is RK0 = 5.6 ± 1.1 (statist. error) ± 0.8 (system.error) This value is about a factor of three higher than RK0 at W = 7 GeV. The cross sections (s/β) dσ/dx is consistent with a scaling behaviour.  相似文献   

8.
The momenta of ~30 000 charged particles from K+ decays were measured using a magnetic spectrometer with streamer chambers. The ratio R = Γ(Kπ2+)/Γ(Kμ2+) = 0.3355 ± 0.0057 was obtained. Our values for the branching ratios are: (63.18±0.43)% for Kμ2+, (21.18±0.33)% for Kπ2+, (3.33±0.51)% for Kμ3+, (4.99±0.54)% for Ke3+.  相似文献   

9.
The magnetic susceptibility and51V Knight shift have been measured in powdered VO2 from the semiconductor-metal transition temperatureT t=341°K to 478°K. The fact that both depend linearly on temperature enables the orbital and spin contributions to both quantities to be evaluated. The orbital and spin susceptibilities at 341°K are found to be 1.30±0.07 and 7.49±0.07μemu g?1, respectively, and the corresponding shifts +0.61±0.04% and ?1.00±0.04%. The existence and magnitude of the orbital term are consistent with the currently accepted two band model of VO2 aboveT t.  相似文献   

10.
Metallic Pd synthesized in porous glass with an average pore diameter of 7 ± 2 nm has been studied using the X-ray diffraction and X-ray line shift methods for the first time. The irregular dependence of the reflection width in X-ray patterns on the diffraction angle has been revealed. This can be caused by crystallite growth mostly in the [111] direction or by tetrahedral distortions of the fcc lattice. The shift (difference in energy) of K α1 lines (ΔE α1 = 19 ± 2 meV) for nanostructured Pd in comparison with the bulk material is first detected. The detected effect is considered within the assumption of the palladium electron redistribution between Pd 5s- and 4d-bands.  相似文献   

11.
About 100 000 K+-decays were observed in a magnetic spectrometer with streamer chambers. The estimation for the radiative decay K+→μ+νμγ, Rexp = [W(K+μ+νμγ)]/[W(K+all)]=(5.8±3.5) x 10?3, at Eγ ? 9 MeV was obtained and the ratio R = [W(K+π+π°)]/[W(K+μ+νμ)] = 0.328 ± 0.005 was measured.  相似文献   

12.
Cadmium oxide semiconductors were prepared by heating CdO which also contained hydroxide and carbonate species formed on storage. Reaction of the impurities on heating, and high temperature annealing, produced an unusually wide range of electrical conductivities, EPR spectra and NMR spectra. Changes in EPR spectra were correlated with the 113Cd shift, which was shown to be proportional to the square root of the relaxation rate, and also proportional to the line width. This allowed the Knight shift contribution to the resonance position to be separated from the paramagnetic shielding (due to covalency). The latter was found to be 234 ± 6 ppm relative to Cd(H2O)2+6. It could then be shown that the Korringa relationship (for degenerate electrons) was satisfied, with T1TK2 = 3.9 ± 0.2 × 10−6 sK. The variations of the asymmetric line shape with Knight shift were examined in the light of various models for impurity semiconductors.  相似文献   

13.
14.
The time-differential perturbed angular correlation technique has been used to measure the magnetic hyperfine fields (mhf) acting on 111Cd impurity on the series of alloys Pd1+xMnSb with 0 ? x ? 1. We observe three diffrent mhf's which for small values of x are of the order of +250, ?250 and ?150 kOe, decreasing slowly for larger values of x. These three fields are associated with 111Cd occupying the sites of Mn, Sb and Pd, respectively. In addition, magnetization measurements on three of the allows (x = 0, 0.4 and 0.8) gave magnetic moments on the Mn atoms of 3.88 ± 0.08, 4.18 ± 0.08, (4.14 ± 0.08)μB and Curie temperatures of 470 ± 2,422 ± 5 and (288 ± 2) K, respectively. Our results together with the existing data for mhf's on various 5sp elements in the Pd2MnSb Heusler alloy are compared with the Blandin-Campbell model and show an agreement which is only qualitative.  相似文献   

15.
Pulsed NMR data for 89Y in the high-Tc superconductor YBa2Cu3O9-δ (δ ≈ 2.1) in both the normal and mixed states are presented. Spin-lattice relaxation exhibits a Korringa temperature dependence in the normal state, with T1T = (4.6 ± 0.1) × 103 s-K. Below Tc, T1 increases much more quickly than for a conventional superconductor. From linewidth measurements, the zero-field penetration depth is estimated to be λ ≈ 3800 Å. The Knight shift in the normal state is small, K ≈ 0.02%. Spin-spin relaxation times, determined by Y-Cu dipolar interactions, decrease below Tc due to the detuning of Cu-Cu interactions by fluxoid field gradients.  相似文献   

16.
The Knight shift of Pd in Ag x Pd1–x has been determined for concentrationsx0.2. In full accordance with the expectations based on the behaviour of the magnetic susceptibility, it was found that the Knight shift of Pd is rapidly reduced in magnitude by adding Ag to Pd. To allow for a detailed interpretation of this finding, we have performed Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) band structure calculations for Ag x Pd1–x . These calculations clearly demonstrate that the decrease in spin susceptibility with increasingx is accompanied with a decrease in core polarization. In contrast to Pd, the negative Knight shift of Ag on the Pd-rich side of the system is caused by the valence band contribution, as it is demonstrated by our calculations. This is caused by an intersite effect in analogy to the transferred hyperfine field found for non-magnetic elements dissolved in a magnetic host.  相似文献   

17.
Nuclear magnetic resonance of cobalt metal was investigated in the paramagnetic and ferromagnetic states and in the critical region below Tc. The Knight shift and spin lattice relaxation times were measured in the paramagnetic phase in the solid and liquid states from 1578 K to 1825 K. The resonant frequency, spin-lattice and spin-spin relaxation times were measured in the ferromagnetic phase from room temperature to 1385 K. The main part of (T1T)-1 results from fluctuating orbital moments in both phases except near Tc where this process forms the background for critical spin relaxation. The critical exponents for T-11 and for the magnetization in the ferromagnetic state were found to be n' = 0.96 ± 0.07 and β = 0.308 ± 0.012, respectively.  相似文献   

18.
The Knight shifts of the silver isotopes 107Ag and 109Ag were determined with high accuracy. Between these shifts there is a difference ΔK = K107 - K109 = ?(17.1 ± 1.1) ppm. The relative isotope effect ΔK/K is not in agreement with the hyperfine structure anomaly 107Δ109.  相似文献   

19.
Microwave spectra have been studied in the ground and v5 = 1 (CC stretching mode) states of methylacetylene. From these data, dipole moments and rotational and centrifugal distortion constants have been determined, as follows: μD(0) = 0.7839 ± 0.0010 D, μD(5) = 0.7954 ± 0.0010 D, B5 = 8508.119 ± 0.003 MHz, DJ(5) = 1.8 ± 0.2 kHz, and DJK(5) = 169 ± 1 kHz. Laser Stark spectra have been obtained for the ν5 band of this molecule and from these spectra the following vibration-rotation parameters have been determined: ν50 = 93.27540 ± 0.00007 cm?1, A5 - A0 = ?227.0 ± 2.3 MHz and DK(5) - DK(0) = ?0.05 ± 0.50 MHz. The higher-J and -K states of the v5 = 1 state appear to be purturbed.  相似文献   

20.
The + Knight shift in platinum has been measured between 20 K and 785 K. It shows a strong temperature dependence and scales with the magnetic bulk susceptibility. A temperature independent contribution of +40 to +60 ppm and a d-electron induced hyperfine field per unpaired d-electron per atom ofB hf,d =–5.03 kG (±8.5%) are obtained. The + Knight shift in PdH0.70 and PdH0.75 shows no dependence on temperature between 20 K andRT and increases fromK ppm forx=0.70 toK ppm forx=0.75, in good agreement with proton Knight shift measurements.  相似文献   

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