共查询到20条相似文献,搜索用时 31 毫秒
1.
D. Yu. Podorozhkin Cheng Tien E.V. Charnaya M.K. Lee L.J. Chang D. Michel J. Haase Yu. A. Kumzerov 《Physica B: Condensed Matter》2012,407(12):2063-2067
NMR studies were carried out on three isotopes, 71Ga, 69Ga, and 115In, in liquid gallium-indium (Ga–In) alloy embedded into porous glasses with 200 and 5 nm pore sizes at two magnetic fields, 9.4 and 17.6 T. Spin-lattice relaxation and the Knight shift were found to depend on pore size. For porous glass with 5 nm pores the relaxation rate was field-dependent which evidenced that the extreme narrowing limit was no longer valid. Magnetization recovery data were used to evaluate the correlation times of atomic mobility and the quadrupole constants under nanoconfinement. 相似文献
2.
Dmitri Y. Podorozhkin Elena V. Charnaya Min Kai Lee Lieh‐Jeng Chang Juergen Haase Dieter Michel Yurii A. Kumzerov Alexsandr V. Fokin 《Annalen der Physik》2015,527(3-4):248-253
The diffusion of gallium in liquid Ga‐Sn alloy embedded into different porous silica matrices was studied by NMR. Spin relaxation was measured for two gallium isotopes, 71Ga and 69Ga, at two magnetic fields. Pronounced rise of quadrupole contribution to relaxation was observed for the nanostructured alloy which increased with decreasing the pore size. The correlation time of atomic mobility was evaluated and found to be much larger than in the relevant bulk melt which evidenced a pronounced diffusion slowdown in the Ga‐Sn alloy under nanoconfinement. It is shown that the diffusion was slower by a factor of 30 for the alloy within 7 nm pores. The spectral densities of electric field gradients at zero frequency were found to double for the finest pores. The Knight shift was found to decrease but slightly for the nanostructured alloy. 相似文献
3.
Nefedov D. Yu. Antonenko A. O. Podorozhkin D. Yu. Uskov A. V. Charnaya E. V. Lee M. K. Chang J. L. Haase J. Michel D. Kumzerov Yu. A. Fokin A. V. Samoilovich M. I. Bugaev A. S. 《Physics of the Solid State》2017,59(2):362-367
The nuclear spin–lattice relaxation and Knight shift of 71Ga, 69Ga, and 115In nuclei in a ternary liquid gallium–indium–tin alloy of the eutectic composition, which was introduced into pores of an opal matrix and porous glasses with pore sizes of 18 and 7 nm, have been investigated and compared with those for the bulk melt. It has been found that longitudinal relaxation is accelerated and the Knight shift is decreased, depending on the size of pores. The correlation time of the atomic motion has been calculated for the nanostructured melt in porous matrices. It has been shown that the atomic mobility in the melt decreases with decreasing size of pores in the glasses.
相似文献4.
A dilute101mRhCr alloy has been investigated by means of low temperature nuclear orientation in the temperature range of 6–60 mK. The magnetic hyperfine field has been found proportional to the macroscopic chromium magnetization and follows even at these low temperatures an Overhauser distribution. The maximum hyperfine field value is Bo (T=6 mK)=7.0(5) T. A Knight shift of –16% affects the external magnetic field at the nuclear site. 相似文献
5.
《Journal of Physics and Chemistry of Solids》2002,63(6-8):1197-1200
69,71Ga and 195Pt NMR/NQR measurements have been carried out for the 5f-antiferromagnet, UPtGa5. From a NMR study using a single crystal sample, Knight shift measurements are reported for two different Ga sites and for Pt. The principal axes of the electrical field gradient tensor at both Ga sites have been determined and the values of the splitting parameter νQ and the asymmetry parameter η have been evaluated. The hyperfine coupling constants with the external field along various directions are also reported for the two Ga sites and Pt. 相似文献
6.
M. Forsthuber H. Nakamura M. Shigal E. Bauer 《Zeitschrift für Physik B Condensed Matter》1997,100(3):395-400
CePd2Ga3, a Kondo lattice exhibiting ferromagnetic order below T C = 6.3 K, has been studied using Ga NMR technique. Measurements of the magnetic susceptibility on an oriented sample proved the strong anisotropy of this quantity, whose major component is in the basal plane. From the analysis of NMR spectra of differently oriented samples, the quadrupole parameters and the temperature-dependent anisotropic Knight-shift have been determined. While the anisotropy of the susceptibility can sufficiently account for the axial anisotropy of the 71Ga Knight shift, the in-plane anisotropy of the shift points towards dipolar effects enhanced by hybridization of the Ce-4f and Ga-s electrons. 相似文献
7.
By means of rapid quenching techniques single phased samples of CuxRh1?x(0?x?1) were obtained. For these alloys the Knight shift of 63Cu and 103Rh has been determined employing pulsed NMR at low temperatures, furthermore the magnetic susceptibility was measured for temperatures between 4.2 and 300 K. While the Knight shift of 103Rh is dominated by s-electron contributions in spite of a high density of d-states at the Fermi level, for the susceptibility, however, the d-electron contributions prevail. In addition the susceptibility shows a pronounced maximum at about 10 at.% Cu. Using the extrapolated Knight shift of copper (x→0) we estimate a net copper hyperfine field of — 15 T in close agreement with the corresponding values for CuPd and CuPt. 相似文献
8.
We report a nuclear magnetic resonance (NMR) study on H+ beam irradiated Bi2Te3 powdered single crystals. In this work, we demonstrate that the beam creates defects within its penetration range giving rise to delocalized charge carriers, thereby making further 125Te NMR Knight shift and line broadening. Upon increasing temperature, the NMR line narrowing manifests the activated motions of thermally excited charge carriers in the irradiated sample. In contrast, it reveals that in the unirradiated sample the free-charge carriers at the Fermi level dominantly contribute to the Knight shift. Our results show that the orbital contribution to the Knight shift in the bulk state of Bi2Te3 becomes predominant in the system with the higher density of defects, as evidenced by modified electronic structures induced by the beam irradiation. 相似文献
9.
S. R. Barth H. R. Ott F. N. Gygax A. Schenck T. M. Rice Z. Fisk 《Hyperfine Interactions》1986,31(1-4):397-402
A systematic μ+SR study of the magnetic heavy-electron systems U2Zn17 and UCu5 in the paramagnetic and in the magnetically ordered state is presented. In both systems the antiferromagnetic nature of the
low-temperature phase could be at least partially confirmed, but the muon reveals significant differences with regard to the
phase transition itself. UCu5 behaves like a model-antiferromagnet showing a drastic increase of the relaxation rate both below and above TN, two spontaneous frequencies in the ordered phase, and a Knight shift above TN which scales with the bulk susceptibility. In contrast U2Zn17 shows a loss of μ+ asymmetry by 20% below TN, which is independent of the external field but can be quenched in sufficiently strong longitudinal fields. No scaling of
the Knight shift and the susceptibility was observed and no critical increase of the relaxation rate λ. Most astonishing is
the strong and nonlinear field dependence of λ above and below TN in both compounds. The absence of longitudinal relaxation demonstrates the static origin of λ. 相似文献
10.
S.K. Malik R. Vijayaraghavan S.K. Garg R.J. Ripmeester 《Solid State Communications》1977,21(3):245-247
The 119Sn Knight shift in SmSn3 has been measured in the temperature range 15—300 K, and it is found that the 4f-contribution to the Knight shift does not show a sign reversal in this temperature interval. The range of crystal field parameters for which simultaneous fit to the magnetic susceptibility and the extended Knight shift results in SmSn3 is obtained can be substantially narrowed from that reported earlier. 相似文献
11.
Bogdan Nowak 《Solid state nuclear magnetic resonance》2010,37(1-2):36-37
Several groups exploring the 195Pt NMR in solids, including metallic and magnetic materials, use different standards for chemical shift (Knight shift) determination. Commonly applied H2PtCl6 and Na2PtCl6 (IUPAC δ scale) lead to considerable underestimation of the shifts since H2PtCl6 has considerable own 195Pt NMR shift due to its Van Vleck paramagnetism. In this Letter new results on 195Pt NMR in heavy fermion system CeInPt4 are presented and rationalized scale for the Knight shift determination is discussed. 相似文献
12.
F.N. Gygax A. Hintermann W. Rüegg A. Schenck W. Studer 《Solid State Communications》1981,38(12):1245-1248
The Knight shift at positive muons implanted in pure palladium has been measured as a function of temperature from 19.8 to 883 K. The Knight shift variation is strictly proportional to the Pd magnetic susceptibility with ΔKμ/Δx=-(0.43±0.02) mole/emu=-(2.39±0.11)kG/μB. A temperature independent term Kμ(x=0)=+45±10 ppm is found. The results are discussed in terms of the electronic structure of H in Pd. 相似文献
13.
We have studied at room temperature the intensities and the Knight shifts of the nuclear magnetic resonances of 69Ga, 71Ga, and 51V in V3?xFexGa for Fe concentrations ranging from x = 0.04 to x = 0.6. The results interpreted in terms of a redistribution of the conduction electrons and a paramagnetism due to the Fe impurities. 相似文献
14.
N.A. Mahadik S.B. Qadri M.V. Rao J.P. Yesinowski 《Applied Physics A: Materials Science & Processing》2007,86(1):67-71
Free-standing GaN films grown by hydride vapor phase epitaxy (HVPE) on c-plane sapphire have been studied for in-plane anisotropic strain. Lattice parameters are obtained from high-resolution X-ray diffraction data and the film quality is determined by measuring the rocking curves and by 71Ga nuclear magnetic resonance (NMR). The in-plane strain was determined using grazing incidence X-ray diffraction and conventional X-ray measurements. It is found that the in-plane lattice parameter varies with depth and has estimated surface strain anisotropy of 4.0791×10-3 up to a thickness of 0.3 μm. The 71Ga NMR experiments reveal different degrees of inhomogeneity amongst the three samples. This is shown by the appearance of an additional broad central-transition peak shifted to higher frequency by a Knight shift from conduction electrons in sample regions having high carrier concentrations. PACS 72.80.Ey; 61.10.-i; 61.72.Hh 相似文献
15.
H. Bertschat H. Haas F. Pleiter E. Recknagel E. Schlodder B. Spellmeyer 《Zeitschrift für Physik A Hadrons and Nuclei》1974,270(3):203-208
The Knight shift and its temperature dependence for a Cd impurity in palladium metal were measured by means of DPAD- and DPAC-methods utilizing the well known 5/2+, 247-keV state in111Cd. The shift at 80 K was found to be KS (CdPd, 80 K)=?0.8(2)%. The observed variation of the KS in the temperature range from 80 K up to 1400 K is 0.5%. For calibration purposes an accurate remeasurement of the magnetic moment of the 5/2+ state in111Cd was necessary and yieldedμ(111Cd, 5/2+, 247 keV)=?0.7697(20) n.m. 相似文献
16.
The temperature dependences of the static nuclear quadrupole interaction and the Knight shift in rhenium metal were investigated for 2K ≦ T ≦150 K by the method of Nuclear Acoustic Resonance (NAR). For the quadrupole interaction ¦e2qQ/h¦ an increase occurs from 255.2(5) MHz at 2 K to 257.2(8) MHz at 150 K in187Re [269.5(7) to 271.5(10) in185Re] whereas for the Knight shift a slight decrease from 1.14(4)% at 2K to 1.10(8)% at 150 K [1.16(6) to 1.12(10)] is found. 相似文献
17.
Mircea Crisan Ioan Grosu Ionel Ţifrea 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(6):140
We calculate the nuclear spin-lattice relaxation time and the Knight shift for the case of gapped graphene systems. Our calculations consider both the massive and massless gap scenarios. Both the spin-lattice relaxation time and the Knight shift depend on temperature, chemical potential, and the value of the electronic energy gap. In particular, at the Dirac point, the electronic energy gap has stronger effects on the system nuclear magnetic resonance parameters in the case of the massless gap scenario. Differently, at large values of the chemical potential, both gap scenarios behave in a similar way and the gapped graphene system approaches a Fermi gas from the nuclear magnetic resonance parameters point of view. Our results are important for nuclear magnetic resonance measurements that target the 13C active nuclei in graphene samples. 相似文献
18.
The observed rapid continuous isothermal change from enhanced paramagnetism to weak diamagnetism with increasing silver mole fraction x of the Pt1?xAgx alloy system is interpreted by means of a semiphenomenological magnetic alloy susceptibility function X(x). The x-dependent Knight shift K(x) of both 109Ag and 195Pt nuclei in Pt1?xAgx is closely related to the alloy susceptibility and therefore can be used in a combined K(x)?X(x)-analysis. 相似文献
19.
R. Feyerherm A. Amato A. Grayevsky F. N. Gygax N. Kaplan A. Schenck 《Zeitschrift für Physik B Condensed Matter》1995,99(1):3-13
Muon spin rotation measurements of the temperature dependence and the anisotropy of the μ+ Knight shift in single crystals of the crystal electric field singlet ground state system PrNi5 reveal pronounced deviations from a linear scaling of the Knight shift with the bulk magnetic susceptibility atT≤50 K. They are explained by a μ+ induced modification of the atomic susceptibility of neighboring Pr3+ ions. From the Knight shift anisotropy atT> 50 K it is determined that the implanted μ+ occupy a single intersitial site, namely the 6i site (0.5, 0, 0.21±0.02). Using this site information, good model fits to
the measured data are obtained assuming a μ+ induced perturbation of the crystal electric field at the Pr3+ ions next to the μ+. Apparently, the presence of the μ+ leads to a lowering of the local symmetry, causing a lifting of the degeneracy and a pronounced rearrangement of the low
lying crystal electric field levels for these ions. 相似文献
20.
The transverse field μSR-signal from μ+ implanted in a CeAs single crystal shows a splitting into two components, displaying a positive and a negative Knight shift,
respectively which both scale reasonably well with the magnetic bulk susceptibility above 10 K. The orientation dependence
of the frequency shifts, measured at 15 K, is fully accounted for by the demagnetization field, implying an isotropic Knight
shift, consistent with the μ+ residing at the only interstitial site of high (cubic) symmetry, i.e., at the position (1/4,1/4,1/4). The occurrence of a
split signal remains unexplained.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献