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1.
SONG Tong-Qiang FAN Hong-Yi 《理论物理通讯》2001,(12)
We derive the two-mode Wigner operator in the 〈ξ| representation and 〈γ| representation, where |ξ〉 is common eigenvector of the mass-weighted relative coordinate and the mass-combinatorial momentum. As an application,we calculate the Wigner function of some two-mode state. 相似文献
2.
《Journal of Physics and Chemistry of Solids》2004,65(8-9):1423-1429
The atomic pair distribution function (PDF) technique is employed to probe the atomic local structural responses in naturally double layered manganites La2−2xSr1+2xMn2O7 in the doping range 0.54≤x≤0.80. Our low temperature neutron powder diffraction measurements suggest the coexistence of two different Jahn-Teller (JT) distorted MnO6 octahedra when its ordered magnetic structure crosses over from type A (0.54≤x≤0.66) to type C/C* (0.74≤x≤0.90) ordering. At all doping levels at low temperature the doped holes reside predominantly in the plane of the bilayer. In the type A magnetic ordering regime, the eg electrons appear to be significantly delocalized in the plane resulting in undistorted octahedra, while in type C/C* regime, elongated JT distorted octahedra are apparent. This is consistent with the presence of inhomogeneous coexisting delocalized and localized electronic states. No evidence of macroscopic phase separation has been observed. Such nanoscale inhomogeneities may explain the magnetically frustrated behavior observed in the spin disordered ‘gap’ region (0.66≤x≤0.74). 相似文献
3.
Based on the field-theory-inspired approach, a new expression for the pion form factor F π is proposed. It takes into account the pseudoscalar meson loops π+π? and $K\bar K$ and the mixing of ρ(770) with heavier ρ(1450) and ρ(1700) resonances. The expression ensures correct analytical properties and describes the data in the wide range of the energy squared ?10 GeV2 ≤ s ≤ 1 GeV2 without introducing the phenomenological Blatt-Weisskopf range parameter R π. 相似文献
4.
5.
Magnetization (down to 1.8 K and up to 9 T) and magnetostriction (down to 4.2 K and up to 30 T) measurements have been performed in the series of polycrystalline intermetallics CeNiSn1?xGex (0≤x≤1), which show a crossover from Kondo-lattice to fluctuating valence behaviors with x increase. Magnetostriction observed can be denominated as “colossal” for a paramagnet (up to 0.68% at 150 K and 30 T), with no sign of saturation. Field, H, induced metamagnetic transitions associated to a change in Ce valence are observed. Three kinds of analysis of magnetostriction have been performed to ascertain the magnetostriction origin. At relatively low field and low temperatures these systems follow well the standard theory of magnetostriction (STM), revealing single-ion crystal field and exchange origins, and a determination of the α-symmetry microscopic magnetoelastic parameters have been performed. The valence transition is well explained in terms of the interconfigurational model, which needs an extension up to power H4. Application of the scaling (thermodynamics corresponding low states) allows the obtainment of the Grüneisen constant, which increases with x. Needed elastic constants measurements are also reported. 相似文献
6.
Magicity,or shell closure,plays an important role in our understanding of complex nuclear phenomena.In this work,we employ one of the state-of-the-art density functional theories,the deformed relativistic HartreeBogoliubov theory in continuum(DRHBc) with the density functional PC-PK1,to investigate the evolution of the N=20,28,50 shell closures in the 20 ≤Z ≤30 region.We show how these three conventional shell closures evolve from the proton drip line to the neutron drip line by studying the cha... 相似文献
7.
《Solid State Ionics》1999,116(1-2):19-27
Lithium de-intercalation from the nearly stoichiometric LiNiO2 phase (z=0.02 in Li1−zNi1+zO2) entails a structural transition from the rhombohedral to the monoclinic symmetry. As this macroscopic lattice distortion appears in a wide composition range (0.50<x<0.75, x in `LixNiO2'), a detailed electron diffraction study has been performed on the intermediate Li0.63Ni1.02O2 composition in order to find the driving force of this transition. A superstructure cell, four times bigger than the one deduced from the X-ray Rietveld refinement, has been derived from the electron diffraction data. The existence of such a superstructure is suggestive of a possible ordering of vacancies among the lithium layers. Indeed, the existence of three lithium crystallographic positions in this supercell allows us to understand, on the one hand, why a monoclinic distortion occurs, and, on the other hand, its composition limits (Li0.50□0.25□0.25′NiO2 and Li0.50Li0.25□0.25′NiO2). Moreover, the presence of twinned crystals has also been shown in this monoclinic phase and has been related to the structural change which occurs on lithium de-intercalation from the pristine rhombohedral Li0.98Ni1.02O2 phase. 相似文献
8.
T. I. Arbuzova I. B. Smolyak S. V. Naumov A. A. Samokhvalov A. V. Korolev 《Journal of Experimental and Theoretical Physics》2001,92(1):100-107
The magnetic properties of La1 ? x CaxMnO3 solid solutions were studied in wide temperature and magnetic field ranges, T = 2–600 K and H ≤ 50 kOe. Semiconducting compositions with 0.6 < × < 0.9 exhibited an unusual temperature behavior of magnetization and susceptibility with well-defined Curie and Néel temperatures. The simultaneous manifestation of both ferromagnetic and antiferromagnetic properties is evidence of the coexistence of two collinear magnetic phases. The content of impurity ions was shown to have a strong influence on the T C and T N values, whereas the ratio between the ferro-and antiferromagnetic phase volumes heavily depended on thermal treatment conditions. The magnetic properties of the whole series of La1 ? x CaxMnO3 solid solutions can be explained in terms of the phase separation model. 相似文献
9.
Cheng Cheng Zhenjie Feng Qing Li Tao Li Qiang Hou Fei Chen Zhongmin Ou Jun-Yi Ge Shixun Cao Jincang Zhang 《Current Applied Physics》2019,19(4):475-479
Bulk samples of K doping K2xFeTe1-xSx with x = 0.07, 0.1, 0.2, 0.3 are successfully prepared by using easy-to-use stable compound K2S as the reactant. The lattice constant calculated from X-ray diffraction patterns indicate that K ions enter the Fe-Te-S layers. K doping is beneficial enhance the superconductivity transition temperature from the R-T curves. The apparent diamagnetic signal is observed in M-T curves when the content of K is smaller than 0.1. However, differential curves (dM/dT) in K-rich samples appear sharp slope mutations, which means that the Meissner effect signal is covered by the increased excess ferromagnetic ions. The number of excess Fe magnetic ions is proportional to K content, which may play an important role in determining the superconductivity. 相似文献
10.
M1 transition energy and rate in the ground configuration of Ag-like ions with 62 ≤ Z ≤ 94
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Systematic calculations and assessments are performed for the magnetic dipole(M1)transition energies and rates between the 2Fo5/2,7/2 levels in the ground configuration 4d104f along the Ag-like isoelectronic sequence with 62≤Z≤94 based on the second-order many-body perturbation theory implemented in the Flexible Atomic Code.The electron correlations,Breit interaction and quantum electrodynamics effects are taken into account in the present calculations.The accuracy and reliability of our results are evaluated through comprehensive comparisons with available measurements and other theoretical results.For transition energies,our results are in good agreement with the recent experimental data obtained from the electron beam ion traps within 0.18%.The maximum discrepancy between our results and those obtained with the large-scale multiconfiguration Dirac–Hartee–Fock calculations by Grumer et al.[Phys.Rev.A 89062501(2014)]is less than 0.13%along the isoelectronic sequence.Furthermore,the corresponding M1 transition rates are also reported.The present results can be used as the benchmark and useful for spectra simulation and diagnostics of astrophysical and fusion plasmas. 相似文献
11.
《中国物理快报》2004,21(1):187-190
Structural measurements have revealed nonlinear changes of lattice parameters in the layered-perovskite manganires La2-xSrxMnO4 with increasing Sr content; these changes can be well understood by means of interactions among the charge, crystal lattice and the orbital degree of freedom in this strongly correlated system. A probably spin-glass transition was detected for the first time in the x=1.75 sample at the temperature of around 44K. Fundamental properties of charge ordering appearing in the range of 1.5 ≤x≤1.75 have been observed at low-temperatures and are interpreted in terms of the Mn^3 -dz^2 orbital ordering. 相似文献
12.
Mohan Singh Bikram Singh Navjeet Kaur Lakhwant Singh 《Indian Journal of Physics》2009,83(8):1099-1107
A comparative study of various stopping power tables and codes for heavy ions in gases has been made through comparison of
computed values and the corresponding experimental data. Ten gaseous media: five monatomic rare gases (He to Xe), two diatomic
gases (H2, N2) and three polyatomic gaseous compounds (CH4, CF4 and CO2) have been chosen to study the stopping power investigations of heavy ions (8 ≤ Z ≤ 92) having energy ranges of ∼0.10–10.00
MeV/n and ∼20.00–57.00 MeV/n. We compare the experimental data of stopping power to values calculated using various tables
and computer codes by ICRU-73, Ziegler et al (SRIM2003.26), Grande and Schiwietz (CasP3.1), Paul and Schinner (MSTAR3.12), and Bazin and Tarasov (LISE ++:2-ATIMA1.2).
On the basis of statistical analysis, we estimate the reliability of these tables and codes. It has been observed that the
MSTAR3.12 code shows the best agreement with the experimental data for projectile ions (8 ≤ Z ≤ 18) in the entire energy range. The SRIM2003.26 code provides good results except for some heavy projectiles (Xe, Pb and
U). The values tabulated by CasP3.1 code underestimate especially at low energy region. No significant trend is observed in
case of LISE++:2-ATIMA1.2 code and ICRU-73 report. 相似文献
13.
14.
V. V. Pogosov A. L. Rakhmanov K. I. Kugel’ 《Journal of Experimental and Theoretical Physics》2000,91(3):588-596
A variational method is proposed to find the magnetic field dependence of the magnetization of type-II superconductors in the mixed state by a self-consistent technique. This model allows for suppression of the order parameter to zero at the centers of Abrikosov vortices and also for the magnetic field dependence of the order parameter. The results can be applied to the entire range of fields H c 1 ≤ H ≤ H c 2 for any values of the Ginzburg-Landau parameter $\kappa > 1/\sqrt 2$ . It is shown that in weak fields where κ ? 1 the behavior of the magnetization can be described exactly in the London approximation provided that the correct value of H c 1 is used. Near the second critical field this dependence shows good agreement with the well-known Abrikosov result. It is also shown that using the concept of isolated vortices and applying the principle of superposition of the fields and currents generated by these vortices to calculate the magnetization gives inaccurate quantitative results even in fairly weak fields. By going beyond these concepts, it was possible to allow more accurately for the influence of the vortex cores on the magnetization behavior in the intermediate range of fields H c 1 ?H ? H c 2 and to identify the range of validity of various approximations used widely in the literature. 相似文献
15.
D. D. Khalyavin I. O. Troyanchuk N. V. Kasper H. Szymczak 《Journal of Experimental and Theoretical Physics》2001,93(4):805-808
Slowly cooled Nd1 ? x BaxCoO3 ? δ samples were two-phase in the concentration interval 0.3 ≤ x ≤ 0.46. One of the phases had O-orthorhombic lattice distortions (Pbnm) characteristic of ferromagnetic samples with x ≤ 0.3, and the other phase had tetragonal distortions (P4/mmm) characteristic of samples with x ≥ 0.46. Tetragonal distortions were caused by ordering of Nd3+ and Ba2+ ions. Samples with ordered neodymium and barium ions (Nd1 ? y Ba1 + y Co2O6 ? γ at ?0.08 ≤ y ≤ 0.08) experienced metal-dielectric and orientation magnetic phase transitions. 相似文献
16.
D. V. Rao R. Cesareo G. E. Gigante 《Applied Physics A: Materials Science & Processing》1996,62(4):381-386
TotalL X-ray fluorescence cross sections have been measured in the atomic region 39 Z 51 excited by 5.47, 6.47, 7.04, 7.57, 8.14, 8.74 and 9.36 keV photons. Experimental cross sections are compared with the theoretical estimates of Chen et al. based on relativistic Dirac-Hartree-Slater theory. Good agreement is observed between experimental results and theoretical estimates in the studied atomic and energy region. Experimental fluorescence yields have been evaluated using the experimental fluorescence cross sections and theoretical subshell photoionization cross sections. Fluorescence yields are fitted by least squares to fifth-order polynomials inZ of the form
n
a
n
z
n
and compared with theoretical and earlier fitted values. The deviation of the average fluorescence yield in the atomic region 46Z 51 with new theoretical estimates of
, calculated using the ECPSSR (Energy loss Coulomb deflection Perturbed Stationary State Relativistic effects) theory of Brandt and Lapicki and the fitted values clearly indicate the weak dependence of the average fluorescence yield on the initial vacancy distribution. 相似文献
17.
B. V. Zhuravlev A. A. Lychagin N. N. Titarenko 《Bulletin of the Russian Academy of Sciences: Physics》2013,77(4):447-450
Nuclear level densities of 47V, 48V, 49V, 53Mn, 54Mn, 57Co, 59Ni and their energy dependences are determined from measurements of the neutron evaporation spectra in the (p, n) reaction. Neutron spectra from the (p, n) reaction on nuclei of 47Ti, 48Ti, 49Ti, 53Cr, 54Cr, 57Fe, and 59Co are measured at proton energies between 7 and 11 MeV. The data are analyzed in terms of statistical equilibrium and pre-equilibrium models of nuclear reactions. 相似文献
18.
SHEN Qing-Biao 《中国物理C(英文版)》1993,17(8):739-744
The contribution on the inelastic scattering spectra of discrete level part mainly comes from direct reactions.For the sigle-particle emission cross section calculated with the statistical theories,when the incident energy is less than 10MeV the main contribution comes from the equilibrium emission,but when the incident energy reaches 20MeV,more than 90% contribution comes from the pre-equilibrium emission.The contribution of the pre-equilibrium process to the second particle emission can be neglected when the incident energy is less than 20MeV and the contribution of the pre-equilibrium process to the third particle emission can be neglected when the incident energy is less than 50MeV. 相似文献
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20.
A. A. Samokhvalov T. I. Arbuzova N. A. Viglin S. V. Naumov I. B. Smolyak A. V. Korolev N. I. Lobachevskaya 《Physics of the Solid State》2000,42(4):719-721
The problem of localized superconductivity has motivated the preparation of Mg1−x
CuxO solid solutions with NaCl structure and 0.01≤x≤0.20, as well as a study of the magnetization and magnetic susceptibility χ in the 2–400 K temperature range and in magnetic fields of up to 5 T. The temperature dependence of χ is described for all
compositions by the Curie-Weiss law, χ = C/(T − θ), where the constant C is close to the value calculated for each composition for μeff = 1.7–1.9μB, and θ is close to zero. For T < 30 K, χ(T) deviates for all compositions toward lower χ, which can be attributed to magnetic ordering of exchange-coupled clusters
in the solid solution. At T∼320–330 K, an anomaly of a diamagnetic type, i.e., a decrease of χ by 6–30% of its paramagnetic value, has been observed
for all compositions against the background of the generally paramagnetic χ(T). A discussion is presented of alternative reasons for this anomaly and of its possible connection with localized superconductivity.
__________
Translated from Fizika Tverdogo Tela, Vol. 42, No. 4, 2000, pp. 701–703.
Original Russian Text Copyright ? 2000 by Samokhvalov, Arbuzova, Viglin, Naumov, Smolyak, Korolev, Lobachevskaya. 相似文献