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1.
2.
V. A. Shaburov A. E. Sovestnov Yu. P. Smirnov A. V. Tyunis 《Physics of the Solid State》1999,41(8):1246-1247
The shifts of the Kα
1 and Kβ
1 lines of all rare-earth (RE) metals (from La to Lu) have been measured experimentally by the x-ray shift method. The population
of the RE-metal 6s and 5d shells has been determined by comparing the experimental and theoretical shifts obtained within the Dirac-Fock (Koopmans)
model. Trivalent metals exhibit a monotonic cross-over from the 6s
≈25d
≈1 to 6s
≈15d
≈2 configuration with increasing atomic number.
Fiz. Tverd. Tela (St. Petersburg) 41, 1361–1362 (August 1999) 相似文献
3.
A. É. Primenko V. D. Kuznetsov N. D. Kushch É. B. Yakubskii 《Journal of Experimental and Theoretical Physics》1997,85(2):415-416
This papr discusses the results of the first investigation of the magnetic properties of the organic superconductor λ-(BETS)2GaCl4. It is shown that the transition to the superconducting state begins at T
c≈7 K, which is considerably lower than the value T
c≈10 K determined from resistive measurements. The estimated value of the critical current density turns out to be two orders
of magnitude lower than in superconductors of the family κ-(ET)2
X.
Zh. éksp. Teor. Fiz. 112, 760–762 (August 1997) 相似文献
4.
M. Gómez Berisso P. Pedrazzini J.G. Sereni O. Trovarelli C. Geibel F. Steglich 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(3):343-349
We present electrical resistivity and specific heat measurements of alloys on the Rh rich side of the phase diagram of the
Ce(Rh1-xPdx)2Si2 system. We compare these results with those obtained at intermediate and low Rh concentrations. The analysis of the concentration
and temperature dependence of the entropy and of the scaling behaviour of C
el
(
T
) and ρ(
T
) clearly confirm a separation of the magnetic phase diagram into two regions: the region x
≤0.3, showing a concentration independent characteristic temperature for the 4
f-electrons with T
0
≈ 45
K, while for x
> 0.3, T0 decreases to T
0
(
x
= 1) ≈ 15
K. At low Pd-content, TN decreases very rapidly from T
N
= 36
K in pure CeRh2Si2 to T
N
= 18
K at x
= 0.1. With higher Pd concentration TN stabilizes at T
N
≈ 15
K whereas the magnitude of the anomalies in C
el
(
T
) and in the susceptibility around TN are further reduced and disappear at x
≈ 0.3. This differs from the behavior found on the Pd-rich side, where TN decreases continuously to zero with increasing Rh content. The pronounced differences observed between both phase boundaries
and the drastic effect of doping on the Rh rich side suggest an itinerant character in CeRh2 Si2, in contrast with the localized character of CePd2Si2. Further evidence for the itinerant character of CeRh2Si2 is given by the ρ(
T
) dependence observed for x
≤0.3, which scales with ρ(
T
) of the prototype itinerant compound YCo2.
Received 31 December 2001 / Received in final form 6 July 2002 Published online 19 December 2002
RID="a"
ID="a"e-mail: berisso@cab.cnea.gov.ar 相似文献
5.
A. Yu. Yakubovskii S. V. Gudenko N. V. Anshukova A. I. Golovashkin L. I. Ivanova A. P. Rusakov 《Journal of Experimental and Theoretical Physics》1999,88(4):732-737
Electron paramagnetic resonance (EPR) spectra of samples of the systems Ba1−x
KxBiO3 and BaPbyBi1−y
O3 are investigated over wide ranges of composition and temperature. Two main lines in the EPR spectrum with factors g
1≈2.1 and g
2≈4.2 are found for all compositions. It is shown that the observed EPR line with g
2≈4.2 is due to oxygen ions. This probably indicates the presence of oxygen ions with different effective charges, i.e., the
existence of charge density waves in the oxygen-ion sublattice in addition to charge density waves in the bismuth sublattice.
Zh. éksp. Teor. Fiz. 115, 1326–1336 (April 1999) 相似文献
6.
M. E. Gaevskii D. V. Shantsev A. V. Bobyl’ Yu. M. Gal’perin T. H. Johansen H. Hauglin 《Physics of the Solid State》1999,41(6):877-880
The paper provides the first demonstration of the efficiency of applying the magneto-optic method to studies of the spatial
and temporal magnetic-field relaxation in an YBa2Cu3O7 film strip after the transport current is switched on. It is shown that the evolution of magnetic flux distribution is adequately
described in terms of a modified Bean model with time-dependent critical current. At a time 50 ms after the current is switched
on, the critical current of the samples studied decreases by ≈15%. This proves the significance of thermally activated magnetic
flux motion (creep) in the regime investigated. The magnetic vortex pinning energy has been estimated as U
0≈20 kT.
Fiz. Tverd. Tela (St. Petersburg) 41, 965–968 (June 1999) 相似文献
7.
The nonadiabatic corrections to the self-energy part Σs(q, ω) of the phonon Green’s function are studied for various values of the phonon vectors q resulting from electron-phonon interactions. It is shown that the long-range electron-electron Coulomb interaction has no
direct influence on these effects, aside from a possible renormalization of the corresponding constants. The electronic response
functions and Σs(q, ω) are calculated for arbitrary vectors qand energy ω in the BCS approximation. The results obtained for q=0 agree with previously obtained results. It is shown that for large wave numbers q, vertex corrections are negligible and Σs(q, ω) possesses a logarithmic singularity at ω=2Δ, where Δ is the superconducting gap. It is also shown that in systems with nesting, Σs(Q, ω) (where Q is the nesting vector) possesses a square-root singularity at ω=2Δ, i.e., exactly of the same type as at q=0. The results are used to explain the recently published experimental data on phonon anomalies, observed in nickel borocarbides
in the superconducting state, at large q. It is shown, specifically, that in these systems nesting must be taken into account in order to account for the emergence
of a narrow additional line in the phonon spectral function S(q, ω)≈−π
−1 Im D
s
(q, ω), where D
s
(q, ω) is the phonon Green’s function, at temperatures T<T
c
.
Zh. éksp. Teor. Fiz. 115, 1799–1817 (May 1999) 相似文献
8.
L. I. Korovin I. G. Lang S. T. Pavlov 《Journal of Experimental and Theoretical Physics》1999,89(4):764-774
Combined polaron states in a rectangular quantum well in a strong magnetic field perpendicular to the well plane are discussed.
These states are due to interaction between two discrete electron levels with different Landau quantum numbers (n and n
1) and different size-quantization quantum numbers (m and m
1) on the one hand and a confined LO phonon on the other under conditions of low temperature when the energy difference between
the electronic levelsis equal or close to the energy of the confined LO phonon. The expression for the resonant magnetic field
H
res at which a combined polaron is formed contains the energy difference between size-quantized levels, so it is a function of
quantum well parameters. The separation ΔE
res between branches in the energy spectrum of a combined polaron and H
res has been calculated as a function of the quantum well width d. The resonant field H
res can be reduced dramatically in comparison with the case m=m
1. The case of size-quantization with n=n
1 has been analyzed. The energy difference ΔE
res is in the range (1–5)· 10−3 eV. The damping of combined polaron states due to the effect of anharmonicity on the LO phonon has been studied. Interband
absorption and features in the reflection spectrum due to interband transitions have been calculated for an arbitrary ratio
between the radiative and “phonon” lifetime of a combined polaron have been investigated.
Zh. éksp. Teor. Fiz. 116, 1419–1439 (October 1999) 相似文献
9.
T. A. Ivanova Yu. V. Yablokov N. S. Zinatullina R. M. Bayazitov 《Physics of the Solid State》1999,41(3):375-378
In studying LaSrAl1−x
NixO4 ceramics, anomalies are detected in the concentration dependences of the lattice parameter c, the electrical resistance, and the sign change of the Hall constant at x≈0.6. It is shown that the collection of observed phenomena can be interpreted as a manifestation of the Jahn-Teller nature
of low-spin Ni3+ centers.
Fiz. Tverd. Tela (St. Petersburg) 41, 418–422 (March 1999) 相似文献
10.
N. E. Sluchanko A. A. Volkov V. V. Glushkov B. P. Gorshunov S. V. Demishev M. V. Kondrin A. A. Pronin N. A. Samarin Y. Bruynseraede V. V. Moshchalkov S. Kunii 《Journal of Experimental and Theoretical Physics》1999,88(3):533-537
The transport properties (Hall coefficient, thermopower, and resistivity) of high-quality single-crystal samples of the classical
mixed-valent compound SmB6 are investigated over a broad temperature range (1.6–300 K) in magnetic fields up to 45 T for the first time following the
quasioptical measurements in the 0.6–4.5 meV frequency range [B. Gorshunov, N. Sluchanko, A. Volkov et al., submitted to Phys. Rev. B (1998)]. Measurements in the intrinsic conduction region permit determination of the gap width
E
g
≈20 meV and evaluation of the behavior of the mobility and concentration of light and heavy charge carriers, as well as the
temperature dependence of the carrier relaxation time, in samarium hexaboride. The results of experimental investigations
in the “impurity” conduction region (E
ex≈3.5 meV) are discussed within the Kikoin-Mishchenko exciton-polaron model of charge fluctuations. Arguments supporting the
formation of a metallic state with an electron-hole liquid in SmB6 at liquid-helium temperatures are presented.
Zh. éksp. Teor. Fiz. 115, 970–978 (March 1999) 相似文献
11.
P. N. Bukivskii Yu. P. Gnatenko A. Kh. Rozhko O. A. Shigil’chev 《Physics of the Solid State》1997,39(3):458-465
It is shown that the temperature dependence of the binding energy of exciton-impurity complexes in the semimagnetic semiconductors
Cd1−x
MnxTe (x≈0.05) is described well in the donor-electron model with an effective characteristic magnetic-polaron energy. The contributions
of the average exchange field and of thermodynamic fluctuations of the magnetization to the binding energy and their variation
with temperature with and without a weak magnetic field (H⩽3.5 kOe) are determined. How doping with scandium, vanadium, and cobalt effects the appearance of the magnetic-polaron in
the experimental crystals was studied.
Fiz. Tverd. Tela (St. Petersburg) 39, 527–535 (March 1997) 相似文献
12.
The energy E of the system as a function of the gauge phase Φ is calculated by exact diagonalization in a two-dimensional Cu4O8 cluster and by the slave-boson method for large systems. It is shown that motion of carriers with charge 2e, i.e., Cooper pairs, is observed for certain values of the parameters in the Hamiltonian. This motion is identified from
the onset of a characteristic maximum of E(Φ) at Φ≈Φ0/2, where Φ0 is the flux quantum. The phase diagram is constructed and the range of values of the model parameters where the effect is
observed is determined.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 2, 78–82 (25 January 1996) 相似文献
13.
E. García-Matres J.L Martínez J. Rodríguez-Carvajal 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(1):59-70
A neutron diffraction study, as a function of temperature, of the title compounds is presented. The whole family (space group
Immm, a
≈ 3.8?, b
≈ 5.8?, c
≈ 11.3?) is structurally characterised by the presence of flattened NiO6 octahedra that form chains along the a-axis, giving rise to a strong Ni-O-Ni antiferromagnetic interaction. Whereas for Y-compound only strong 1D correlations exist
above 1.5 K, presenting the Haldane gap characteristic of 1D AF chain with integer spin, 3D AF ordering is established simultaneously
for both R and Ni sublattices at temperatures depending on the rare earth size and magnetic moment. The magnetic structures
of R2BaNiO5 ( R
=
Nd, Tb, Dy, Ho, Er and Tm) have been determined and refined as a function of temperature. The whole family orders with a magnetic
structure characterised by the temperature-independent propagation vector
= (1/2, 0, 1/2). At 1.5 K the directions of the magnetic moments differ because of the different anisotropy of the rare earth ions. Except
for Tm and Yb (which does not order above 1.5 K), the magnetic moment of the R3+ cations are close to the free-ion value. The magnetic moment of Ni2+ is around 1.4
, the strong reduction with respect to the free-ion value is probably due to a combination of low-dimensional quantum effects
and covalency. The thermal evolution of the magnetic structures from T
N
down to 1.5 K is studied in detail. A smooth re-orientation, governed by the magnetic anisotropy of R3+, seems to occur below and very close to T
N
in some of these compounds: the Ni moment rotates from nearly parallel to the a-axis toward the c-axis following the R moments. We demonstrate that for setting up the 3D magnetic ordering the R-R exchange interactions cannot
be neglected.
Received 19 July 2001 相似文献
14.
Results are presented from the first stage of studies on the passage of an electron beam with energy 100–500 eV in a magnetic
field of 300–700 Oe through the curvilinear solenoid of the KRéL unit, the latter being a prototype of the closing segment
of the Drakon stellarator system, in the plasma-beam discharge regime. The ion density at the end of the curvilinear part
of the chamber, n
i
≈8×108–1010 cm−3, the electron temperature T
e
≈4–15 eV, and the positions at which the beam hits the target for different distances from it to the electron source are determined
experimentally. The motion of the electron beam is computationally modeled with allowance for the space charge created by
the beam and the secondary plasma. From a comparison of the experimentally measured trajectories and trajectories calculated
for different values of the space charge, we have obtained an estimate for the unneutralized ion density of the order of 5×107 cm−3.
Zh. Tekh. Fiz. 69, 22–26 (February 1999) 相似文献
15.
It is inferred from the position of the 2Δ peak in the electron light scattering spectra that in a sample with high T
c
≈90 K the ratio 2Δ/T
c
is approximately equal to 6 and 7 for different polarizations, while in overdoped samples with T
c
≈40 and 35 K the 2Δ peak is observed only in x′y′ polarization with a substantially lower ratio 2Δ/T
c
≈3.2. With decreasing T
c
in Tl2Ba2CuO6+x
crystals, a transition occurs from strong to weak coupling; the superconducting gap remains anisotropic at different doping
levels.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 11, 760–765 (10 December 1996) 相似文献
16.
G. Li S.-J. Feng F. Liu Y. Yang R.-K. Zheng T. Qian X.-Y. Guo X.-G. Li 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(1):5-11
The magnetic transport properties have been measured for La0.67-xYxCa0.33MnO3 ( 0 ⩽
x
⩽ 0.14) system. It was found that the transition temperature T
p
almost linearly moves to higher temperature as H increases. Electron spin resonance confirms that above T
p
, there exist ferromagnetic clusters. From the magnetic polaron point of view, the shift of T
p
vs. H was understood, and it was estimated that the size of the magnetic polaron is of 9.7 ∼ 15.4 ? which is consistent with the magnetic correlation length revealed by the small-angle neutron-scattering technique. The
transport properties at temperatures higher than T
p
conform to the variable-range hopping mechanism.
Received 27 August 2002 / Received in final form 2 December 2002 Published online 14 March 2003 相似文献
17.
B. Gorshunov C.A. Kuntscher P. Haas M. Dressel F.P. Mena A.B. Kuz'menko D. van der Marel T. Muranaka J. Akimitsu 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(2):159-161
Far-infrared reflectivity studies on the polycrystalline intermetallic compound MgB2 with a superconducting transition temperature T
c
= 39 K were performed at temperatures 20 K to 300 K. We observe a significant raise of the superconducting-to-normal state reflectivity
ratio below 70
cm
-1
, with a maximum at about 25-30
cm
-1
, which gives a lower estimate of the superconducting gap of 2Δ(0)
≈ 3-4 meV.
Received 7 March 2001 and Received in final form 18 April 2001 相似文献
18.
The quantum yield, ΦΔ, of singlet oxygen generation under two-photon excitation has been determined for a fluorene derivative. A photochemical
method was developed using 1,3-diphenylisobenzofuran (DPBF), a chemical quencher of 1O2, and 2-(9,9-didecyl-7-nitrofluoren-2-yl)benzothiazole (1) as a two-photon photosensitizer (PS). The photochemical kinetics of the quencher was measured by two different fluorescence
methods. Fluorene 1 exhibited relatively high singlet oxygen quantum yield, ΦΔ ≈ 0.4 ± 0.1, and had a two-photon absorption cross-section of 28 ± 5 GM. Thus, 1 may have potential for use as a two-photon PS in the near-IR spectral region for biomedical applications. 相似文献
19.
A spin-polaron approach is developed on the basis of a generalized Kondo lattice model for a two-dimensional antiferromagnet
(CuO2 plane model). This approach makes it possible to describe the splitting of polaron bands of carriers both in the presence
of long-range magnetic order (T=0) and for a finite spin-correlation length (T≠0) and also can account for the strong deviation from the Luttinger theorem and the shadow-bands effect at both zero and
finite temperatures.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 5, 386–391 (10 September 1998) 相似文献
20.
S. V. Demishev A. V. Semeno N. E. Sluchanko N. A. Samarin I. B. Voskoboinikov M. V. Kartsovnik A. E. Kovalev N. D. Kushch 《Journal of Experimental and Theoretical Physics》1997,84(3):540-544
Resonant microwave absorption in a (BEDO-TTF)2ReO4(H2O) organic conductor single crystal at a temperature of 1.9 K, a magnetic field of up to 70 kOe, and in the frequency band
between 30 and 120 GHz has been studied. A spectral component due to the cyclotron resonance (CR) of two-dimensional charge
carriers has been identified for ν⩾80 GHz and H⩾10 kOe. The effective mass m(ω) increases with the frequency from m≈0.8m
0 at ν=80 GHz to m≈0.95m
0 at ν=120 GHz. Measurements of the CR line position and FWHM as functions of frequency yield an independently determined imaginary
part of the memory function M(ω), which controls the dynamic magnetoconductivity, and the relaxation time τ(ν=100 GHz)≈2.9×10−11 s, which is more than thirty times the value of this parameter in the low-frequency limit τ(ν→0). The anomalous behavior of the CR line position and FWHM is caused by the dispersion of both real and imaginary parts
of M(ω), which are probably due to strong Fermi-liquid effects.
Zh. éksp. Teor. Fiz. 111, 979–987 (March 1997) 相似文献