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1.
The NMR of 55Mn in the quasi-one-dimensional noncollinear anti-ferromagnet CsMnI3 is investigated at T=1.3 K in magnetic fields up to ∼80 kOe and angles between the field and C
6 axis ϕ≈ 0.5° and ϕ=7°. A new reorientational magnetic phase transition is observed in a field H
c1≈39.0 kOe. The magnetic structure for H>H
c1 is determined. The average Mn2+ spins of the magnetic sublattices in the new phase are determined from an analysis of the NMR spectrum to be 〈 S
C
〉=1.63 and 〈S
D
〉=1.72.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 12, 988–993 (25 June 1998) 相似文献
2.
M. N. Khlopkin 《JETP Letters》1999,69(1):26-30
The specific heat of a V3Si single crystal (T
c=17 K, H
c2=20 T) in magnetic fields up to 8 T isinvestigated experimentally for three orientations of the field relative to the crystallographic
directions — H∥〈001〉, H∥〈110〉, and H∥〈111〉. Both the upper critical magnetic field and the specific heat of the mixed state are observed to depend on the orientation
of the magnetic field relative to the crystallographic directions (anisotropy): The critical field reaches its maximum value
and the specific heat its minimum value in a field along the 〈001〉 direction. The anisotropy scale in both phenomena increases
as the magnetic field and reaches 3% in a 6 T field. The interrelationship of the upper critical field anisotropy and the
specific-heat anisotropy in type-II superconductors is studied. It is shown that the anisotropy of the specific heat in the
mixed state in weak fields can serve as a criterion for nontrivial pairing.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 1, 26–29 (10 January 1999) 相似文献
3.
The redistribution of the electronic polarization in deuterium atoms is analyzed theoretically and the various polarization
moments are shown to influence the magnetic resonance signal of deuterium. The analysis gives expressions that relate the
amplitudes of the magnetic resonance signals for various Zeemann sublevels of the D atom to the electronic and nuclear polarizations
of these atoms and their nuclear alignment. Experimental data on the optical orientation and spin exchange in a D-Cs mixture
are used to determine the electronic and nuclear orientation and nuclear alignment of the D atoms, which are found to be 〈S
z〉=0.1, 〈I
z〉=0.27, and 〈Q
zz=0.027.
Zh. Tekh. Fiz. 67, 22–26 (January 1997) 相似文献
4.
A. S. Borovik-Romanov S. V. Petrov A. M. Tikhonov B. S. Dumesh 《Journal of Experimental and Theoretical Physics》1998,86(1):197-205
The NMR spectrum of the quasi-one-dimensional easy-plane antiferromagnetic CsMnBr3, which has trigonal spin lattice, is investigated in detail. The measurements were performed on a wide-band NMR decimeter
microwave-band spectrometer over a wide range of magnetic fields at temperatures 1.3–4.2 K. All three branches of the NMR
spectrum previously found by us [JETP Lett. 64, 225 (1996)] are severely distorted because of the dynamic interaction with the Goldstone mode in the antiferromagnetic resonance
spectrum. The experimental results in fields up to 40 kOe are described satisfactorily by an equation obtained by Zaliznyak
et al. [JETP Lett. 64, 473 (1996)]. Formulas are obtained in our work that agree very well with experiment at all fields up to the “collapse” field
H
c
of all sublattices. The unbiased NMR frequency in CsMnBr3 is determined to be v
n0=416 MHz (T=1.3 K) in zero external magnetic field, and in this way the reduction in the spontaneous moment due to the quasi-one-dimensional
nature of the system of Mn2+ spins, which according to our data amounts to 28%, is determined more accurately. The field dependences of the directions
of the magnetic sublattices with respect to the magnetic field are obtained from the NMR spectra, confirming the equations
of Chubukov [J. Phys. Condens. Matter 21, 441 (1988)]. The results on the field dependence of the width and intensities of the NMR lines are discussed, along with
three observed anomalies: 1) a strong increase in the NMR frequency for nuclei in sublattices that are perpendicular to the
magnetic field; 2) the nonmonotonic temperature dependence of the resonance field for the lower branch of the spectrum; 3)
the presence of two branches of the NMR spectrum in large H
c
fields, in which the CsMnBr3 must be a quasi-one-dimensional antiferromagnetic.
Zh. éksp. Teor. Fiz. 113, 352–368 (January 1998)
Deceased. 相似文献
5.
The NMR of Mn55 nuclei is measured in the quasi-one-dimensional antiferromagnets CsMnBr3, RbMnBr3, and CsMnI3 in magnetic fields upto 8 T attemperatures in the range 1.3–4.2 K. The average moments of the magnetic sublattices and their
field dependences, which turned out to be comparatively strong and different for magnetically non-equivalent Mn2+ ions, are determined from the hyperfine-field data obtained. As a result, the magnetizations of separate sublattices in an
external magnetic field ∼8 T differ by more than 5%. The results obtained agree qualitatively with the theory of the suppression
of quantum fluctuations by a magnetic field.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 11, 724–729 (10 December 1997)
Deceased. 相似文献
6.
R. T. Sibatov 《JETP Letters》2011,93(9):503-507
Distributions of the conductance G of a long quantum wire with the fractal distribution of barriers have been obtained in the successive incoherent tunneling
regime. The asymptotic behavior (in the limit L → ∞) of moments 〈G
k
(L)〉, average power of the shot noise 〈S(L)〉, and Fano factor agree with the results of the work [C. W. J. Beenakker et al., Phys. Rev. B 79, 024204 (2009)], and the distributions themselves describe well the Monte Carlo simulation results. The equation that has
been obtained for the distributions of the resistance and conductance agrees with the recent fractional differential generalization
of the Dorokhov-Mello-Pereyra-Kumar equation for the quasi-one-dimensional multichannel disordered semiconductors with a self-similar
distribution of scatterers. 相似文献
7.
V. I. Belokon’ K. V. Nefedev O. A. Goroshko O. I. Tkach 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(10):1413-1416
The temperature dependence of the order parameter (〈M
2〉, the mean-square spin excess per spin) for a system with a finite number of spins of the 1D Ising model was investigated.
It was shown that there is a nonzero temperature T
s below which 〈M
2〉 rapidly tends to unity. The analogy between the 1D ensemble of a finite number of spins and a system of superparamagnetic
particles is discussed. 相似文献
8.
The effect of a polarized conduction-electron cloud back on a magnetic impurity dissolved in a metal is studied. It is shown
that at a temperature T
c
much higher than the Kondo temperature the system becomes unstable against symmetry breaking and that a state with 〈S
z
〉 ≠ 0 is established. The behavior of 〈 S
z
〉 is derived for all temperatures and magnetic fields except for a very narrow region around T
c
and for very low temperatures. The minute role of Kondo-type processes in establishing the symmetry-broken state is pointed
out.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 3, 184–189 (10 August 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
9.
The effect of doping CdIn2S4 single crystals by copper (3 mol %) on their X-ray dosimetric characteristics is investigated. It is found that the characteristic
X-ray conductivity of CdIn2S4〈Cu〉 single crystals increases 3–16 times compared with undoped CdIn2S4 at effective radiation hardness V
a = 25−50 keV and dose rate E = 0.75−78.05 R/min. Moreover, the persistence of the crystal characteristics completely disappears and the supply voltage
of a CdIn2S4〈Cu〉 X-ray detector decreases fivefold. The dependence of the steady X-ray-induced current in CdIn2S4〈Cu〉 on the X-ray dose is described as ΔI
E, 0 ∝ E
α, where 0.6 ≤ α ≤ 1.8. 相似文献
10.
Wenwei Ge Hong Liu Xiangyong Zhao Xiaobing Li Xiaoming Pan Di Lin Haiqing Xu Xiangping Jiang Haosu Luo 《Applied Physics A: Materials Science & Processing》2009,95(3):761-767
In this paper, a single crystal of 0.96Na0.5Bi0.5TiO3-0.04BaTiO3 with dimensions of Φ 30×10 mm was grown by the top-seeded-solution growth method. X-ray powder diffraction results show that the as-grown crystal
possesses the rhombohedral perovskite-type structure. The dielectric, piezoelectric and electrical conductivity properties
were systematically investigated with 〈001〉, 〈110〉 and 〈111〉 oriented crystal samples. The room-temperature dielectric constants
for the 〈001〉, 〈110〉 and 〈111〉 oriented crystal samples are found to be 650, 740 and 400 at 1 kHz. The (T
m, ε
m) values of the dielectric temperature spectra are almost independent of the crystal orientations; they are (306°C, 3718),
(305°C, 3613) and (307°C, 3600) at 1 kHz for the 〈001〉, 〈110〉 and 〈111〉 oriented crystal. The optimum poling conditions were
obtained by investigating the piezoelectric constants d
33 as a function of poling temperature and poling electric field. For the 〈001〉 and 〈110〉 crystal samples, the maximum d
33 values of 146 and 117 pC/N are obtained when a poling electric field of 3.5 kV/mm and a poling temperature of 80°C were applied
during the poling process. The as-grown 0.96Na0.5Bi0.5TiO3-0.04BaTiO3 crystal possesses a relatively large dc electrical conductivity, especially at higher temperature, having a value of 1.98×10−11 Ω−1⋅m−1 and 3.95×10−9 Ω−1⋅m−1 at 25°C and 150°C for the 〈001〉 oriented crystal sample. 相似文献
11.
The statistics of energy levels for a disordered conductor are considered in the critical energy window near the mobility
edge. It is shown that, if the critical wave functions are multifractal, the one-dimensional gas of levels on the energy axis
is compressible, in the sense that the variance of the level number in an interval is 〈 (δN)2〉∼χ〈N〉 for 〈N〉≫1. The compressibility, χ=η/2d, is given exactly in terms of the multifractal exponent η =d−D
2 at the mobility edge in a d-dimensional system.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 5, 355–360 (10 September 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
12.
A. V. Lazuta 《JETP Letters》1997,65(4):363-368
Recent results on the effect of magnetic field on the sound velocity V in aluminosilicate glasses doped with dysprosium are analyzed on the basis of a minimal model for the ground state of Dy3+ (Kramers ion with J=15/2) described by a wave function ϕ
± = ϕ
±
J
m + ηϕ
± 1/2. The first term represents a state with a large J projection on the local crystal field axis and the random parameter η(〈η〉=0, 〈η
2〉≪1) introduces a small admixture of the state ϕ
±1/2 into the ground state. The relative variation of V due to the resonance interaction of sound waves with this state split by H is determined as a function of H and T. It possesses a universal asymptotic behavior. Our results are in reasonable agreement with the experiment. A possible structure
of the crystal fields that can induce this state is discussed.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 4, 341–346 (25 February 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
13.
J. K. Baria 《Czechoslovak Journal of Physics》2004,54(4):469-485
A model pseudopotential depending on an effective core radius but otherwise parameter free is used to study the interatomic
interactions, phonon dispersion curves (inq and r-space analysis), phonon density of states, mode Grüneisen parameters, dynamical elastic constants (C
11,C
12 andC
44), bulk modulus (B), shear modulus (C′), deviation from Cauchy relation (C
12–C
44), Poisson’s ratio (σ), Young’s modulus (Y), behavior of phonon frequencies in the elastic limit independent of the direction (Y
1), limiting value in the [110] direction (Y
2), degree of elastic anisotropy (A), maximum frequencyω
max, mean frequency 〈ω〉, 〈ω
2〉1/2=(〈ω〉/〈ω
−1〉)1/2, fundamental frequency 〈ω
2〉, and propagation velocities of the elastic constants in Cu, Ag, Au, Ni, Pd, and Pt. The contribution of s-like electrons
is calculated in the second-order perturbation theory for the model potential while that of d-like electrons is taken into
account by introducing repulsive short-range Born-Mayer like term. Very recently proposed screening function due to Sarkar
et al. has been used to obtain the screened form factor. The theoretical results are compared with experimental findings wherever
possible. A good agreement between theoretical investigations and experimental findings has proved the ability of our model
potential for predicting a large number of physical properties of transition metals. 相似文献
14.
A. Fledderjohann A. Klümper K.-H. Mütter 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(4):559-565
The low energy behaviour of the two-dimensional antiferromagnetic Heisenberg model is studied in the sector with total spins
S = 0,1,2 by means of a renormalization group procedure, which generates a recursion formula for the interaction matrix ΔS
(n+1) of 4 neighbouring “n clusters” of size 2n × 2n, n = 1,2,3,... from the corresponding quantities ΔS
(n). Conservation of total spin S is implemented explicitly and plays an important role. It is shown, how the ground state energies
ES
(n+1), S = 0,1,2 approach each other for increasing n, i.e. system size. The most relevant couplings in the interaction matrices
are generated by the transitions 〈S’,m’;n+1|Sq
*|S,m;n+1〉 between the ground states |S,m;n+1〉 (m = -S,...,S) on an (n+1)-cluster of size 2n+1 × 2n+1, mediated by the staggered spin operator Sq
*. 相似文献
15.
M. O. Vlasova N. D. Galanina V. S. Demidov A. A. Nedosekin A. Ya. Ostapchuk V. A. Sadykov N. A. Khaldeeva A. L. Endalov M. A. Martem’yanov A. K. Ponosov F. M. Sergeev M. Yu. Tel’nov 《JETP Letters》1996,64(4):258-262
The polarization of the leading Λ hyperons produced on carbon and lead target nuclei by 4–10 GeV neutrons in the angle range
Θ<8.5° with respect to the beam and with only neutral-particle accompaniment is measured: 〈Π〉=−0.096±0.018 for C and 〈Π〉=−
0.128±0.047 for Pb. The dependence of the polarization on the transverse momentum and the Feynman variable is measured. The
normalized invariant cross section as a function of p
⊥
2
is found to be approximated by the function A exp(−Bp
⊥
2
), where the parameter B is independent of the kind of nucleus (B=8.71±0.09 (GeV/c)−2 for carbon and B=8.83±0.18 (GeV/c)−2 for lead).
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 4, 237–240 (25 August 1996) 相似文献
16.
D. M. Sedrakyan D. A. Badalyan V. M. Gasparyan A. Zh. Khachatryan 《Journal of Experimental and Theoretical Physics》1997,84(2):317-321
We find the dependence of the ensemble-averaged resistance, 〈ρ
L〉, of a one-dimensional chain consisting of periodically spaced random delta-function potentials of the chain length L, the incident-electron energy, and the chain disorder parameter w. We show that generally the 〈ρ
L〉 vs L dependence can be written as a sum of three exponential functions, two of which tend to zero as L℩∞. Hence the asymptotic expression for 〈ρ
L〉 is always an exponential function of L. Such an expression for 〈ρ
L〉 means that the electronic states are indeed localized and makes it possible (which is important) to find the dependence
of the localization radius on the incident-electron energy and the force with which an electron interacts with the sites of
the chain. We also derive a recurrence representation for 〈ρ
L〉, which proves convenient in numerical calculations.
Zh. éksp. Teor. Fiz. 111, 575–584 (February 1997) 相似文献
17.
M. I. Daunov I. K. Kamilov A. B. Magomedov 《Journal of Experimental and Theoretical Physics》1997,84(2):309-316
We use the data on the pressure (up to P=1.5 GPa) and field (up to H=17 kOe) dependence of the Hall coefficient and the resistivity at 77.6 and 300 K in p-CdSnAs2〈Cu〉 to calculate the effective kinetic characteristics of the charge carriers, the density and mobility of the conduction
electrons and the holes of the deep acceptor and valence bands, in an interval of excess-acceptor densities N
ext ranging from 1010–1017 cm−3. We establish that in a heavily doped semiconductor with a deep impurity band at the tail of the density of states of the
intrinsic band, with unequal donor and acceptor densities, a a heavily doped and fully compensated semiconductor state is
realized under hydrostatic compression. The threshold value of the pressure that initiates the transition into such a state,
P
c, depends on the extent to which the impurity band is populated. In p-CdSnAs2〈Cu〉 at N
ext=N
A, where N
A is the density of deep acceptors, and T⩽77.6 K the value of P
c amounts to 10−4 GPa. As the population of the deep acceptor band grows, P
c increases and in the limit becomes infinite. We discuss the special features of the electrophysical properties of p-CdSnAs2〈Cu〉 arising from the absence of an energy gap between the states of the conduction band and those of the deep acceptor band.
Zh. éksp. Teor. Fiz. 111, 562–574 (February 1997) 相似文献
18.
D. E. Feldman 《JETP Letters》1999,70(2):135-140
The random field and random anisotropy N-vector models are studied with the functional renormalization group in 4−ε dimensions. The random anisotropy Heisenberg (N=3) model has a phase with an infinite correlation length at low temperatures and weak disorder. The correlation function
of the magnetization obeys a power law 〈m(r
1)m(r
2)〉∼|r
1−r
2|− 0.62ε. The magnetic susceptibility diverges at low fields as χ∼H
−1+0.15ε. In the random field N-vector model the correlation length is finite at arbitrarily weak disorder for any N>3.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 2, 130–135 (25 July 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
19.
The wave mechanics of two impenetrable hard core particles in a 1-D box is analyzed. Each particle in the box behaves like
an independent entity represented by a macro-orbital (a kind of pair waveform). While the expectation value of their interaction, 〈 V
HC
(x) 〉, vanishes for every state of two particles, the expectation value of their relative separation, 〈 x 〉, satisfies 〈 x 〉≥λ/2 (or q ≥ π/d, with 2d=L being the size of the box). The particles in their ground state define a close-packed arrangement of their wave packets (with
〈 x 〉= λ/2, phase position separation Δϕ = 2π and momentum |q
o| = π/d) and experience a mutual repulsive force (zero point repulsion) f
o
=h
2/2md
3 which also tries to expand the box. While the relative dynamics of two particles in their excited states represents usual
collisional motion, the same in their ground state becomes collisionless. These results have great significance in determining
a correct microscopic understanding of widely different many-body systems. 相似文献
20.
M. E. Guzhva V. V. Lemanov P. A. Markovin W. Kleemann 《Physics of the Solid State》1997,39(4):618-624
Temperature-induced variations of light refraction and dielectric permittivity in single-crystal Sr1−x
BaxTiO3 (x=0.02, 0.05, 0.07, and 0.14), Sr1−x
CaxTiO3 (x=0.014), and in nominally pure strontium titanate have been studied within the 17–300 K temperature range. The spontaneous
polar contribution to the refractive index has been isolated. It was used to calculate the temperature and concentration dependences
of the polarization autocorrelation function 〈P
s
2〉
in the Sr1−x
BaxTiO3 system. For x⩽0.07, the polarization P
s=〈P
s
2
〉1/2 varies proportional to (x−x
g)1/2, where x
g=0.0027 is the new critical concentration in Sr1−x
BaxTiO3, below which short-range polar order vanishes.
Fiz. Tverd. Tela (St. Petersburg) 39, 704–710 (April 1997) 相似文献