共查询到20条相似文献,搜索用时 656 毫秒
1.
V. K. Balkhanov Yu. B. Bashkuev 《Journal of Experimental and Theoretical Physics》2010,110(3):469-472
The temperature dependences of the ac resistivity R and ac capacitance C of arsenic selenide were measured more than four decades ago [V. I. Kruglov and L. P. Strakhov, in Problems of Solid State Electronics, Vol. 2 (Leningrad Univ., Leningrad, 1968)]. According to these measurements, the frequency dependences are R ∝ ω−0.80±0.01 and ΔC ∝ ω−0.120±0.006 (ω is the circular frequency and ΔC is measured from the temperature-independent value C
0). According to fractal-geometry methods, R ∝ ω1−3/h
and ΔC ∝ ω−2+3/h
, where h is the walk dimension of the electric current in arsenic selenide. Comparison of the experimental and theoretical results
indicates that the walk dimensions calculated from the frequency dependences of resistivity and capacitance are h
R
= 1.67 ± 0.02 and h
C
= 1.60 ± 0.08, which are in agreement with each other within the measurement errors. The fractal dimension of the distribution
of conducting sections is D = 1/h = 0.6. Since D < 1, the conducting sections are spatially separated and form a Cantor set. 相似文献
2.
B. S. Dumesh M. I. Kurkin S. V. Petrov A. M. Tikhonov 《Journal of Experimental and Theoretical Physics》1999,88(6):1221-1228
The spectrum and intensities of NMR lines are investigated experimentally and theoretically for excitation by an alternating
magnetic field h‖ parallel to a static field H in the quasi-one-dimensional, six-sublattice antiferromagnet CsMnBr3. According to theory, two new NMR lines, which are not excited by a transverse magnetic field h
⊥, are observed near the phase transition from triangular to collinear structure (H=H
c
) [JETP 86, 197 (1998)].
Zh. éksp. Teor. Fiz. 115, 2228–2241 (June 1999) 相似文献
3.
Leonard P. Gamberg 《Pramana》2009,72(1):55-68
The naive time reversal odd (‘T-odd’) parton distribution and fragmentation functions are explored. We use the spectator model
framework to study flavour dependence of the Boer-Mulders (h
1⊥ ) and Sivers (f
1T⊥) functions as well as the ‘T-even’ but chiral odd function h
1L⊥. These transverse momentum-dependent parton distribution functions are of significance for the analysis of azimuthal asymmetries
in semi-inclusive deep inelastic scattering, as well as for the overall physical understanding of the distribution of transversely
polarized quarks in unpolarized hadrons. In this context we also consider the Collins mechanism and the fragmentation function
H
1⊥. As a by-product of this analysis we calculate the leading twist unpolarized cos(2ϕ) asymmetry, and sin(2ϕ) single spin asymmetry for a longitudinally polarized target in semi-inclusive deep inelastic scattering.
相似文献
4.
Summary In this work we report on the anisotropic physical properties of silver-sheathed Bi-2223 tapes fabricated by means of hot
extrusion and repeated pressing and sintering processes. The obtained Bi-2223/Ag short tapes, having critical current densitiesJ
c of 20–30 kA/cm2 at 77 K, 0 T, were measured in external magnetic fields up to 0.5T applied in two different orientations (i.e. μ0H‖(a,b)-planes and μ0H ⊥(a,b)-planes). The magnetic characterizations were performed in a wide range of temperatures and magnetic fields to study
the first magnetization curve of tapes evaluating the lower critical fields μ0Hc1⊥ab and ⊥0Hc1#x2016;ab and their dependences on temperature. TheJ
c values at different fields in the temperature range 4.6–90 K, calculated from the magnetization data by the critical state
model, are also presented.
Paper presented at the ?VII Congresso SATT?, Torino, 4–7 October 1994. 相似文献
5.
V. N. Zavaritskii 《JETP Letters》1999,70(8):556-562
The effect of a magnetic field H⊥(ab) on the transverse current-voltage characteristics (IVCs) of the mixed state of a single crystal of the layered superconductor
Bi2Sr2CaCu2Oy (BSCCO) is investigated. It is established that in a wide range of temperatures and fields above the irreversibility line
the initial part of the IVC is described by the law V∝I
γ with γ≃1. As the current increases further, this law is replaced by a section where V∝exp(I). It is established that the multivalued, multibranch characteristics, interpreted as a manifestation of an internal Josephson
effect, do not change appreciably when the crystal passes into a state with nonzero linear resistance. The character of the
dependence of the characteristic switching current on the first resistive branch, I
J
(H,T), is determined.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 8, 543–548 (25 October 1999) 相似文献
6.
Victor Dotsenko 《Journal of statistical physics》2006,122(2):197-216
The explicit form of the Griffiths singularity in the random ferromagnetic Ising model in external magnetic field is derived.
In terms of the continuous random temperature Ginzburg-Landau Hamiltonian it is shown that in the paramagnetic phase away
from the critical point the free energy as the function of the external magnetic field h in the limit h → 0 has the essential singularity of the form exp [−(const)/hD/3] (where 1 < D < 4 is the space dimensionality). It is demonstrated that in terms of the replica formalism this contribution to the free
energy comes due to non-perturbative replica instanton excitations. 相似文献
7.
A theory is constructed for the dynamics and braking of domain walls in ferromagnets when a magnetic field is applied perpendicular
to the axis of easy magnetization (i.e., a transverse field H
⊥). The theory is valid for velocities v up to the limiting domain wall velocity v c. The Landau-Lifshitz equations in the dissipationless approximation are used to investigate the motion of domain walls and
the change in the character of the wall motion as its velocity v approaches v
c. The force acting on a domain wall due to viscous friction is calculated within the framework of generalized relaxation theory,
and the dependence of the domain wall velocity v on the forcing field H
z is investigated. Calculations of the braking force show that the contributions of various dissipation mechanisms to the friction
force have different dependences on the domain wall velocity, which affects the form of the function v=v(H
z). The shapes of the curves v(H
z) differ very markedly from one another for different values of the field H
⊥. The theory developed here can be used to describe the experimental results, in particular the almost linear behavior of
v=v(H
z) for small H
⊥ and its strongly nonlinear behavior when H
⊥∼H
a, whereas these data cannot be reconciled within the standard theory based on relaxation terms of Hilbert type.
Zh. éksp. Teor. Fiz. 112, 953–974 (September 1997) 相似文献
8.
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
9.
P. Rahimi-Moghaddam Y. Upadrashta M. J. Nilges J. A. Weil 《Applied magnetic resonance》2003,24(1):113-125
Electron paramagnetic resonance spectra of manganese-containing plasticine putty have been obtained both at 9.4 and 94.2 GHz
(room temperature). It has been possible to analyze both, quantitatively by computer-based simulation and exact diagonalization
of a general spin-Hamiltonian, by use of an appropriate powder technique. A fine fit was obtained for both frequencies with
an isotropicg-2.00117, uniaxial55Mn hyperfine valuesA
∥/g
c
β
c = −93.5 G (where ‖ implies direction (ℤ) andA
⊥/g
c
β
c = −94.3 G, a nuclear quadrupole effectP
z(55Mn)=0, and a uniaxial electronic quadrupole matrix (D/g
c
β
c = 3D
Z/2g
c
β
c = −82.8 G). The electronic octupole energy was taken into account via the single parameterB
40/g
c
β
c = −0.024 G. The plasticine has been demonstrated to afford a fine intensity and magnetic-field standard, say, for use with
free radicals such as spin-trap adducts. Examples provided are 2,2-diphenyl-l-picrylhydrazyl, and hydroxyl radical generated
by the Fenton reaction and spin-trapped with 5,5-dimethyl-1-pyroline-N-oxide. 相似文献
10.
B. Canals D.A. Garanin 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(4):439-447
Thermodynamic quantities and correlation functions (CFs) of the classical antiferromagnet on the checkerboard lattice are
studied for the exactly solvable infinite-component spin-vector model, D↦∞. In contrast to conventional two-dimensional magnets with continuous symmetry showing extended short-range order at distances
smaller than the correlation length, r
ξ
c∝ exp(T
*/T), correlations in the checkerboard-lattice model decay already at the scale of the lattice spacing due to the strong degeneracy
of the ground state characterized by a macroscopic number of strongly fluctuating local degrees of freedom. At low temperatures,
spin CFs decay as <
>∝ 1/r
2 in the range a
0≪r≪ξ
c∝T
-1/2, where a0 is the lattice spacing. Analytical results for the principal thermodynamic quantities in our model are very similar with
MC simulations, exact and analytical results for the classical Heisenberg model (D = 3) on the pyrochlore lattice. This shows that the ground state of the infinite-component spin vector model on the checkerboard
lattice is a classical spin liquid.
Received 16 November 2001 and Received in final form 12 February 2002 相似文献
11.
The dynamic Stark effect of the spectral lines Hβ and of the neutral helium lines λ=402.6 nm (23
P
0−53
D) and λ=438.8 nm (21
P
0−51
D) emitted from a discharge tube was used for probing rf electric fields in a transverse waveguide. Calculations accounting
for the pertubation of the atomic states by strong unidirectional fields prove to be suitable in order to interprete the main
experimental results. If the waveguide is terminated with a metallic reflector and the plasma in the discharge tube becomes
overdense—then representing a slightly permeable mirror—a resonant enhancement of the electric field strength may be achieved
by tuning. This enhancement is well recognizable in the spectral line contours. 相似文献
12.
G. V. Arzamastseva F. V. Lisovskii E. G. Mansvetova 《Journal of Experimental and Theoretical Physics》1998,87(6):1136-1147
New phase transitions induced by a magnetic field and accompanied by a change in the symmetry or the period of the distribution
of the magnetization vector are observed in biperiodic stripe domain structures of iron garnet films with a positive anisotropy
constant. A symmetry classification of the observed types of domain structures is derived, and the form of the state diagram
of the films is determined in the H∥H⊥ plane, where H∥ and H⊥ are the components of the magnetic field vector perpendicular and parallel to the normal to the surface.
Zh. éksp. Teor. Fiz. 114, 2089–2110 (December 1998) 相似文献
13.
J. Kaupužs R. V.N. Melnik J. Rimshans 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(4):363-370
Monte Carlo simulations of magnetization and susceptibility in the 3D XY
model are performed for system sizes up to L=384 (significantly exceeding the
largest size L=160 considered in work published previously), and fields h
≥ 0.0003125 at two different coupling constants β=0.5, and
β=0.55 in the ordered phase. We examine the prediction of the standard
theory that the longitudinal susceptibility χ∥ has a Goldstone mode singularity
such that χ∥ ∝h-1/2 holds when h↦0. Most
of our results, however, support another theoretical prediction that the
singularity is of a more general form χ∥ ∝hρ-1,
where 1/2<ρ<1 is a universal exponent related to the ∼hρ
variation of the magnetization. 相似文献
14.
The behavior of isotherms of the magnetization σ(H) and the longitudinal λ‖ and transverse λ⊥ magnetostriction of the polycrystalline ferrite CoFeCrO4 with frustrated magnetic structure has been investigated for the first time in magnetic fields up to H=50 kOe at T=4.2 K. It is found that the magnetization grows with increasing field due to two different paraprocesses.
Fiz. Tverd. Tela (St. Petersburg) 41, 2042–2043 (November 1999) 相似文献
15.
The electromagnetic mass splittings of heavier hadrons are estimated in the framework of gauge theory model where ligher quarks
are taken to behave relativistically and the spatial wave functions are described by the spin-spin interaction affected relative
distances between quarks. The predictions for (Ξ−-Ξ0), (Σ*0−Σ*+), (Ξ*−-Ξ*0), (D
c
+−D
c
0) and (D
c
*+
−D
c
*0
) are in fair agreement with the experimental data available whereas those for (D
b
−
−D
b
0
) and (D
b
*−
−D
b
*0
) are in qualitative agreement with other theoretical estimates. 相似文献
16.
17.
Chen Li-chuan A. Rabenau W. Weppner 《Applied Physics A: Materials Science & Processing》1978,17(3):233-237
The ionic and electronic conductivities of Ag2Tl6I10 single crystals have been studied as a function of crystallographic orientation and temperature from 20 to 135°C. EMF as
well as AC and DC techniques have been employed. The highly anisotropic material is predominantly an Ag+-ion conductor parallel toc-direction, with the Ag+ ions moving through linear channels that are not interconnected. The conductivity σ‖c
=1.6×10−7Ω−1cm−1 at 25°C, with an activation enthalpy for σ‖c
of 0.38 eV. The conduction perpendicular toc-direction has been found to be predominantly electronic with a value of σ⊥c
=3×10−9Ω−1cm−1 at 25°C and an activation enthalpy for σ⊥c
of 0.64 eV. This is the first observation of one-dimensional Ag+ conduction and this type of orientation-dependent change from ionic to electronic conduction.
On leave from Institute of Physics, Academia Sinica, Peking, China. 相似文献
18.
M. A. Zelikman 《Technical Physics》1997,42(9):1019-1026
The behavior of planar (laminar) vortices in a three-dimensional, ordered Josephson medium as a function of the parameter
I, which is proportional to the critical junction current and the cell size, is investigated with allowance for pinning due
to the cellular structure of the medium. The minimum possible distances between two isolated vortices are calculated. A system
of vortices formed in a sample in a monotonically increasing external magnetic field is analyzed. The minimum distance from
the outermost vortex to the nearest neighbor is proportional to I
−1.1. For I⩽1.3 each vortex contains a single flux quantum Φ0, and the distance between them does not decrease in closer proximity to the boundary but remains approximately constant,
implying that the magnetic field does not depend on the coordinate in the region penetrated by vortices. These facts contradict
the generally accepted Bean model. The sample magnetization curve has a form typical of type II superconductors. Allowance
for pinning raises the critical field H
c and induces a sudden jump in the curve at H=H
c.
Zh. Tekh. Fiz. 67, 38–46 (September 1997) 相似文献
19.
S. V. Grigor’ev S. A. Klimko S. V. Maleev A. I. Okorokov V. V. Runov D. Yu. Chernyshov 《Journal of Experimental and Theoretical Physics》1997,85(6):1168-1179
A magnetic phase transition in carbon-doped (0.1 and 0.7 at. %) Fe70Ni30 Invar alloys was investigated by the method of depolarization of a transmitted neutron beam and by small-angle scattering
of polarized neutrons. It is shown that for both alloys, two characteristic length scales of magnetic correlations coexist
above T
c. Small-angle scattering by critical correlations with radius R
c is described well by the Ornstein-Zernike (OZ) expression. The longer-scale (second) correlations, whose size can be estimated
from depolarization data, are not described by the OZ expression, and hypothetically can be modeled by a squared OZ expression,
which in coordinate space corresponds to the relation 〈M(r)M(0)〉∝exp(−r/R
d), where R
d is the correlation length of the second scale. The temperature dependence of the correlation radius R
c was obtained: R
c ∝ ((T−T
c)/Tc)−ν
, where ν≈2/3 is the critical exponent for ferromagnets, over a wide temperature range up to T
c
exp
, at which the correlation radius becomes constant and equals its maximum value R
c(T
c)=R
c
max
. The maximum correlation radius established (R
c
max
=140 Å and 230 Å for the first and second alloys, respectively) characterizes the length-scale of the fluctuation for which
the appearance of critical correlations first results in the formation of a ferromagnetic phase, and the phenomenon itself
exhibits a “disruption” of the second-order phase transition at T=T
c
exp
, as a result of which a first-order transition arises. Temperature hysteresis was also detected in the measured polarization
of the transmitted beam and intensity of small-angle neutron scattering in the alloy above T
c, confirming the character of this magnetic transition as a first-order transition close to a second-order transition.
Zh. éksp. Teor. Fiz. 112, 2134–2155 (December 1997) 相似文献
20.
The field dependences of the transverse resistance of a single crystal of the layered superconductor Bi2Sr2CaCu2Oy (BSCCO-2212) with T
c
0≃92 K are studied in magnetic fields up to 50 T in the perpendicular orientation H⊥(ab). It is established that in the resistive region the resistance is a power-law function of the field, and the temperature
dependence of the barrier height for flux creep is obtained. It is found that in a wide temperature range, 50–125 K, the transverse
magnetoresistance of the crystal in the normal state and under conditions of superconductivity suppression by a strong magnetic
field is negative and can be approximated by a linear law with a temperature-dependent slope.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 5, 420–425 (10 September 1998) 相似文献