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1.
V. V. Popov P. P. Konstantinov Yu. V. Rud’ 《Journal of Experimental and Theoretical Physics》2011,113(4):683-691
Electrical resistivity ρ and Hal coefficient R are measured as a function of the temperature (T = 1.7−310 K) and the magnetic field (up to H = 28 kOe) in zero-gap semiconductor CuFeS2 samples subjected to hydrostatic compression and under various heat-treatment conditions. At low temperatures, anomalies
are observed in the kinetic effects related to the presence of ferromagnetic clusters: the magnetoresistance at T = 4.2 K and T = 20.4 K acquires a hysteretic character and thermopower α changes its sign at T < 15 K. The temperature dependence of conduction-electron concentration n in CuFeS2 has a power form in the temperature range T = 14−300 K, which is characteristic of the intrinsic conductivity in zero-gap semiconductors. In CuFeS2, we have n(T) ∝ T
1.2; in isoelectron compound Cu1.13Fe1.22Te2, we have n(T) ∝ T
1.93. Heat treatment is found to affect the intrinsic conductivity of CuFeS2, as the action of hydrostatic compression (carrier concentration changes); that is, the carrier concentration changes. However,
a power form of the n(T) and ρ(T) dependences is retained. 相似文献
2.
V. I. Tsebro O. E. Omel’yanovskii E. F. Kukovitskii N. A. Sainov N. A. Kiselev D. N. Zakharov 《Journal of Experimental and Theoretical Physics》1998,86(6):1216-1219
Bulk samples of carbon multilayer nanotubes with the structure of nested cones (fishbone structure) suitable for transport
measurements, were prepared by compressing under high pressure (∼25 kbar) a nanotube precursor synthesized through thermal
decomposition of polyethylene catalyzed by nickel. The structure of the initial nanotube material was studied using high-resolution
transmission electron microscopy. In the low-temperature range (4.2–100 K) the electric resistance of the samples changes
according to the law ln R ∝ (T
0/T)1/3, where T
0∼7 K. The measured magnetoresistance is quadratic in the magnetic field and linear in the reciprocal temperature. The measurements
have been interpreted in terms of two-dimensional variable-range hopping conductivity. It is suggested that the space between
the inside and outside walls of nanotubes acts as a two-dimensional conducting medium. Estimates suggest a high value of the
density of electron states at the Fermi level of about 5×1021 eV−1 cm−3.
Zh. éksp. Teor. Fiz. 113, 2221–2228 (June 1998) 相似文献
3.
The crystallization and glass transition kinetics using differential scanning calorimetry (DSC) in 50AgI–33.33Ag2O–16.67[(V2O5)1−x
–(MoO3)
x
] superionic glassy system is discussed. Thermal stability of glass, studied using various criteria, does not vary significantly
with glass former variation. However, the activation energies for structural relaxation (E
s) at glass transition temperature and crystallization (E
c) obtained using Moynihan and Kissinger, Matusita-Sakka formulations found to exhibit interesting trends with MoO3 substitution in the glass matrix. It is noticed that the electrical conductivity (σ)–temperature (T) cycles obtained at a typical heating rate of 1 °C/min do exhibit significant thermal events. The conductivity after first
heating cycle at room temperature is found to be increasing with MoO3 content and maximum for x = 0.3 (~10−3 Ω−1 cm−1 at 30 °C) which is comparable to that of the host 50AgI–33.33Ag2O–16.67V2O5 glassy system. The parameters obtained from σ–T plots and DSC scans do complement each other in a particular range of composition. 相似文献
4.
E. Z. Meilikhov 《Journal of Experimental and Theoretical Physics》1999,88(4):819-825
Models of thermally activated linear and high-field nonlinear conductivity of a dielectric phase in granular metals (nanocomposites),
i.e., aggregates of small metallic grains in a dielectric matrix, have been suggested. Given a sufficiently large spread of
grain sizes, the temperature dependence of the nanocomposite conductivity should be described by a universal “power-1/2” law:
G∝exp[−(T
0/T)1/2]. An analytical expression for T
0 has been obtained. It is found that there are two regimes of nonlinear conductivity in a high electric field, namely, a low-field
regime, when both the number and mobility of carriers change with the field strength, and a high-field regime, when only the
mobility of carriers is variable. Analytical expressions for the nonlinear conductance in both regimes have been obtained.
Zh. éksp. Teor. Fiz. 115, 1484–1496 (April 1999) 相似文献
5.
V. Yu. Yushankhai 《Hyperfine Interactions》1989,50(1-4):775-779
On the basis of current theoretical views on the critical phenomena in isotropic Heisenberg ferromagnets the power temperature
behavior Λ=c(τ)λ0τ-w has been derived for the muon spin relaxation rate Λ as π-T
c
−1
(T-T
c
) → 0+. It is shown that the crossover from an exchange critical regime to a dipolar one is accompanied not only with the change
in the critical exponentw in the above law, but also with the reduction of the coefficientc(π). A comparison with the temperature behaviour of the inverse nuclear relaxation timet
R
−1
measured in the PAC experiment is carried out. 相似文献
6.
M. A. Anisimov A. V. Bogach V. V. Glushkov S. V. Demishev N. A. Samarin V. B. Filipov N. Yu. Shitsevalova A. V. Kuznetsov N. E. Sluchanko 《Journal of Experimental and Theoretical Physics》2009,109(5):815-832
The magnetoresistance Δρ/ρ of single-crystal samples of praseodymium and neodymium hexaborides (PrB6 and NdB6) has been measured at temperatures ranging from 2 to 20 K in a magnetic field of up to 80 kOe. The results obtained have
revealed a crossover of the regime from a small negative magnetoresistance in the paramagnetic state to a large positive magnetoresistive
effect in magnetically ordered phases of the PrB6 and NdB6 compounds. An analysis of the dependences Δρ(H)/ρ has made it possible to separate three contributions to the magnetoresistance for the compounds under investigation. In
addition to the main negative contribution, which is quadratic in the magnetic field (−Δρ/ρ ∝ H
2), a linear positive contribution (Δρ/ρ ∝ H) and a nonlinear ferromagnetic contribution have been found. Upon transition to a magnetically ordered state, the linear
positive component in the magnetoresistance of the PrB6 and NdB6 compounds becomes dominant, whereas the quadratic contribution to the negative magnetoresistance is completely suppressed
in the commensurate magnetic phase of these compounds. The presence of several components in the magnetoresistance has been
explained by assuming that, in the antiferromagnetic phases of PrB6 and NdB6, ferromagnetic nanoregions (ferrons) are formed in the 5d band in the vicinity of the rareearth ions. The origin of the quadratic contribution to the negative magnetoresistance is
interpreted in terms of the Yosida model, which takes into account scattering of conduction electrons by localized magnetic
moments of rare-earth ions. Within the approach used, the local magnetic susceptibility χloc has been estimated. It has been demonstrated that, in the temperature range T
N < T < 20 K, the behavior of the local magnetic susceptibility χloc for the compounds under investigation can be described with good accuracy by the Curie-Weiss dependence χloc ∝ (T − Θ
p
)−1. 相似文献
7.
A. U. Sheleg V. G. Hurtavy S. N. Mustafaeva E. M. Kerimova 《Physics of the Solid State》2011,53(3):472-475
The temperature dependences of the electrical conductivity and the permittivity of TlInSe2 and TlGaTe2 crystals unirradiated and irradiated with 4-MeV electrons at a doze of 1016 cm−2 have been investigated. It has been established that electron irradiation leads to a decrease in the electrical conductivity
σ and the permittivity ɛ over the entire temperature range under study (90–320 K). It has been revealed that the TlInSe2 and TlGaTe2 single crystals undergo a sequence of phase transitions characteristic of crystals of this type, which manifest themselves
as anomalies in the temperature dependences σ = f(T) and ɛ = f(T). Electron irradiation at a doze of 1016 cm−2 does not affect the phase transition temperatures of the crystals under investigation. 相似文献
8.
Magnetic and thermal properties of CuFeS<Subscript>2</Subscript> at low temperatures 总被引:1,自引:0,他引:1
The magnetic moment M, the magnetic susceptibility χ, and the thermal conductivity of chalcopyrite CuFeS2, which is a zero-gap semiconductor with antiferromagnetic ordering, have been measured in the temperature range 10–310 K.
It has been revealed that the quantities χ(T) and M(T) increase anomalously strongly at temperatures below ∼100 K. The temperature dependence M(T) is affected by the magnetic prehistory of the sample. An analysis has demonstrated that the magnetic anomalies are associated
with the presence of a system of noninteracting magnetic clusters in the CuFeS2 sample under investigation. The formation of the clusters is most likely caused by the disturbance of the ordered arrangement
of Fe and Cu atoms in the metal sublattice of the chalcopyrite, which is also responsible for the phase inhomogeneity of the
crystal lattice. The inhomogeneity brings about strong phonon scattering, and, as a result, the temperature dependence of
the thermal conductivity coefficient exhibits a behavior characteristic of partially disordered crystals. 相似文献
9.
Variations in the temperature behavior of resistivity, ρ(T), in the ab plane of the anisotropic single-crystal high-T
c
superconductor BiSrCuO (2201 phase) have been observed at the insulator-metal (IM) transition. At low temperatures, as one
approaches the transition, the Mott relation for two dimensions, ln ρ ∝ T
−1/3, changes to ln ρ ∝ T
−1/2, which corresponds to hopping conduction with a Coulomb gap in the density of states. Negative temperature slopes were revealed
in the samples near the transition. Estimates suggest that superconductivity in these samples sets in from the Anderson insulator
state. The behavior of the width of the superconducting transition and of the temperature of its onset, T
con, at the IM transition has been studied from measurements of the ac magnetic susceptibility. It is shown that in the vicinity
of the IM transition the superconducting transition becomes broader, and the onset of the transition T
con shifts toward higher temperatures. This behavior is attributed to nonuniform superconductivity resulting from formation in
the crystal of superconducting droplets with different values of T
c
, which is caused by fluctuations in the local density of states due to the inherent disorder in the crystal. In these conditions,
superconductivity has a percolation character.
Fiz. Tverd. Tela (St. Petersburg) 40, 1190–1194 (July 1998) 相似文献
10.
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
11.
R. Yimnirun A. Ngamjarurojana R. Wongmaneerung S. Wongsaenmai S. Ananta Y. Laosiritaworn 《Applied Physics A: Materials Science & Processing》2007,89(3):737-741
The temperature scaling of the ferroelectric hysteresis was investigated in hard lead zirconate titanate (PZT) bulk ceramic.
The power-law temperature scaling relations were obtained for hystersis area 〈A〉, remnant polarization Pr, and coercivity EC in the forms of 〈A〉∝T-0.9650, Pr∝T-0.0261, and EC∝T-0.8823, respectively, which are mostly comparable to those of its soft counterpart. The observation that Pr decayed more slowly with temperature than in soft PZT was attributed to the presence of the complex defects in hard PZT.
However, the product of Pr and EC still provided the similar scaling law on the T dependence in comparison with 〈A〉.
PACS 77.80.-e; 77.80.Fm; 77.84.-s; 77.84.Dy 相似文献
12.
S. Rabinovich 《Journal of Experimental and Theoretical Physics》2011,112(4):637-641
A simple assumption of the emergence in gas of small atomic clusters consisting of c particles each leads to a phase separation (first-order transition). It reveals itself by the emergence of a “forbidden”
density range starting at a certain temperature. Defining this latter value as the critical temperature predicts the existence
of an interval with the anomalous heat capacity behavior c
p
∝ ΔT
−1/c
. The value c = 13 suggested in the literature yields the heat capacity exponent α = 0.077. 相似文献
13.
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
14.
Summary The relaxation processes of glass-forming polymethylacrylate have been studied in a wide temperature range above the glass
transition temperatureT
g by means of light scattering measurements. Experimental spectra give evidence of a self-similar behaviourI(ω) ∝ ω−(1−a) over a spectral range of 2–3 decades, consistent with the predictions of the mode-coupling theory. Different from the prediction
of the theory, the value ofa is strongly temperature dependent. This behaviour has been attributed to the presence of a slow secondary relaxation located
in the GHz frequency region, whose strength progressively increases with temperature.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献
15.
L. S. Parfen’eva T. S. Orlova N. F. Kartenko N. V. Sharenkova B. I. Smirnov I. A. Smirnov H. Misiorek A. Jezowski T. E. Wilkes K. T. Faber 《Physics of the Solid State》2010,52(6):1115-1122
This paper reports on measurements performed in the temperature range 5–300 K for the thermal conductivity κ and electrical
resistivity ρ of high-porosity (cellular pores) biocarbon preforms prepared by pyrolysis (carbonization) of beech wood in
an argon flow at carbonization temperatures of 1000 and 2400°C. X-ray structure analysis of the samples has been performed
at 300 K. The samples have revealed the presence of nanocrystallites making up the carbon matrices of these biocarbon preforms.
Their size has been determined. For samples prepared at T
carb = 1000 and 2400°C, the nanocrystallite sizes are found to be in the ranges 12–25 and 28–60 κ(T) are determined for the samples cut along and across the tree growth direction. The thermal conductivity κ increases with
increasing carbonization temperature and nanocrystallite size in the carbon matrix of the sample. Thermal conductivity measurements
conducted on samples of both types have revealed an unusual temperature dependence of the phonon thermal conductivity for
amorphous materials. As the temperature increases from 5 to 300 K, it first increases in proportion to T, to transfer subsequently to ∼T
1.5 scaling. The results obtained are analyzed. 相似文献
16.
The heavy-fermion metal CePd1−x
Rh
x
can be tuned from ferromagnetism at x = 0 to the nonmagnetic state at some critical concentration x
c
. The non-Fermi liquid behavior (NFL) at x ≃ x
c
is recognized by the power-law dependence of the specific heat C(T) given by the electronic contribution susceptibility X(T) and volume expansion coefficient α(T) at low temperatures: C/T ∝ X(T) ∝ α(T)/T∝ 1/ √T. We also demonstrate that the behavior of the normalized effective mass M
N
*
observed in CePd1−x
Rh
x
at x ≃ 0.8 agrees with that of M
N
*
observed in paramagnetic CeRu2Si2 and conclude that these alloys exhibit the universal NFL thermodynamic behavior at their quantum critical points. We show
that the NFL behavior of CePd1−x
Rh
x
can be accounted for within the frameworks of the quasiparticle picture and fermion condensation quantum phase transition,
while this alloy exhibits a universal thermodynamic NFL behavior that is independent of the characteristic features of the
given alloy such as its lattice structure, magnetic ground state, dimension, etc.
The text was submitted by the authors in English. 相似文献
17.
The temperature variation of the lattice parameter of CsPbCl3 in the cubic phase has been studied by x-ray method, from a determination of the precision lattice parameter at various temperatures,
ranging from 50°C to 400°C. The coefficient of thermal expansion of CsPbCl3 can be expressed by the quadratic equation,α
T
= 21.6 × 10−6 + 2.44 × 10−9
T + 5.90 × 10−11
T
2. 相似文献
18.
Bi4V2O11 exists in three phases viz. α, β, and γ. High temperature γ-phase can be stabilized to room temperature owing to its higher
conductivity by the partial substitution of metallic cations for vanadium in Bi4V2O11. Phase transitions from α → β and β → γ are composition and temperature-dependent. Mn2+-doped compounds Bi4V2−x
Mn
x
O11−
δ
(0 ≤ x ≤ 0.4) have been synthesized by solid state reaction technique and investigated by X-ray diffraction and ionic conductivity
measurement. High ionic conducting γ-phase is stabilized for x ≥ 0.2. The ionic conductivity of the series of Bi4V2−x
Mn
x
O11−
δ
samples has been measured by using ac impedance spectroscopy technique. The conductivity data do show departure from its
simple Arrhenius behavior for all of the compositions. The highest conductivity observed for x = 0.2 sample can be attributed to lower activation energy. 相似文献
19.
Doubly substitution of vanadium by Cu and Co in the limit of 10% in Bi4V2O11, has led to the formation of the Bi4V1.8Cu0.2−xCoxO10.7 solid solution. X-ray diffraction shows that all the compositions present a tetragonal symmetry. The thermal analysis has
revealed that the polymorph γ' phase, which is formed by a partial ordering of oxygen ions in the γ high temperature form,
is stabilized at room temperature. The influence of sintering temperature on the microstructure of the samples was investigated
by the scanning electron microscopy (SEM). The ceramics sintered at 820 °C for more than 3 hours present micro-craks. The
evolution of the electrical conductivity with temperature and the degree of substitution has been investigated by impedance
spectroscopy. The sample with x=0.1 presents the highest value of the conductivity ≈4.6×10−2 S·cm−1 at 600 °C. 相似文献
20.
A. Abdelghany 《Applied Physics A: Materials Science & Processing》1990,50(5):463-464
We have measured the thermal conductivity in both the solid and liquid states for two amorphous samples. The first was selenium doped with indium and the second was selenium doped with iodine. The concentration of In and I in both samples was 50000 ppm in weight, which is equal to 3.33% for indium and 3.02% for iodine additives in atomic percent. The measurements were taken in the temperature range from 100 to 470°C and were carried out using the concentric cylindrical wall. It was found that the thermal conductivity of both samples is of the phonon type; its temperature dependence follows the relation K
ph T
–1, and can be explained by the influence of thermal effects on the lattice structure. 相似文献