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1.
D. A. Balaev A. A. Dubrovskiy S. I. Popkov K. A. Shaikhutdinov O. N. Mart’yanov M. I. Petrov 《Journal of Experimental and Theoretical Physics》2010,110(4):584-593
The transport properties (R(T) and R(H) dependences at various values of the transport current in magnetic fields up to 65 kOe) and low-temperature heat capacity
in magnetic fields up to 90 kOe of the BaPb0.75Bi0.25O3 superconductor (T
C
≈ 11.3 K) are investigated with the goal of clarifying the mechanisms determining the nonmonotonic behavior and hysteresis
of its magnetoresistance R(H). The type of R(H) hysteretic dependences for BaPb0.75Bi0.25O3 is analogous to that observed in granular high-T
c
superconductors (HTSCs); however, unlike classical HTSC systems, the field width of the magnetoresistance hysteresis loop
for polycrystalline BaPb0.75Bi0.25O3 depends on the transport current. This means that although the mechanisms responsible for the magnetoresistance hysteresis
(the influence of the magnetic flux trapped in superconducting regions on the effective field in Josephson interlayers) are
identical in these objects, the transport current in BaPb0.75Bi0.25O3 may considerably affect the diamagnetic response of the superconductor. A considerable effect of transport current on the
field in which the R(H) dependences have a peak and exhibit hysterestic properties is observed. Such a behavior can be adequately interpreted using
the model of the spatially inhomogeneous superconductor-insulator state proposed by Gorbatsevich et al. [JETP Lett. 52, 95 (1990)]. The nonmonotonic dependence of quantity C/T (C is the heat capacity) on the magnetic field discovered in the present study also agrees with the conclusions based on this
model. 相似文献
2.
A. T. Burkov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(10):1392-1394
Results on the experimentally investigated dependence of the electrical resistivity of quasibinary alloys R
x
Y1−x
Co2, where R stands for magnetic rare earth elements, on temperature (2–300 K), composition (x = 0–1), and magnetic field (0–15 T) are presented. Non-Fermi liquid behavior of electrical resistivity in a magnetic field
was observed in paramagnetic Gd
x
Y1−x
Co2 alloys. The relative magneto-thermopower of these alloys exhibits diverging behavior with decreasing temperature, indicating
anomalous temperature variation of the thermopower in the non-Fermi liquid regime. 相似文献
3.
N. E. Sluchanko V. V. Glushkov S. V. Demishev M. V. Kondrin K. M. Petukhov A. A. Pronin N. A. Samarin Y. Bruynseraede V. V. Moshchalkov A. A. Menovsky 《JETP Letters》1998,68(10):817-822
The temperature dependence of the Hall coefficient in the interval 1.8–300 K is investigated in detail in high-quality single-crystal
samples of a Kondo insulator — iron monosilicide. It is established that the parameter R
H
(T,H=12.5 kOe) changes sign twice in the temperature interval employed, and at temperatures below T
m
≈7 K an anomalous (magnetic) component appears in the angular and field dependences of the Hall voltage. The results of the
experimental investigations of R
H
(T,H
0
) in FeSi are discussed on the basis of the phase diagram in the model of an excitonic insulator.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 10, 774–778 (25 November 1998) 相似文献
4.
S. V. Grigoriev N. A. Grigoryeva K. S. Napol’skii A. P. Chumakov A. A. Eliseev I. V. Roslyakov H. Eckerlebe A. V. Syromyatnikov 《JETP Letters》2011,94(8):635-641
Magnetic properties of spatially ordered arrays of interacting nanofilaments have been studied by means of small-angle diffraction
of polarized neutrons. Several diffraction maxima or rings that correspond to the scattering of the highly ordered structure
of pores/filaments with hexagonal packing have been observed in neutron scattering intensity maps. The interference (nuclear-magnetic)
and pure magnetic contributions to the scattering have been analyzed during the magnetic reversal of the nanofilament array
in a field applied perpendicular to the nanofilament axis. The average magnetization and the interference contribution proportional
to it increase with the field and are saturated at H = H
S
. The magnetic reversal process occurs almost without hysteresis. The intensity of the magnetic contribution has hysteresis
behavior in the magnetic reversal process for both the positive and negative fields that form the field dependence of the
intensity in a butterfly shape. It has been shown that this dependence is due to the magnetostatic interaction between the
filaments in the field range of H ≤ H
S
. A theory for describing the magnetic properties of the arrays of interacting ferromagnetic nanofilaments in the magnetic
field has been proposed. 相似文献
5.
C. Papastaikoudis E. Rocoffylou W. Tselfes K. Chountas 《Zeitschrift für Physik B Condensed Matter》1976,25(2):131-134
The Hall coefficientR
H
of aluminium-base gallium solid solution alloys have been measured as a function of concentration and magnetic field at 4.2 K. The low field Hall coefficientR
0 at first increases rapidly and is always positive. But as soon as the electron scattering is predominantly governed by the induced Ga impurities, the Hall coefficientR
0 remains constant and the Kohler rule is fulfilled, because then only the concentration of the identical Ga atoms is enlarged. The positive values ofR
0 show that the anisotropic scattering of the electrons on the Ga atoms is the cause of this effect. 相似文献
6.
A. V. Vedyaev A. B. Granovskii A. V. Kalitsov F. Brouers 《Journal of Experimental and Theoretical Physics》1997,85(6):1204-1210
A theoretical study is performed of the anomalous Hall effect in granular alloys with giant magnetoresistance. The calculation
is carried out within the Kubo formalism and the Green’s function method. The mechanism of asymmetric scattering of the spin-polarized
current carriers is considered with allowance for a size effect associated with scattering not only by one grain, but also
with more complicated processes of transport among two and three grains. It is shown that scattering of conduction electrons
by the interfaces of the grains and the matrix has a substantial effect on the magnitude of the anomalous Hall effect and
determines its sign. In general, correlation between the quantities ρ
H and ρ
2 is absent, where ρ
H is the Hall resistivity and ρ is the total resistivity of the granular alloy. However, numerical calculation shows that for certain values of the model
parameters ρ
H∼ρ
3.8 and for these same parameter values the amplitude of the giant magnetoresistance reaches 40%, which is found to be in quantitative
agreement with the experimental data for Co20Ag80 alloys [P. Xiong, G. Xiao, J. Q. Wang et al., Phys. Rev. Lett. 69, 3220 (1992)]. It is also shown that increasing the resistivity of the matrix leads to a significant growth in the anomalous
Hall effect, and more substantial growth for alloys with small grain size, which is in good agreement with experiment [A.
B. Pakhomov, X. Yan, and Y. Xu, J. Appl. Phys. 79, 6140 (1996); [X. N. Jing, N. Wang, and A. B. Pakhomov, Phys. Rev. B 53, 14032 (1996)].
Zh. éksp. Teor. Fiz. 112, 2198–2209 (December 1997) 相似文献
7.
A. B. Granovskii M. V. Kuz’michev J. P. Clerc 《Journal of Experimental and Theoretical Physics》1999,89(5):955-959
The features of the optical and magnetooptical properties of granular alloys with giant magnetoresistance in the IR region
are examined in reference to the magnetorefractive effect and the equatorial Kerr effect. Calculations are performed within
the semiclassical approximation with consideration of spin-dependent scattering in the bulk of the granules and on their surfaces
(interfaces). The expressions obtained for σ
xx(ω) and σ
xy(ω) are found to be sensitive to scattering on the surfaces and in the bulk of the granules, as well as to granule size, the
type of impurities trapped on the interfaces, the frequency of the incident light, and the external magnetic field. For granular
thin films exhibiting giant magnetoresistance, the theory predicts significant relative changes in the optical reflection
and transmission coefficients when the sample is magnetized to saturation (0.02% and 20%, respectively, for giant magnetoresistance
of the order of 20%), as well as Kerr and Faraday effects that are nonlinear with respect to magnetization.
Zh. éksp. Teor. Fiz. 116, 1762–1769 (November 1999) 相似文献
8.
Yu. O. Mikhailovsky D. E. Mettus A. P. Kazakov V. N. Prudnikov Yu. E. Kalinin A. S. Sitnikov A. Gerber D. Bartov A. B. Granovsky 《JETP Letters》2013,97(8):473-477
The concentration dependence of the coefficient R s characterizing the anomalous Hall effect (AHE) has been studied by measuring the electrical resistivity ρ, magnetoresistance, and the magnetic field dependence of magnetization and Hall resistivity of (Co41Fe39B20) x (Al-O)100 ? x nanocomposite thin films. It has been demonstrated that the AHE coefficient increases by more than an order of magnitude with a decrease in the percentage x of the amorphous ferromagnetic metal from 60 to 30 and its behavior is described by the relation R s ~ ρ m , where m = 0.46 ± 0.1. At the same time, the coefficient characterizing the normal Hall effect grows by a factor of less than 10. The mechanisms underlying the giant Hall effect in nanocomposites have been discussed. 相似文献
9.
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
10.
A theoretical framework for treating the effects of magnetic fieldH on the pairing theory of superconductivity is considered, where the field is taken in an arbitrary direction with respect
to crystal axes. This is applicable to closed, as well as open normal state Fermi surface (FS), including simple layered metals.
The orbital effects of the magnetic field are treated semiclassically while retaining the full anisotropic paramagnetic contribution.
Explicit calculations are presented in the limits |H| → |H
c2(T)|,T ∼ 0 andT →T
c(|H|), |H| ∼ 0. Effects of weak nonmagnetic impurity scattering, without vertex corrections, have also been taken into account in a
phenomenological way. The final results for the case of open FS and layered materials are found to differ considerably from
those of the closed FS. For example, an important parameter,h(T=0)=|Hc2(0)|/[-Tδ|H
c2
T|δT]T{s0} for the case of a FS open ink
z-direction with thek
z-bandwidth, 4t
3, very small compared to the Fermi energy,E
F, is close to 0.5906, compared to 0.7273 for the closed FS, in the clean limit. Analytical results are given for the magnetic
field dependence ofT
c and the temperature dependence of H
c2 for a model of layered superconductors with widely open FS. For a set of band structure parameters for YBa2Cu3O7 used elsewhere, we find reasonable values for the upper critical fieldH
c2(0), the slope (dH
c2/dT)T
c0, anisotropic coherence lengths ζi(T=0),i=x, y, z, and (dT
c/d|H|)|H| → 0. 相似文献
11.
The dependences of the electrical resistivity ρ and the Hall coefficient R on the magnetic field have been measured for single-crystal samples of the n-Bi0.93Sb0.07 semiconductor alloys with electron concentrations in the range 1 × 1016 cm−3 < n < 2 × 1018 cm−3. It has been found that the measured dependences exhibit Shubnikov-de Haas quantum oscillations. The magnetic fields corresponding
to the maxima of the quantum oscillations of the electrical resistivity are in good agreement with the calculated values of
the magnetic fields in which the Landau quantum level with the number N intersects the Fermi level. The quantum oscillations of the Hall coefficient with small numbers are characterized by a significant
spin splitting. In a magnetic field directed along the trigonal axis, the quantum oscillations of the resistivity ρ and the
Hall coefficient R are associated with electrons of the three-valley semiconductor and are in phase with the magnetic field. In the case of
a magnetic field directed parallel to the binary axis, the quantum oscillations associated both with electrons of the secondary
ellipsoids in weaker magnetic fields and with electrons of the main ellipsoid in strong magnetic fields (after the overflow
of electrons from the secondary ellipsoids to the main ellipsoid) are also in phase. In magnetic fields of the quantum limit
ħω
c
/2 ≥ E
F, the electrical conductivity increases with an increase in the magnetic field: σ22(H) ∼ H
k
. A theoretical evaluation of the exponent in this expression for a nonparabolic semiconductor leads to values of k close to the experimental values in the range 4 ≤ k ≤ 4.6, which were obtained for samples of the semiconductor alloys with different electron concentrations. A further increase
in the magnetic field results in a decrease of the exponent k and in the transition to the inequality σ22(H) ≤ σ21(H). 相似文献
12.
A method is developed for reconstructing the dependence of the surface impedance of Z
s
(H) of high-T
c
superconductors (HTSCs) on the amplitude of an ac magnetic field from measurements of the nonlinear radiophysical characteristics
of microwave HTSC resonators. It is shown that the nonuniformity of the structure of the electromagnetic field in a resonator
lead to integral equations for Z
s
(H). The corresponding integral equations are obtained for certain types of resonators. The errors of the conventional methods
employing algebraic relations for Z
s
(H) are analyzed. The Tikhonov regularization method, developed in the theory of ill-posed inverse problems, is used to reconstruct
the functions Z
s
(H) from the integral equations. Numerical experiments on the reconstruction of Z
s
(H) were performed, and the requirements for the accuracies and other characteristics of the experimental data were determined
from them.
Zh. Tekh. Fiz. 68, 78–86 (August 1998) 相似文献
13.
A study is reported of the electrical resistance and thermopower of FexNi80−x
Cr20 fcc alloys within the 44⩽x⩽70 at. % range. It is shown that, at low temperatures, they typically exhibit minima in the temperature dependences of electrical
resistance. The appearance of these anomalies is attributed to the formation of a gap in the conduction electron spectrum
due to the onset of long-or short-range antiferromagnetic order in the alloys. The effect of magnetic field on the magnetic
states appearing in frustrated antiferromagnetic alloys has been studied, and an H-T magnetic phase diagram constructed.
Fiz. Tverd. Tela (St. Petersburg) 40, 101–105 (January 1998) 相似文献
14.
The current-voltage characteristics of granular YBa2Cu3O6.95 high-temperature superconductor samples have been measured at a temperature of 77.3 K in external transverse magnetic fields
H
ext with a strength of up to H
ext ≈ 500 Oe for low transport current densities (0.1 A/cm2 ≤ j ≤ 0.6 A/cm2). The current-voltage characteristics obtained have been used to construct dependences of the magnetoresistance ρ on the
quantities j (ρ(j)
Hext=const) and H
ext(ρ(H
ext)
j = const). It has been revealed that the current and field dependences of the magnetoresistance exhibit anomalies at H
ext ≥ H
c1g
, where H
c1g
is the lower critical field of superconducting grains. A comparative analysis of the dependences ρ(j)H
ext = const and ρ(H
ext)
j = const has made it possible to develop concepts regarding the influence of the processes of redistribution of the magnetic field
between grain boundaries and superconducting grains on the transport and galvanomagnetic properties of granular high-temperature
superconductors. It has been established that the field dependences of the magnetoresistance exhibit specific features associated
with the beginning of penetration of Josephson vortices into grain boundaries in the magnetic field H
c1J
and with the breaking of a continuous chain of Josephson junctions in the magnetic field H
c2J
. 相似文献
15.
A. D. Balaev V. A. Gavrichkov S. G. Ovchinnikov V. K. Chernov T. G. Aminov G. G. Shabunina 《Journal of Experimental and Theoretical Physics》1998,86(5):1026-1029
In the magnetic field range ΔH=8–60 kOe we observed and studied the anomalous oscillations in the magnetic field dependence of the resistance and magnetization
of single crystals of n-HgCr2Se4. The absence of periodicity in 1/H in the ΔH=8–20 kOe range can be explained by the non-Fermi-liquid behavior of the electron subsystem and agrees with the theory of
the de Haas-van Alphen in systems with intermediate valence. In stronger fields, ΔH=20–60 kOe, the amplitude of the fundamental harmonic decreases, with the number and amplitude of the higher-order harmonics
increasing. As a result, noise is superimposed on the signal as magnetic field strength grows. The temperature dependence
of the magnetization is the sum of the monotonic spin-wave contribution and the oscillating part.
Zh. éksp. Teor. Fiz. 113, 1877–1882 (May 1998) 相似文献
16.
K. Yu. Guslienko 《Physics of the Solid State》1998,40(10):1697-1701
A phenomenological model is developed for the giant magnetoresistance of granular media comprising ferromagnetic granules
in a nonmagnetic metal matrix. Both volume and surface spin-dependent scattering by the ferromagnetic granules are taken into
account. The internal electric fields are inhomogeneous because of the different conductivities of the granules and the matrix.
The dependence of the effective conductivity of the medium on the average magnetization is calculated and used to explain
the giant magnetoresistance effect. The magnetoresistance is plotted as a function of the volume concentration of ferromagnetic
granules and the granule radius. Experiments on Co-Cu and Co-Ag granular films are discussed.
Fiz. Tverd. Tela (St. Petersburg) 40, 1871–1875 (October 1998) 相似文献
17.
V. A. Kul’bachinskii I. A. Churilov P. D. Mar’yanchuk R. A. Lunin 《Journal of Experimental and Theoretical Physics》1997,85(5):989-993
The galvanomagnetic properties of single crystals of the semimagnetic semiconductors Hg1−x
MnxTe1−y
Sey with 0.01<y<0.1 and x=0.05 and 0.14 in the temperature range 4.2–300 K are investigated. The features of the temperature dependence of the Hall
coefficient R
H and the complicated behavior of R
H in a magnetic field are attributed quantitatively to the existence of three groups of current carriers, viz., electrons and
two types of holes, for which the temperature dependences of the densities and mobilities are obtained. A transition from
p-type to n-type conductivity is observed as the Se content is increased, and the negative magnetoresistance simultaneously gives way
to positive magnetoresistance.
Zh. éksp. Teor. Fiz. 112, 1809–1815 (November 1997) 相似文献
18.
M. K. Aliev G. R. Alimov T. M. Muminov B. A. Olimov Kh. I. Turkmenov I. Kholbaev L. I. Leonyuk R. F. Rumi 《Physics of the Solid State》1999,41(1):11-14
Y1Ba2Cu3O7−x
single crystals are investigated near T
c
≈92 K in fields 0<H⩽9 kOe using a modified ESR spectrometer. The temperature modulation method is used for the first time, together with the
traditional magnetic modulation method, to detect microwave responses in single crystals. Superconducting-transition peaks
shifted relative to one another in temperature and differing in shape are observed in the temperature dependence of the corresponding
signals ∂R/∂H and ∂R/∂T (R — microwave absorption). The evolution of these peaks as a function of the field and the angle π between H and the c axis of the single crystal is traced. It is shown that the difference in the temperature dependences of the derivatives ∂R/∂H and ∂R/∂T is due to the broadening of the superconducting transition characteristic of HTSCs.
Fiz. Tverd. Tela (St. Petersburg) 41, 14–17 (January 1999) 相似文献
19.
Yu. N. Ovchinnikov A. M. Dyugaev 《Journal of Experimental and Theoretical Physics》1999,88(4):696-709
The magnetic field dependence of the average spin of a localized electron coupled to conduction electrons with an antiferromangetic
exchange interaction is found for the ground state. In the magnetic field range μH∼0.5T
c
(T
c
is the Kondo temperature) there is an inflection point, and in the strong magnetic field range μH≫T
c
, the correction to the average spin is proportional to (T
c
/μ H)2. In zero magnetic field, the interaction with conduction electrons also leads to the splitting of doubly degenerate spin
impurity states.
Zh. éksp. Teor. Fiz. 115, 1263–1284 (April 1999)
Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor 相似文献
20.
K. Winzer 《Zeitschrift für Physik B Condensed Matter》1986,64(2):159-163
The temperature dependence of the Hall coefficient and the magnetic field dependence of the Hall resistivity of CeCu6 have been determined in the temperature range 80 mK<T<10 K and in magnetic fields up to 10T. The Hall coefficientR
H shows a very strong temperature dependence with two extrema and a change of sign, and the Hall resistivity xy has a strong field dependence with up to two changes of sign. The observed behavior can partially be explained by the field- and temperature dependence of the skew scattering contribution to the Hall coefficient. 相似文献