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1.
V. Ya. Kravchenko 《Journal of Experimental and Theoretical Physics》2002,94(3):603-626
A set of kinetic equations for the distribution functions of carriers differing both by the energy spectrum and by the spin projection is used to investigate the conductivity of a multilayer sample (alternating layers of magnetic (m) and nonmagnetic (n) metals). The boundary conditions on the interlayer surfaces are derived in an approximation in which the surface scattering is divided into “specular” and “diffuse” scattering and is characterized by scattering parameters (reflection and transmission) which are related to each other by relations dependent on spin projections and on the type of spectrum. The problem on the longitudinal (with respect to the layers) current is treated; situations are analyzed in which the variation in conductivity due to the change of mutual orientation of magnetization in successive m layers from antiparallel to parallel may be of the order of the values of the conductivity proper (the so-called giant magnetoresistance effect). This is possible only in the case of thin (compared with the free path) n layers (in m layers, the ratios of the characteristic dimensions may be arbitrary) and in the mandatory presence of specular surface scattering. Results are given for different possible ratios of Fermi momenta of electron groups and for different fractions of specular and diffuse scattering. The possibility of realizing the effects of both signs is demonstrated. 相似文献
2.
《Superlattices and Microstructures》1998,24(4):263-267
The magnetoresistance of antidot lattices and the magnetic field dependence of the three-terminal resistance of transverse electron focusing (TEF) devices is studied in a 2DEG in the lattice-matched In0.53Ga0.47As/InP heterojunction system, as a function of temperature. Ballistic effects are observed in both types of mesoscopic devices at temperatures exceeding 100 K, and are considerably more robust than Shubnikov–de Haas (SdH) oscillations. Two effects influence the decay in the amplitude of the magnetoresistance peaks in the antidot structures, and of the focusing peaks in the TEF devices: the thermal smearing of the Fermi surface, and the increase in the electron scattering time with increasing temperature due to the increase in electron–phonon scattering. We deduce the temperature dependencies of the scattering times for the different geometries.Copright 1998 Academic Press 相似文献
3.
本文就声子散射与电离杂质散射的两种散射机构探讨了半导体n型锗的横向磁阻。在简并强磁场情况下,得出声子散射机构在〈111〉,〈110〉和〈100〉三个方向上锗的横向磁阻的表示式。磁阻的平均值的相对大小(ρt<111>)/ρ0:(ρt<110>)/ρ0:(ρt<100>)/ρ0=1:1.7:1.1,并且磁阻具有振荡形式。在非简并量子极限情况下分别对声子散射和杂质散射得出锗的横向磁 相似文献
4.
The effect of specimen size on the electrical resistivity at 4.2 K of copper whiskers having transverse dimensions in the
order of the electron mean-free path was measured. The experimental data are interpreted by means of a modified Nordheim formula
adapted to the exact theory of Dingle. Assuming for copper the value of the productQ
0·λ obtained from the free electron model a specularity parameterp for the surface scattering of conduction electrons is deduced from the diameter dependence of the sample resistivity. Values
ofp=0.45 (up to 0.66 in an individual case) andp=0.18 are calculated exhibiting that significant specular reflection is present. Differences in the amount of specular reflection
appear to arise from differences in the microscopically observed surface conditions of the whiskers. 相似文献
5.
A. V. Frolov A. P. Orlov P. D. Grigoriev V. N. Zverev A. A. Sinchenko P. Monceau 《JETP Letters》2018,107(8):488-492
The magnetoresistance of a TbTe3 two-dimensional conductor with a charge-density wave (CDW) has been measured in a wide temperature range and in magnetic fields of up to 17 T. At temperatures well below the Peierls transition temperature and in high magnetic fields, the magnetoresistance exhibits a linear dependence on the magnetic field caused by the scattering of normal charge carriers by “hot” spots of the Fermi surface. In the sliding CDW regime in low magnetic fields, a qualitative change in the magnetoresistance has been observed associated with the strong scattering of carriers by the sliding CDW. 相似文献
6.
研究了典型的层状钙钛矿结构超导单晶Sr2RuO4在c方向的磁阻(Δρ/ρ0)(H∥ab,J∥c)的变化.实验发现,磁阻表现出强烈的各向异性,并且随着温度T的降低,磁阻效应越明显;当在平面ab内旋转磁场H的方向时,磁阻成周期性变化;实验表明,磁场沿(110)方向时,出现磁阻的极大值.分别从Sr2RuO4的费米面的各向异性、载流子散射率、c方向能带色散的各向异性等方面来解释这些输运性质.
关键词:
2RuO4')" href="#">Sr2RuO4
磁阻 相似文献
7.
S. I. Pesotskii R. B. Lyubovskii V. I. Nizhankovskii W. Biberacher M. V. Kartsovnik K. Andres J. A. A. J. Perenboom N. D. Kushch E. B. Yagubskii H. Kobayashi 《Journal of Experimental and Theoretical Physics》2000,90(3):527-534
Quantum oscillations of de Haas-van Alphen and Shubnikov-de Haas and semiclassical angular oscillations of the magnetoresistance have been observed in the quasi-two-dimensional organic metal α-(BETS)2TlHg(SeCN)4. The quantum oscillations are connected with the cylindrical part of the Fermi surface. The angular oscillations are associated with the carrier motion on both the cylindrical part and quasi-planar sheets of the Fermi surface. The values of the Dingle temperature, T D ≈ 2–3 K, and the effective mass, m* ≈ 1.03m 0, have been defined. The possibility of the weakening of multibody interactions has been shown in this compound. 相似文献
8.
Tabulated pseudopotentials are used to obtain the 4 OPW wave functions and Fermi surface of Al and the scattering potentials of Ge, Mg, Zn, and Ga impurities. The anisotropic relaxation time is calculated in Born approximation and iterating the Boltzmann equation for zero magnetic field. The coefficients of Hall effect, transverse and longitudinal magnetoresistance are described by Fermi surface integrals. Without adjusted parameters our numerical results agree surprisingly well with experiment. 相似文献
9.
A. A. Sinchenko Yu. I. Latyshev A. P. Orlov A. A. Ivanov P. Monceau 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(2):199-204
We have measured the Hall effect and the transverse
magnetoresistance in NbSe3 single crystals. In the liquid helium
temperature range we observed an absolute negative magnetoresistance
(NMR) — the value of the resistance under magnetic field being much
lower than that at zero field — in NbSe3 single crystals with a
thickness less than 5 μm with the magnetic field oriented in the
(b, c) plane. We show that this NMR effect is observed in the
magnetic field range in which the Hall constant changes its sign.
The results are qualitatively explained by the change of the surface
scattering contribution to the magnetoconductance in the magnetic
field range near the Hall voltage zero crossing. 相似文献
10.
L. N. Luk’yanova Yu. A. Boikov V. A. Danilov O. A. Usov M. P. Volkov V. A. Kutasov 《Physics of the Solid State》2014,56(5):941-947
The galvanomagnetic properties of p-type bismuth telluride heteroepitaxial films grown by the hot wall epitaxy method on oriented muscovite mica substrates have been investigated. Quantum oscillations of the magnetoresistance associated with surface electronic states in three-dimensional topological insulators have been studied in strong magnetic fields ranging from 6 to 14 T at low temperatures. The cyclotron effective mass, charge carrier mobility, and parameters of the Fermi surface have been determined based on the results of analyzing the magnetoresistance oscillations. The dependences of the cross-sectional area of the Fermi surface S(k F), the wave vector k F, and the surface concentration of charge carriers n s on the frequency of magnetoresistance oscillations in p-type Bi2Te3 heteroepitaxial films have been obtained. The experimentally observed shift of the Landau level index is consistent with the value of the Berry phase, which is characteristic of topological surface states of Dirac fermions in the films. The properties of topological surface states of charge carriers in p-type Bi2Te3 films obtained by analyzing the magnetoresistance oscillations significantly expand fields of practical application and stimulate the investigation of transport properties of chalcogenide films. 相似文献
11.
R. B. Lyubovskiĭ S. I. Pesotskiĭ J. A. A. J. Perenboom E. I. Zhilyaeva O. A. Bogdanova R. N. Lyubovskaya 《Journal of Experimental and Theoretical Physics》2008,106(6):1137-1141
Quantum magnetization and magnetoresistance oscillations are detected in the quasi-two-dimensional organic metal (BEDO-TTF)5[RbHg(SCN)4]2 for the first time. The magnetization oscillation spectrum corresponds to a calculated Fermi surface provided that a magnetic breakdown is realized. The magnetoresistance oscillation spectrum contains additional frequencies, one of which can unambiguously be related to quantum interference. An analysis of the angular dependence of the magnetoresistance oscillation amplitude indicates that the many-body interactions in this metal are weak. 相似文献
12.
H. Guyot J. Dumas M. V. Kartsovnik J. Marcus C. Schlenker I. Sheikin D. Vignolles 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(1):25-30
The purple molybdenum bronze KMo6O17 is a quasi-two-dimensional
compound which shows a Peierls transition towards a commensurate metallic
charge density wave (CDW) state. High magnetic field measurements have
revealed several transitions at low temperature and have provided an unusual
phase diagram “temperature-magnetic field”. Angular studies of the
interlayer magnetoresistance are now reported. The results suggest that the
orbital coupling of the magnetic field to the CDW is the most likely
mechanism for the field induced transitions. The angular dependence of the
magnetoresistance is discussed on the basis of a warped quasi-cylindrical
Fermi surface and provides information on the geometry of the Fermi surface
in the low temperature density wave state. 相似文献
13.
M. Heinecke K. Winzer J. Noffke H. Kranefeld H. Grieb K. Flachbart Yu. B. Paderno 《Zeitschrift für Physik B Condensed Matter》1995,98(2):231-237
To examine the Fermi surface of LuB12, measurements of the de Haas-van Alphen (dHvA) effect were made at temperatures between 0.35 and 2 K in magnetic fields up to 12 Tesla. Oscillations in the susceptibility occurred above 5 Tesla in any field direction relative to the single crystal sample. From the Fourier transform of the data obtained, we conclude the Fermi surface of both conduction bands to have multiple extremal cross sections. For some of these orbits, the temperature dependence of the dHvA signal was investigated to determine the corresponding cyclotron mass. For a better understanding, a Full Potential Linearized Augmented Plane Wave-(FLAPW-) band structure calculation was carried out and the shapes of the Fermi surfaces were determined. In addition, we investigated the transverse magnetoresistance as a function of the field and the field direction. Its anisotropy, as well as the Shubnikov-de Haas (SdH) oscillations occurring in certain geometries, are in agreement with the results of the dHvA measurements. 相似文献
14.
D. Vignolles A. Audouard V. N. Laukhin J. Béard E. Canadell N. G. Spitsina E. B. Yagubskii 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(4):383-388
The oscillatory magnetoresistance spectrum of the
organic metal (BEDO)5Ni(CN)4. 3C2H4(OH)2 has
been studied up to 50 T, in the temperature range from 1.5 K to
4.2 K. In high magnetic field, its Fermi surface corresponds to a
linear chain of quasi-two-dimensional orbits coupled by magnetic
breakdown (MB). The scattering rate consistently deduced from the
data relevant to the basic α and the MB-induced β
orbits is very large which points to a significant reduction of
the chemical potential oscillation. Despite of this feature, the
oscillations spectrum exhibits many frequency combinations. Their
effective masses and (or) Dingle temperature are not in agreement
with either the predictions of the quantum interference model or
the semiclassical model of Falicov and Stachowiak. 相似文献
15.
G. Seibold F. Becca F. Bucci C. Castellani C. Di Castro M. Grilli 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(1):87-97
The concept of frustrated phase separation is applied to investigate its consequences for the electronic structure of the
high T
c
cuprates. The resulting incommensurate charge density wave (CDW) scattering is most effective in creating local gaps in k-space when the scattering vector connects states with equal energy. Starting from an open Fermi surface we find that the
resulting CDW is oriented along the (10)- and (or) (01)-direction which allows for a purely one-dimensional or a two-dimensional
“eggbox type” charge modulation. In both cases the van Hove singularities are substantially enhanced, and the spectral weight
of Fermi surface states near the M-points, tends to be suppressed. Remarkably, a leading edge gap arises near these points, which, in the eggbox case, leaves
finite arcs of the Fermi surface gapless. We discuss our results with repect to possible consequences for photoemission experiments.
Received 14 June 1999 相似文献
16.
U. Beierlein C. Hess C. Schlenker J. Dumas R. Buder D. Groult E. Steep D. Vignolles G. Bonfait 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(2):215-226
Resistivity, thermoelectric power and magnetotransport measurements have been performed on single crystals of the quasi two-dimensional
monophosphate tungsten bronzes (PO2)4(WO3)2m for m
=5 with alternate structure, between 0.4 K and 500 K, in magnetic fields of up to 36 T. These compounds show one charge density
instability (CDW) at 160 K and a possible second one at 30 K. Large positive magnetoresistance in the CDW state is observed. The anisotropic Shubnikov-de Haas and de Haas-van Alphen
oscillations detected at low temperatures are attributed to the existence of small electron and hole pockets left by the CDW
gap openings. Angular dependent magnetoresistance oscillations (AMRO) have been found at temperatures below 30 K. The results are discussed in terms of a weakly corrugated cylindrical Fermi surface. They are shown to be consistent
with a change of the Fermi surface below 30 K.
Received 23 November 1999 and Received in final form 23 March 2000 相似文献
17.
The theoretically predicted and long-sought intrinsic saturation of the transverse magnetoresistance of the alkali metals
has finally been observed after sufficiently reducing the masking effect of the large superimposed linear magnetoresistance
which is attributed to such classical considerations as geometry, Hall angle and non-uniform current distribution. The observed
saturation values were about 100 times smaller than those observed previously in complicated metals but were still much too
large to be explained only by Fermi surface anisotropy. The saturation phenomena contradict Kohler's rule but can be plausibly
explained by mean free path anisotropy due predominantly to electron-phonon scattering mechanisms. 相似文献
18.
P. Entel 《Zeitschrift für Physik B Condensed Matter》1976,23(4):321-330
The influence of Fermi surface anisotropy on the superconducting transition temperature of strong coupling superconductors containing magnetic and nonmagnetic impurities is investigated. It is found that the concentration dependent transition temperature shows typical departures from the corresponding curve of a single-band isotropic superconductor. These departures occur either for very small (
ij) or for very large (
ij0) interband scattering of conduction electrons on nonmagnetic impurities (i, j label the states in different bands or in different zones of the Fermi surface). In the case of unequal cut-off frequencies for different zones on the Fermi surface it is shown that all effects of unequal cut-offs can be eliminated by introducing effective electron-phonon pairing interactions. In the presence of impurities these effective pairing interactions become weakly impurity dependent giving rise to a new pair-weakening mechanism. Quantitative results on the basis of a simple two-band or two-zone model are presented. 相似文献
19.
The magnetoresistance anisotropy of 2H?NbSe2 was studied at 9.3 K and 35 K. Data indicate that the Fermi surface above and below the charge-density-wave onset temperature includes one or more sheets that are highly elongated (and possibly open) along the [0001] direction. The magnetoresistance at 9.3 K exhibits an anomalous linear dependence on magnetic field for all field directions studied, similar to that reported previously for [0001] 相似文献
20.
Petr Ondrejkovic Martin Kempa Maxim Savinov Petr Bednyakov Jiri Kulda Philippe Bourges 《Phase Transitions》2016,89(7-8):808-815
ABSTRACTUniaxial relaxor ferroelectric Sr0.61Ba0.39Nb2O6 single crystal has been investigated in the vicinity of its phase transition using neutron scattering and dielectric spectroscopy. A global-type thermal hysteresis is evidenced by both techniques in the ferroelectric phase and up to about 15 K above Tc. In addition, a part of the transverse neutron diffuse scattering in the 001 Brillouin zone, presumably related to static nanodomain structure, can be suppressed by prior poling the crystal in electric field of 3 kV/cm. The remaining part of the transverse neutron diffuse scattering and the real part of permittivity show a similar temperature dependence. The temperature position of the maximal scattering intensity Tmax depends significantly on the scattering wave vector. Tmax shifts monotonically to higher temperature with the increasing wave vector in all investigated cooling and heating regimes. It is concluded that the critical fluctuations have space correlations which depend on frequency and wave vector. 相似文献