共查询到20条相似文献,搜索用时 31 毫秒
1.
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
2.
Charge density wave (CDW) depinning and sliding regimes have been studied in NbSe3 at low temperatures down to 1.5 K under magnetic field of 19 T oriented along the c-axis. We found that the threshold field for CDW depinning becomes temperature independent below T
0 ≈ 15 K. Also CDW current to frequency ratio characterizing CDW sliding regime increases by factor 1.7 below this temperature.
The results are discussed as a crossover from thermal fluctuation to tunneling CDW depinning at T < T
0. Besides, we found that CDW sliding strongly suppresses the amplitude of Shubnikov-de Haas oscillations of magnetoresistance. 相似文献
3.
The magnetoresistance of NbSe3 single crystals is measured as a function of magnetic field for different field orientations. A possibility of studying the Fermi surface by using the dependence of the Shubnikov-de Haas oscillation phase on the rotation angle of the magnetic field is demonstrated. The results of the study show that the quasi-momenta of carriers that are not condensed in the charge density wave are predominantly oriented along the conducting chains. 相似文献
4.
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
5.
Y. B. Lin Z. G. Huang Y. M. Yang S. Wang S. D. Li F. M. Zhang Y. W. Du 《Applied Physics A: Materials Science & Processing》2011,104(1):143-147
(La0.7Sr0.3MnO3)
x
/(YBa2Cu3O7)
y
composites were prepared by mixing La0.7Sr0.3MnO3 powders and the sol–gel-derived YBa2Cu3O7 matrix, followed by high-temperature calcinations. Their structural, magnetic properties and magnetoresistance effect have
been investigated systematically. A giant positive magnetoresistance (PMR) at low magnetic field is observed at low temperatures.
In the case of (La0.7Sr0.3MnO3)1/(YBa2Cu3O7)9 composite, the PMR achieves 260% under a magnetic field of 5800 Oe. However, the PMR value sharply decreases with increasing
temperature and no magnetoresistance effects are found above metal-insulator transition temperature. The enhancement of spin-dependent
scattering at the grain boundaries should be responsible for the observed PMR. In addition, the temperature dependence of
resistance under magnetic field could be explained by the competition between diamagnetism and paramagnetism in YBCO phase.
At low temperature, the diamagnetism is predominant over paramagnetism and the interface scattering between LSMO grains is
enhanced correspondingly. As a result, the low-temperature resistance increases and large PMR appears. 相似文献
6.
L. S. Lobanovsky I. O. Troyanchuk S. V. Trukhanov S. N. Pastushonok V. I. Pavlov 《Technical Physics》2003,48(9):1159-1164
The electrical properties of and the magnetoresistive effect in RCu3Mn4O12 (R=rare-earth ion or Th) are studied. In all compounds of this series, the magnetoresistive effect amounts to 20% at liquid nitrogen temperature in the presence of a field of 0.9 T. An increase in the magnetoresistance with decreasing temperature and a high sensitivity to weak magnetic fields at low temperatures point to the intergranular nature of the effect. The magnetoresistance shows a peak in the vicinity of the Curie temperature TC. Based on the dependences of the magnetoresistance on an external magnetic field, it is assumed that the magnetoresistance peak near TC is related to the charge carrier scattering by magnetic inhomogeneities as in substituted orthomanganites. We believe that the magnetoresistance value near the magnetic ordering temperature depends on the synthesis conditions and the effect of the intergranular spacer on the transport properties of these compounds. 相似文献
7.
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
8.
L. S. Ewe I. Hamadneh H. Salama N. A. Hamid S. A. Halim R. Abd-Shukor 《Applied Physics A: Materials Science & Processing》2009,95(2):457-463
The magnetotransport and magnetoresistive (MR) properties of manganese-based La0.67Ca0.33MnO3 perovskite with different grain sizes are reported. The electrical resistivity was measured as a function of temperature
in magnetic fields of 0.5 and 1 T. The insulator–metal transition temperature, T
IM, shifted to a higher temperature with the application of the magnetic field. In zero field, T
IM is almost constant (∼271 K) for all samples except for the sample with the largest grain size, where T
IM=265 K. The temperature dependence of resistivity was fitted with several equations in the metallic (ferromagnetic) region
and the insulating (paramagnetic) region. The density of states at the Fermi level, N(E
F), and the activation energy of electron hopping were estimated by fitting the resistivity versus temperature curves. The
ρ–T
2 curves are nearly linear in the metallic regime, but the ρ–T
2.5 curves exhibit a deviation from linearity. The variable range hopping model and small polaron hopping model fit the data
well in the high-temperature region, indicating the existence of the Jahn–Teller distortion that localizes the charge carriers.
MR was found to increase with an increase in the magnetic field, an effect which is attributed to the intergrain spin tunneling
effect. 相似文献
9.
L. Seetha Lakshmi K. Dörr K. Nenkov A. Handstein V. S. Sastry K.-H. Müller 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):115-121
We report the charge state modification effects at the Mn site on the ground
state properties of colossal magnetoresistive manganites. Ta5+
substitution results in an appreciable increase in the lattice parameters
and unit cell volume due to increased Mn3+ concentration. The
ferromagnetic-metallic ground state modifies to a cluster glass insulator
for
. The reduction in the transition temperatures with
increasing x is ∼39 K/at.%. Besides the modification of majority carrier concentration due to increased Mn3+ concentration and enhanced local structural effects, the local
electrostatic potential of the substituent seems to contribute to the
unusually strong reduction of the transition temperatures of the compounds.
Thermo magnetic irreversibility just below Curie temperature (Tc),
non-saturation of magnetization, two distinct magnetic transitions in ac
susceptibility in an appropriate static field: close to Tc and other at
low temperature (the spin freezing temperature (Tg)) and non-stationary
dynamics with a characteristic maximum in the magnetic viscosity close to
Tg confirm a cluster glass state for
. These results
find additional support from a linear low temperature magnetic specific heat
of x = 0.10 with a characteristic broad maximum close to Tg. 相似文献
10.
A. Yu. Mollaev I. K. Kamilov R. K. Arslanov T. R. Arslanov U. Z. Zalibekov V. M. Novotortsev S. F. Marenkin 《JETP Letters》2010,91(9):478-480
The magnetic susceptibility χ/χ0 and the longitudinal Δρ
zz
/ρ0 and transverse Δρ
xx
/ρ0 magnetoresistances have been measured as functions of the hydrostatic pressure P ≤ 7 GPa at room temperature in the high-temperature ferromagnetic semiconductor Cd0.7Mn0.3GeAs2 with a chalcopyrite structure and the Curie temperature T
c = 355 K. A pressure-induced metamagnetic transition from the low-magnetization state to the high-magnetization state has
been observed in Cd0.7Mn0.3GeAs2 near the magnetic ordering temperature. This transition is accompanied by the hysteresis of the magnetic susceptibility and
magnetoresistance. 相似文献
11.
S. I. Vorob’ev E. I. Golovenchits V. P. Koptev E. N. Komarov S. A. Kotov V. A. Sanina G. V. Shcherbakov 《JETP Letters》2010,91(10):512-517
The magnetic properties of the EuMn2O5 multiferroic (samples consisting of single crystals and ceramic samples) have been investigated by the muon-spin-relaxation
(μSR) method in the temperature range of 10–300 K. Below the magnetic ordering temperature T
N = 40 K, the loss of the polarization of muons and the effect of the external magnetic field have been observed. Both phenomena
can be explained by an additional channel of the depolarization of muons owing to the appearance of muons in a medium with
a low electron density due to the charge separation process (the redistribution of the electron density in the phase transition
process). The “memory” phenomenon has been revealed in a sample in the external magnetic field; the memory relaxation time
depends on the size of the structure units of the samples (single crystals or ceramic grains). 相似文献
12.
We present LDA band structure of novel hole doped high temperature superconductors (T
c
∼ 30 K) K
x
Fe2Se2 and Cs
x
Fe2Se2 and compare it with previously studied electronic structure of isostructural FeAs superconductor BaFe2As2 (Ba122). We show that stoichiometric KFe2Se2 and CsFe2Se2 have rather different Fermi surfaces as compared with Ba122. However at about 60% of hole doping Fermi surfaces of novel
materials closely resemble those of Ba122. In between these dopings we observe a number of topological Fermi surface transitions
near the Γ point in the Brillouin zone. Superconducting transition temperature T
c
of new systems is apparently governed by the value of the total density of states (DOS) at the Fermi level. 相似文献
13.
S. Sahling J. C. Lasjaunias R. Mélin P. Monceau G. Reményi 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):9-17
We have investigated the effect of the magnetic field (B) on the very
low-temperature equilibrium heat capacity ceq of the quasi-1 D organic
compound (TMTTF)2Br, characterized by a commensurate Spin Density
Wave (SDW) ground state. Below 1 K, ceq is dominated by a Schottky-like
AST-2 contribution, very sensitive to the experimental time scale,
a property that we have previously measured in numerous DW compounds. Under
applied field (in the range 0.2–7 T), the equilibrium dynamics, and hence
ceq extracted from the time constant, increases enormously. For B
≥ 2–3 T, ceq varies like B2, in agreement with a
magnetic Zeeman coupling. Another specific property, common to other
Charge/Spin density wave (DW) compounds, is the occurrence of metastable
branches in ceq, induced at very low temperature by the field exceeding
a critical value. These effects are discussed within a generalization to
SDWs in a magnetic field of the available Larkin-Ovchinnikov local model of
strong pinning. A limitation of the model when compared to experiments is
pointed out. 相似文献
14.
We present the results a study of structure by neutron diffraction and data on the magnetic properties (linear and nonlinear
(second and third order) susceptibilities) of polycrystalline La0.88MnO2.95. This compound exhibits an insulator-metal (IM) phase transition at T
IM
≈ 253 K (above the Curie temperature, T
C
≈ 244 K) and reveals colossal magnetoresistance. The crystal structure is found to be rhombohedral, and the space group is
R3c. Analysis of magnetic properties shows that at T* ≈ 258 K > T
C
, isolated paramagnetic clusters occur in the paramagnetic matrix; their concentration increases upon cooling. We observed
no noticeable differences between the temperature evolution of the clustered state of this manganite with its insulator-metal
transition and in the insulator La0.88MnO2.91. Possible scenarios of the paramagnet-ferromagnet and I-M transitions in a self-organized clustered structure are discussed. 相似文献
15.
A. Bhattacharyya S. Chatterjee S. Giri S. Majumdar 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(3):347-351
The magnetotransport and magnetic properties of the binary intermetallic compound Ho2In have been investigated. Clear signature of long range ferromagnetic order in the resistivity and the magnetization data
at TC = 85 K is observed. A further spin reorientation type transition is also apparent in our measured data at around Tt = 32 K. The sample exhibits negative magnetoresistance (peak value of –14% at 5 T) over a wide temperature range that extends
well above TC. Substantially large magneto-caloric effect is also observed in the sample (maximum value of –8.5 J kg-1K-1 for 0 → 5 T), which peaks around the TC of the sample. The observed magnetoresistance and magnetocaloric effect are related to the suppression of spin disorder by
an external magnetic field. Ho2In can be an interesting addition to the list of rare-earth based magnetic refrigerant materials showing magneto-caloric effect
across a second order phase transition. 相似文献
16.
A new method is described for attaining high magnetoresistance in inhomogeneous magnetic materials, which makes use of the formation of a depleted layer and a contact potential difference at the interface separating two semiconductors with different Fermi levels and the magnetic-field-induced variation in the contact potential difference and thickness of the interface layer. The proposed model of the magnetoresistive structure is realized on the basis of the HgCr2Se4 magnetic semiconductor. Layers of n-HgCr2Se4 up to a few tens of microns thick were prepared on the surface of p-HgCr2Se4 bulk single crystals by the diffusion technique. Application of a magnetic field stimulated in the structures a strong (by a factor of more than 200) increase of the current flowing through the n-layer. 相似文献
17.
We investigated the stability of magnetic moments in
Al69.8Pd12.1Mn18.1. This alloy exists in both, the
icosahedral (i) and the decagonal (d) quasicrystalline form.
The transition from the i- to the d-phase is achieved by a
simple heat treatment. We present the results of measurements of
the 27Al NMR-response, the dc magnetic susceptibility, and
the low-temperature specific heat of both phases. In the
icosahedral compound, the majority of the Mn ions carries a
magnetic moment. Their number is reduced by approximately a factor
of two by transforming the alloy to its decagonal variety. For
both compounds, we have indications for two different local
environments of the Al nuclei. The first reflects a low density of
states of conduction electrons and a weak coupling of the Al
nuclei to the Mn-moments. The second type of environment implies a
large d-electron density of states at the Fermi level and a
strong coupling to the magnetic Mn moments. Spin-glass freezing
transitions are observed at Tdecaf=12 K for the
decagonal, and Ticof=19 K for the icosahedral phase. 相似文献
18.
Vortex excitations have been detected at temperatures both below and above the critical temperature when investigating local
magnetic fields on the surface of a Bi2Sr2Ca2Cu3O10 single crystal by means of an electron paramagnetic resonance (EPR) probe. A thin layer of a diphenyl picrylhydrazyl organic
radical deposited on the crystal surface is used as the EPR probe. A narrow EPR signal makes it possible to detect weak distortions
of the magnetic field appearing at T ≿ T
c. The analysis of the temperature dependences of the resonance field and the EPR linewidth is thebasis of the assumption of
the vortex nature of magnetic excitations in this temperature range. 相似文献
19.
Yu. P. Sukhorukov A. V. Telegin A. B. Granovskii E. A. Gan’shina S. V. Naumov N. V. Kostromitina L. V. Elokhina J. Gonzalez 《Journal of Experimental and Theoretical Physics》2010,111(3):355-362
The reflection and magnetic reflection spectra, magnetic resistance, electrical properties, and equatorial Kerr effect in
La0.7Ca0.3MnO3 crystals have been complexly investigated. The measurements have been performed in wide temperature and spectral ranges in
magnetic fields up to 3.5 kOe. It has been found that magnetic reflection is a high-frequency response in the infrared spectral
range to the colossal magnetore-sistance near the Curie temperature. Correlation between the field and temperature dependences
of the magnetic reflection and colossal magnetoresistance has been revealed. The previously developed theory of the magnetorefractive
effect for metallic systems makes it possible to explain the experimental data at the qualitative level. Both demerits of
the theory of the magnetorefractive effect in application to the magnets and possible additional mechanisms responsible for
the magnetic reflection are discussed. 相似文献
20.
Features have been observed in the current dependences of the torsion angle, φ(I), for samples of a quasi-one-dimensional conductor TaS3 irradiated by a high-frequency (HF) field. The features appear at the same current values as the Shapiro steps on the current-voltage
characteristics, i.e., correspond to the synchronization of the motion of a charge-density wave (CDW) by the HF field. The
shape of the features in the φ(I) dependences indicates a decrease in the inhomogeneous deformation of the CDW under the synchronization conditions. The investigation
of torsion appears to be a highly sensitive method for determining the spatial coherence of the CDW. 相似文献