共查询到20条相似文献,搜索用时 15 毫秒
1.
A. I. Ponomarev L. D. Sabirzyanova A. A. Ivanov A. S. Moskvin Yu. D. Panov 《JETP Letters》2005,81(8):394-399
Nominally electron doped antiferromagnetic tetragonal nonsuperconducting Nd2?xCe x CuO4+δ(x=0.12) has been shown to manifest strong angular dependence of the in-plane magnetoresistance on the orientation of the external magnetic field within the ab plane in many aspects similar to that observed in hole doped YBa2Cu3O7?δ and La2?xSrxCuO4. Specific fourfold angular magnetoresistance anisotropy amounting to several percents was observed in oxygen annealed films at low temperatures and in an external magnetic field up to 5.5 T. The strong temperature dependence and fourfold symmetry observed in our sample points to a specific role of rare-earth (Nd) ions in magnetoresistance anisotropy. At low temperature T = 1.4 K, we observed the unusual transformation of magnetoresistance response with increasing the external magnetic field, which seems to be a manifestation of a combined effect of a crossover between first and second order spin-flop transitions and a field-dependent rare-earth contribution to quasiparticle magnetotransport. 相似文献
2.
T. B. Charikova G. I. Kharus N. G. Shelushinina O. E. Petukhova A. A. Ivanov 《Journal of Experimental and Theoretical Physics》2012,114(3):496-502
We report on the results of analyzing the temperature dependences of the resistivity of the Nd2 − x
Ce
x
CuO4 + δ electronic superconductor with x = 0.14 (underdoped range), x = 0.15 (optimal doping), and x = 0.18 (overdoped range) and with various degrees of annealing in an oxygen-free atmosphere in magnetic fields up to H = 90 kOe (H ‖ c, J ‖ ab) in the temperature range T = (0.4–300) K. It is shown that the observed differences in the dependences of the slope of the upper critical field (dHc2 /dT)|Tc (dH_{c2} /dT)|_{T_c } on the degree of disorder in the Nd2 − x
Ce
x
CuO4 + δ system upon a change in the cerium doping level indicate a change in the symmetry of d-type pairing to anisotropic s pairing. 相似文献
3.
The magnetic structure of intermetallic compounds Ce2Fe17 − x
Mn
x
(0 ≤ x ≤ 3) was studied using neutron diffraction. The neutron diffraction patterns measured at 4.2 K contain satellites indicating
a modulated structure with the wave vector k = [0, 0, τ]. As the concentration x increases, the value of τ increases, while the average magnetic moment of Fe/Mn atoms decreases. A change in the magnitudes
of the average magnetic moment and wave vector k is explained by competition between exchange interactions at distances of nearest neighbor transition element atoms. 相似文献
4.
O. A. Savinskaya A. P. Nemudry A. N. Nadeev S. V. Tsybulya N. Z. Lyakhov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(8):1053-1054
The structure of high-temperature SrFe1 − x
Mo
x
O3 − z
(0 ≤ x ≤ 0.5) phases was studied. Such studies are necessary to understand the mechanism of oxygen transport in membrane materials
used for high-temperature oxygen separation. 相似文献
5.
A. V. Germanenko G. M. Minkov O. E. Rut A. A. Sherstobitov B. N. Zvonkov 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(2):219-222
The temperature dependence of the conductivity of the two-dimensional hole gas in an asymmetric GaAs/In x Ga1 ? x As/GaAs quantum well has been investigated. It is shown that fast spin relaxation leads to metallic-like behavior of the temperature dependence of the conductivity. 相似文献
6.
T. E. Hargreaves J. Akimitsu D. F. Brewer N. E. Hussey H. Noma A. L. Thomson 《Czechoslovak Journal of Physics》1996,46(3):1213-1214
Measurements are presented of the low temperature specific heat of three polycrystalline samples of Pr2?x Ce x CuO4 in magnetic fields of 0, 2 and 4 Tesla. The residual specific heat contribution in zero field seems to have a form αT n (n<1) for all of the samples, whether superconducting or non-superconducting. The behaviour in magnetic fields is similar to that reported for other high Tc superconductors where a change in exponent of the residual term occurs at some crossover temperature in magnetic fields. 相似文献
7.
L. T. Denisova L. G. Chumilina N. V. Belousova V. M. Denisov 《Physics of the Solid State》2016,58(9):1933-1937
Orthovanadates Ce1–xBixVO4 (1 ≥ x ≥ 0) have been produced by solid-phase synthesis from initial oxides CeO2, Bi2O3, and V2O5 upon step-by-step burning. The high-temperature heat capacity of Ce1–xBixVO4 has been measured by differential scanning calorimetry. The experimental data on Cp = f(T) were used to calculate the thermodynamic properties (the enthalpy changes, the entropy changes, and the Gibbs energy). 相似文献
8.
G. M. Abramova G. Petrakovskiy R. Zuberek A. Nabialek M. Boem V. Sokolov A. F. Bovina 《JETP Letters》2009,90(3):207-210
The magnetostriction of Fe
x
Mn1 − x
S (x = 0.27) single crystals in strong magnetic fields up to 120 kOe has been investigated. It has been found that the magnetostriction
reaches colossal values (±3 × 10−4) atypical of compounds of 3d elements. It has been found that the magnetostriction changes sign when varying temperature and magnetic field; this behavior
indicates an important role of the spin-phonon interactions in the formation of the magnetic order in solid solutions of iron-manganese
sulfides. 相似文献
9.
G. I. Makovetskiĭ A. I. Galyas O. F. Demidenko K. I. Yanushkevich L. I. Ryabinkina O. B. Romanova 《Physics of the Solid State》2008,50(10):1826-1829
This paper reports on the results of investigations into the structural, electrical, and thermoelectrical properties of sulfides Co x Mn1 ? x S (0 ≤ x ≤ 0.4) in the temperature range 80–950 K. It is established that the thermopower coefficient α decreases significantly with an increase in the cobalt concentration in the lattice of the α-MnS compound. The Co x Mn1 ? x S compounds with cobalt concentrations in the range 0 ≤ x ≤ 0.3 are semiconductors with hole conduction (α > 0), whereas the compound with x = 0.4 exhibits metallic conduction (α < 0). It is found that the band gap E g of the compounds under investigation varies in the range from 1.46 eV for α-MnS (x = 0) to 0.26 eV for Co x Mn1 ? x S (x = 0.4). 相似文献
10.
L. S. Parfen’eva I. A. Smirnov H. Misiorek J. Mucha A. Jezowski F. Ritter W. Assmus 《Physics of the Solid State》2002,44(7):1212-1217
Samples of various compositions were obtained in the homogeneity range of the Yb-In-Cu system (YbIn1?xCu4+x), from stoichiometric (YbInCu4) to YbIn0.905Cu4.095. Their lattice constant (at 300 K and in the range 20–100 K), total thermal conductivity, and electrical resistivity (from 4 to 300 K) were measured. All the compositions studied exhibited an isostructural phase transition at T v ?40–80 K driven by a change in the Yb ion valence state. It was shown that within the YbIn1?xCu4+x homogeneity range, the lattice thermal conductivity κph decreases with increasing x; at T>T v , κph grows with temperature and the Lorenz number (which enters the Wiedemann-Franz law for the electronic component of thermal conductivity) of the light heavy-fermion system, to which YbIn1?xCu4+x belongs for T<T v , behaves as it does in classical heavy-fermion systems. Thermal cycling performed through T v generates stresses in the YbIn1?xCu4+x lattice, which entails an increase in the electrical resistivity and a decrease in the thermal conductivity. “Soft anneal” (prolonged room-temperature aging of samples) makes the effect disappear. A conclusion is drawn as to the nature of the effects observed. 相似文献
11.
New Rb3PO4-based ceramic materials with high rubidium-cation conductivity in the Rb3–2x Pb x PO4 system have been synthesized and studied. Introduction of Pb2+ cations leads to a sharp increase in the conductivity of rubidium orthophosphate due to formation of cation vacancies and, at temperatures 350–550°C, also due to the stabilization of high-temperature cubic modification Rb3PO4. At high temperatures, the electrolytes prepared have very high ion conductivity higher than 10–1 S cm–1 at 700°C, which is higher than the values previously obtained in similar systems with additions of tin and cadmium ions. The factors influencing the transport properties of the materials under study are discussed. 相似文献
12.
I. O. Troyanchuk V. A. Khomchenko H. Szymczak M. Baran 《Journal of Experimental and Theoretical Physics》2003,97(6):1231-1239
The magnetic properties of manganites of the Nd1?xCaxMnO3 system with x≤0.15 have been studied. It is shown that, in the 0.06≤x≤0.1 interval, the results can be interpreted using a model according to which the concentrational transition from a weakly ferromagnetic (WFM) state (x=0) to a ferromagnetic (FM) state (x>0.15) proceeds via a mixture of the exchange-coupled FM and WFM phases. In the vicinity of T=9 K, samples with 0.06≤x≤0.1 exhibit a spontaneous magnetic phase transition involving reorientation of the magnetization vectors of the WFM and the exchange-coupled FM phases. In the temperature interval between 5 and 20 K, a sample with the composition Nd0.92Ca0.08MnO2.98 exhibits metamagnetic behavior. Magnetic phase diagrams in the H?T and T?x coordinates are presented. The appearance of the spin-reorientation transitions is explained in terms of the magnetic analog of the Jahn-Teller effect with allowance for the fact that, according to the neutron diffraction data, the magnetic moments of neodymium ions in the FM phase are parallel to the magnetic moments of manganese ions. 相似文献
13.
G. S. Patrin V. V. Beletskiĭ N. V. Volkov D. A. Velikanov O. V. Zakieva 《Journal of Experimental and Theoretical Physics》2007,105(1):1-3
The results of experimental investigation of magnetic and electric properties of Fe1?x Dy x Si crystals are reported. It is shown that the magnitude and position of the anomaly observed in the temperature dependences of magnetization are controlled to a considerable extent by the external magnetic field. It is found that the introduction of Dy ions leads to a weak magnetoresistive effect. 相似文献
14.
V. G. Kytin V. A. Kul’bachinskii D. S. Glebov L. I. Burova A. R. Kaul O. V. Reukova 《Journal of Experimental and Theoretical Physics》2010,111(2):225-230
The results of experiments on electrical conductivity and magnetic properties of thin cobalt-doped zinc oxide films are reported.
The results indicate the predominance of the hoping conduction mechanism at low temperatures and the band mechanism at high
temperatures. An increase in the cobalt concentration from 1.5 to 6.3 at % leads to the reduction of the electrical conductivity
of the films. The contribution of hopping conduction to the conductivity increases due to a decrease in the crystallinity
of the films and localization of a part of electron states upon an increase in the cobalt concentration. For cobalt-containing
films, a hysteresis of the magnetic moment as a function of the magnetic field is observed. The dependence of the shape of
the magnetization curves on the cobalt concentration is irregular. The paramagnetic contribution to the magnetic susceptibility
increases with the cobalt concentration. 相似文献
15.
S. F. Dubinin V. I. Sokolov A. V. Korolev S. G. Teploukhov Yu. G. Chukalkin V. D. Parkhomenko N. B. Gruzdev 《Physics of the Solid State》2008,50(6):1087-1090
The spin system of a Zn1 ?x Cr x Se bulk crystal (x = 0.045) was studied using thermal-neutron diffraction and magnetic measurements. Previously, it was reported in the literature that thin films (~200 nm thick) of this type of semiconductors exhibit a ferromagnetic order. In this study, the ferromagnetic order is found to be absent in the bulk crystal. 相似文献
16.
Charge density calculations and electronic band structures for Ga
x
Al1 − x
Sb with x = 1.0, 0.5 and 0.0 are presented in this work. The calculations are performed using the empirical pseudopotential method.
The charge density is computed for a number of planes, i.e. z = 0.0, 0.125 and 0.25 A
0 by generating the potential through a number of potential parameters available in the literature. The virtual crystal approximation
was applied for the semiconducting alloy. The characteristics of the band structure and charge density are observed to be
affected by the potential parameters. Calculated band gaps and the nature of gaps are in good agreement with the experimental
data reported. The ionicity is also reasonably in good agreement with other scales proposed in the literature; however the
formulation needs to be improved. The present work also demands indirect experimental band gap for the alloy.
相似文献
17.
Mitsuo Kataoka 《Czechoslovak Journal of Physics》1996,46(4):1857-1858
To clarify the origin of the giant magnetoresistance (GMR) observed in La1?x A x MnO3 (A2+=Sr2+, Pb2+, Ba2+ and Ca2+), we have investigated theoretically the electrical resistivity ρ of carriers in the background of Mn spins which interact with each other through the double exchange interaction. It has been found that extraordinarily large pin fluctuations caused by the instability of the ferromagnetic state are responsible for the transport anomalies including the GMR. 相似文献
18.
The electronic structure and ground state parameters of B2 RuAl-based refractory alloys have been investigated in the framework of the density functional theory using the exact muffin-tin
orbital method in combination with the coherent potential approximation. It has been demonstrated that the number of states
at the Fermi level for the Ru1 − x
Me
x
Al alloys as a function of the alloying metal content has a minimum, which indicates a change in the Fermi surface topology
and the presence of specific features in the behavior of elastic constants. It has been concluded that the electronic structure
of the alloys can be described in terms of the rigid band model. The nonlinear variations of the lattice parameters of the
alloys has been explained. 相似文献
19.
Hyoungjoon Kim Yong-Hee Park Ilsoo Kim Jungwon Kim Heon-Jin Choi Woochul Kim 《Applied Physics A: Materials Science & Processing》2011,104(1):23-28
The recent demonstration of thermal conductivity of rough electrolessly etched Si nanowire (Hochbaum et al., Nature, 451:163,
2008) attracted a lot of interest, because it could not be explained by the existing theory; thermal conductivity of rough Si
nanowires falls below the boundary scattering of the thermal conductivity. However, nanoscale pores presented in the nanowires
(Hochbaum et al., Nano Letters, 9:3550–3554, 2009) hinder one to be fully convinced that the surface roughness solely made a contribution to the significant reduction in thermal
conductivity. In this study, we synthesized vapor–liquid–solid (VLS) grown rough Si1−x
Ge
x
nanowire and measured and theoretically simulated thermal conductivity of the nanowire. The thermal conductivity of rough
Si0.96Ge0.04 nanowire is an order of magnitude lower than that of bulk Si0.96Ge0.04 and around a factor of four times lower than that of smooth Si0.96Ge0.04 nanowire. This significant reduction could be explained by the fact that the surface roughness scatters medium-wavelength
phonons, whereas the long-wavelength phonons are scattered by phonon boundary scattering, and the short-wavelength phonons
are scattered by alloy scattering. 相似文献
20.
A. P. Menushenkov R. V. Chernikov V. V. Sidorov K. V. Klementiev P. A. Alekseev A. V. Rybina 《Journal of Experimental and Theoretical Physics》2007,105(1):99-104
The particular features of the local electronic and local crystal structures of the mixed-valence compound Sm1 ? x Y x S are studied by the XAFS spectroscopy methods in the temperature range 20–300 K for the yttrium concentration x = 0.17, 0.25, 0.33, and 0.45. The temperature behavior of the valence of Sm, as well as of the lengths and the Debye-Waller factors of the bonds Sm-S, Sm-Sm(Y), Y-S, and Y-Sm(Y), has been determined. The violation of the Vegard law has been observed. A model for the estimation of the energy width of the 4f level and of its position with respect to the Fermi level is proposed. 相似文献