共查询到20条相似文献,搜索用时 359 毫秒
1.
S. I. Vorob’ev D. S. Andrievskii S. G. Barsov A. L. Getalov E. I. Golovenchits E. N. Komarov S. A. Kotov A. Yu. Mishchenko V. A. Sanina G. V. Shcherbakov 《Journal of Experimental and Theoretical Physics》2016,123(6):1017-1024
A comparative μSR study of ceramic samples of the EuMn2O5 and Eu0.8Ce0.2Mn2O5 multiferroics is performed in the temperature range from 15 to 300 K. It is found that the Ce doping of the EuMn2O5 sample slightly reduces the temperature of the magnetic phase transition from T N = 45 K for the EuMn2O5 sample to T N = 42.5 K for the Eu0.8Ce0.2Mn2O5 sample. Below the temperature T N for both samples, there are two types of localization of a thermalized muon with different temperature dependences of the precession frequency of the magnetic moment of the muon in an internal magnetic field. The higher frequency in both samples refers to the initial antiferromagnetic matrix. The behavior of this frequency in Eu0.8Ce0.2Mn2O5 follows the Curie–Weiss law with the exponent β = 0.29 ± 0.02, which differs from the value β = 0.39 standard for 3D Heisenberg magnetics and is observed in EuMn2O5, because of the strong frustration of the doped sample. The temperature-independent low frequency is due to the presence of Mn3+–Mn4+ ferromagnetic pairs located along the b axis of the antiferromagnetic matrix and in the regions of phase separation, which contain such ion pairs and e g electrons recharging them. In both samples, polarization losses are the same (about 20%) and are associated with the formation of Mn4+–Mn4+ + Mu complexes near Mn3+–Mn4+ ferromagnetic pairs. In the temperature interval from 25 to 45 K, the separation of the Eu0.8Ce0.2Mn2O5 structure into two fractions where the relaxation rates of polarization of muons differ by an order of magnitude is revealed. This effect is due to a change in the state of regions of phase separation (1D superlattices) at the indicated temperatures. Such effect in EuMn2O5 is significantly weaker. 相似文献
2.
Kiichirou?Koyasu Wilko?Westh?user Marco?Niemietz Jan?Heinen Gerd?Gantef?r 《Applied Physics A: Materials Science & Processing》2009,96(3):679-684
Using time-resolved photoelectron spectroscopy, the decay channels of AuO2− and Au2O2− following photoexcitation with 3.1-eV photons have been studied. For AuO2−, a state with a rather long lifetime of 30 ps has been identified. Its decay path could not be determined but photodesorption
can be excluded. For Au2O2−, the spectra indicate O2 desorption after 3.1-eV photoexcitation on a time scale of 1 ps. While comparing these results on Au
n
O2− with analogous data on Ag
n
O2− clusters, a discernible pattern emerges: for dissociatively bound O2(AuO2−, Ag3O2−), there are long-living excited states which do not decay by oxygen desorption, while for molecular chemisorption (Au2O2−, Ag2O2−, Ag4O2−, Ag8O2−), the 3.1-eV photoexcitation triggers fast O2 desorption with a high quantum yield. 相似文献
3.
L. T. Denisova N. V. Belousova N. A. Galiakhmetova V. M. Denisov E. O. Golubeva 《Physics of the Solid State》2018,60(7):1303-1307
Differential scanning calorimetry has been used to study the influence of temperature on the heat capacity of synthesized vanadates Zn2V2O7, (Cu0.56Zn1.44)V2O7, and (Cu1.0Zn1.0)V2O7. It is found that dependences Cp = f(T) have extremes. The thermodynamic properties of Zn2V2O7 have been determined. 相似文献
4.
High field electrical switching on blown films of MoO3(60%)–P2O5(40%), MoO3(50%)–WO3(10%)–P2O5(40%), and MoO3(45%)–WO3(15%)–P2O5(40%) having different thicknesses was studied and compared. Switching was observed using two terminal samples. S-type current–voltage
characteristic (current-controlled negative resistance—CCNR) with memory was observed in molybdenum–phosphate glasses, but
N-type characteristic (voltage-controlled negative resistance—VCNR) with threshold in tungsten–molybdenum–phosphate glasses
was observed. The important observation was that with the addition of WO3 to binary MoO3–P2O5 led to a change of I–V characteristic from CCNR with memory to VCNR with threshold. The measurements of density and molar volume showed linear relation
between MoO3 content and density which decreased with the increase of MoO3 content. The samples’ thickness had no significant effect on threshold voltage. The attained results also indicated that
the electrode material had no effect on switching property of devices. The switching behavior of the devices did not show
any dependence on the polarity of the applied voltage. In terms of the effect of heat on the switching behavior of molybdenum–phosphate
glasses, it was found that threshold voltage decreases with increasing of temperature. Finally, the switching phenomenon was
explained by thermal (formation of crystalline filaments) and electronic models. 相似文献
5.
Yu. A. Lupitskaya D. A. Kalganov K. V. Abdrakhmanova 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2017,11(1):87-91
Features of the formation of lead-ferroniobate compounds in the xBaCO3–(1 – x)PbO–Fe2O3–Nb2O5 system by solid-phase synthesis are investigated. For perovskite-type lead-ferroniobate solid solution, a single-phase concentration region is revealed at 1233 K. The crystalline structures of the synthesized compounds are refined using Rietveld analysis and the Pm3?m and R3m space groups. Ceramic samples of lead ferroniobate are studied by scanning electron microscopy. 相似文献
6.
N. A. Kalanda G. G. Gorokh M. V. Yarmolich A. A. Lozovenko E. Yu. Kanyukov 《Physics of the Solid State》2016,58(2):351-359
A method has been developed for fabricating nanoporous matrices based on anodic aluminum oxide for the deposition of ferromagnetic nanoparticles in them. The modes of deposition of strontium ferromolybdate thin films prepared by the ion-plasma method have been worked out, and the magnetic and magnetoresistive properties, structure, and composition of the films have been investigated. It has been revealed that the microstructure and properties of the strontium ferromolybdate films deposited by ionplasma sputtering depend on the deposition rate and the temperature of the substrate. Based on the measurement of the electrical resistivity of nanoheterostructures in a magnetic field, it has been found that the magnetoresistance reaches 14% at T = 15 K and B = 8 T, which is due to the manifestation of tunneling magnetoresistance. 相似文献
7.
Huanfu Zhou Hong Wang Minghui Zhang Xi Yao 《Applied Physics A: Materials Science & Processing》2009,95(2):513-516
A new Li2O–Nb2O5–TiO2 (LNT) ceramic with the Li2O:Nb2O5:TiO2 mole ratio of 5.5:1:7 was prepared by solid state reaction route. The phase and structure of the ceramic were characterized
by X-ray diffraction and scanning electron microscopy (SEM). The microwave dielectric properties of the ceramics were studied
using a network analyzer. The microwave dielectric ceramic has low sintering temperature (∼1075°C) and good microwave dielectric
properties of ε
r=42, Q×f=16900 GHz (5.75 GHz), and τ
f
=63.7 ppm/°C. The addition of B2O3 can effectively lower the sintering temperature from 1075 to 875°C and does not induce degradation of the microwave dielectric
properties. Obviously, the LNT ceramics can be applied to microwave low temperature-cofired ceramics (LTCC) devices. 相似文献
8.
A series of glasses [(TeO2)
x
(B2O3)1−x
]1−y
[Ag2O]
y
with x = 70 and y = 10, 15, 20, 25 and 30 mol% were synthesised by rapid quenching. Longitudinal and shear ultrasonic velocity were measured
at room temperature and at 5 MHz frequency. Elastic properties, Poisson's ratio, microhardness, softening temperature and
Debye temperature have been calculated from the measured density and ultrasonic velocity at room temperature. The experimental
results indicate that the elastic constants depend upon the composition of the glasses and the role of the Ag2O inside the glass network is discussed. Estimated parameters based on Makishima–Mackenzie theory and bond compression model
were calculated in order to analyse the experimental elastic moduli. Comparison between the experimental elastic moduli data
obtained in the study and the calculated theoretically by the mentioned above models has been discussed. 相似文献
9.
V. Ta Phuoc C. Sellier B. Corraze E. Janod C. Marin 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(2):181-186
Polarized infrared reflectivity was measured as a function of temperature on a quasi-one dimensional β-Sr0.17V2O5 single crystal. Along the conduction direction, the optical conductivity exhibits a weak electronic background in the far
infrared and a large mid infrared band. Sum rule analysis shows that both far infrared and midinfrared bands arise from 3d
vanadium electrons. As temperature is decreased, the mid infrared band slightly narrows and redshifts, but does not exhibit
drastic change. In contrast, the spectral weight grows at low frequencies and peaks appear in the phonon energy range. In
the transverse direction, β-Sr0.17V2O5 shows an insulator-like behaviour at all temperatures. The optical response is compared with the iso-electronic and iso-structural
compound β-Na0.33V2O5. Although spectra are very similar in both compounds at room temperature, their temperature dependence differs. However,
some general trends indicate that charge carriers are of the same nature in both compounds. The results suggest that electron-
phonon coupling is relevant to explain the optical properties of β-Sr0.17V2O5. The optical response along the conducting direction is assigned to an adiabatic small polaron absorption, in intermediate
or strong electron-phonon coupling regime. In this framework, the optical conductivity is in qualitative agreement with recent
Dynamical Mean Field Theory results over a wide temperature range. 相似文献
10.
Neutron diffraction and magnetic studies of a TbBaCo2O5 + γ polycrystalline sample with a perovskite-like layered structure have revealed that spontaneous magnetization appears at 305 K and decreases sharply below 200 K. It has been shown that the crystal structure is described by space group Pmmm with a 2a p · a tp · 2a p unit cell. The magnetic structure in the high-temperature magnetic phase consists of the G-type antiferromagnetic and ferromagnetic components, whereas the magnetic structure in the low-temperature phase is a G-type antiferromagnetic. The ferromagnetic component appears due to the noncollinearity of the magnetic moments of Co3+ ions, which are in the high-spin state in pyramids and in the low-spin state in octahedrons. The antiferromagnetic component is present in the octahedral sublattice, because oxygen vacancies are partially ordered. 相似文献
11.
Yan-Ying Wang Yan-Jing Hao Qiong-Yu Lai Ji-Zheng Lu Yuan-Duan Chen Xiao-Yang Ji 《Ionics》2008,14(1):85-88
A new Li4Ti5O12–SnO2 composite anode material for lithium-ion batteries has been prepared by loading SnO2 on Li4Ti5O12 to obtain composite material with improved electrochemical performance relative to Li4Ti5O12 and SnO2. The composite material was characterized by X-ray diffraction and scanning electron microscopy. The results indicated that
SnO2 particles have encapsulated on the surface of the Li4Ti5O12 uniformly and tightly. Electrochemical results indicated that the Li4Ti5O12–SnO2 composite material increases the reversible capacity of Li4Ti5O12 and has good cycling reliability. At a current rate of 0.5 mA/cm2, the material delivered a discharge capacity of 236 mAh/g after 16 cycles. It suggests the existence of synergistic interaction
between Li4Ti5O12 and SnO2 and that the capacity of the composite is not a simple weighted sum of the capacities of the individual components. In the
composite material, SnO2 can act as a bridge between the spinel particles to reduce the interparticle resistance and as a good material for the Li
intercalation/deintercalation. Thus, electrochemical performance of the Li4Ti5O12 spinel can be improved by the surface modification with SnO2, and the stability of Li4Ti5O12 also serves to buffer the internal stress caused by the volume changes in lithium insertion and extraction reactions. 相似文献
12.
O. M. Bordun I. I. Kukharskii V. V. Dmitruk V. G. Antonyuk V. P. Savchin 《Journal of Applied Spectroscopy》2008,75(5):681-684
Luminescence photoexcitation spectra of α-Bi2O3 ceramics are investigated. Luminescence spectra were deconvoluted into fundamental components using the Alentsev-Fok method.
It is established that the luminescence spectra of α-Bi2O3 ceramics consist of three fundamental bands with maxima at 2.75, 2.40, and 1.97 eV. A comparison of the results with those
from an investigation of luminescence of various modifications of bismuth oxide and bismuth germanates suggests that luminescence
of these compounds is caused by radiation processes that occur in structural complexes that contain the bismuth ion in a nearest
oxygen environment.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 672–676, September–October, 2008. 相似文献
13.
R. Nigam A. V. Pan S. X. Dou 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,74(4):429-436
We investigate in detail the dc magnetization and nonlinear ac susceptibility behavior of the superconducting ferromagnet
RuSr2Eu1.5Ce0.5Cu2O10-
δ (Ru1222) to develop a comprehensive understanding of the spin glass and superparamagnetism in this material.
The structural properties of the system result in the formation of magnetic (ferromagnetic) clusters of different sizes, shapes
and properties.
The magnetic clustering of the system leads to observation of various features in dc magnetization and ac susceptibility consistent
with superparamagnetism and cluster spin glass states, which can coexist or stand alone, depending on the temperature range
considered.
Experimental results of magnetic measurements in combination with their analysis have enabled us to explain and distinguish
these phenomena, as well as to propose a temperature dependent scenario of the system behavior. 相似文献
14.
V. I. Nikolaichik L. A. Klinkova 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(12):1418-1420
Samples of high-temperature superconducting oxide EuBa2Cu3O6 + δ (Eu-123) with total cationic composition Eu: Ba: Cu = 1: 2: 3 are investigated by means of local X-ray microanalysis and high-resolution transmission electron microscopy. The cationic nonstoichiometry of Eu-123 oxide is revealed. The particles of the studied samples are inhomogeneous in structure on the nanoscale, with two types of inhomogeneities: one with typical sizes of one to several nanometers, and one with typical sizes of 10 to 20 nm, respectively. 相似文献
15.
We investigated influence of bidirectional square wave current with long periods and dc current on the evolution of the voltage-time
(V - t) curves in superconducting polycrystalline bulk Y1Ba2Cu3O7-δ (YBCO) material at the temperatures near the critical temperature. In a well-defined range of amplitudes and periods of driving
current, and temperatures, novel type of non-linear dynamic responses was observed by means of the V-t curves. It was seen
that such a non-linear response to bidirectional square wave current sometimes reflects itself as regular sinusoidal-like
voltage oscillations. The sinusoidal-like and non-sinusoidal oscillations were discussed mainly in terms of the dynamic competition
between pinning and depinning and
significant relaxation effects which appear in this competing process. The density fluctuations associated with the current
induced self-magnetic flux (SMF) lines and semi-elastic coupling of SMF lines with the pinning centers were also considered
as possible physical mechanisms in the interpretation of the experimental results. 相似文献
16.
Silver-based quaternary glasses were prepared by splat quenching technique. X-ray diffraction and differential scanning calorimetry
were done for confirming their amorphous nature. The conductivity of the glasses was measured in the frequency range from
1 Hz to 32 MHz from room temperature to 373 K. Conductivity data, which obeys the Arrhenius type behavior, shows minimum at
30 mol% Ag2O, suggesting that the conductivity mechanisms are different above and below these two regions. The minimum in conductivity
is accompanied by an inverse behavior of activation energy. Experimental data suggests that a polaron hopping mechanism operates
in the electronically conducting domain of 20 ≤ × ≤ 30, and an interstitial pair mechanism operates in the ionically conducting
domain of 35 ≤ × ≤ 55. 相似文献
17.
M. V. Gorev V. S. Bondarev I. N. Flerov Ph. Sciau J. -M. Savariault 《Physics of the Solid State》2005,47(12):2304-2308
The temperature dependence of the heat capacity of two compositions in the solid solution system BaTi1?xZrxO3 (x = 0.25, 0.35) was measured using adiabatic calorimetry. In the T-x phase diagram, these compounds occupy positions near the crossover from conventional ferroelectric behavior to the relaxor state. Both compounds reveal diffuse heat capacity anomalies: two anomalies in the temperature ranges 250–350 and 150–200 K at x = 0.35 and one anomaly within the range ~150–320 K at x = 0.25. The results obtained are discussed together with structural and dielectric measurements. 相似文献
18.
We present strong non-linear dynamic responses developing due to magnitude
and type of driving current in bulk polycrystalline superconducting
Y1Ba2Cu3O7-δ sample at zero magnetic field.
Several novel types of dynamic changes induced by the transport current were
observed via the time evolution of the voltage (V - t curves). The physical
observations appearing in V - t curves were interpreted mainly with the
reorganization of driving current in a multiply connected network of
weak-link structure. It was found that such a dynamic process could cause an
enhancement or suppression in superconducting order parameter due to the
magnitude of the driving current and coupling strength of weak link
structure together with the chemical and anisotropic states of the sample.
It was shown that the general behavior of decays evolving in V - t curves is
consistent with an exponential relation which is analogous to the glassy
state relaxation. 相似文献
19.
L. Ma A. K. Ray 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,81(1):103-113
Hybrid density functional theory has been used to systematically
study the electronic, geometric, and magnetic properties of strongly
correlated materials PuO2±x
, UO2±x
, and
U0.5Pu0.5O2±x
with x = 0.25. The calculations have been
performed using the all-electron full- potential
linearized augmented plane
wave plus local orbitals basis (FP-L/APW+lo)
method. Each compound has been studied at the ferromagnetic (FM) and
anti-ferromagnetic (AFM) configurations with and without spin-orbit coupling
(SOC) and full geometry optimizations. The optimized lattice constants, bulk
moduli, and band gaps are reported. Total energy calculations indicate that
the ground states are AFM for all compounds studied here and the band gaps
are typically higher than 1.0 eV, characteristic of semiconductors. The
total energy is lowered significantly and the band gaps increase with the
inclusion of SOC. The chemical bonds between the actinide metals and oxygen
atoms are primarily ionic in character. 相似文献
20.
Composite solid electrolytes in the system (1???x)Li2CO3–xAl2O3, with x?=?0.0–0.5 (mole), were synthesized by a sol–gel method. The synthesis carried out at low temperature resulted in voluminous and fluffy products. The obtained materials were characterized by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy/energy-dispersive X-ray, Fourier transform infrared spectroscopy and AC impedance spectroscopy. Structural analysis of the samples showed an amorphous feature of Li2CO3 and traces of α-LiAlO2, γ-LiAlO2 and LiAl5O8. The prepared composite samples possess high ionic conductivities at 130–180 °C on account of the presence of lithium aluminates as well as the formation of a high concentration of an amorphous phase of Li2CO3 via this sol–gel preparative technique. 相似文献