共查询到20条相似文献,搜索用时 936 毫秒
1.
N. E. Sluchanko A. V. Bogach V. V. Glushkov S. V. Demishev S. Yu. Gavrilkin N. Yu. Shitsevalova V. B. Filipov S. Gabani K. Flachbart 《JETP Letters》2010,91(2):75-78
The behavior of the specific heat near the quantum critical point x ∼ 0.3 in the Tm1 − x
Yb
x
B12 system has been studied. Detailed measurements have been performed on high-quality single-crystalline Tm0.74Yb0.26B12 samples within a wide temperature range of 1.9–300 K in a magnetic field up to 9 T. The temperature dependence of the magnetic
contribution to the specific heat has a logarithmic divergence of the form C/T ∼ lnT at T < 4 K, which can be attributed to the quantum critical behavior regime suppressed by the external magnetic field. The Schottky
anomaly of the magnetic contribution to the specific heat in Tm0.74Yb0.26B12 has been analyzed. 相似文献
2.
A comparative investigation of the magnetic properties of amorphous nanogranular composites (Co41Fe39B20)
x
(SiO
n
)100 − x
and (Co86Nb12Ta2)
x
(SiO
n
)100 − x
has been performed in the subpercolation region at temperatures in the range 4.2–300 K. The thermomagnetic dependences in
the range 4.2–300 K and the processes of magnetization reversal and remanent magnetization relaxation at liquid-helium temperatures
have been studied. It has been established that the average anisotropy constants of amorphous nanograins are equal to 3.6–7.0
kJ/m3 for the (Co41Fe39B20)
x
(SiO
n
)100 − x
composites and 5–8 kJ/m3 for the (Co86Nb12Ta2)
x
(SiO
n
)100 − x
composites. The fundamental differences in the concentration dependences of the anisotropy constant K
eff and the coercive force H
C
have been revealed for the two systems under investigation. It has been demonstrated that, as the concentration of the metal
phase increases, the quantities K
eff and H
C
increase for the (Co86Nb12Ta2)
x
(SiO
n
)100 − x
composites and decrease for the (Co41Fe39B20)
x
(SiO
n
)100 − x
composites. 相似文献
3.
A. V. Nazarenko A. G. Razumnaya M. F. Kupriyanov Yu. V. Kabirov A. G. Rudskaya P. Yu. Teslenko N. B. Kofanova 《Physics of the Solid State》2011,53(8):1599-1602
The (1 − x)BiFeO3−x
YMnO3 solid solutions have been found to undergo the following sequence of phase transformations with increasing x: R3c → Pbnm → C2 → Pnma → P63
cm. It has been established that the Pbnm and Pnma phases have different orientations of atomic displacements and can exhibit antiferroelectric properties. 相似文献
4.
The crystal structure and magnetic properties of Bi1 − x
A
x
FeO3 − x/2 (A = Ca, Sr, Pb, Ba), Bi1 − x
A
x
(Fe1 − x
Ti
x
)O3, and Bi1 − x
A
x
(Fe1 − x/2Nb
x/2)O3 solid solutions have been studied. It is shown that the homogeneous polar weak ferromagnetic state occurs in the vicinity
of a morphotropic phase boundary in the systems where dopant ions lead to the reduction of the unit cell volume in the polar
phase. In the case of A = Ca, the non-polar phase also exhibits weak ferromagnetism and the spontaneous magnetizations in
the polar and nonpolar phases differ only slightly. 相似文献
5.
The exciton absorption spectra of thin films of (Cs1 − x
Rb
x
)2CdI4 solid solutions have been investigated and the refractive index n(λ) in their transparency window in the concentration range of 0 ≤ x ≤ 1 has been measured. The exciton-band parameters and optical permittivity ɛ∞(x) have been found to linearly depend on the concentration. It is established that excitons are incorporated into the CdI2 sublattice of the solid solutions and belong to intermediate-coupling ones. The characteristics of excitons in ferroelastics
are compared with the corresponding parameters for CdI2, RbI, and CsI, which are used as components to synthesize ternary compounds. 相似文献
6.
Ruiting Sun Xiaoli Wang Jing Shi Le Wang 《Applied Physics A: Materials Science & Processing》2011,104(1):129-133
New perovskite solid solution ceramics of (1−x)BaTiO3-xBi(Mg1/2Ti1/2)O3 ((1−x)BT-xBMT, x≤0.09) were synthesized by the solid-state reaction technique. X-ray diffraction studies have revealed a stable single perovskite
structure for all samples. Dielectric measurements were carried out at different frequencies and temperatures. The polarization
evolutions with temperatures were measured to investigate the ferroelectric properties. All the compositions show features
of ferroelectrics with diffuse phase transition, though the temperature T
m
of their dielectric constant maximum ε
m
is frequency dependent. The dielectric constant peak ε(T) of (1−x)BT-xBMT ceramics become broad with increasing BMT content. During the temperature range of ε(T) peak summit, (1−x)BT-xBMT ceramics present quasi-linear dielectric phenomenon under high electric field with very high dielectric constant. 相似文献
7.
The atomic and magnetic structures of La0.5Ca0.5CoO3 cobaltite have been studied by the neutron diffraction technique at high pressures of up to 4 GPa in the 10- to 300-K temperature
range. The pressure dependences of the structural parameters have been obtained. The Curie temperature increases with the
pressure with the coefficient dT
C/dP = 1 K/GPa, demonstrating the stability of the ground ferromagnetic (FM) state. The pressure dependence of the ground FM state
in La0.5Ca0.5CoO3 is in drastic contrast with that for La1 − x
Ca
x
CoO3 at a lower calcium content (x < 0.3). For the latter compound, the pressure suppressed the ground FM state and a large negative pressure coefficient of
the Curie temperature (dT
C/dP ∼ −10 K/GPa) was observed. The nature of such a phenomenon is analyzed in the framework of the double exchange model also
taking into account the changes in the electron configuration of Co3+ ions. 相似文献
8.
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
9.
A. M. Pashaev B. G. Tagiev O. B. Tagiev Kh. B. Ganbarova 《Journal of Applied Spectroscopy》2011,78(2):266-271
We have ground bulk samples to obtain nanoparticles of (Ga2S3)1–x
(Eu2O3)
x
solid solutions, the sizes of which were determined using an atomic force microscope. The photoluminescence spectra of the
nanoparticles were studied in the temperature interval 77–300 K. We have established the mechanisms for emission and transfer
of energy from the matrix to the rare-earth ion, and we determined the Stokes shift (ΔS = 0.7 eV), the Huang–Rhys parameter
(S = 16), and the optical phonon energy (ħ−ω = 23 meV). 相似文献
10.
G. A. Komandin A. S. Prokhorov V. I. Torgashev E. S. Zhukova B. P. Gorshunov A. A. Bush 《Physics of the Solid State》2011,53(4):736-744
The spectra of complex permittivity of a Ba2Mg2Fe12O22 single crystal belonging to the family of Y-type hexaferrites have been measured over a wide temperature range (10–300 K) with the aim of determining the dynamic parameters
of the phonon and magnetic subsystems in the terahertz and infrared frequency ranges (3–4500 cm−1). A factor-group analysis of the vibrational modes has been performed, and the results obtained have been compared with the
experimentally observed resonances. The oscillator parameters of all nineteen phonon modes of E
u
symmetry, which are allowed by the symmetry of the Ba2Mg2Fe12O22 crystal lattice, have been calculated. It has been found that, at temperatures below 195 and 50 K, the spectral response
exhibits new absorption lines due to magnetic excitations. 相似文献
11.
V. A. Ryzhov P. L. Molkanov A. V. Lazuta V. V. Runov V. P. Khavronin I. O. Troyanchuk 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(10):1477-1480
We present the results from studying the magnetic properties (linear and nonlinear susceptibilities and the depolarization
of polarized neutrons) of Nd1 − x
Ba
x
MnO3 manganite, x = 0.3, with Curie temperature T
C ≈ 140 K and dielectric-to-metal transition temperature T
DM ≈ 129 K. Its critical behavior corresponds to that of an isotropic 3-D ferromagnet at temperatures above T*≈ 144 K, but a strong nonlinear response in weak magnetic fields and depolarization are observed at temperatures below T*. It is shown that this nontraditional behavior is related to the generation of ferromagnetic clusters in the paramagnetic
matrix that form a conducting percolative network at temperatures near T
DM. 相似文献
12.
Yu. G. Chukalkin A. E. Teplykh A. N. Pirogov D. G. Kellerman 《Physics of the Solid State》2010,52(12):2545-2551
The specific features of the crystal structure and the magnetic state of stoichiometric lithium manganite in the structurally
ordered Li[Mn2]O4 and disordered Li1 − δMnδ[Mn2 − δLiδ]O4 (δ = 1/6) states have been investigated using neutron diffraction, X-ray diffraction, and magnetic methods. The structurally
disordered state of the manganite was achieved under irradiation by fast neutrons (E
eff ≥ 1 MeV) with a fluence of 2 × 1020 cm−2 at a temperature of 340 K. It has been demonstrated that, in the initial sample, the charge ordering of manganese ions of
different valences arises at room temperature, which is accompanied by orthorhombic distortions of the cubic spinel structure,
and the long-range antiferromagnetic order with the wave vector k = 2π/c(0, 0, 0.44) is observed at low temperatures. It has been established that the structural disordering leads to radical changes
in the structural and magnetic states of the LiMn2O4 manganite. The charge ordering is destroyed, and the structure retains the cubic symmetry even at a temperature of 5 K. The
antiferromagnetic type of ordering transforms into ferrimagnetic ordering with local spin deviations in the octahedral sublattice
due to the appearance of intersublattice exchange interactions. 相似文献
13.
S. C. Ma D. H. Wang Z. C. Zhong L. J. Shen H. C. Xuan Q. Q. Cao Y. W. Du 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,84(2):167-171
Partial Nd-substitution effects on the magnetic and magnetocaloric properties in spin-reorientation Pr1−x
Nd
x
Co4Al (x = 0, 0.2, 0.4, 0.6, 0.8) alloys are investigated. All these alloys undergo two successive spin-reorientation transitions.
Accordingly, the successive positive and negative magnetic entropy changes (Δ
S
M
) for all these alloys are obtained. With the increase of Nd content, the spin reorientation transition temperatures increase
from about 170 and 186 K for x = 0 to room temperature (276 and 294 K) for x = 0.8, covering a wide temperature interval. More interestingly, the values of positive Δ
S
M
values increase gradually from 0.1 to 0.9 J/kg K−1, while the negative Δ
S
M
decrease from 1.3 to 0.2 J/kg K−1 in the field change of 10 kOe. In addition, the series has an appreciable relative cooling power, which is therefore suitable
to be used in a magnetic refrigerator. 相似文献
14.
K. P. Andryushin A. A. Pavelko I. A. Verbenko O. N. Razumovskaya L. A. Shilkina V. A. Aleshin L. A. Reznichenko 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(8):1082-1084
Ceramic samples of bismuth ferrite and solid solutions of Bi1 − x
A
x
FeO3 type (where A = Lu, Yb, Tm, Er, Ho, Dy, Tb, Gb, Eu, Sm, Nd, Pr, La; 0.05 ≤ x ≤ 0.20; Δx = 0.05) were prepared. Spectra of the real part of electrical conductivity were studied within the range 10−4–10−6 Hz. The dependence of the samples’ thermal stability and electrical conductivity on the size of the substituting ions was
established. 相似文献
15.
S. Sambasivam D. Paul Joseph Jung Hyun Jeong Byung Chun Choi Kwon Taek Lim Sang Su Kim Tae Kwon Song 《Journal of nanoparticle research》2011,13(10):4623-4630
Diluted magnetic semiconductor (DMS) nanoparticles of Sn1−x
Er
x
O2 (x = 0.0, 0.02, 0.04, and 0.1) were prepared by sol–gel method. The X-ray diffraction patterns showed SnO2 rutile structure for all samples with no impurity peaks. The decrease in crystallite size with Er concentration was confirmed
from TEM measurements (from 12 to 4 nm). The UV–Visible absorption spectra of Er-doped SnO2 nanoparticles showed blue shift in band gap compared to undoped SnO2. The electron spin resonance analysis of Er-doped SnO2 nanoparticles indicate Er3+ in a rutile lattice and also decrease in intensity with Er concentration above x = 0.02. Temperature-dependent magnetization studies and the inverse susceptibility curves indicated increased antiferromagnetic
interaction with Er concentration. 相似文献
16.
The preparation of (La9.33−2x/3Sr
x
□0.67−x/3)Si6O24O2 (0 ≤ x ≤ 2) samples with different amounts of cation vacancies is reported. Structure and unit-cell parameters were deduced by Rietveld
analysis of XRD patterns. Structural features that enhance oxygen conductivity in Sr-doped apatites are discussed. Up to three
components were detected in 29Si MAS-NMR spectra which change with the amount and distribution of cation vacancies. In general, oxygen conductivity increases
with the amount of vacancies at La1 (6h) sites, passing through a maximum for x = 0.4. In the case of activation energy, a minimum is detected near x = 1.2, indicating that entropic and enthalpic change in different ways. The presence of cation vacancies should enhance oxygen
hopping along c-axis; however, the analysis of the frequency dependence of conductivity suggests that oxygen motions are produced along three
axes. 相似文献
17.
The results of the experimental study of the specific features of changes in the temperature and concentration dependences
of the thermopower coefficient and the critical temperature in the Y0.85 − x
Ca0.15Pr
x
Ba2Cu3O
y
system as the praseodymium content increases are presented. The results obtained have been analyzed based on the narrow band
model, the energy spectrum and charge carrier system parameters have been determined, and their behavior with an increase
in the doping level has been analyzed. It has been found that both superconducting properties and parameters of the normal
state of Y0.85 − x
Ca0.15Pr
x
Ba2Cu3O
y
vary differently in various doping ranges. Based on a comparison of the results obtained with the available data for the
case of single doping of YBa2Cu3O
y
with praseodymium, conclusions have been drawn regarding the mechanism of the energy spectrum modification in the studied
compound. The Fermi-level pinning effect has been revealed in the region of a local peak of the density-of-states function,
and the energy position of this peak has been determined. It has been shown that the consideration of the Fermi level dynamics
caused by the specific features of the structure and transformation of the Y0.85 − x
Ca0.15Pr
x
Ba2Cu3O
y
energy spectrum upon doping makes it possible to explain the observed dependence of the critical temperature on the praseodymium
content. 相似文献
18.
S. Yu. Paranchich L. D. Paranchich M. D. Andriichuk V. R. Romanyuk V. N. Makogonenko Yu. V. Tanasyuk T. A. Mel’nichuk 《Journal of Applied Spectroscopy》2007,74(1):81-85
We present the results of experimental studies of the optical properties of cobalt-doped Cd
x
H1−x
Se (x = 0.18) single crystals with cobalt ion concentrations of NCo = 5·1018, 5·1019, and 1·1020 cm−3 at T = 90 K and 300 K. The composition (x = 0.18) of the Cd
x
Hg1−x
Se solid solution was selected so that the hypothetical resonance level is found on the bottom of the conduction band. We
show that the cobalt ions in the mercury selenide can form a resonance donor level only for cobalt concentrations NCo < 5·1018 cm−3. For NCo ∼ 5·1018 cm−3, the cobalt ions substitute for mercury atoms, forming a solid solution and leading to an increase in the bandgap width and
a change in the physical properties. The solubility of cobalt in the HgSe lattice can be greater than 5%–10%.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 73–77, January–February, 2007. 相似文献
19.
We report on the effect of oxygen partial pressure and vacuum annealing on structural and optical properties of pulsed laser-deposited
nanocrystalline WO3 thin films. XRD results show the hexagonal phase of deposited WO3 thin films. The crystallite size was observed to increase with increase in oxygen partial pressure. Vacuum annealing changed
the transparent as-deposited WO3 thin film to deep shade of blue color which increases the optical absorption of the film. The origin of this blue color could
be due to the presence of oxygen vacancies associated with tungsten ions in lower oxidation states. In addition, the effects
of VO2 content on structural, electrochemical, and optical properties of (WO3)1−x
(VO2)
x
nanocomposite thin films have also been systematically investigated. Cyclic voltammogram exhibits a modification with the
appearance of an extra cathodic peak for VO2–WO3 thin film electrode with higher VO2 content (x ≥ 0.2). Increase of VO2 content in (WO3)1−x
(VO2)
x
films leads to red shift in optical band gap. 相似文献
20.
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