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1.
N. M. Olekhnovich A. V. Pushkarev Yu. V. Radyush 《Journal of Applied Spectroscopy》2009,76(4):518-522
A technique for analysis of the electric modulus spectrum of dielectric ceramics based on the elimination of the direct current
conductivity (σ
dc
) contribution has been developed. Expressions are given for the real (M′
ac
) and imaginary (M′′
ac
) parts of the complex electrical modulus related only to the dielectric polarization and not containing the contribution
of σ
dc
. The frequency dependence of M′′
ac
and the M′′
ac
– M′
ac
diagram for BiMg1/2Ti1/2O3 and BiMg1/2Zr1/2O3 perovskite ceramics are analyzed. 相似文献
2.
V. V. Lemanov A. V. Sotnikov E. P. Smirnova M. Weihnacht 《Physics of the Solid State》2002,44(11):2039-2049
Ceramic samples of (1−x)SrTiO3-xSrMg1/3Nb2/3O3 and (1−x)SrTiO3-xSrSc1/2Ta1/2O3 were prepared, and their dielectric properties were studied at x=0.005–0.15 and 0.01–0.1, respectively, at frequencies 10 Hz–1 MHz and at temperatures 4.2–350 K. A giant dielectric relaxation
was observed in the temperature range 150–300 K, and not so strong but well-developed relaxation was found in the temperature
range 20–90 K. The activation energy U and the relaxation time τ0 were determined to be 0.21–0.3 eV and from 10−11 to 10−12 s for the high-temperature relaxation and 0.01–0.02 eV and 10−8–10−10 s for the low-temperature relaxation, respectively. The additional local charge compensation of the heterovalent impurities
Mg2+ and Nb5+ (or Sc3+ and Ta5+) by free charge carriers or the host ion vacancies is suggested to be the underlying physical mechanism of the relaxation
phenomena. On the basis of this mechanism, the Maxwell-Wagner model and the model of reorienting dipole centers Mg2+ (or Sc3+) associated with the oxygen vacancy are proposed to explain the high-temperature relaxation with some arguments in favor
of the latter model. The polaron-like model with the Nb5+-Ti3+ center is suggested as the origin of the low-temperature relaxation. The reasons for the absence of ferroelectric phase transitions
in the solid solutions under study are also discussed.
From Fizika Tverdogo Tela, Vol. 44, No. 11, 2002, pp. 1948–1957.
Original English Text Copyright ? 2002 by Lemanov, Sotnikov, Smirnova, Weihnacht.
This article was submitted by the authors in English. 相似文献
3.
We have generated thep-cyanobenzyl radical in supersonic free expansion, and measured the vibrationally and rotationally resolved laser induced fluorescence (LIF) excitation spectra and the LIF dispersed spectra from the single vibronic levels (SVL) in the green-blue region. The lowest energy band at 20 738 cm−1with the strongest intensity in the excitation spectrum has been assigned to the 000band of the visible spectrum, on the basis of the vibronic structures in the SVL dispersed spectra. Based on the band type of the 000band,a-type, determined from the rotationally resolved LIF excitation spectrum, we have definitely assigned the visible band to theD122B1–D012B1electronic transition. We have found, on the grounds of the vibrational analysis of the dispersed spectra, that the vibronic structure of the 22B1–12B1electronic transition of the benzyl type is characterized by totally symmetric fundamental modes, 1, 8a, and 9a. 相似文献
4.
The optical excitation functions (OEFs) for four series of spectral lines of the Zn atom at the transitions 4sn
1
s
1
S
0 → 4s4p
1
P
1∘ (n
1 = 6–10), 4sn
2
s
3
S
1 → 4s4p
3
P
2∘ (n
2 = 6−8), 4sn
3
d
1
D
2 → 4s4p
1
P
1∘ (n
3 = 4−6), 4sn
4
d
3
D
1, 2, 3 → 4s4p
3
P
2∘ (n
4 = 4−7) excited by a monoenergetic (0.04–0.08 eV) electron beam with energies from the excitation threshold to 18–19 eV are
measured. In the energy dependences of the excitation cross sections, the effect of post-collision interaction of slow (scattered)
and fast (emitted after the autoionization state decay) electrons is observed and described. This interaction leads to the
capture of a slow electron into the listed discrete levels and the appearance of maxima in the excitation functions. The energies
of the maxima are used to determine the energies and widths of single autoionization states or their groups by approximate
formulas of the classical approach. The autoionization levels of the zinc atom responsible for the maxima observed are determined.
Possible transfer of the orbital angular momentum between electrons is analyzed. 相似文献
5.
A. D. Smirnov 《Optics and Spectroscopy》2007,102(1):18-22
The vibrational, rotational, and centrifugal distortion constants have been calculated for the electronic states A
1Σ
u
+
, B
1Πu, C
1Πu, D
1Σ
u
+
, and E
1Σ
u
+
of the Cs2 molecule. The calculation was performed on the basis of the semiempirical potential energy curves constructed in this paper.
The calculated spectroscopic constants are compared with the experimental data.
Original Russian Text ? A.D. Smirnov, 2007, published in Optika i Spektroskopiya, 2007, Vol. 102, No. 1, pp. 23–27. 相似文献
6.
7.
8.
9.
The influence of the replacement of Mn ions in the La0.7Ca0.3Mn1 − y
Fe
y
O3 compounds (0 ≤ y ≤ 0.09) by another transitional metal, Fe, was studied. The radii of both ions are almost identical, which makes the effect
of the transitional metal on the physical properties of manganites more transparent. The crystal structure of three samples
(with y = 0, 0.03, 0.09) is studied in the temperature range T = 1.5–300 K by neutron powder diffraction. All investigated samples belong to the orthorhombic space group Pnma (62). It is confirmed that Fe ions occupy the Mn positions in the unit cell. As the Fe concentration increases, the saturation
value of the spontaneous magnetic moment and the Curie temperature decrease, but the ground state remains ferromagnetic for
0 ≤ y ≤ 0.1. The saturation values of the magnetic moments at T = 1.5 K are m
FM = 3.72(3), 3.40(3), and 3.27(3) μ
B
/Mn for the samples with an Fe concentration y = 0, 0.03, and 0.09, respectively.
Original Russian Text ? A.I. Kurbakov, V.S. Zakhvalinskii, R. Laiho, 2007, published in Fizika Tverdogo Tela, 2007, Vol. 49,
No. 4, pp. 691–695. 相似文献
10.
11.
The equilibrium structure of flue gas SO2 is optimized using the density functional theory (DFT)/B3P86 method and CC-PV5Z basis. The result shows that it has a bent (C2v, X1A1) ground state structure with an angle of 119.1184°. The vibronic frequencies and the force constants are also calculated. Based on the principles of atomic and molecular reaction statics (AMIIS), the possible electronic states and reasonable dissociation limits for the ground state of SO2 molecule are determined. The potential functions of SO and 02 are fitted by the modified Murrell-Sorbie+c6 (M-S+c6) potential function and the fitted parameters, the force constants and the spectroscopic constants are obtained, which are all close to the experimental values. The analytic potential energy function of the SO2 (X1A1) molecule is derived using the many-body expansion theory. The contour liues are constructed, which show the static properties of SO2 (XIA1), such as the equilibrium structure, the lowest energies, the most possible reaction channel, etc. 相似文献
12.
The infrared (IR) spectrum of PD3 has been recorded in the 1580–1800 cm−1 range at a resolution of 0.0027 cm−1. About 2400 rovibrational transitions with J′=K′22 have been measured and assigned to the ν1 (A1) and ν3 (E) stretching fundamentals. These include 506 “perturbation-allowed” transitions with selection rules Δ(k−l)=±3. Splittings of the K′′=3 lines have been observed. Effects of strong perturbations are evident in the spectrum. Therefore the rovibrational Hamiltonian adopted for the analysis explicitly takes into account the Coriolis and k-type interactions between the v1=1 and v3=1 states, and includes also several essential resonances within these states. The rotational structure in the v1=1 and v3=1 vibrational states up to J′=K′=18 was reproduced by fitting simultaneously all experimental data. Thirty-four parameters reproduced 1950 transitions retained in the final cycle with a standard deviation of the fit equal to 4.9 × 10−4 cm−1 (about the precision of the experimental measurements). 相似文献
13.
根据实验研究成果提出纳米晶合金软磁性能受其介观结构影响的观点,建立了Fe基纳米晶合金的球状介观结构模型,分别求出只有交变磁场或交变磁场和静磁场作用时纳米晶粒球的频率函数——D函数.分析表明,两种D函数都是复变函数,其实部Re(D)为纳米晶电感性质和电容性质的反映,虚部Im(D)为纳米晶电阻性质的反映,据此建立了Fe基纳米晶合金介观结构的等效RLC并联模型.由该模型求得合金产生极值巨磁电阻的条件为vextGMI=v|Re(D)=0,决定因素有μ,σ,ω,R和Hex及微观磁结构.
关键词:
Fe基纳米晶合金
等效RLC并联模型
球状介观结构模型
频率函数 相似文献
14.
15.
We report on ab-initio frozen-phonon calculations for the five A1g
Raman-active-modes of YBa2Cu3O7 atq=0. The determination of the equilibrium positions of the atoms Ba, Cu(2), O(2), O(3), O(4) as well as of phonon frequencies
and respective eigenvectors is based on the calculation of atomic forces within the LAPW-method. The general agreement between
our results and experimental structural data and phonon frequencies is good. Deviations are discussed in connection with the
local-density approximation. 相似文献
16.
T. S. Orlova J. Y. Laval Ph. Monod V. S. Zakhvalinski? V. M. Egorov Yu. P. Stepanov 《Physics of the Solid State》2009,51(1):99-105
The effect of copper doping on charge-orbital ordering in La1/3Ca2/3Mn1 − y
Cu
y
O3 (0 ≤ y ≤ 0.07) is studied by measuring the temperature dependences of the magnetization, the electrical resistivity, and the heat
capacity in combination with an electron microscopic investigation of the structure. It is demonstrated that copper doping
leads to a lowering of the charge ordering temperature T
CO and that this decrease is proportional to the decrease in the Mn3+ ion concentration. In the temperature range 5–300 K, the semiconducting pattern of the electrical resistivity persists for
all values of 0 ≤ y ≤ 0.07. Electron microscope studies have shown that the presence of copper suppresses the formation of a regular superstructure,
which is characteristic of the undoped starting compound, beginning already from low concentrations (y = 0.01). Differential scanning calorimetry revealed a substantial decrease in the transition entropy at the onset of charge
ordering in copper-doped samples as compared to the starting compound. Doping with copper destroys long-range charge-orbital
ordering and retains apparently only short-range order.
Original Russian Text ? T.S. Orlova, J.Y. Laval, Ph. Monod, V.S. Zakhvalinskiĭ, V.M. Egorov, Yu.P. Stepanov, 2009, published
in Fizika Tverdogo Tela, 2009, Vol. 51, No. 1, pp. 91–97. 相似文献
17.
对熔体急冷法制备的非晶合金 Fe52Co34Hf7B6Cu1 进行了不同频率的中频磁脉冲处理, 用透射电子显微镜、穆斯堡尔谱、正电子湮没寿命谱等方法研究了处 理前后试样的微观结构及结构缺陷变化. 结果表明,经中频磁脉冲处理后,样品发生了部分纳米晶化, 晶化量随磁脉冲频率增加而增加, 当磁脉冲频率为2000 Hz时, 晶化量达33.1%; 在淬态非晶样品中, 正电子在类单空位中的湮没寿命τ1为150.5 ps, 强度 I1为77.7%, 在微孔洞中的湮没寿命τ2为349.7 ps,强度I2为22.3%; 随磁脉冲频率的增加, τ1, τ2值呈现减小的变化趋势, 与淬态非晶相比, I1有所增加, I2下降, τ1, τ2的平均值τ大幅降低. 相似文献
18.
The 2ν3 overtone (A1, E) and the ν1 + ν3 (E) combination bands of the oblate symmetric top 14NF3 were studied by FTIR spectroscopy with a resolution of 2.5 × 10−3 cm−1. Nearly 500 lines up to Kmax/Jmax = 30/43 were observed for the weak A1 component reaching the v3 = 20 substate (1803.1302 cm−1), the majority of which corresponded to reinforced K = 3p-type transitions. For the strong E component reaching the v3 = 2±2 substate (1810.4239 cm−1), about 3550 transitions were assigned up to Kmax/Jmax = 65/69, favoring a clear observation of the ℓ(4, −2) and ℓ(4, 4) splittings within the kℓ = −2 and +4 sublevels, respectively. The two v3 = 2 substates are linked by the ℓ(2, 2)- and ℓ(2, −1)-type interactions, providing severe crossings, respectively, at K′ = 6 and near K′ = 24 on the v3 = 2+2 side. A model working in the D-reduction and including all these ℓ-type interactions could reproduce together 3695 nonzero weighted experimental data (NZW) through 33 free parameters with a standard deviation of σ = 0.357 × 10−3 cm−1. As for the ν1 + ν3 (E) combination band, about 3690 lines were assigned up to Kmax/Jmax = 45/55. Its v1 = v3 = 1 upper state (1931.577 5 cm−1) was treated using the same model recently applied to the v3 = 1 (E, 907.5413 cm−1) state. It yielded 21 free parameters through 3282 NZW experimental data, adjusted with σ = 0.344 × 10−3 cm−1 in the D-reduction. For the two excited states, the small and unobserved ℓ(0, 6) interaction was tested as useless. To confirm the adequacy of the vibrationally isolated models used, some other reductions of the Hamiltonian were tried. For the v3 = 2 state, the D-, L-, and LD-reductions led to similar σ’s, while the Q one was not successful. For the v1 = v3 = 1 state, the D- and Q-reductions gave comparable σ’s, while the QD-reduction was not as good. The corresponding unitary equivalence relations are generally more nicely fulfilled for the v3 = 2 state than for the v1 = v3 = 1 state. The three derivable anharmonicity constants in cm−1 are x33 = −4.1528, g33 = +1.8235 and x13 = −7.9652. 相似文献
19.
Temperature dependence of the critical current in YBa2Cu3O7−δ and Bi2Sr2Ca1Cu2O8 Josephson junctions
B.A. Aminov N.B. Brandt Nguyen Min Thuy Ya.G. Ponomarev M.V. Sudakova A.R. Kaul I.E. Graboi Yu.D. Tretiakov J. Wittig S.P. Kobeleva L.M. Fisher L. Rosta 《Physica C: Superconductivity and its Applications》1989,160(5-6)
We have studied the stationary Josephson effect on YBa2Cu3O7−δ (Tc=90 K) and Bi2Sr2Ca1Cu2 O8 (Tc=80 Kand 87 Kfortwosamplesofdifferentorigin) ceramic based junctions. The temperature dependence of the critical current near Tc has been found as Ic≈(Tc-T)
for the Y-Ba-Cu-O samples indicating that they should be classified as S-N-I-N-S type junctions. The I-V curves of the Bi-Sr-Ca-Cu samples show the typical behaviour of S-I-S structures. Using Ambegaokar-Baratoff's theory for Bi2Sr2Ca1Cu2O8, the temperature dependence of the superconducting state gap Δ(T) was calculated and it was evaluated that 1.452Δ(0)/kBTc3.5. 相似文献
20.
The modification of the temperature dependences of the thermopower coefficient for the Tl2Ba2Ca1 − x
Y
x
Cu2 − y
Co
y
O
z
system is investigated as a function of the dopant content. The model of an asymmetric narrow band is shown to be applicable
to high-temperature superconductors in the thallium system. The parameters of the band spectrum and charge carrier system
for samples of a close-to-optimum composition are determined by analyzing the temperature dependences of the thermopower coefficient
within the narrow band model. The character and mechanism of their variation in the course of the transition to an underdoped
regime are analyzed together with the dynamics of changes in the superconducting properties. The critical temperature T
c
is found to correlate with the effective conduction-band width W
D
. It was shown that the dependence T
c
(W
D
) for Tl2Ba2Ca1 − x
Y
x
Cu2 − y
Co
y
O
z
has a close-to-universal character, but the suppression of T
c
upon the broadening of the band occurs faster than in the case of the yttrium system.
Original Russian Text ? O.A. Martynova, V.é. Gasumyants, 2007, published in Fizika Tverdogo Tela, 2007, Vol. 49, No. 9, pp.
1537–1542. 相似文献