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1.
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
2.
Haruhiko Obara Akihito Sawa Hirofumi Yamasaki Shin Kosaka 《Czechoslovak Journal of Physics》1996,46(Z3):1749-1750
Anisotropy and Hall effect measurements have been performed in calcium-doped, i.e., overdoped YBa2Cu3Oy ((Y1−xCax)Ba2Cu3Oy) thin films witha andc axis orientations. In highly overdoped films (x=0.4), the anisotropy of the normal resistivity decreases and a drastic change
in Hall conductivity in the mixed state is observed. The change in Hall conductivity in the overdoped region is consistent
with recent experimental results for La2−xSrxCuO4 films and seems to be common in highT
c
superconductors. 相似文献
3.
V. É. Gasumyants E. V. Vladimirskaya M. V. Elizarova I. B. Patrina 《Physics of the Solid State》1999,41(3):350-354
Temperature dependences of the resistivity and Seebeck coefficient of Y(Ba1−x
Lax)2Cu3Oy and YBa2Cu3−x
CoxOy samples (x=0–0.25) have been measured under maximum sample saturation with oxygen, as well as following their anneal in an oxygen-deficient
atmosphere. The T
c (x) dependences for as-prepared samples were found to pass through a maximum at x=0.05, which persists after annealing for Y(Ba1−xLax)2Cu3Oy and disappears for YBa2Cu3−x
CoxOy. A phenomenological model of the band spectrum in normal phase has been used to determine the parameters of the conduction
band and of the carrier system, and to analyze their variation with the dopant type and content, as well as with annealing.
Despite the differences observed in the T
c (x) dependence, the critical temperatures for all the sample series studied were found to correlate with the conduction-band
effective width. The mechanism of the effect of impurities on the band-structure parameters and the reasons for the different
influence of annealing on the properties of Y(Ba1−x
Lax)2Cu3Oy and YBa2Cu3−x
CoxOy are discussed.
Fiz. Tverd. Tela (St. Petersburg) 41, 389–394 (March 1997) 相似文献
4.
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
5.
The temperature dependence of the thermoelectric power in samples of Y1−x
PrxBa2Cu3Oy (x=0−0.6) is investigated. The principal parameters of the system of charge carriers are determined on the basis of an analysis
of this dependence within a narrow-conduction-band model, and their variation with increasing praseodymium content is analyzed.
It is found that an increase in x leads to a very weak increase in the electron filling and considerable broadening of the conduction band accompanied by strong
localization of the charge carriers. It is concluded on the basis of a comparative analysis of the results obtained and data
for the YBa2Cu3Oy system in the case of aliovalent substitutions in the barium and copper sites that the valence of praseodymium in Y1−x
PrxBa2Cu3Oy is very close to 3+. It is shown that there is a universal correlation between the effective width of the conduction band
and the critical temperature following various cation substitutions in the Y-Ba-Cu-O system. It is concluded that the main
reason for suppression of the superconducting properties of Y1−x
PrxBa2Cu3Oy is the strong modification of the band spectrum caused by praseodymium.
Fiz. Tverd. Tela (St. Petersburg) 39, 1520–1525 (September 1997) 相似文献
6.
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
7.
W. K. Dawson C. H. Halim S. P. Weathersby J. A. Flint J. C. Lam T. J. Hoffman C. Boekema KC. B. Chan R. L. Lichti D. W. Cooke M. S. Jahan J. E. Crow 《Hyperfine Interactions》1991,63(1-4):219-226
Key results of zero-field (ZF) and transverse-field (TF) muon-spin-relaxation (μSR) experiments on superconducting and insulating
RBa2Cu3O
y
(R123
y
, with R=Eu, Gd, Pr and Pr/Y:y=6, 7) are examined. The chemical behavior of the positive muon probe is addressed, and muon-oxygen bonding is shown to occur
in all these cuprates. To explain magnetic fields at muon-probe sites in Pr
x
Y1−x
Ba2Cu3O
y
(0<=x<0.5,y=7 andx=0,y=6) samples, improvements on the reported magnetic structures from neutron diffraction are necessary. Cu magnetism in Pr123y (y=6,7) is observed belowT
N1, which is near RT. The magnetism seen belowT
N2 can be interpreted assuming an additional ordering in the Cutt-O chain layers. Alternatively, Pr ordering is also considered
as the cause of the second phase transition. Considering the specific muon-probe location, a more detailed interpretation
can be provided for the μSR parameters, measured in the normal and mixed states of these unconventional superconductors. 相似文献
8.
M. V. Elizarova O. A. Martynova D. V. Potapov V. é. Gasumyants L. P. Mezentseva 《Physics of the Solid State》2005,47(3):434-438
Temperature dependences of the electrical resistivity and Seebeck coefficient have been studied on a series of samples of
the Y1−x
CaxBa2Cu3−x
ZnxOy system (x = 0–0.25). The effect exerted by a combination of the impurities under study on the properties of the normal phase was established.
The experimental data obtained were analyzed quantitatively in terms of a phenomenological model of electron transport. The
parameters of the band responsible for conduction in the normal phase and of the carrier system were calculated for all the
samples studied. A mechanism of zinc doping-induced band structure modification in the yttrium system is proposed that accounts
for the transformation of the temperature dependence of the Seebeck coefficient and the dynamics of superconducting properties
in this compound.
__________
Translated from Fizika Tverdogo Tela, Vol. 47, No. 3, 2005, pp. 422–426.
Original Russian Text Copyright ? 2005 by Elizarova, Martynova, Potapov, Gasumyants, Mezentseva. 相似文献
9.
K RuckW Pitschke G Krabbes M WolfD Eckert K.-H Müller 《Journal of Physics and Chemistry of Solids》2002,63(10):1901-1907
Phases of the composition Ca1−x−yMgxCu2+yO3 have been prepared for the first time. The compounds are isostructural with the known end-members CaCu2O3 and MgCu2O3 showing a two-leg spin-ladder-like connection of copper and oxygen atoms within the Cu2O3-layer. Opposite the spin ladders this layer is folded, which results in a long-range antiferromagnetic ordering of these phases. The Néel temperature can be adapted by variation of x in Ca1−x−yMgxCu2+yO3 between 24 and 80 K. Several structural features, which influence the magnetic ordering, are discussed. 相似文献
10.
Investigation was performed on luminescent properties of novel Gd2−x
Eu
x
MoB2O9 (0.02≤x≤2.0) phosphors. The excitation spectra consist of broad band and intense narrow lines. The 4f-4f transitions are situated
in a favorable position for excitation by GaN chip emission. The emission spectra consist of transitions from the 5D0 level to the lower 7F manifold, and the emission shows no concentration quenching at higher doping level. The decay time spectra of the 5D0 → 7F2 emission are recorded. Under 395 nm excitation, the intensity of 5D0 → 7F2 transition of GdEuMoB2O9 is 1.2 times stronger than that of commercial Eu3+:Y2O2S phosphor. Gd2MoB2O9:Eu3+ phosphors are promising candidates for near-UV-based solid-state-lighting (SSL). 相似文献
11.
The temperature dependences of the resistivity and of the Seebeck coefficient S is studied in three series of Y1−x
CaxBa2Cu3−x
CoxOy samples (x=0–0.3) differing in oxygen content. It was found that the critical temperature decreases for y≈7.0, and S(T=300 K) increases with doping, whereas oxygen deficiency results in a nonmonotonic variation of these quantities with increasing
x. The band structure parameters have been determined from an analysis of the S(T) relations using a phenomenological theory of electron transport. It was found that an increase in x results in a gradual increase in band asymmetry, which is caused by calcium-induced creation of additional states in the
band responsible for conduction in the normal phase. An analysis has shown that high impurity concentrations in oxygen-deficient
Y1−x
CaxBa2Cu3−x
CoxOy samples bring about an additional ordering of the structure, which may be caused by formation of a cobalt superlattice. It
has also been shown that, in the case of Ca and Co codoping, the dependence of critical temperature on effective conduction-band
width coincides with the universal correlation relation observed in the YBa2Cu3Oy system with single substitutions in various lattice sites.
Fiz. Tverd. Tela (St. Petersburg) 41, 1363–1371 (August 1999) 相似文献
12.
Yu. P. Sukhorukov N. N. Loshkareva E. A. Ganshina A. R. Kaul O. Yu. Gorbenko E. V. Mostovshchikova A. V. Telegin A. N. Vinogradov I. K. Rodin 《Physics of the Solid State》2004,46(7):1241-1251
The optical, magnetooptical, and electric properties of epitaxial (La1−x
Prx)0.7Ca0.3MnO3 films (0≤x≤1) grown by MOCVD on LaAlO3 and SrTiO3 substrates were studied. It is shown that the decrease in the average cation radius resulting from isovalent substitution
of the Pr for La ions brings about a lowering of the Curie temperature, the metal-insulator transition temperature, and the
temperatures of the maxima in magnetotransmission (MT) and magnetoresistance (MR). These temperatures depend only weakly on
the substrate type. Substitution of La by Pr does not change the shape of the spectral response of the transverse Kerr effect.
For concentrations x≤0.50, the maximum values of the Kerr effect and of the MT vary insignificantly, which should be assigned to the existence
of a singly connected ferromagnetic metallic region at low temperatures. In films with x=0.75, the presence of ferromagnetic metallic drops in an antiferromagnetic insulating matrix was revealed. The totality of
the experimental data obtained suggest that nanoscopic magnetic and electronic nonuniformities exist both in films with a
singly connected metallic region and in an x=1 film, which is an antiferromagnetic insulator.
__________
Translated from Fizika Tverdogo Tela, Vol. 46, No. 7, 2004, pp. 1203–1213.
Original Russian Text Copyright ? 2004 by Sukhorukov, Loshkareva, Gan’shina, Kaul’, Gorbenko, Mostovshchikova, Telegin, Vinogradov,
Rodin. 相似文献
13.
The thermopower in the YBa2−x
LaxCu3Oy system (x=0–0.5) has been studied. An analysis made in terms of the narrow-band model revealed trends in the variation of the main
band parameters with increasing lanthanum concentration. The dependence of the conduction band width on lanthanum concentration
was found to pass through a weak minimum at x=0.05–0.1, which correlates in position with the maximum in the concentration dependences of the critical temperature and
degree of sample orthorhombicity. The results obtained and their comparison with Fe, Co→Cu substitution data permit a conclusion
that the main factor affecting the properties of the YBa2Cu3Oy system under nonisovalent substitution of various cations is the increasing disorder in the chain-oxygen subsystem caused
by increasing impurity content.
Fiz. Tverd. Tela (St. Petersburg) 40, 17–22 (January 1998) 相似文献
14.
L. A. Klinkova V. I. Nikolaichik N. V. Barkovskii 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(8):1103-1105
The phase composition of Y
z
Ba5Cu7O
y
(1) and Y
z
Ba3Cu5O
y
(2) samples with a variable percentage of yttrium up to the stoichiometric composition of the Y
n
Ba
m
Cu
m + n
O
y
series is investigated by X-ray phase and elemental analyses, electron diffraction, and high resolution imaging in a transmission
electron microscope at a temperature of 930°C in the crystallization field of a matrix oxide (Ba: Cu) of 5: 6 composition
on the phase diagram of the BaO-CuO
x
system at P(O2) = 21 kPa. The substantial effect of yttrium oxide’s presence on the phase composition of both objects is found, providing
evidence of a complex ionic equilibrium within the melt. The fine-domain oxide structure of the YBa2Cu3O6 tetragonal form, which is due to the coexistence of oxides of an Y
n
Ba
m
Cu
m+n
O
y
homologous series of (Y: Ba: Cu) 235, 123, and 257 composition is revealed. The domain size for these phases is 20–50 ?.
The domains are joined coherently along axis c. 相似文献
15.
测量了温度范围为4.2—300K的Y1-xPrxBa2Cu3O7+δ(x=0,0.1,0.2,0.4,0.5,0.61.0)的红外反射谱,发现在低温下Ba模有双模行为,随着x值增大双模强度反转,在YBa2Cu3O7+δ中已被判定为Y模的位于194cm-1的反射峰的位置与Pr的含量无关,即用Pr部份或全部替代Y时此峰不发生频移。建议Pr在Y1-xPrxBa2Cu3O7+δ,中是正4价,Pr的替代使原来可移动的空穴被定域在Pr的周围,使超导电性受到压制。
关键词: 相似文献
16.
17.
L. S. Kamzina E. V. Snetkova I. P. Raevski A. S. Emelyanov Jiayue Xu Weidong Xiang 《Physics of the Solid State》2007,49(4):762-768
The effect of a dc electric field on the nucleation and evolution of the phase with long-range order in a cubic nonpolar matrix
in 〈001〉-oriented (100 − x)PbMg1/3Nb2/3O3-xPbTiO3 single-crystal relaxors as the content of PbTiO3 is gradually increased (6 ≤ x ≤ 20, where x is the PbTiO3 content given in molecular percent) is investigated. The optical properties of these solid solutions are studied in different
modes of application of an electric field. It is shown that an applied electric field with a strength above a threshold value
induces a first-order ferroelectric phase transition with a temperature hysteresis occurring between measurements performed
under cooling and heating of the crystal in the electric field. As the PbTiO3 content or electric field strength increases, the hysteresis becomes less pronounced and the first-order phase transition
is suppressed. At x ∼ 20, the induced transition resembles a second-order rather than first-order transformation. It is assumed that, for compositions
with x > 10 in electric fields higher than 4 kV/cm, the formation of the rhombohedral phase is accompanied by the appearance of
another (possibly, monoclinic) phase associated with the rotation of the polarization vector from the [111] direction of the
rhombohedral phase to the [001] direction of the tetragonal phase.
Original Russian Text ? L.S. Kamzina, E.V. Snetkova, I.P. Raevskiĭ, A.S. Emel’yanov, Jiayue Xu, Weidong Xiang, 2007, published
in Fizika Tverdogo Tela, 2007, Vol. 49, No. 4, pp. 725–730. 相似文献
18.
The structural, superconducting and magnetic properties of La2Cu1−xZnxO4+δ (0≤x≤0.1) chemically oxidized by NaClO at room temperature were studied. All the samples before and after oxidation are single phase with orthorhombic structure, as indicated by their powder X-ray diffraction analysis. The iodometric titration results indicate that Zn-substituted La2Cu1−xZnxO4 is more favorable for the insertion of the excess oxygen, as compared to the Zn-free La2CuO4. The Tc suppression rate resulting from Zn substitution in La2Cu1−xZnxO4+δ is −12.4 K/%. The effective magnetic moment induced by the non-magnetic Zn ion is the order of one Bohr magneton, which decreases with increasing the Zn concentrations in the range examined. The latter two results are qualitatively well consistent with those obtained in La2−xSrxCu1−yZnyO4 with the Sr optimal doping. This reveals that the non-magnetic Zn ions play the same role in both of the La2Cu1−xZnxO4+δ with the excess oxygen content of about 0.1 and the La2−xSrxCu1−yZnyO4 with the Sr optimal doping. 相似文献
19.
L. A. Klinkova V. I. Nikolaichik N. V. Barkovsky 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(8):1160-1162
The phase composition of specimens in the primary crystallization field of the Y
n
Ba
m
Cu
m + n
O
y
oxide series with compositions of (Y:Ba:Cu) 235, 123, and 257 was investigated by means of X-ray powder diffraction, X-ray
microprobe analysis, electron diffraction, and high resolution imaging in a transmission electron microscope. Y
n
Ba
m
Cu
m + n
O
y
oxides have the YaBa2Cu3O6 tetragonal structure and can be represented in the general form as 123 oxides. It was found that the crystallization field
of 123 oxides corresponds to the crystallization fields of the Ba
m
Cu
m + n
O
y
oxide series with the BaCuO2 cubic structure. These crystallization fields are located in the matrix phase diagram of the BaO-CuO
x
system at P(O2) = 21 kPa in the range of 50–90 mol % CuO and 910–1000°C. The 123 oxides are formed according to an intercalation mechanism
with the participation of barium-copper oxide matrices with the composition (Ba: Cu) 3: 5, 2: 3, and 5: 7 相似文献
20.
The Pr1+xBa2-xCu3O7± solid solution was investigated by means of X-ray powder diffraction combined with Rietveld analysis. A Pr123 single phase could be synthesized under Pr-rich conditions by sintering at 950 °C in air. The solubility range of Pr1+xBa2-xCu3O7± solid solution is 0.08x0.80. The structure of Pr1+xBa2-xCu3O7± for 0.08x<0.30 is orthorhombic. The structure transforms into tetragonal for 0.30x0.80. To form the Pr123 single phase, the Ba sites in the Pr123 structure must have partial Pr ions, and the least amount is x=0.08. Ba ions cannot occupy the sites of Pr ions. In the Pr123 structure, Ca ions can replace Pr ions; the highest value is x=0.4 in the PrBa2-xCaxCu3O7± system under our experimental conditions. However, Ca ions cannot replace Ba ions. The ionic radius plays a more important role than the chemical properties in the substitution between Pr, Ba and Ca ions in the Pr123 structure. PACS 61.50.Ah; 64.70.Kb; 61.72.Ff 相似文献