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1.
We report on a tunneling study of underdoped submicron Bi2Sr2-xLaxCuO6+δ (La-Bi2201) intrinsic Josephson junctions (IJJs), whose self-heating is sufficiently suppressed. The tunneling spectra are measured from 4.2 K up to the pseudogap opening temperature of T* = 260 K. The gap value found from the spectral peak position is about 35 meV and has a weak temperature dependence both below and above the superconducting transition temperature of Tc = 29 K. Since the superconducting gap should have a value of 10-15 meV, our results indicate that the pseudogap (~35 meV) plays an important role in the underdoped La-Bi2201 intrinsic tunneling spectroscopy down to the lowest temperature of 4.2 K. However, the contribution of the superconducting gap can be separated by normalizing the spectra to the one near and above Tc, which shows that the IJJs can be a useful tool for the study of the electronic properties of the La-Bi2201 cuprate superconductors. 相似文献
2.
Jie Song Bing-Lin Hong Jun Zheng Pei Lin Ming-Sen Zheng Qi-Hui Wu Quan-Feng Dong Shi-Gang Sun 《Applied Physics A: Materials Science & Processing》2010,98(2):455-460
Ti-substituted LiMn2O4 (LiMn2−x
Ti
x
O4, x=0, 0.15, 0.30, 0.45, 0.60, and 0.75) has been synthesized using solid-state reactions. Their crystal and electronic structures
were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ultraviolet photoelectron spectroscopy
(UPS). XRD data suggested that the lattice parameters of LiMn2−x
Ti
x
O4 increase due to the replacement of Mn by Ti ions. XPS results indicated that the substituted Ti ions were in +4 oxidation
state; consequently, the normal oxidation state of Mn ions has been detected by measuring the binding energy splitting of
Mn 3s states, which decreases with the content of substituted Ti. The valence band spectra suggested that the intensity of
e
g
level of Mn 3d orbitals increased due to the increase of the Mn3+/Mn4+ ratio. 相似文献
3.
V. S. Rusakov N. I. Chistyakova I. A. Burkovsky A. M. Gapochka T. L. Evstigneeva 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(3):389-393
A M?ssbauer study of the structural and charge states of 57Fe and 119Sn atoms in the compounds of Cu3 −x
Fe
x
SnS4 and Cu2Fe1 − x
Zn
x
SnS4 systems was performed. It was shown that the iron atoms in the compounds of both systems were in the divalent and trivalent
states occupying the tetrahedral positions of the structure. The character of the changes of the degree of covalency of the
Fe2+-S, Fe3+-S and Sn4+-S bonds during the isomorphic substitution in the systems was established. 相似文献
4.
I. B. Krynetskii A. Krapf V. P. Martovitskii N. P. Shabanova S. Yu. Gavrilkin V. I. Kovalenko A. P. Rusakov A. I. Golovashkin 《Bulletin of the Lebedev Physics Institute》2011,38(12):349-353
The thermal expansion of single crystals of the Bi2Sr2−x
La
x
CuO6+δ
high-temperature superconducting (HTSC) system in the insulating phase with compositions having no superconducting transition
to a temperature of 1.8 K (x ≥ 0.8) is measured in an arbitrary direction in the (ab) plane in the temperature range of 7–50 K. Temperature regions of material compression upon heating are found. The study
of anomalies in magnetic fields of 3 and 6 T, parallel and perpendicular to the c-axis revealed an anisotropic and nonmonotonic effect of the field on thermal expansion. Such anomalies for the n-type Nd2−x
Ce
x
CuO4−δ
HTSC sample also having no superconducting transition are detected for the first time. The results show that the anomaly
nature is caused by anisotropic electronic ordering, probably, by the charge density wave in the CuO2 plane and superconductivity fluctuations in the insulating phase. 相似文献
5.
I. I. Polovinko S. V. Rykhlyuk V. B. Koman I. D. Karbovnyk 《Journal of Applied Spectroscopy》2009,76(1):116-120
We propose a new method for obtaining K2Co
x
Ni1–x
(SO4)2⋅6H2O (x = 0, 0.4, 0.8, 1) crystals, involving the use of the chlorides (CoCl2⋅6H2O and NiCl2⋅6H2O) in an aqueous solution instead of the widely used sulfates. We have studied the transmission spectra of the grown single
crystals in the range λ = 200–900 nm and the IR reflectance spectra in the 2.5–20 μm region. We have observed a change in
the position and intensity of the absorption bands as a function of the composition of the crystals. Based on the Tanabe–Sugano
diagrams, we determined the crystal field splitting (Dq) and its dependence on the nickel concentration.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 126–130, January–February, 2009. 相似文献
6.
The behavior of the spontaneous magnetization σ
s
(T) and coercive force H
c
(T) of dilute nickel ferrites NiGa
x
Al
x
Fe2 − 2x
O4 (x = 0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8) has been studied. Above the transition temperature T
t
, the coercive force H
c
is found to reveal an anomalous behavior for compositions with x ≥ 0.4, namely, the temperature dependence of the coercive force H
c
(T) exhibits a maximum in the range from T
t
to T
C. For the reduced temperature θ2 = 0.8 T
C, at which ferrites with the substitution x ≥ 0.4 reside in the spin glass state, the coercive force H
c
is observed to increase sharply with x. The assumption is made that the clusters prevailing in the spin glass state are no larger than 3 nm in size.
Original Russian Text ? L.G. Antoshina, A.B. Korshak, 2009, published in Fizika Tverdogo Tela, 2009, Vol. 51, No. 5, pp. 900–903. 相似文献
7.
T. I. Krasnenko N. A. Zhuravlev L. A. Perelyaeva 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(3):371-373
The local structure of pyroanion groups in the incommensurate phase X-Zn2 − 2x
Cd2x
V2O7 (0.11 ≤ x ≤ 0.48) with a zero volumetric expansion coefficient is studied. Comparative analysis of IR and NMR spectra of samples in
the X-phase and of ZnCdV2O7 revealed that vanadium atoms have a similar structural and an identical charge environment. Additional bands in the IR spectra
of the X-phase in the range of end vibrations are due to the influence of the cation sublattice. 相似文献
8.
E. I. Lakhno E. I. Burmakin I. V. Korzun G. Sh. Shekhtman 《Physics of the Solid State》2012,54(3):504-507
The rubidium monoferrite RbFeO2-based solid solutions with the composition Rb2 − 2x
Fe2 − x
P
x
O4 have been synthesized, and their crystal structure and the temperature and concentration dependences of the total and electron
conductivities have been studied. The introduction of P5+ ions has been found to sharply decrease the electron conductivity that prevails in pure rubidium monoferrite and, at the
same time, to increase the ionic conductivity. The latter becomes dominant as the phosphorus concentration increases. The
maximum rubidium-cation conductivity of the materials under study is ∼3 × 10−2 S/cm at 300°C and ∼3 × 10−1 S/cm at 700°C. The results have been compared with the previously obtained data for similar solid solutions based on rubidium
monogallate and monoaluminate. 相似文献
9.
P. A. Popov P. P. Fedorov V. M. Reiterov E. A. Garibin A. A. Demidenko I. A. Mironov V. V. Osiko 《Doklady Physics》2012,57(3):97-99
The thermal conductivity of single crystals of Ca1 − x
Er
x
F2 + x
(x = 0.01, 0.05, 0.07, and 0.10) and Ca1 − x
Tm
x
F2 + x
(x = 0.02, 0.04, and 0.06) solid solutions is studied in the temperature ranges 50–300 and 298–673 K. With increasing content
of rare-earth elements, the behavior of thermal conductivity in these solid solutions changes from the characteristic of defect
single crystals to glasslike. The concentration dependences of thermal conductivity for the two systems differ insignificantly. 相似文献
10.
11.
Bulk superconducting samples of type Tl0.5Pb0.5Sr1.6Ba0.4CaCu2−x
Ru
x
O7−δ, (Tl, Pb)/Sr-1212, with 0.0 ≤ x ≤ 0.525 were prepared by the conventional one-step solid-state reaction technique. The prepared samples were investigated
using X-ray powder diffraction, electrical resistivity and electron paramagnetic resonance (EPR) measurements. Enhancement
of the phase formation, superconducting transition temperature T
c and hole carriers concentration P was observed up to x = 0.075. For x > 0.075, a reverse trend was observed. EPR spectra were measured at different temperatures (120–290 K) for all prepared samples.
The number of spins N participating in the resonance and the paramagnetic susceptibility χ were calculated as a function of both Ru-content and
temperature. N and χ increased as the Ru-content increased. A linear relationship between logN and 1/T was established, from which the activation energy E
a was calculated as a function of the Ru-content. The temperature dependence of χ was fitted according to Curie–Weiss type
of magnetic behavior. Curie constant C, Curie temperature θ, the effective magnetic moment μ and the electronic specific heat γ were estimated as a function of the Ru-content. 相似文献
12.
Here we report the synthesis, chemical stability, and electrical conductivity of Ti-doped perovskite-type BaCe0.8-x
Ti
x
Y0.2O3-δ
(x = 0.05, 0.1, 0.2, and 0.3; BCTY). Samples were synthesized by conventional solid state (ceramic) reaction from corresponding
metal salts and oxides at elevated temperature of 1,300–1,500 °C in air. The powder X-ray diffraction confirmed the formation
of a simple cubic perovskite-type structure with a lattice constant of a = 4.374(1), 4.377(1), and 4.332(1) ? for x = 0.05, 0.1, and 0.2 members of BCTY, respectively. Like BaCe0.8Y0.2O3-δ
(BCY), Ti substituted BCTY was found to be chemically not stable in 100% CO2 and form BaCO3 at elevated temperature. The bulk electrical conductivity of BCTY decreased with increasing Ti content and the x = 0.05 member exhibited the highest conductivity of 2.3 × 10−3 S cm−1 at 650 °C in air, while a slight increase in the conductivity, especially at low temperatures (below 600 °C), was observed
in humidified atmospheres. 相似文献
13.
Yu. I. Talanov L. F. Salakhutdinov T. Adachi R. I. Khasanov 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(2):136-138
Excitations of the vortex type in the regions of temperatures both below and above critical temperature T
c are found by studying the local magnetic fields on the surface of Bi2Sr2Ca1 − x
Y
x
Cu2O8 + y
single crystals by means of EPR. The narrow EPR signal of the surface paramagnetic probe allows us to observe weak distortions
of the magnetic field that arise when T > T
c. The behavior of the signal broadening agrees with the hypothesis about the existence of vortices in this temperature region. 相似文献
14.
N. V. Kazak N. B. Ivanova V. V. Rudenko A. D. Vasil’ev D. A. Velikanov S. G. Ovchinnikov 《Physics of the Solid State》2009,51(5):966-969
Ludwigite single crystals of compositions Co3O2BO3 and Co3 − x
Fe
x
O2BO3 (x ≈ 0.14) have been synthesized. The crystal structure is investigated at room temperature, and the magnetization is studied
in the temperature range T = 4.2–100 K in magnetic fields of up to 600 Oe. The orthorhombic symmetry is revealed, and the unit cell parameters are determined.
A number of features are established for the temperature dependence of the magnetization. In unsubstituted Co3O2BO3, two magnetic transitions are found at T
C1 = 43 K and T
C2 = 15 K. At temperatures below 40 K, spin-glass state is revealed. Substitution of iron ions for cobalt ions leads to a noticeable
shift in the magnetic transitions toward the high-temperature range: T
C1 = 83 K and T
C2 = 74 K. A ferromagnetic ordering of the P type is found in the Co3 − x
Fe
x
O2BO3 (x ≈ 0.14) compound.
Original Russian Text ? N.V. Kazak, N.B. Ivanova, V.V. Rudenko, A.D. Vasil’ev, D.A. Velikanov, S.G. Ovchinnikov, 2009, published
in Fizika Tverdogo Tela, 2009, Vol. 51, No. 5, pp. 916–919. 相似文献
15.
M. D. Saksena M. N. Deo K. Sunanda S. H. Behere Ashok Jadhav 《Indian Journal of Physics》2011,85(3):485-495
The emission spectrum of the A
2
Π
r
-X
2
Σ
+ band system of MgCl molecule (360–380 nm) has been recorded on BOMEM DA8 Fourier transform spectrometer at an apodized resolution
of 0.035 cm−1. The spectra have been excited under flowing conditions in a demountable stainless steel hollow cathode lamp (400 V, 250
mA) containing anhydrous MgCl2 and Ar. The resulting spectra are very intense and the 0-0, 1-1, 1-0 bands of A
2
Π
1/2-X
2
Σ
+ sub-transition and the 0-0 band of A
2
Π
3/2-X
2
Σ
+ sub-transition have been rotationally analyzed. Improved molecular constants have been derived using a least-squares fit
program in which optical data of earlier analyzed 0-1 and 0-2 bands (A
2
Π
1/2-X
2
Σ
+) was also included. The Λ-doubling constants in the v′ = 0, 1 levels of the A
2
Π
1/2 sub-state are as expected, i.e. p
1 > p
0, where as it is found that the spin-doubling constants of the v″ = 0, 1 and 2 levels of the ground state X
2
Σ
+, decrease with the increase in v, i.e.
γ
0 > γ
1 > γ
2. This is indicative of the presence of some nearby state, influencing the spin-doubling. 相似文献
16.
O. M. Fedorova A. M. Jankin L. B. Vedmid G. A. Dorogina I. A. Zvereva 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(8):1159-1160
The mechanisms of formation of NdSr2− x
Ca
x
Mn2O7 (0 ≤ x ≤ 2.0) solid solution have been studied. The dependence of its volume magnetic susceptibility on the calcium concentration
is obtained. The stability of this solid solution is compared with that of similar solid solutions in lanthanum-containing
systems. 相似文献
17.
V. V. Mazurenko A. N. Rudenko Ya. O. Kvashnin V. G. Mazurenko Yu. N. Novoselov V. A. Pustovarov A. I. Kukharenko S. O. Cholakh 《Journal of Experimental and Theoretical Physics》2011,112(5):877-883
The ab initio numerical calculations of the electronic structure of simple oxides BeO and SiO2 and complex oxides Be2SiO4 and Be2Si
x
Ge1 − x
O4 with the phenacite structure have been performed using the electron density functional theory. The calculations indicate
that the main feature of the systems under investigation is the presence of oxygen states in both the valence and conduction
bands. The splitting of the bottom of the conduction band has been revealed in the electronic structure of the Be2Si
x
Ge1 − x
O4 system. The splitting width is about 1.5 eV. The main contribution to the formation of a narrow subband of the conduction
band comes from the 2s and 2p states of oxygen and the 4d state of germanium. Microscopic models of the spatial localization of the electron density on lower energy states of the
conduction band of oxide crystals have been developed using the Wannier function technique. The reflection spectra of BeO,
SiO2, and Be2SiO4 have been analyzed. The reported calculations of the electronic structure imply the exciton nature of the 9.7-eV reflection
peak in the Be2SiO4 crystal. 相似文献
18.
M. S. Lebedev 《Optics and Spectroscopy》2009,107(5):776-779
Capabilities of the method of laser null ellipsometry for the study of optical parameters of thin films of multicomponent
alloys are demonstrated. Films of alloys (HfO2)
x
(Al2O3)1 − x
on single-crystal silicon are obtained by the chemical vapor deposition with the use of the following volatile compounds:
hafnium dipivaloylmethanate (IV) and aluminum acetylacetonate (III). The selection of initial sets for their optical parameters
is justified. The selected model is shown to correspond to experimental data. In films deposited from the mixture of precursors,
the refractive index increases from a substrate to a film surface. Due to the separation of sources, films described by a
single-layer model were deposited. This fact is indicative of the homogeneous distribution of components over the film thickness. 相似文献
19.
In the EPR of (La1––x
Gd
y
Ce
x
)Al2 a bottleneck in the relaxation of the conduction electrons to the lattice is present at sufficiently high Gd-concentrations. The bottleneck can be broken by decreasing the Gd-concentration or by adding Cerium as a spin-flip-scatterer.g-factor and line broadening are measured for (La1–y
Gd
y
)Al2 and (La1––x
Gd
y
Ce
x
)Al2 as a function of temperature and Gd- and Ce-concentrations. The Cerium induced relaxationsrate
eL
(Ce) increases linearly with Ce-concentration up tox0.025. This corresponds to the fact, well known by measurements of the Kondo anomalies, that Cerium impurities show no significant interaction up to rather high concentrations. 相似文献