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1.
Superconductivity was achieved in Ti-doped iron-arsenide compound Sr4Cr0.8Ti1.2O6Fe2As2 (abbreviated as Cr-FeAs-42622). The X-ray diffraction measurement shows that this material has a layered structure with the space group of P4/nmm, and with the lattice constants a = b = 3.9003 Å and c = 15.8376 Å. Clear diamagnetic signals in ac susceptibility data and zero-resistance in resistivity data were detected at about 6 K, confirming the occurrence of bulk superconductivity. Meanwhile we observed a superconducting transition in the resistive data with the onset transition temperature at 29.2 K, which may be induced by the nonuniform distribution of the Cr/Ti content in the FeAs-42622 phase. 相似文献
2.
K.?Koyasu M.?Niemietz W.?Westh?user G.?Gantef?r 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(1):59-62
The decay path of an Ag8(O2)- cluster photoexcited by a 3.1 eV photon is elucidated using time-resolved photoelectron spectroscopy. Photoabsorption results
in the formation of an excited state giving rise to a peak in the photoelectron spectra with well-resolved vibrational finestructure.
With a lifetime of about 100 fs this bound state decays into an anti-bonding state which dissociates into O2 and Ag8- on a timescale of 10 ps. In the photoelectron spectra, this corresponds to a broad maximum shifting gradually towards higher
binding energy while the O2 and Ag8- separate. Finally, the spectrum of bare Ag8- appears. This process is unique to small clusters, because on metal surfaces excited state lifetimes are too short to allow
for direct dissociation. 相似文献
3.
V.C. Selvaraju S. Asokan V. Srinivasan 《Applied Physics A: Materials Science & Processing》2003,77(1):149-153
The I–V characteristics of bulk As40Te60-xSex and As35Te65-xSex glasses have been studied with a current sweep of 0–18 mA-0, over a wide range of compositions (4≤x≤22). All the glasses
studied showed a threshold electrical switching behaviour. The number of switching cycles withstood by the samples has been
found to depend on the ON-state current. It is seen that the switching voltages increase with increase in selenium content.
Further, the switching voltages are found to be almost independent of the thickness of the sample (d), in the range 0.18–0.3 mm.
Also, the switching voltages and the number of switching cycles withstood by the samples are found to decrease with temperature.
Received: 6 November 2002 / Accepted: 8 November 2002 / Published online: 29 January 2003
RID="*"
ID="*"Corresponding author. Fax: +91-80/360-0135, E-mail: sasokan@isu.iisc.ernet.in 相似文献
4.
Spin-wave resonances have been observed in superlattices arising due to the phase separation and self-organization of charge carriers in Eu0.8Ce0.2Mn2O5 single crystals. The resonances are found within the 5–80 K temperature range at frequencies close to 30 GHz. Similar resonances with intensities about an order of magnitude lower are also observed in EuMn2O5. The latter suggests the existence of charge transfer processes between the manganese ions of different valences in EuMn2O5. 相似文献
5.
Using the effective field theory with correlations, we study mixed spin?3/2 and spin?1/2 Ising models with random bonds and crystal-field interactions on the honeycomb lattice. The nearest-neighbour couplings Jij are taken as random variables with distribution P(Jij) = pδ(Jij ? J)+(1 ? p)δ(Jij ? αJ), where J > 0 and |α| ≤ 1. In a certain range of negative values of α, the phase diagrams exhibit re-entrant behaviour. In detail, we investigate separately two kinds of disorder: Bond dilution (α = 0) and random ±J interactions (α = ?1). In both cases, the influence of the an-isotropy on the phase diagrams shows some new outstanding features. 相似文献
6.
The LHCb experiment is in preparation, to be ready for the start of the LHC. The physics which will be performed by LHCb is
reviewed, focussing on what can be learnt fromB
s
0
mesons. 相似文献
7.
T.-J. Wang J.-C. Gao Yu. M. Andreev S. A. Bereznaya T. N. Kopylova Z. V. Korotchenko G. V. Lanskii T. D. Malinovskaya A. N. Morozov S. Yu. Sarkisov 《Russian Physics Journal》2007,50(6):560-565
The most probable parameters of the pure, doped, and mixed GaSe1−xSx (x ≤ 0.4) crystals (solid solutions) are presented together with the results of investigations of their crystal structure
and defects, optical and mechanical properties, and damage thresholds.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 35–40, June, 2007. 相似文献
8.
Powder neutron diffraction and Hi-Q neutron diffraction data have been recorded and analysed in order to obtain the local and long range order of Cu in Cudoped
CeO2 with three doping levels of Cu. Rietveld method and MCGR techniques of data analysis for the two types of data reveal that
the Cu ion is in the 2+ oxidation state and has a vacancy in its first coordination shell. These deductions from the data
analysis fit well with the mechanism of catalysis we propose. 相似文献
9.
简单地将两个空的锡罐用一根长线连接起来,一个人把一个罐子放在耳朵上,就可以听到另一个人对着另一端罐子的轻声说话,一根简单的线可以使声音传播得比在空气中还远。 相似文献
10.
In this study, diode applications of Crystal Violet (CV) and PEDOT materials were studied. The Ni/p-Si/Al, Ni/CV/p-Si/Al and Ni/PEDOT:PSS/CV/p-Si/Al diodes were fabricated. The I–V (current-voltage) characteristics of all diodes were analyzed at room temperature, it was determined that the PEDOT:PSS and CV materials improved the basic diode parameters. Also, I–V characteristics of Ni/PEDOT:PSS/CV/p-Si/Al of diode were investigated for different temperature values. It has been determined that the basic diode parameters are strongly dependent on temperature. It was determined that while the barrier height (Φb) increased with increasing temperature, the ideality factor (n) and the series resistance (Rs) values decreased. Using temperature-dependent measurements, it was determined that the potential barrier and ideality factor values at the contact interface has a double Gaussian distribution. In addition, C–V (capacitance-voltage) measurements of these diodes were analyzed depending on the frequency. It was found that the diode capacitance decreased with increasing frequency. 相似文献
11.
O.-H. Kwon H. Yoo D.-J. Jang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):69-75
While the intercalation of C60 and the formation of C
60
-
in the supercages of NaX and NaY are confirmed by using 129Xe NMR and ESR, the photophysical properties of C60 and C
60
-
are characterized by monitoring transient reflectance spectra and kinetics, fluorescence kinetics, and diffuse reflectance
spectra. C
60
-
is considerably more abundant in NaY than in NaX. This difference is explained in terms of polarity difference between two
zeolites. Both C60 and C
60
-
have remarkably elongated excited-state lifetimes due to their collision-free environment in zeolitic nanocavities although
C
60
-
has much shorter lifetimes than C60. C
60
-
, in particular, shows intense absorption and emission due to its reduced symmetry in zeolites.
Received 13 July 2001 and Received in final form 8 October 2001 相似文献
12.
A. E. Teplykh S. G. Bogdanov É. Z. Valiev A. N. Pirogov Yu. A. Dorofeev A. A. Ostroushko A. E. Udilov V. A. Kazantsev A. E. Kar’kin 《Physics of the Solid State》2003,45(12):2328-2333
Nanocrystalline samples of the manganites La0.9Ag0.1MnO3, La0.7Ag0.3MnO3, and La0.7Sr0.3MnO3 were synthesized through pyrolysis and isothermally annealed. The atomic, subatomic, and magnetic structures of these manganites were studied using magnetic, x-ray, and neutron diffraction measurements. Increasing the annealing temperature from 600 to 1200°C coarsens the grains from 30–40 to 600–700 nm in size. All the samples studied have rhombohedral structure and are ferromagnets. The Curie temperature decreases for the samples doped by silver and increases for the samples doped by strontium as the anneal temperature is increased. The magnetization of the Mn ions increases with nanoparticle size in all the three systems, which indicates the presence of a size effect. 相似文献
13.
N. Oshimo 《The European Physical Journal C - Particles and Fields》2005,39(3):383-388
The measurability of generation mixing is studied on pair production of sneutrinos in e
+
e
- collisions and their subsequent decays into two different charged leptons e and μ with two lighter charginos. The analyses are made systematically in a general framework of the supersymmetric extension
of the standard model. The production and decay process depends on the parameters of the chargino sector as well as those
of the sneutrino sector. Although generation-changing interactions are severely constrained by radiative charged-lepton decays,
sizable regions in the parameter space could still be explored at e
+
e
- colliders in the near future.
Received: 6 October 2004, Revised: 14 November 2004, Published online: 14 January 2005
PACS:
11.30.Hv, 12.15.Ff, 12.60.Jv, 14.80.Ly 相似文献
14.
Single crystals of Eu0.62Bi0.38MnO3 and Eu0.53Bi0.32Sr0.15MnO3 solid solutions crystallizing in an orthorhombically distorted perovskite structure were prepared. At temperatures above 120 K, Eu0.62Bi0.38MnO3 exhibits the properties of structural glass while remaining a dielectric at all temperatures. There is no long-range magnetic order in this compound. Eu0.53Bi0.32Sr0.15MnO3 behaves as a semiconductor above 120 K and exhibits a jump in conductivity at T = 175 K associated with a metal-insulator transition occurring within limited regions of the crystal. In these regions, there appears a ferromagnetic moment (due to double exchange mediated by charge carriers) and local electric polarization. 相似文献
15.
Stanislav V. Averin Petr I. Kuznetzov Victor A. Zhitov Nikolai V. Alkeev 《Optical and Quantum Electronics》2007,39(3):181-192
Solar-blind MSM photodetectors based on the AlGaN heterostructures have been fabricated and investigated. The influence of
material properties on device parameters is discussed. Effect of different buffer layers on the detector performances has
been examined. Detectors exhibit low dark currents and high sensitivity within the range of 250–290 nm. Effect of optical
excitation energy on GaN-based MSM-detector performance is analyzed and discussed. At high excitation level the detector speed
of response is limited by the field screening caused by the space-charge of the holes. The impulse response of GaN-based MSM-detector
is compared favorably with GaAs MSM-device. 相似文献
16.
Jyotsna Galgale Nupinder Kaur Preeti Singh Manik Manake N. K. Gaur R. K. Singh 《Pramana》2004,63(2):413-417
An extended three-body force shell model (ETSM) has been applied to investigate the static and dynamic properties of KCN
x
Cl1−x
for the compositionx = 0.56 and 1.0 at 300 K. The phonon dispersion curves computed by us are compared with the single crystal neutron diffraction
data. The unusual features of these curves are the upward curvature seen in some of the acoustic branches. This is a result
ofK-dependent softening of the phonon due to translation-rotation coupling. The transverse acoustic branch is more soft near
the zone centre. 相似文献
17.
A miniature tunable TEA CO2 laser using isotope 13C16O2 as the active medium is developed to extend the spectral range of CO2 lasers for further application. The optimization of the energy parameters of the tunable TEA 13C16O2 laser and the same laser using 12C16O2 are studied. When a gas mixture (13C16O2: N2: He = 1: 1: 3) at a total pressure of 6.4 × 104 Pa is used, the TEA 13C16O2 laser of a 45-cm3 active volume obtains 51 emission lines in the [0001–1000] and [0001–0200] bands. The maximum pulse energy of the TEA 13C16O2 laser is about 357 mJ. The same laser using the conventional gas mixture (12C16O2: N2: He = 1: 1: 3) at a pressure of 6.66 × 104 Pa is measured to obtain 69 laser emission lines and the maximum pulse energy of laser radiation is about 409 mJ. 相似文献
18.
Peng-Ming Zhang Xi-Guo Lee Shao-Feng Wu 《International Journal of Theoretical Physics》2007,46(12):3234-3241
We investigate the solitons in the CP
N
model in terms of the decomposition of gauge potential. Based on the φ-mapping topological current theory, the charge and position of solitons is determined by the properties of the typical component.
Furthermore, the motion and the bifurcation of multi-soliton is discussed. And the knotted solitons in high dimension is explored
also. 相似文献
19.
D. Hennequin P. Verkerk 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,57(1):95-104
The dynamics of cold atoms in conservative optical lattices obviously depends on the geometry of the lattice. But very similar
lattices may lead to deeply different dynamics. In a 2D optical lattice with a square mesh, it is expected that the coupling
between the degrees of freedom leads to chaotic motions. However, in some conditions, chaos remains marginal. The aim of this
paper is to understand the dynamical mechanisms inhibiting the appearance of chaos in such a case. As the quantum dynamics
of a system is defined as a function of its classical dynamics – e.g. quantum chaos is defined as the quantum regime of a
system whose classical dynamics is chaotic – we focus here on the dynamical regimes of classical atoms inside a well. We show
that when chaos is inhibited, the motions in the two directions of space are frequency locked in most of the phase space,
for most of the parameters of the lattice and atoms. This synchronization, not as strict as that of a dissipative system,
is nevertheless a mechanism powerful enough to explain that chaos cannot appear in such conditions. 相似文献