共查询到20条相似文献,搜索用时 31 毫秒
1.
D. P. Kozlenko S. V. Trukhanov E. V. Lukin I. O. Troyanchuk B. N. Savenko 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(4):361-365
The crystal and magnetic structures of the oxygen deficient manganites
La0.7Sr0.3MnO3-d (d = 0.15, 0.20) have been studied by means
of powder neutron diffraction over the 0–5.2 GPa pressure and 10–290 K
temperature ranges. La0.7Sr0.3MnO2.85 exhibits a coexistence
of rhombohedral
and tetragonal (I4/mcm) crystal structures and below
Tg ~ 50 K a spin glass state is formed.
La0.7Sr0.3MnO2.80 exhibits a tetragonal (I4/mcm) crystal structure.
Below Tg ~ 50 K a phase separated magnetic state is formed,
involving coexistence of C-type AFM domains with spin glass domains. In both
compounds the crystal structure and magnetic states remain stable upon
compression. The factors leading to the formation of different magnetic
states in La0.7Sr0.3MnO3-d (d = 0.15, 0.20) and their specific
high pressure behavior, contrasting with that of the stoichiometric
A0.5Ba0.5MnO3 (A = Nd, Sm) compounds showing pressure-induced
suppression of the spin glass state and the appearance of the FM state, are analysed. 相似文献
2.
A. Salmoun R. Brédy J. Bernard L. Chen S. Martin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(1):55-61
Electron capture processes in collision between slow
X7+ (X = N, O and Ne) ions and C60 fullerene have been
investigated using coincident measurements of the number n of ejected
electrons, the mass and charge of the multicharged C60
r+ recoil ions and their fragments Cm
i+ and the final charge state of the
outgoing projectiles X(q-s)+ (
). The
collision velocity is about 0.4 a.u. The partial cross-sections σr
s , corresponding to r electrons transferred to the projectile with only s electrons stabilized, have been measured. Cross-sections
for collisions “inside” and those “outside” the C60
cage have been separated by analyzing the kinetic energy of the outgoing
projectile. The mean final charge state for frontal collisions has been
measured to 3.1, 2.6 and 2.5 for N7+, O7+ and Ne7+
respectively. These results show the importance of the core effect on the
stabilisation processes of captured electrons. 相似文献
3.
J. Voigt E. Kentzinger U. Rücker W. Schweika D. Wermeille W. Schmidt Th. Brückel 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(4):441-451
We have investigated the structural and magnetic properties of
Er|Tb
multilayers by different scattering methods. Diffuse X-ray scattering under
grazing incidence reveals the interface structure in
Er|Tb
bilayers and trilayers, indicating vertically correlated roughness between the Er and Tb interfaces. The magnetic properties
of
ErnEr|TbnTb
superlattices have been studied as a function of the superlattice composition (indices denote the number of atomic layers).
Coupled ferromagnetic structures exist in all investigated samples. The phase transition temperature varies with the Tb layer
thickness.
Modulated magnetic order is short range for all samples beside the
Er20|Tb5
superlattice, the sample with the smallest Tb layer thickness.
We observe dipolar antiferromagnetic coupling between single ferromagnetic Tb layers in all samples, with the onset of this
ordering depending on the Tb layer thickness. Due to competing interactions, exchange coupling is limited to the interface
near region. Therefore long range modulated magnetic order is observed in the
Er20|Tb5
superlattice only, where the interface regions overlap.
The distinct differences to the magnetic structure of an Er0.8Tb0.2
alloy film are explained by a highly anisotropic arrangement of neighbouring
atoms due to the correlated roughness. 相似文献
4.
S. Duffe T. Irawan M. Bieletzki T. Richter B. Sieben C. Yin B. von Issendorff M. Moseler H. Hövel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):401-408
The low energy deposition of silver cluster cations with
561 (±5) atoms on a cold fullerene covered gold surface has
been studied both by scanning tunneling microscopy and molecular
dynamics simulation. The special properties of the
C60/Au(111) surface result in a noticeable fixation of the
clusters without a significant change of the cluster shape. Upon
heating to room temperature we observe a flattening or shrinking
of the cluster samples due to thermal activation. Similar changes were observed also for mass selected Ag clusters with other
sizes. For comparison
we also studied Ag islands of similar size, grown by low
temperature deposition of Ag atoms and subsequent annealing. A
completely different behavior is observed with much broader size
distributions and a qualitatively different response to
annealing. 相似文献
5.
C. Tang K. Deng W. Tan Y. Yuan Y. Liu J. Yang X. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):125-128
The formation mechanism, geometric structures, and
electronic properties of a metal-substituted fullerene
C58Fe2 have been studied using frontier orbital theory
(FOT) and density functional theory (DFT). FOT predicts that two
Fe atoms prefer to substitute the two carbons of a [6,6] double
bond of C60 yielding a structure denoted as C58Fe2-3, which
is different from the two equivalent substitution sites, i.e., the
sites on the opposite of C60 cage or in the nearest
neighboring sites of a pentagonal ring for C58X2 (X=N and
B), and also different from the cross sites of a hexagonal ring
for C58Si2. Five possible structures of C58Fe2 are
optimized using DFT to see whether FOT works. The DFT calculations
support the prediction of FOT. The Mulliken charge of Fe atom in
C58Fe2-3 shows that the two Fe atoms of C58Fe2-3
lose 0.70 electron to the carbons of the cage, and the net spin
populations of Fe atom indicate that each Fe atom has 1.11 μB
magnetic moments, while each of the four nearest neighboring
carbons has
magnetic moments. Thus, the two Fe
atoms have ferromagnetic interaction with each other, and have
weak antiferromagnetic interaction with their four nearest
neighboring carbons, leaving 2.0 μB magnetic moments for the
molecule. 相似文献
6.
A. N. Enyashin V. V. Ivanovskaya Yu. N. Makurin A. L. Ivanovskii 《Physics of the Solid State》2004,46(8):1569-1573
A comparative analysis of the stability factors and electronic structure of two possible crystalline forms of small fullerene C28 and endohedral fullerene Zn@C28 with diamond and lonsdaleite structures is performed using a cluster model. Atoms of elements that, when placed inside C28 cages, have no significant effect on the stability of free small-fullerene molecules are shown to be able to dramatically change the electronic properties and reactivity of the C28 skeleton and to be favorable for forming small-fullerene crystalline modifications, which are covalent crystals. In contrast, if the presence of foreign atoms inside C28 cages stabilizes the isolated nanoparticles, then molecular crystals (such as C60 fullerites) are formed due to weak van der Waals forces. 相似文献
7.
J. Zhao J. Wang J. Jellinek S. Yoo X. C. Zeng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,34(1-3):35-37
The structural properties of medium-sized silicon clusters (Si40, Si45 and Si50) have been studied using an unbiased global genetic algorithm search incorporated with a tight-binding model, followed by gradient-corrected density functional calculations. Stuffed fullerene cages are obtained as energetically favorite structures. The stuffing/cage ratio (m/n for Sim@Sin) can be understood by a space filling picture. The present results, along with our recent works on SiN (N=27-39) clusters [20], suggest that stuffed fullerene cages are the preferred structural growth pattern of medium-sized silicon clusters. 相似文献
8.
Gas-sensing studies on SnO<Subscript>2</Subscript> or NASICON-type composite materials 总被引:1,自引:0,他引:1
NASICON powders were prepared by solid-state synthesis, a fraction was ion exchanged by Li or K, verified by X-ray diffraction and
energy dispersive X-ray analysis, blended with tin oxide powder, transferred to thick film pastes, and dispensed on a commercial
sensor substrate (Heraeus, Germany). Simultaneous gas sensitivity measurements on nine SnO2/NASICON-type (, x = 0, 2.2, 3, M = Li, Na, K) composites in thermocyclic sensor operation mode by exposure to different concentrations of Ethanol,
Toluene, Propylene, CO, and H2 in humidified synthetic air show a strong correlation of the gas-sensing properties with the mobile ion concentration and
type of the solid electrolyte additive. 相似文献
9.
A. Korzenev 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):606-609
New results on the longitudinal inclusive spin asymmetry A
1
d in the range 1 < Q
2 < 100(GeV/c)^2 and 0.004 < x < 0.7 are presented. From these results we derive the spin-dependent structure function g
1
d which we use to evaluate the scale-invariant flavor-singlet axial charge
. The contribution of the measured region is evaluated by a QCD fit of the world data. The data were obtained by the COMPASS
experiment at CERN using a 160GeV polarized muon beam scattered off a large double-cell polarized 6LiD target. The results are in agreement with those from previous experiments and improve considerably the statistical accuracy
in the region x < 0.03. 相似文献
10.
J. P. Marques F. Parente P. Indelicato 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):457-465
In this paper, we used the multiconfiguration Dirac-Fock method to compute with high precision the influence of the hyperfine
interaction on the [Ar]
P0 level lifetime in Zn-like ions for stable and some quasi-stable isotopes of nonzero nuclear spin between Z=30 and Z=92. The
influence of this interaction on the
[Ar]
P
P0 separation energy is also calculated for the same ions. 相似文献
11.
Resonant magnetic X-ray scattering was employed to investigate the magnetic state of epitaxial a* oriented thin films of the heavy fermion superconductor UNi2Al3. The observed incommensurate propagation vector as well as the Ne
l temperature correspond to
those of bulk samples. The 1200
film shows magnetic order with a correlation length >800 ? parallel to the growth axis. Out of the three possible magnetic
domains the one with the moment direction perpendicular to the film surface is not realized. 相似文献
12.
I. Vilfan 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(2):277-284
The properties of
nanowires were investigated with
ab initio calculations based on the density-functional theory.
The molecules build weakly coupled one-dimensional chains, like
and Mo6S9-xIx, and the crystals are
strongly uniaxial in their mechanical and electronic properties.
The calculated moduli of elasticity and resilience along the chain axis are
c11 = 320 GPa and ER = 0.53 GPa, respectively.
The electronic band structure and optical conductivity indicate
that the
crystals are good quasi-one-dimensional conductors.
The frequency-dependent complex dielectric tensor ε, calculated
in the random-phase approximation, shows a strong Drude peak in
ε∥, i.e., for the electric field polarised parallel to
the chain axis, and several peaks related to interband transitions.
The electron energy loss spectrum is weakly anisotropic and has a strong peak
at the plasma frequency ħωp ≈20 eV.
The stability analysis shows that
is metastable against the
formation of the layered
. 相似文献
13.
The structures of two phases of the (NH4)3Nb(O2)2F4 crystal, namely, the parent cubic phase and the most distorted low-temperature phase, have been determined from data of an
X-ray diffraction experiment performed for a powder sample. The profile and structural parameters have been refined according
to the procedure implemented in the DDM program. The results obtained have been discussed with invoking the group-theoretical
analysis of the complete order parameter condensate, which takes into account the critical and noncritical atomic displacements
and allows the interpretation of the obtained experimental data. It has been found that the most probable sequence of structural
transformations occurring in the crystal can be schematically represented in the following form:
_boxclose_boxclose_boxclose_boxclose_boxclose_boxclose_boxclose_boxclose] _5^ + (11 - 7)C2/mP2_1 /m | #xA; P2_1 /n. | #xA; |
#xA;\begin{gathered}
Fm\bar 3m\xrightarrow[{(\eta 1,\eta 1,\eta )}]{{\Gamma _5^ + (11 - 7)}}C2/m\xrightarrow[{(\eta 1,\eta 1,\eta )(0,0,0,0,0,\xi ,0 - \xi ,0,0,0,0)}]{{\Gamma _5^ + (11 - 7) \otimes \Sigma _2 (4 - 2)}}P2_1 /m \hfill \\
\xrightarrow[{(\eta 1,\eta 1,\eta )(0,0,0,0,0,\xi ,0 - \xi ,0,0,0,0)(0,0,0,0,0,\varepsilon ,0,\varepsilon ,0,0,0,0)}]{{\Gamma _5^ + (11 - 7) \otimes \Sigma _2 (4 - 2) \otimes \Sigma _3 (4 - 3)}}P2_1 /n. \hfill \\
\end{gathered}
相似文献
14.
H. M. Huang K. L. Yao 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,83(3):319-323
The electronic structures and magnetic properties of Si3CaC4 in zinc-blende phase has been studied by employing the first-principles method based on density functional theory (DFT).
The calculations predict stable ferromagnetic ground state in Si3CaC4, resulting from calcium substitution for silicon. The calculated total magnetic moment is 2.00 μ
B per supercell, which mainly arises from the Ca and neighboring C atoms. Band structures and density of states studies show
half-metallic (HM) ferromagnetic property for Si3CaC4. The ferromagnetic coupling is generally observed between the Ca and C atoms. The ferromagnetism of Si3CaC4 can be explained by the hole-mediated double exchange mechanism. The sensitivity of half-metallicity of Si3CaC4 as a function of lattice constant is also discussed, and the half-metallicity can be kept in a wider lattice constant range. 相似文献
15.
The lifetimes of the 615 and 619 keV levels in 181Ta have been remeasured by using a
-
delayed coincidence set up with fast plastic (Pilot U) and BaF2 detectors. The presently measured values for both levels have been found to be in strong disagreement with results reported earlier. For the 615 keV level, the half-life has been found to be
ns in striking contrast to the earlier reported value of 17.6
s. The half-life of the 619 keV level has been found to be
ps, whereas values of 0.87 ns and 2.4 ns were reported previously. The nanosecond half-life of the 615 keV level has been confirmed from a separate measurement by employing a NaI(Tl)-Pilot U detector combination. The importance of lifetime measurements for the 615 keV level in perturbed angular correlation studies is discussed.Received: 17 December 2003, Revised: 19 April 2004, Published online: 19 October 2004PACS:
23.20.-g Electromagnetic transitions - 21.10.Tg Lifetimes 相似文献
16.
F. Song L. Han C. Zou J. Su K. Zhang L. Yan J. Tian 《Applied physics. B, Lasers and optics》2007,86(4):653-660
Upconversion blue emissions of Tm3+-ion-heavy-doped NaY(WO4)2 crystals are investigated with three different near-infrared pump mechanisms. The dependence of upconversion efficiency on
the pump mechanism is analyzed from the scope of the concentration quenching effect. Three cross-relaxation processes, , , and , which influence the upconversion dominantly in the Tm3+-heavy-doped system, are demonstrated theoretically and experimentally. The results indicate that Yb3+ ions can weaken the concentration quenching effect of Tm3+ ions significantly so that the blue emission efficiency can be enhanced by one order of magnitude. At the same time, the
wavelength of the pump source also has considerable influence on both the population of some crucial energy levels and the
upconversion mechanism. Experiments show that the upconversion blue emission in Tm3+/Yb3+ co-doped NaY(WO4)2 crystal under 980-nm laser diode excitation is the most intensive of these three different near-infrared pump mechanisms.
The conclusions are confirmed by spectra measurements and calculations of Judd–Ofelt theory and Miyakawa–Dexter theory.
PACS 42.70.Hj; 78.55.-m 相似文献
17.
Results from RHIC have shown that there is an enhanced baryon/meson ratio in the intermediate transverse momentum range (2<pT<6 GeV/c) in Au+Au collisions at both =130 and 200 GeV. This was initially demonstrated by measurements of the p̄/π- ratio which was then extended in pT by the Λ/K0
S ratio. The data were successfully described by models utilising different hadronization mechanisms: those having recombination
of quarks and others having an interplay between flow, jet quenching and incorporating baryon junction loops. The strange
particle data from the first Au+Au run at =200 GeV gave tantalising hints that the observed enhancement of baryons compared to mesons was diminished by a pT of 6 GeV/c, but a lack of statistics in this range made a definitive statement impossible. Here we present an extended analysis
of identified strange baryons and mesons in Au+Au collisions at =200 GeV using data obtained by the STAR experiment from the 2004 running period. The increase in statistics extends the
measurement of Λ hyperons out to at least 7 GeV/c and K0
S mesons out to 9 GeV/c. This data allows us to place limits on the range where in-vacuum fragmentation functions are applicable
and the effect of baryon dominance is reduced. We also discuss the prospects for making these measurements using multiply-strange
baryons and mesons (Ω and ϕ). 相似文献
18.
A. Pashkin K. Thirunavukkuarasu Y.-L. Mathis W. Kang C. A. Kuntscher 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(4):285-290
We present measurements of the infrared response of the
quasi-one-dimensional organic conductor (TMTSF)2FSO3 along
(E
) and perpendicular (E
) to the
stacking axis as a function of temperature. Above the
metal-insulator transition related to the anion ordering the
optical conductivity spectra show a Drude-like response. Below the
transition an energy gap of about 1500 cm-1 (185 meV) opens,
leading to the corresponding charge transfer band in the optical
conductivity spectra. The analysis of the infrared-active
vibrations gives evidence for the long-range crystal structure
modulation below the transition temperature and for the
short-range order fluctuations of the lattice modulation above the
transition temperature. We also report about a new infrared mode
at around 710 cm-1 with a peculiar temperature behavior, which
has so far not been observed in any other (TMTSF)2X salt
showing a metal-insulator transition. A qualitative model based on
the coupling between the TMTSF molecule vibration and the
reorientation of electrical dipole moment of the FSO3 anion is
proposed, in order to explain the anomalous behavior of this new
mode. 相似文献
19.
É. Biémont A. Ellmann P. Lundin S. Mannervik L.-O. Norlin P. Palmeri P. Quinet D. Rostohar P. Royen P. Schef 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):211-219
The difficulty associated with an accurate determination of transition rates for forbidden lines in lowly ionized heavy elements
is illustrated in the case of Nd II. We have investigated the radiative decay of the low-lying metastable levels in Nd+ including the two levels
K11/2 and
I13/2. In these two particular cases, using different theoretical approaches, we find that the decay is dominated by the M1 channels
but that the E2 contributions are of the same order of magnitude. These levels have also been studied experimentally by lifetime
measurements with the heavy ion storage ring CRYRING of Stockholm University. The difficulties encountered when performing
such experiments are underlined and discussed. 相似文献
20.
L. Zhuang K.H. Wong G.K.H. Pang 《Applied Physics A: Materials Science & Processing》2007,89(2):543-546
Wide band gap MgxZn1-xO alloy films were grown on LaAlO3(100) (LAO) substrates by pulsed laser deposition. Structural characterization by X-ray and electron diffraction reveals a
single cubic phase of c-MgxZn1-xO (c-MZO) with composition x>0.6 and heteroepitaxial relationships of (100)c-MZO
(100)LAO (out-of-plane) and (011)c-MZO
(010)LAO
(in-plane). The strain relaxation is analyzed in detail under the framework of domain matching epitaxy. The sequence of 5/4,
4/3 domains observed departs from the ideal 1:4 ratio, indicating a complex strain relaxation mechanism.
PACS 71.55.GS; 74.25.GZ; 81.15.Fg 相似文献
|