共查询到20条相似文献,搜索用时 10 毫秒
1.
F. Pfuner J. G. Analytis J.-H. Chu I. R. Fisher L. Degiorgi 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(4):513-517
We report on a thorough optical investigation of BaFe2As2 over a broad spectral range and as a function of temperature, focusing our attention on its spin-density-wave (SDW) phase
transition at TSDW = 135 K. While BaFe2As2 remains metallic at all temperatures, we observe a depletion in the far infrared energy interval of the optical conductivity
below TSDW, ascribed to the formation of a pseudogap-like feature in the excitation spectrum. This is accompanied by the narrowing of
the Drude term consistent with the dc transport results and suggestive of suppression of scattering channels in the SDW state.
About 20% of the spectral weight in the far infrared energy interval is affected by the SDW phase transition. 相似文献
2.
M. Aoki K. Miwa T. Noritake N. Ohba M. Matsumoto H.-W. Li Y. Nakamori S. Towata S. Orimo 《Applied Physics A: Materials Science & Processing》2008,92(3):601-605
We have investigated the structural and dehydriding properties of Ca(BH4)2. It was found that Ca(BH4)2 undergoes a structural phase transformation from an orthorhombic low-temperature (LT) modification into a tetragonal high-temperature
(HT) modification between 433 K and 523 K. The amount of hydrogen desorbed from Ca(BH4)2 during the pressure–composition (p–c) isotherm measurement was 5.9 mass%. This hydrogen desorption is caused by the partial dehydrogenation of Ca(BH4)2 accompanied by the formation of CaH2 and orthorhombic intermediate phases. 相似文献
3.
S. Vatnik M. C. Pujol J. J. Carvajal X. Mateos M. Aguiló F. Díaz V. Petrov 《Applied physics. B, Lasers and optics》2009,95(4):653-656
The three thermo-optic coefficients of the biaxial laser host KLu(WO4)2 are measured at 633 nm by a deflection method. Their values at 300 K amount to ∂
n
g
/∂
T=−7.4×10−6 K−1; ∂
n
m
/∂
T=−1.6×10−6 K−1 and ∂
n
p
/∂
T=−10.8×10−6 K−1. Nearly athermal propagation directions are found for polarizations along the N
m
and N
p
dielectric axes. 相似文献
4.
Tingyin Ning Cong Chen Yueliang Zhou Heng Lu Dongxiang Zhang Hai Ming Guozhen Yang 《Applied Physics A: Materials Science & Processing》2009,94(3):567-570
CaCu3Ti4O12 (CCTO) thin films were successfully prepared on LaAlO3 substrates by pulsed laser deposition technique. We measured the nonlinear optical susceptibility of the thin films using
Z-scan method at a wavelength of 532 nm with pulse durations of 25 ps and 7 ns. The large values of the third-order nonlinear
optical susceptibility, χ
(3), of the CCTO film were obtained to be 2.79×10−8 esu and 3.30×10−6 esu in picosecond and nanosecond time regimes, respectively, which are among the best results of some representative nonlinear
optical materials. The origin of optical nonlinearity of CCTO films was discussed. The results indicate that the CCTO films
on LaAlO3 substrates are promising candidate materials for applications in nonlinear optical devices. 相似文献
5.
F. Guo J. Ru H. Li N. Zhuang B. Zhao J. Chen 《Applied physics. B, Lasers and optics》2009,94(3):437-441
Lithium terbium molybdate (LiTb(MoO4)2) single crystal was grown by the Czochralski method. The lattice parameters of the crystal were determined by X-ray diffraction
analysis. The absorption coefficient and the Faraday rotation spectrum (B=1.07 T) were investigated at wavelengths of 400–1500 nm at room temperature. Verdet constants of LiTb(MoO4)2 crystal at 532-, 633- and 1064-nm wavelengths were measured by the extinction method. The results show that LiTb(MoO4)2 crystal has a larger magneto-optical figure of merit than that of terbium gallium garnet at wavelengths of 600–1500 nm. 相似文献
6.
Z.-S. Liu 《Applied Physics A: Materials Science & Processing》2009,95(2):443-445
In a rare-earth antiferromagnet, two neighboring magnetic ions order spontaneously in opposite directions below the Néel temperature.
Especially when it is placed in an external magnetic field, the two magnetic ions react to the field in different ways, so
that they usually have different magnitudes and orientations below the magnetic transition temperature. Therefore, to describe
the magnetic structure of an antiferromagnet, the single-ion ferromagnetic-like model is inadequate. To solve this problem,
a two-ion model for rare-earth antiferromagnets is proposed and used in this work to investigate the magnetic properties of
DyNi2B2C. The magnetic susceptibility curves obtained with this model show good agreements with experimental data. 相似文献
7.
R. Moubah S. Colis C. Ulhaq-Bouillet G. Schmerber N. Viart M. Drillon A. Dinia D. Muller J. J. Grob 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(3):315-319
Layered cobalt oxides Ca3Co4O9 thin films have been grown directly on c-cut sapphire substrates using pulsed laser deposition. X-ray diffraction and transmission
electron microscopy characterizations show that the deposited films present the expected monoclinic structure and a texture
along the direction perpendicular to the Al2O3(001) plane. The Ca3Co4O9 structure presents six variants in the film plane. Rutherford backscattering spectroscopy shows that the films are stoichiometric
and that the film thickness agrees with the nominal value. The susceptibility χ of the films, recorded along the c-axis of
the substrate, after field cooling and zero field cooling in an applied field of 1 kOe shows two magnetic transitions at 19
and 370 K which agree well with previous findings on single crystal samples. In turn, at low temperature (5 K), the magnetization
curve along the c-axis exhibits coercive field and remanent magnetization much smaller than those reported for bulk samples,
which can be related to the influence of structural variants and structural defects. 相似文献
8.
S. Ramasubramanian M. Rajagoplan R. Thangavel J. Kumar 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(2):265-268
Elastic and Thermodynamical properties of Ti1-xZrxC have been investigated using LAPW + lo within the density-functional theory with the generalized gradient approximation.
We have studied the stability of the alloy Ti1-xZrxC as a function of Zr composition in rocksalt (B1) structure by calculating the elastic constants C11, C12 and C44 using the tetragonal and trigonal distortions. Mechanical properties such as Poisson ratio, bulk, shear and Young’s modulii
of Ti1-xZrxC are calculated. The Debye temperature and hardness are also computed for the first time to our knowledge for Ti1-xZrxC in various compositions. 相似文献
9.
Summary This work reports the electronic structure of GaInAsSb quaternary alloy by recursion method. A five-orbital sp3s* per atom model was used in the tight-binding representation of the Hamiltonian. The local density of states (LDOS), integrated
density of states (IDOS) and structural energy (ST.E) were calculated for Ga, In, As and Sb sites in Ga0.5 In0.5 As0.5 Sb0.5 and GaInAsSb lattice matched to GaAs and the same alloy lattice matched to GaSb. There are 216 atoms in our cluster arranged
in a zincblend structure. The results are in good agreement with available information about the alloy. 相似文献
10.
The absorption spectra, fluorescence spectrum and fluorescence decay curve of Nd3+ ions in CaNb2O6 crystal were measured at room temperature. The peak absorption cross section was calculated to be 6.202×10−20 cm2 with a broad FWHM of 7 nm at 808 nm for E//a light polarization. The spectroscopic parameters of Nd3+ ions in CaNb2O6 crystal have been investigated based on Judd-Ofelt theory. The parameters of the line strengths Ω
t
are Ω
2=5.321×10−20 cm2,Ω
4=1.734×10−20 cm2,Ω
6=2.889×10−20 cm2. The radiative lifetime, the fluorescence lifetime and the quantum efficiency are 167 μs, 152 μs and 91%, respectively. The fluorescence branch ratios are calculated to be β
1=36.03%,β
2=52.29%,β
3=11.15%,β
4=0.533%. The emission cross section at 1062 nm is 9.87×10−20 cm2. 相似文献
11.
Ali H. Reshak S. Auluck I. V. Kityk Y. Al-Douri R. Khenata A. Bouhemadou 《Applied Physics A: Materials Science & Processing》2009,94(2):315-320
We report theoretical calculations of the band structure and density of states for orthorhombic LiGaS2 (LGS) and LiGaSe2 (LGSe). These calculations are based on the full potential linear augmented plane wave (FP-LAPW) method within a framework
of density functional theory. Our calculations show that these crystals have similar band structures. The valence band maximum
(VBM) and the conduction band minimum (CBM) are located at Γ, resulting in a direct energy band gap. The VBM is dominated by S/Se-p and Li-p states, while the CBM is dominated by Ga-s,
S/Se-p and small contributions of Li-p and Ga-p. From the partial density of states we find that Li-p hybridizes with Li-s
below the Fermi energy (E
F), while Li-s/p hybridizes with Ga-p below and above E
F. Also, we note that S/Se-p hybridizes with Ga-s below and above E
F. 相似文献
12.
J. Jun C. Jin H. Kim J. Kang C. Lee 《Applied Physics A: Materials Science & Processing》2009,96(4):813-818
The structure and photoluminescence properties of TiO2-coated ZnS nanowires were investigated. ZnS nanowires were synthesized by thermal evaporation of ZnS powder and then coated
with TiO2 by using the metal organic chemical vapor deposition (MOCVD) technique. We performed scanning electron microscopy, transmission
electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy, and photoluminescence (PL) spectroscopy
to characterize the as-synthesized and TiO2-coated ZnS nanowires. TEM and XRD analyses revealed that the ZnS core and the TiO2 coatings had crystalline zinc blende and crystalline anatase structures, respectively. PL measurement at room temperature
showed that the as-synthesized ZnS nanowires had two emissions: a blue emission centered in the range from 430 to 440 nm and
a green emission at around 515 nm. The green emission was found to be dominant in the ZnS nanowires coated with TiO2 by MOCVD at 350°C for one or more hours, while the blue emission was dominant in the as-synthesized ZnS nanowires. Also the
mechanisms of the emissions were discussed. 相似文献
13.
F. Pfuner L. Degiorgi K. Y. Shin I. R. Fisher 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(1):11-16
We investigate the rare-earth polychalcogenide R2Te5 (R=Nd, Sm and Gd) charge-density-wave (CDW) compounds by optical reflectivity measurements. We obtain the optical conductivity
through Kramers-Kronig transformation of the reflectivity spectra. From the real part of the optical conductivity we then
extract the excitation energy of the CDW gap and estimate the fraction of the Fermi surface which is gapped by the formation
of the CDW condensate. In analogy to previous findings on the related RTen (n=2 and 3) families, we establish the progressive closing of the CDW gap and the moderate enhancement of the metallic component
upon chemically compressing the lattice. 相似文献
14.
H. He W. Y. Zhang 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(4):457-463
The spin-states of cobalt based perovskite compounds depend sensitively
on the valence state and local crystal environment of Co ions and the
rich physical properties arise from strong coupling among charge, spin,
and orbital degrees of freedom. While extensive studies have been carried
out in the past, most of them concentrated on the isotropic compound
LaCoO3. In this paper, using the unrestricted Hartree-Fock approximation
and the real-space recursion method, we have investigated the competition
of various magnetically ordered spin-states of anisotropic double-layered
perovskite Sr2Y0.5Ca0.5Co2O7. The energy
comparison among these states shows that the nearest-neighbor
high-spin-intermediate-spin ferromagnetically ordered state is the relevant
magnetic ground state of the compound. The magnetic structure and sizes of
magnetic moments are consistent with the recent experimental observation. 相似文献
15.
D. Do S. S. Kim S. W. Yi J. W. Kim 《Applied Physics A: Materials Science & Processing》2009,94(3):697-701
Ferroelectric and dielectric properties of bilayered ferroelectric thin films, SrBi4Ti4O15 grown on Bi4Ti3O12, were investigated. The thin films were annealed at 700°C under oxygen atmosphere. The bilayered thin films were prepared
on a Pt(111)/Ti/SiO2/Si substrate by a chemical solution deposition method. The dielectric constant and dielectric loss of the bilayered thin
films were 645 and 0.09, respectively, at 100 kHz. The value of remnant polarization (2P
r) measured from the ferroelectric thin film capacitors was 60.5 μC/cm2 at electric field of 200 kV/cm. The remnant polarization was reduced by 22% of the initial value after 1010 switching cycles. The results showed that the ferroelectric and dielectric properties of the SrBi4Ti4O15 on Bi4Ti3O12 ferroelectric thin films were better than those of the SrBi4Ti4O15 grown on a Pt-coated Si substrate suggesting that the improved properties may be due to the different nucleation and growth
kinetics of SrBi4Ti4O15 on the c-axis-oriented Bi4Ti3O12 layer or on the Pt-coated Si substrate. 相似文献
16.
T. Rudolf Ch. Kant F. Mayr M. Schmidt V. Tsurkan J. Deisenhofer A. Loidl 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(2):153-160
We studied the optical properties of antiferromagnetic ZnCr2Se4 by infrared spectroscopy up to 28,000 cm-1 and for temperatures from 5 to 295 K. At the magnetic phase transition at 21 K, one of the four phonon modes reveals a clear
splitting of 3 cm-1 as a result of spin-phonon coupling, the other three optical eigenmodes only show shifts of the eigenfrequencies. The antiferromagnetic
ordering and the concomitant splitting of the phonon mode can be suppressed in a magnetic field of 7 T. At higher energies
we observed a broad excitation band which is dominated by a two-peak-structure at about 18,000 cm-1 and 22,000 cm-1, respectively. These energies are in good agreement with the expected spin-allowed crystal-field transitions of the Cr3+ ions. The unexpected strength of these transitions with d-d character is attributed to a considerable hybridization of the
selenium p with the chromium d orbitals. 相似文献
17.
M. A. Algatti R. P. Mota R. Y. Honda M. E. Kayama K. G. Kostov R. S. Fernandes T. C.A.M. Azevedo N. C. Cruz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):325-328
This paper deals with plasma polymerization processes of diethylene glycol dimethyl ether. Plasmas were produced at 150 mtorr
in the range of 10 W to 40 W of RF power. Films were grown on silicon and quartz substrates. Molecular structure of plasma
polymerized films and their optical properties were analyzed by Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible
spectroscopy. The IR spectra show C–H stretching at 3000–2900 cm-1, C=O stretching at 1730–1650 cm-1, C–H bending at 1440–1380 cm-1, C–O and C–O–C stretching at 1200–1000 cm-1. The concentrations of C–H, C–O and C–O–C were investigated for different values of RF power. It can be seen that the C–H
concentration increases from 0.55 to 1.0 au (arbitrary unit) with the increase of RF power from 10 to 40 W. The concentration
of C–O and C–O–C decreases from 1.0 to 0.5 au in the same range of RF power. The refraction index increased from 1.47 to 1.61
with the increase of RF power. The optical gap calculated from absorption coefficient decreased from 5.15 to 3.35 eV with
the increase of power. Due to its optical and hydrophilic characteristics these films can be applied, for instance, as glass
lens coatings for ophthalmic applications. 相似文献
18.
Z. Lu Z. Yang 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(4):455-460
First-principles electronic structure calculations of noble metals (NM=Pd, Pt)/Ce0.75Zr0.25O2 systems are presented. It is found that: the NM adatoms do not prefer to stay at the atop or the bridge sites of the cations
(Ce and Zr), but prefer to be adsorbed at or around the anion sites. The most preferable adsorption sites for both the Pd
and Pt adatoms are the O-bridge sites neighboring the Zr dopant. The Pt adatom show much stronger interaction with the Ce0.75Zr0.25O2(111) surface than does the Pd adatom. The interactions of the NM/Ce0.75Zr0.25O2(111) interfaces are stronger than those of the corresponding NM/ceria(111) interfaces. There are some metal induced gap states
(MIGS) appeared in the gaps of the NM/Ce0.75Zr0.25O2(111) interfaces, which are important to catalytic properties of the NM/Ce0.75Zr0.25O2(111) catalysts. 相似文献
19.
N. Bouarissa 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(2):153-158
Dependencies of electronic structure and lattice properties of InN with zinc-blende structure on hydrostatic pressure are
presented based on band structures computed using the empirical pseudopotential method. The pressure behavior of the pseudopotential
form factors have been analyzed. The effect of pressure on the density of states has been examined. Trends in bonding and
ionicity under pressure are also discussed. Our results show as well that the absolute value of the Fourier transform of the
valence charge density might be useful in the prediction of the phase transition in zinc-blende materials.
Received 25 May 2001 and Received in final form 16 January 2002 相似文献
20.
M. Kodu T. Avarmaa H. Mändar R. Jaaniso 《Applied Physics A: Materials Science & Processing》2008,93(3):801-805
This paper reports the first results obtained on monobarium gallate thin films grown on silicon and platinum coated substrates
by pulsed laser deposition. The influence of oxygen background pressure and substrate (or post-annealing) temperature on the
film properties was studied. The films were characterized by XRD, RHEED, AFM, photoelectron and electrical impedance spectroscopy.
The structure analysis showed that the films crystallized into a hexagonal phase, most probably into (metastable) α-BaGa2O4. Depending on deposition conditions, films with different (from nearly epitaxial to polycrystalline) textures were obtained. 相似文献