共查询到20条相似文献,搜索用时 31 毫秒
1.
Mariana Barturen Mahmoud Eddrieff Julián Milano Sebastián Bustingorry Horia Popescu Nicolas Jaouen Fausto Sirotti Massimiliano Marangolo 《The European Physical Journal B - Condensed Matter and Complex Systems》2013,86(4):191
We show by a combined magnetic force microscopy and synchrotron radiation spectroscopy study that stripe-like patterned magnetic domains are present in Fe1?x Ga x thin films. These stripes, whose origin is attributed to an out-of-plane magnetic component, can be rotated by an external magnetic field. 相似文献
2.
J. Zhu S. L. Ban S. H. Ha 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(2):67
The binding energy of an exciton screened by the electron-hole plasma in a wurtzite
GaN/In
x
Ga1−x
N quantum well (in
the case of 0.1 < x < 1 within which the interface phonon
modes play a dominant role) is calculated including the exciton-phonon interaction by a
variational method combined with a self-consistent procedure. The coupling between the
exciton and various longitudinal-like optical phonon modes is considered to demonstrate
the polaronic effect which strongly depends on the exciton wave function. All of the
built-in electric field, the exciton-phonon interaction and the electron-hole plasma
weaken the Coulomb coupling between an electron and a hole to reduce the binding energy
since the former separates the wave functions of the electron and hole in the
z direction and the later two enlarge the exciton Bohr radius. The
electron-hole plasma not only restrains the built-in electric field, but also reduces the
polaronic effect to the binding energy. 相似文献
3.
M. Wośko B. Paszkiewicz K. Tarnowski B. Ściana D. Radziewicz W. Salejda R. Paszkiewicz M. Tłaczała 《Opto-Electronics Review》2011,19(4):418-424
The paper presents the application of non-modulation reflectance method for composition profiling of epitaxial AlxGa−xAs/GaAs structures. This non-destructive method is based on spectral measurements and theoretical reflectance spectrum matching.
This is a very accurate and sensitive method of determining the Al composition in AlxGa1−xAs layers and structures with resolution down to 1 nm. In this work, the authors describe theoretic principles of this method
and present experimental results of characterization of different AlGaAs structures to prove the potential of the worked out
method. 相似文献
4.
This paper presents the results of conduction band discontinuities calculation for strained/relaxed Si1?x Ge x /Si1?y Ge y heterointerfaces in Γ 15C , Γ 2′C and L upper bands minima, as well as the room-temperature strained (vs. relaxed) band gaps deduced from the classical model-solid theory. Based upon the obtained data, we propose a type-I W-like Si1?y Ge y /Si1?x Ge x /Ge/Si1?x Ge x /Si1?y Ge y quantum wells heterostructure optimized in terms of compositions and thicknesses. Electronic states and wave functions are found by solving Schrödinger equation without and under applied bias voltage. An accurate investigation of the optical properties of this heterostructure is done by calculating the energies of the interband transitions and their oscillator strengths. Moreover, a detailed computation of the bias-voltage evolution of the absorption spectra is presented. These calculations prove the existence of type-I band alignment at Γ 2′C point in compressively strained Ge quantum wells grown on relaxed Ge-rich Si1?y Ge y buffers. The strong absorption coefficient (> 8 × 103 cm-1) and the large Stark effect (0.1 eV @ 2 V) of the Γ 2′C transitions thresholds open up perspectives for application of these heterostructures for near-infrared optical modulators. 相似文献
5.
A. Mitsuda T. Okuma M. Sugishima H. Wada K. Sato K. Kindo 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(2):71
The ternary compound EuPtP exhibits two valence transitions at T
1 = 235 K and T
2 = 190 K. In order to examine a field-induced valence transition of Eu, we synthesized EuPtP1−x
As
x
compounds with 0.05 ≤ x ≤ 0.5 and studied the magnetic and valence behavior. The substitution of As for P increases the lattice volume linearly and
decreases both valence transition temperatures, T
1 and T
2, in contrast to the behavior under external pressures. The magnetization process in a pulsed magnetic field revealed that
EuPtP0.5As0.5 exhibits an onset of metamagnetic transition above 50 T with a large hysteresis, which evidences a first-order field-induced
valence transition. The analysis of the magnetization curves of x = 0.5 at various temperatures has demonstrated that the field-induced transition is essentially the same as the transition
induced by temperature at T
1. 相似文献
6.
V. N. Mughnetsyan A. A. Kirakosyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2009,44(3):140-144
The effect of interdiffusion of Al and Ga atoms on the confining potential and band structure of a three-dimensional superlattice, composed of initially spherical GaAs/Ga1?xAlxAs quantum dots, is investigated in the framework of the modified Wood-Saxon potential model. It is shown that the interdiffusion leads to the disappearance of the quantum dots’ spherical symmetry and to the broadening of the superlattice energy minibands. 相似文献
7.
Second harmonic generation coefficients of GaN and AlxGa1–xN (x=0.08) thin films deposited by MOCVD on a sapphire 0001 substrate were deduced through the standard Maker fringes method. Measurements were performed at =1064 nm using a Nd:YAG Q-Switched laser. The measured ratio between the d33 and d31 coefficients allowed one to retrieve information on the degree of crystallinity of the thin film samples that was found to be higher in thicker films. The presence of tiny oscillations in the SHG detected signal as a function of the incidence angle of the fundamental beam on the samples is discussed and related to the reflectance at the sample-air interfaces. Finally, nonlinear coefficients for three AlxGa1–xN/GaN multiple quantum well (MQW) samples (x=0.08 and x=0.15) were determined and compared to the values obtained for GaN crystalline thin films. PACS 42.65.Ky, 78.66.Fd, 78.67.De, 78.67.Pt 相似文献
8.
M. V. Yakunin G. A. Al’shanskii Yu. G. Arapov V. N. Neverov G. I. Harus N. G. Shelushinina O. A. Kuznetsov A. de Visser L. Ponomarenko 《Physics of the Solid State》2005,47(1):49-53
The structure of the quantum-well valence band in a Ge(111) two-dimensional layer is calculated by the self-consistent method. It is shown that the effective mass characterizing the motion of holes along the germanium layer is almost one order of magnitude smaller than the mass for the motion of heavy holes along the [111] direction in a bulk material (this mass is responsible for the formation of quantum-well levels). This creates a unique situation in which a large number of subbands appear to be populated at moderate values of the layer thickness d w and the hole concentration p s . The depopulation of two or more upper subbands in a 38-nm-thick germanium layer at a hole concentration p s = 5 × 1015 m?2 is revealed from the results of measuring the magnetoresistance in a strong magnetic field aligned parallel to the germanium layers. The destruction of the quantum Hall state at a filling factor ν = 1 indicates that the two lower subbands merge together in a self-formed potential profile of the double quantum well. It is demonstrated that, in a quasi-two-dimensional hole gas, the latter effect should be sensitive to the layer strain. 相似文献
9.
Single crystals of iron borate FeBO3, with part of the iron ions substituted for by Ga diamagnetic ions, were grown through spontaneous crystallization from a melt solution. The chemical composition of the crystals thus prepared, Fe1?xGaxBO3 (x=0, 0.15, 0.25, 0.3), was derived from x-ray microprobe analysis data. Mössbauer spectroscopy and magnetometry were employed to determine the hyperfine interaction parameters (effective magnetic fields at the iron nucleus sites, quadrupole splittings, isomer chemical shifts) and Néel temperatures for these crystals and to derive their temperature behavior. 相似文献
10.
This paper presents step by step the procedure of determination of the quantum efficiency of luminescence of Mn2+ ions in the Zn1−x−yBexMnySe crystals. The method is based on the photoacoustic spectroscopy approach. In the paper, the experimental spectra of absorbance,
transmission, absorption and photoacoustic spectra of the samples are presented and analyzed from the point of view of the
possibility of determination of the quantum efficiency of Mn2+ ion luminescence at room temperature. It was determined experimentally that in the investigated crystals the quantum efficiency
of luminescence in the Mn2+ ions is about 35%, 40%, 32% for the absorption peaks at 430 nm, 470 nm, and 510 nm, respectively, for Zn0.75Be0.2Mn0.05Se crystal. 相似文献
11.
U. P. Verma N. Devi S. Sharma P. Jensen 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,81(4):381-386
First-principles calculations based on the density functional theory are
performed to study the structural properties, spin-polarized electronic band
structures, density of states and magnetic properties of the zinc blende
In1−
x
Mn
x
Sb (x = 0.125, 0.25, 0.50, 0.75, 1.0).
The calculated lattice constants of In1−
x
Mn
x
Sb
obey the Vegard’s law with a marginal upward bowing. With the increase of Mn
concentration in In1−
x
Mn
x
Sb, a transition from
the semi-metallic to the half-metallic behavior happens such that the
majority-spin valence states crosses the Fermi level and the minority-spin
states have a gap at the Fermi level. A large exchange splitting
(∼ 4 eV) is observed between Mn 3d states of the majority-spins
and the minority-spins. The total magnetic moment of
In1−
x
Mn
x
Sb half-metallic ferromagnets per Mn
atom basis is 4μ
B. The total magnetic moment per Mn atom
indicate that Mn atoms act as acceptors in InSb and contribute to holes in
the lattice of InSb. Due to p-d hybridization, the free space charge of Mn
reduces that results a loss in its magnetic moment. The loss in the magnetic
moment of the Mn atoms is converted into a small local magnetic moments on
the In and Sb sites. 相似文献
12.
M. Kumar T. Nautiyal S. Auluck 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,73(3):423-432
We report a systematic study of the electronic, optical, and magneto-optical
properties of the Fe4−xCox (x = 1–3) compounds using the
full-potential linearized augmented plane waves (FPLAPW) method within the
local spin density approximation (LSDA). Pure Fe (x = 0) and Co (x = 4) have
also been studied, the latter in hcp as well as bcc structure, to offer a
better comparison. A good agreement is obtained between calculated optical
conductivity spectra and experimental data. We note that the magneto-optical
properties of these compounds are found to be more akin to those of
bcc Co (which has MOKE very similar to that of bcc Fe) than to those of hcp
Co. This shows strong impact of the environment on the MOKE of these
compounds. With respect to the elemental values, the magnetic moments at Fe
sites are found to be larger in general, while those at Co sites are almost
the same. However, interestingly, despite their larger magnetic moment, the
Kerr rotation remains comparable to that of bcc Fe for most of the energy
range. The origin of Kerr spectra has been explained in terms of optical
transitions. 相似文献
13.
The behavior of the magnetic system of a surface layer of macroscopic Fe1?xGaxBO3 crystal (x=0, 0.3) in the vicinity of the Néel temperature TN was studied. The studies were made by a method involving simultaneous gamma, x-ray, and electron Mössbauer spectroscopy that made it possible to obtain information simultaneously from surface layers and from the bulk of a macroscopic crystal. It was found that the temperature TN(L) at which a thin layer at a depth L from the surface switches to a disordered state is lower than TN for the bulk and is lower the closer this layer is to the surface. In the vicinity of TN, a nonuniform state is observed in which the bulk of the crystal is magnetically ordered and the surface layer is disordered. The transition temperature TN(L) decreases from TN to its surface value within a surface layer of a “critical” thickness. 相似文献
14.
Raman scattering is performed to access phase stability in the boron-implanted Hg0.7Cd0.3Te with fluences ranging from 1 × 1012 to 1 × 1015 cm?2. Threshold fluence for the formation of an amorphous phase is invoked here using Thomas–Fermi statistical model. Asymmetric broadening and red shift of the Raman active HgTe-like LO phonon mode are observed with varying fluencies. Electrical properties such as sheet carrier concentration and mobility are also changed with the fluence and reach their saturated values beyond threshold fluence of 5 × 1013 cm?2. Threshold fluence for the formation of amorphous phase is also validated by the Raman measurements and electrical transport properties in the implanted layers. The excess free energy of 6.8 kJ/mole is found corresponding to the threshold fluence for phase transition. 相似文献
15.
In this work series of LiNiyCo1−yPO4 (y=0, 0.2, 0.4, 0.6, 0.8 and 1) phospho olivines were synthesized by solution co-precipitation technique and characterized
by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and impedance spectroscopic analysis. The XRD patterns of LiNiyCo1−yPO4 (y=0.2, 0.4, 0.6 and 0.8) revealed that they are essentially single phase and have an Olivine-type XRD patterns similar to
those of their parent compounds LiCoPO4 and LiNiPO4. An increase in wave number for most of the dominant infrared bands in PO4 vibrational region for the substitution of Co by Ni in LiCoPO4 indicated the strengthening of both the P-O and Li/Ni-O bonds.
Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003. 相似文献
16.
I. O. Troyanchuk M. V. Bushinsky D. V. Karpinsky V. Sirenko V. Sikolenko V. Efimov 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,73(3):375-381
The Bi1−xAxFeO3−
δ (A = Sr, Pb)
systems have been studied using the X-ray, neutron powder
diffraction and magnetization measurements in a magnetic field up to
14 T. It was found that around x ∼ 0.06 the crystal symmetry
changes from a rhombohedral (space group R3c) to
pseudo-tetragonal. In the composition range
0.07 ≤ x ≤ 0.14 the phases with different symmetry of
the unit cell coexist independent of synthesis conditions. The
neutron powder diffraction shows that the iron ions have average
oxidation state close to 3+. The magnetic structure for
Bi0.5Sr0.5FeO3−
δ is found to be G-type
antiferromagnetic with magnetic moment of about
3.8 μB/Fe3+. The weak ferromagnetic state due to
magnetoelectric interactions was revealed in the lightly doped
rhombohedrally distorted compositions. No evidence for a spontaneous
magnetization was observed for the pseudo-tetragonal phases. These
compositions show irreversible nonlinear magnetization vs. field
behavior apparently due to small local deviations from the
collinearity of the magnetic moments. 相似文献
17.
The optical activity of uniaxial γ1-(GaxIn1?x )2Se3 crystals (x=0.1, 0.2, 0.3, 0.4) is studied at T=295 and 77 K in the spectral range 0.5–0.8 πm. It is found that the cationic substitution In → Ga leads to a nonlinear increase in the specific rotation of the plane of polarization ρ and the component g 33 of the gyration tensor. It is shown that the gyrotropy of the crystals studied is determined by high-energy transitions whose energy exceeds the energy of the edge transitions and that the gyrotropy observed has a molecular origin. 相似文献
18.
E. V. Aghababyan N. P. Harutyunyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2009,44(4):197-199
The dynamic magnetic susceptibility (χac) of magnetically ordered Gd5Si2?xGe2?xSn2x compounds with the partial substitution for silicon and germanium atoms by isovalent tin atoms (2x = 0 ? 0.1) has been investigated experimentally. From the temperature dependence of χac the Curie temperatures of these alloys are determined. It is established that tin-doped alloys have higher Curie temperatures as compared to Gd5Si2Ge2 (ΔT C ≈ 15 K). 相似文献
19.
A. N. Georgobiani A. M. Evloev N. P. Datskevich V. P. Tokarev E. V. Perlov S. V. Semendyaev 《Bulletin of the Lebedev Physics Institute》2009,36(10):296-298
The results of the study of photoluminescence and its excitation spectra in Tl
x
Cu1−x
GaSe2 single crystals are presented. The crystals under study are layered and characterized by anisotropic optical properties.
In this respect, it is important to investigate optical properties of the crystals under study. 相似文献
20.
The temperature and magnetic-field dependences of the magnetocaloric effect in manganites La1−x
Ag
x
MnO3 (x = 0.1; 0.15; 0.2) and La1−x
K
x
MnO3 (x = 0.1; 0.11; 0.13; 0.15; 0.175) were studied by a direct method. Large changes in the sample temperature were detected as
a magnetic field changed by ΔH = 10 kOe. Temperatures of the magnetocaloric effect maxima are near room temperatures. Field dependences of the magnetocaloric
effect show no signs of saturation in fields to 30 kOe. 相似文献