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251.
V. A. Nikitenko K. É. Tarkpea I. V. Pykanov S. V. Mukhin S. G. Stoyukhin P. G. Pas'ko 《Journal of Applied Spectroscopy》2000,67(5):883-887
The principal results of the investigation of thermally stimulated electron–hole and ionic processes in hydrothermal and gas-phase ZnO single crystals preexcited at low temperatures, based on simultaneous study of photo-EPR and thermoluminescence (TL), are presented. The nature of the traps determining the TL peaks at 17, 24, 40, 53, 90–110, 140–150, and 160–200 K is discussed. In particular, it has been established that the lithium paramagnetic centers (LiZn
+–OI) play the role of hole traps in ZnO giving green and red TL in the temperature range 160–200 K and, in the case of association with small-sized donors, also TL in the temperature range 90–110 K. The other traps are electronic in character, and in the presence of acceptor lithium in the crystals, they form yellow-orange TL. Optical quenching of TL has been evaluated, and it has been found that there is a difference E 0.75 eV between the thermal and optical energies of ionization of lithium acceptors. Irreversible ionic processes associated with the healing of cationic vacancies at T 360–420 K have been revealed. 相似文献
252.
V. D. Anan’ev A. A. Belyakov M. V. Bulavin A. E. Verkhoglyadov S. A. Kulikov K. A. Mukhin E. P. Shabalin 《Technical Physics》2014,59(2):283-286
The first criticality of a new KZ-202 neutron moderator on the IBR-2M reactor is achieved. The moderator consists of thermal and cold units. The former is a room-temperature comb water moderator; the latter, a moderator using a mixture of aromatic hydrocarbons (mesitylene and m-xylene). The cold moderator is filled with granules of this mixture, which are supplied by a cold helium flow, and operates at 30 K. The combination of two units in one moderator makes it possible to simultaneously take the thermal and cold neutron spectra for extracted-beam spectrometers. The arrangement of the thermal and cold moderators is numerically optimized by the Monte Carlo method. The use of the cold moderator allows a 13-fold increase in the cold neutron intensity from its surface. 相似文献
253.
A. M. Kuz’menko A. A. Mukhin V. Yu. Ivanov A. M. Kadomtseva L. N. Bezmaternykh 《JETP Letters》2011,94(4):294-300
Resonance modes that are due to magnetic excitations in the exchange-coupled subsystems of rare-earth ions (R = Nd3+, Sm3+, and Gd3+) and Fe3+ ions have been detected in submillimeter transmission spectra (0.1–0.6 THz) of RFe3(BO3)4 iron borate-multiferroic single crystals. The strong interaction between spin oscillations of the Fe and R subsystems has
been revealed, which determines the behavior of the modes depending on the anisotropy of the exchange splitting of the ground
doublet of the R ion. It has been shown that the intensities of coupled modes (contributions to the magnetic permeability)
depend strongly on the difference between the g factors of Fe and R ions. This dependence makes it possible to determine the sign of the latter g factor. In particular, a noticeable intensity of exchange Nd modes in NdFe3(BO3)4 is due to an increase in their contribution at g
⊥, ‖Nd < 0, while in GdFe3(BO3)4 with g
Gd ≈ g
Fe ≈ 2, the Fe and Gd contributions compensate each other and the exchange (Gd) mode is not observed. In spite of the weak interaction
of Sm ions with the magnetic field, SmFe3(BO3)4 exhibits resonance modes, which are attributed to the excitation of Sm ions through the Fe subsystem. 相似文献
254.
S. Jandl S. MansouriA.A. Mukhin V. Yu IvanovA. Balbashov M.M. GospodinoV. Nekvasil M. Orlita 《Journal of magnetism and magnetic materials》2011,323(8):1104-1108
In DyMnO3 orthorhombic single crystals, the weak Raman active phonon softening below T=100 K is correlated with the study of infrared active Dy3+ CF excitations as a function of temperature and under applied magnetic field. We detect five H13/2 CF transitions that we predict with appropriate CF Hamiltonian and we confirm that the magnetic easy axis lies in the ab plane. While the CF energy level shifts below T=100 K reflect different displacements of the oxygen ions that contribute to the phonon softening, lifting of the ground state Kramers doublet degeneracy (∼30 cm−1) is observed below TN=39 K due to the anisotropic Mn3+−Dy3+ interaction, which could be responsible for the stability of the bc-cycloid ferroelectric phase. 相似文献
255.
Numerical modeling of photovoltaic efficiency of n‐type GaN nanowires on p‐type Si heterojunction 下载免费PDF全文
In this Letter, we investigate the photovoltaic properties of heterojunction solar cells based on n‐GaN nanowire (NW)/ p‐Si substrate heterostructures by means of numerical modeling. Antireflection properties of the NW array on the top of Si substrate were studied theoretically to show an order of magnitude enhancement in antireflection properties in comparison to the pure Si surface (2.5% vs. 33.8%). In order to determine the optimal morphology and doping levels of the structure with maximum possible efficiency we simulated its properties. The carried out simulation showed that the maximum efficiency should be more than 20% under AM1.5D illumination. The proposed design opens new perspectives and opportunities in the field of heterojunction tandem solar cell researches.
256.
V. A. Khokhlov A. Yu. Prokhorov Yu. V. Medvedev Yu. Nikolaenko A. Mukhin V. P. Pashchenko G. G. Levchenko V. G. Prokhorov N. I. Solin V. L. Svetchnikov J. S. Park J. B. Kim G. Y. P. Lee 《Technical Physics》2011,56(10):1475-1486
The magnetic and transport properties of anion- and cation-deficient Nd0.52Sr0.48MnO3 films with different thicknesses, as well as of two films from this system grown on different SrTiO3 and LaAlO3 substrates, are studied. Below Curie temperature T C, the films with different thicknesses exhibit phase separation: they represent magnetic clusters (drops) embedded in a nonconducting paramagnetic (at T > T N, where T N is the Néel temperature) or antiferromagnetic (T < T N) matrix. The temperature dependences of the resistivity of the films are well described in terms of the polaron mechanism of conduction. In external magnetic field H = 0.01 T, the drops may reach 15 nm in size. They consist of magnetic polarons with a small radius (1–2 nm). The drops are shown to interact with each other in the films. Because of competition between drop-drop dipole interaction and the magnetic energy, the drops disintegrate into droplets with a size comparable to that of a magnetic polaron in a field of 1 T. An explanation is given for the discrepancy between our results and the frequently observed growth of the drops with a rise in the external magnetic field. As the film gets thicker, the fraction of the ferromagnetic phase grows with thickness nonlinearly. In the film grown on SrTiO3 (compressed by 0.9%), the characteristic Néel and Curie temperatures are lower than in the film grown on LaAlO3. The diameters of ferromagnetic drops (both maximal at H = 0.01 T and minimal at H = 1 T) turn out to be roughly the same as in the films with different thicknesses. 相似文献
257.
We find theoretically that competition between ∼K
f
q
4 and ∼Qq
2 terms in the Fourier-transformed conformational energy of a single-lipid chain, in combination with interchain entropic repulsion
in the hydrophobic part of the lipid (bi)layer, may cause a crossover on the bilayer pressure-area isotherm P(A)∼(A−A
0)−α. The crossover manifests itself in the transition from α = 5/3 to α = 3. Our microscopic model represents a single-lipid
molecule as a worm-like chain with a finite irreducible cross-section area A
0, a flexural rigidity K
f
, and a stretching modulus Q in a parabolic potential with the self-consistent curvature B(A) formed by entropic interactions between hydrocarbon chains in the lipid layer. The crossover area A* obeys the relation Q/√K
f
B(A*) ≈ 2. We predict a peculiar possibility of deducing the effective elastic moduli K
f
and Q of an individual hydrocarbon chain from the analysis of the isotherm with such a crossover. Also calculated is the crossover-related
behavior of the area compressibility modulus K
A
, the equilibrium area per lipid A
t
, and the chain order parameter S(θ).
The text was submitted by the authors in English. 相似文献
258.
Ivanov V. Yu. Kuz’menko A. M. Tikhanovskii A. Yu. Pronin A. A. Mukhin A. A. 《JETP Letters》2023,117(1):38-43
JETP Letters - In TbFeO3 orthoferrite at temperatures below the antiferromagnetic ordering temperature for the terbium subsystem (~3.2 K), the electric polarization Pa(Hb) induced by a... 相似文献