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1.
The local magnetic and valence states of impurity iron ions in the rhombohedral La0.75Sr0.25Co0.98 57Fe0.02O3 perovskite were studied using Mössbauer spectroscopy in the temperature range 87–293 K. The Mössbauer spectra are described by a single doublet at 215–293 K. The spectra contained a paramagnetic and a ferromagnetic component at 180–212 K and only a broad ferromagnetic sextet at T < 180 K. The results of the studies showed that, over the temperature range 87–295 K, the iron ions are in a single (tetrahedral) state with a valence of +3. In the temperature range 180–212 K, two magnetic states of Fe3+ ions were observed, one of which is in magnetically ordered microregions and the other, in paramagnetic microregions; these states are due to atomic heterogeneity. In the magnetically ordered microregions in the temperature range 87–212 K, the magnetic state of the iron ions is described well by a single state with an average spin S = 1.4 ± 0.2 and a magnetic moment μ(Fe) = 2.6 ± 0.4μ B . 相似文献
2.
H. Cherkani-Hassani S. Cherkani-Hassani D. S. Belic J. J. Jureta J. Lecointre P. Defrance 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,58(1):75-83
Absolute cross-sections for electron-impact ionization and dissociation of
C2H2+ and C2D2+ have been measured for electron energies
ranging from the corresponding thresholds up to 2.5 keV. The animated
crossed beams experiment has been used. Light as well as heavy fragment ions
that are produced from the ionization and the dissociation of the target
have been detected for the first time. The maximum of the cross-section for
single ionization is found to be (5.56 ± 0.03)× 10-17 cm2 around 140 eV. Cross-sections for dissociation of C2
H2+ (C2D2+) to ionic products are seen to decrease for two orders
of magnitude, from C2D+ (12.6 ± 0.3) × 10-17 cm2 over CH+(9.55 ± 0.06) × 10-17 cm2,
C+ (6.66 ± 0.05) × 10-17 cm2, C2+ (5.36 ± 0.27) × 10-17 cm2, H+ (4.73 ±
0.29) × 10-17 cm2 and CH2+ (4.56 ± 0.27) × 10-18 cm2 to H2+ (5.68 ± 0.49) ×
10-19 cm2. Absolute
cross-sections and threshold energies have been compared with the scarce
data available in the literature. 相似文献
3.
J. Mahoney V. Tarnovsky K. H. Becker 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):289-293
We measured absolute partial cross sections for the formation of all singly
charged positive ions produced by electron impact on SiCl2 and SiCl
from threshold to 200 eV using the fast-neutral-beam technique. Some of the
cross section curves exhibit an unusual energy dependence with a pronounced
low-energy maximum at an energy around 30 eV, which may be indicative of the
presence of indirect ionization channels. Dissociative ionization channels
are dominant for both species. The experimentally determined total single
ionization cross sections for both species agree very well with calculated
cross sections using the Deutsch-M?rk (DM) formalism. A brief summary of
the ionization cross sections determined for all four SiClx (x=1–4)
species is given highlighting similarities and differences. 相似文献
4.
A. F. Sadykov Yu. V. Piskunov A. P. Geraschenko V. V. Ogloblichev A. G. Smol’nikov I. Yu. Arapova Z. N. Volkova A. A. Bush 《JETP Letters》2017,105(11):715-720
Comprehensive NMR investigation of low-frequency spin dynamics of LiCu2O2 (LCO) and NaCu2O2 (NCO) low-dimensional helical magnets in the paramagnetic state has been carried out for the first time. Temperature dependences of the spin–lattice relaxation rate and anisotropy on various LCO/NCO nuclei have been determined at various orientations of single crystals in an external magnetic field. The spatial asymmetry of spin fluctuations in LCO multiferroic has been discovered. The quantitative analysis of the anisotropy of spin–lattice relaxation in LCO/NCO has allowed estimating the contributions of individual neighboring Cu2+ ions to the transferred hyperfine field on Li+(Na+) ions. 相似文献
5.
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
6.
V. N. Petrov A. B. Ustinov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(3):395-400
The magnetic properties of the magnetite Fe3O4(110) surface have been studied by spin resolved Auger electron spectroscopy (SRAES). Experimental spin resolved Auger spectra
are presented. The results of calculation of Auger lines polarization carried out on the basis of electronic state density
are presented. Problems related to magnetic moments of bivalent (Fe2+) and trivalent (Fe3+) ions on the Fe3O4(110) surface are discussed. It is established that the deposition of a thin bismuth film on the surface results in significant
growth of polarization of iron Auger peaks, which is due to additional spin-orbit scattering of electrons by bismuth atoms. 相似文献
7.
V. M. Apatin V. N. Lokhman D. D. Ogurok D. G. Poydashev E. A. Ryabov 《Journal of Experimental and Theoretical Physics》2011,112(1):1-9
The results of the investigation of the multiphoton ionization of (CF3I)
n
clusters by ultraviolet laser radiation are reported. The yields of the I2+ and I+ ions, which are the products of the multiphoton ionization, have been measured as functions of the intensity of the ultraviolet
radiation at the wavelengths of 308 and 232.5 nm. The degree of multiphoton ionization has been determined and appears to
depend on the wavelength of radiation. The velocity distributions of the products have been measured in detail for various
wavelengths and various polarizations of radiation. The anisotropy parameters of the velocity distributions of the produced
ions and their kinetic energy have been determined. After analysis of the data, a mechanism of the multiphoton ultraviolet
ionization of the clusters under investigation has been proposed. This mechanism depends on the used wavelengths. 相似文献
8.
H. Cherkani-Hassani D. S. Belic J. J. Jureta J. Lecointre P. Defrance 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,58(1):85-94
Absolute cross-sections for electron-impact dissociative ionization of C2
H2+ and C2 D2+ to CH+, C+, C2+ , H+, CH2+
and C2D+ fragments are determined for electron energies ranging
from the corresponding threshold to 2.5 keV. Results obtained in a crossed
beams experiment are analyzed to estimate the contribution of dissociative
ionization to each fragment formation. The dissociative ionization cross
sections are seen to decrease for more than an order of magnitude, from
CH+ (5.37±0.10) × 10-17 cm2 over C+ (4.19±
0.16) × 10-17 cm2, C2D+ (3.94±0.38) ×
10-17 cm2, C2+ (3.82±0.15) × 10-17 cm2
and H+ (3.37±0.21) × 10-17 cm2 to CH2+
(2.66±0.14) × 10-18 cm2. Kinetic energy release
distributions of fragment ions are also determined from the analysis of the
product velocity distribution. Cross section values, threshold energies and
kinetic energies are compared with the data available from the literature.
Conforming to the scheme used in the study of the dissociative excitation of
C2H2+
( C2 D2+ )\left( {\rm C}_2 {\rm D}_2^+ \right), the cross-sections are presented in
a format suitable for their implementation in plasma simulation codes. 相似文献
9.
R. B. Morgunov F. B. Mushenok S. M. Aldoshin N. A. Sanina 《Journal of Experimental and Theoretical Physics》2009,109(4):667-675
The effect of irradiation by ultraviolet light on the effective magnetic moment of a paramagnetic single crystal based on
photochrome spiropyran (Sp) and chromium oxalates Sp3Cr(C2O4)3 molecules is detected. It is shown that the deviation of the temperature dependence of the magnetic moment from the Curie
law is caused not by the exchange interaction, but by electron redistribution between Cr3+ and Cr4+ ions and spiropyran molecules Sp0 and Sp+. Analysis of the angular dependence of EPR spectra makes it possible to determine the contribution of Cr3+ ions to the magnetic properties of the crystals and to determine the crystal field parameters D = 0.619 cm−1 and E = 0.024 cm−1. Irradiation of hydrated samples by ultraviolet light leads to intensity redistribution of EPR lines attributed to Cr3+ and Sp0. Thermally stimulated paramagnetism of triplet states of spiropyran ions Sp+ and the SpI salt is observed. 相似文献
10.
K. A. Subbotin Yu. N. Osipova D. A. Lis V. A. Smirnov E. V. Zharikov I. A. Shcherbakov 《Optics and Spectroscopy》2017,123(1):49-55
Concentration series of disordered scheelitelike Yb:NaGd(MoO4)2 and Yb:NaLa(MoO4)2 single crystals are grown by the Czochralski method. The actual concentrations of Yb3+ ions in the crystals are determined by optical-absorption spectroscopy. The luminescence of Yb3+ ions in these crystals in the region of 1 μm is studied under UV and IR excitation. In the case of UV excitation, this luminescence appears as a result of nonradiative excited state energy transfer from donor centers of unknown nature to ytterbium. The character of the concentration dependence of Yb3+ luminescence indicates that the energy transfer at high Yb concentrations occurs with active participation of a cooperative mechanism, according to which the excitation energy of one donor center is transferred simultaneously to two Yb3+ ions. In other words, the quantum yield of this transfer exceeds unity, which can be used to increase the efficiency of crystalline silicon (c-Si) solar cells. 相似文献
11.
D. Hreniak W. Stręk P. Głuchowski M. Bettinelli A. Speghini 《Applied physics. B, Lasers and optics》2008,91(1):89-93
Nd3+:Y3Al5O12 (Nd:YAG) powders were prepared by the Pechini method in the temperature range of 800 to 1400 °C. The pure garnet phase of
the obtained materials was confirmed by XRD studies. The size of the grains was controlled by the annealing temperature of
the samples. Their morphologies were investigated by TEM and porosity measurements (BET). The effect of annealing temperature
on the morphology and luminescence properties of Nd:YAG nanocrystallites was studied, and the results were compared to the
properties of a Nd:YAG single crystal. A significant enhancement of the 4F3/2→4I9/2/4F3/2→4I11/2 intensity ratio with decreasing grain size was observed. It was found that the decay times of the Nd3+ luminescence depends on the specific surface and is significantly longer for well crystallized nanocrystalline grains than
for single crystals having the same concentration of Nd3+ ions. The role of crystallinity and specific surface on the radiative processes is analyzed.
PACS 78.55.-m; 78.20.Ci; 78.67.Bf; 78.68.+m 相似文献
12.
A. M. Vorotynov G. A. Petrakovskiĭ Ya. G. Shiyan L. N. Bezmaternykh V. E. Temerov A. F. Bovina P. Aleshkevych 《Physics of the Solid State》2007,49(3):463-466
Single crystals of yttrium aluminum borate YAl3(BO3)4 doped with manganese ions are studied using electron paramagnetic resonance spectroscopy. It is shown that manganese ions introduced at low concentrations into the sample predominantly occupy yttrium ion sites in the crystal structure. The shape of the electron paramagnetic resonance spectrum unambiguously indicates that the valence of manganese ions in this case is equal to 2+. The parameters of the spin Hamiltonian of Mn2+ ions in the YAl3(BO3)4 matrix are determined at room temperature. The magnitude and sign of the fine structure parameter D allow the conclusion that the YAl3(BO3)4 single crystals doped with manganese ions have a strong crystal field at the yttrium ion sites and easy-axis anisotropy. 相似文献
13.
I. A. Gudim A. A. Demidov E. V. Eremin D. K. Shukla 《Physics of the Solid State》2018,60(10):1989-1998
The magnetic and magnetodielectric properties of Ho0.5Nd0.5Fe3(BO3)4 ferroborate with the competing Ho–Fe and Nd–Fe exchange couplings have been experimentally and theoretically investigated. Step anomalies in the magnetization curves at the spin-reorientation transition induced by the magnetic field B ║ c have been found. The spontaneous spin-reorientation transition temperature TSR ≈ 8 K has been refined. The measured magnetic properties and observed features are interpreted using a single theoretical approach based on the molecular field approximation and calculations within the crystal field model of the rare-earth ion. Interpretation of the experimental data includes determination of the crystal field parameters for Ho3+ and Nd3+ ions in Ho0.5Nd0.5Fe3(BO3)4 and parameters of the Ho–Fe and Nd–Fe exchange couplings. 相似文献
14.
A. V. Dmitriev E. V. Vladimirova M. V. Kandaurov A. Yu. Chufarov D. G. Kellerman 《Physics of the Solid State》2017,59(12):2360-2364
Samples of BiFe0.93Mn0.07O3 with different specific surface area were synthesized for the first time by ultrasonic spray pyrolysis. The resulting powders consist of porous particles of a spherical shape of medium size ~0.5 μm and have record values of residual magnetization and coercive force. It is found that the magnetic properties of the porous powder particles are determined by the distortion of the crystal lattice and the presence of uncompensated magnetic moments of iron ions on the surface. 相似文献
15.
E. V. Eremin N. V. Volkov K. A. Sablina O. A. Bayukov M. S. Molokeev V. Yu. Komarov 《Journal of Experimental and Theoretical Physics》2017,124(5):792-804
The indirect-coupling model is used to analyze the exchange magnetic structure of Pb3Mn7O15 in the hexagonal setting. The ratios of manganese ions Mn4+/Mn3+ in each nonequivalent position are determined. Pb3(Mn0.95Ge0.05)7O15 and Pb3(Mn0.95Ga0.05)7O15 single crystals are grown by the solution–melt method in order to test the validity of the proposed model. The structural and magnetic properties of the single crystals are studied. The magnetic properties of the grown single crystals are compared with those of nominally pure Pb3Mn7O15. 相似文献
16.
Li3V2(PO4)3 glass-ceramic nanocomposites, based on 37.5Li2O-25V2O5-37.5P2O5 mol% glass, were successfully prepared via heat treatment (HT) process. The structure and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD patterns exhibit the formation of Li3V2(PO4)3 NASICON type with monoclinic structure. The grain sizes were found to be in the range 32–56 nm. The effect of grain size on the dynamics of Li+ ions in these glass-ceramic nanocomposites has been studied in the frequency range of 20 Hz–1 MHz and in the temperature range of 333–373 K and analyzed by using both the conductivity and modulus formalisms. The frequency exponent obtained from the power law decreases with the increase of temperature, suggesting a weaker correlation among the Li+ ions. Scaling of the conductivity spectra has also been performed in order to obtain insight into the relaxation mechanisms. The imaginary modulus spectra are broader than the Debye peak-width, but are asymmetric and distorted toward the high frequency region of the maxima. The electric modulus data have been fitted to the non-exponential Kohlrausch–Williams–Watts (KWW) function and the value of the stretched exponent β is fairly low, suggesting a higher ionic conductivity in the glass and its glass-ceramic nanocomposites. The advantages of these glass-ceramic nanocomposites as cathode materials in Li-ion batteries are shortened diffusion paths for Li+ ions/electrons and higher surface area of contact between cathode and electrolyte. 相似文献
17.
G. A. Petrakovskii L. N. Bezmaternykh I. A. Gudim D. Sheptyakov O. A. Bayukov A. M. Vorotynov D. A. Velikanov A. F. Bovina 《Physics of the Solid State》2005,47(11):2114-2118
The magnetic susceptibility and specific heat of single crystals of the Ba2Fe2GeO7 barium ferrigermanate are investigated. It is revealed that the temperature dependence of the magnetic susceptibility exhibits a kink at a temperature T = 8.5 K. The number of nonequivalent positions of Fe3+ ions and their occupancies are determined using Mössbauer spectroscopy. It is shown that the Fe3+ ions located in tetrahedral positions T2 are ordered incompletely, which is inconsistent with the results obtained previously. An assumption is made regarding the possible ground magnetic state of the Ba2Fe2GeO7 compound. 相似文献
18.
Vasily Lavrentiev Jiri Vacik Hiroshi Naramoto Kazumasa Narumi 《Applied Physics A: Materials Science & Processing》2009,95(3):867-873
The structure transformation occurring in fullerene film under bombardment by 50 keV C60+ cluster ions is reported. The Raman spectra of the irradiated C60 films reveal a new peak rising at 1458 cm−1 with an increase in the ion fluence. This feature of the Raman spectra suggests linear polymerization of solid C60 induced by the cluster ion impacts. The aligned C60 polymeric chains composing about 5–10 fullerene molecules have been distinguished on the film surface after the high-fluence
irradiation using atomic force microscopy (AFM). The surface profiling analysis of the irradiated films has revealed pronounced
sputtering during the treatment. The obtained results indicate that the C60 polymerization occurs in a deep layer situated more than 40 nm below the film surface. The deep location of the C60 polymeric phase indirectly confirms the dominant role of shock waves in the detected C60 phase transformation. 相似文献
19.
Yu. V. Zorenko V. I. Gorbenko G. B. Stryganyuk V. N. Kolobanov D. A. Spasskii K. Blazek M. Nikl 《Optics and Spectroscopy》2005,99(6):923-931
The luminescence of excitons and antisite defects (ADs) was investigated, as well as the specific features of the excitation energy transfer from excitons and ADs to the activator (Ce3+ ion) in phosphors based on Lu3Al5O12:Ce (LuAG:Ce) single crystals and single-crystalline films, which are characterized by significantly different concentrations of ADs of the Lu Al 3+ type and vacancy-type defects. The luminescence band with λmax = 249 nm in LuAG:Ce single-crystal films is due to the luminescence of self-trapped excitons (STEs) at regular sites of the garnet lattice. The excited state of STEs is characterized by the presence of two radiative levels with significantly different transition probabilities, which is responsible for the presence of two excitation bands with λmax = 160 and 167 nm and two components (fast and slow) in the decay kinetics of the STE luminescence. In LuAG:Ce single crystals, in contrast to single-crystal films, the radiative relaxation of STEs in the band with λmax = 253.5 nm occurs predominantly near Lu Al 3+ ADs. The intrinsic luminescence of LuAG:Ce single crystals at 300 K in the band with λmax = 325 nm (τ = 540 ns), which is excited in the band with λmax = 175 nm, is due to the radiative recombination of electrons with holes localized near Lu Al 3+ ADs. In LuAG:Ce single crystals, the excitation of the luminescence of Ce3+ ions occurs to a large extent with the participation of ADs. As a result, slow components are present in the luminescence decay of Ce3+ ions in LuAG:Ce single crystals due to both the reabsorption of the UV AD luminescence in the 4f-5d absorption band of Ce3+ ions with λmax = 340 nm and the intermediate localization of charge carriers at ADs and vacancy-type defects. In contrast to single crystals, in phosphors based on LuAG:Ce single-crystal films, the contribution of slow components to the luminescence of Ce3+ ions is significantly smaller due to a low concentration of these types of defects. 相似文献
20.
V. N. Makhov T. V. Uvarova M. Kirm S. Vielhauer 《Bulletin of the Lebedev Physics Institute》2016,43(12):348-351
Thermal quenching of interconfigurational 5d-4f luminescence of Er3+ and Tm3+ ions in BaY2F8 crystals is studied in the temperature range of 330–790 K. The quenching temperatures are ~575 and ~550 K for Er3+ and Tm3+, respectively. It is shown that quenching of 5d-4f luminescence of Tm3+ ions is caused by thermally stimulated ionization of 5d electrons to the conduction band. 相似文献