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1.
Nuclear spin-lattice relaxation rate measurements of Rb87 in the isotropic antiferromagnet RbMnF3 have been performed from 27 to 500°K. Both the high temperature value of the relaxation rate and its temperature dependence are well explained by a theoretical calculation essentially based on Moriya's theory. 相似文献
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The 87Rb and 19F nuclear relaxation rates in antiferromagnetic RbMnF3 are calculated as a function of temperature. The large difference in the relaxation rates of both nuclei as well as their temperature dependences are well accounted for over a considerable temperature range by a two-magnon process induced by the dipolar and “contact” parts of the hyperfine interaction. 相似文献
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Kh. G. Bogdanova V. A. Golenishchev-Kutuzova M. R. Nazipov M. M. Shakirzyanov S. V. Petrov 《Physics of the Solid State》1999,41(2):265-268
Magnetoacoustic resonance on nuclear spin waves is measured in the cubic antiferromagnet RbMnF3. A resonance change with respect to a constant magnetic field H
0 with maximum damping at H
0≈4×103 Oe is observed in the amplitude of an acoustic pulse passing through a sample owing to excitation of nuclear spin waves under
nuclear magnetoacoustic resonance conditions. A study of the angular dependence of the damping revealed a 90° periodicity
consistent with the fact that the [001] direction, around which the rotation takes place, is a four-fold axis of the crystal.
An analysis of the dispersion law for nuclear spin waves shows that longitudinal ultrasound propagating along the [001] axis
perpendicular to H
0 excites a branch of nuclear spin waves whose frequency depends on the magnitude of the constant magnetic field.
Fiz. Tverd. Tela (St. Petersburg) 41, 297–300 (February 1999) 相似文献
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It is shown that metallic condensation should occur in Si even under condition of heavy doping. The density of delocalized donor-electrons strongly influences the equilibrium density of holes within the drop and in that fashion the half-width of the electron-hole recombination line. It is therefore possible to derive properties of the semiconductor-metal transition from a study of the electron-hole drop in doped samples. This is confirmed by an application to Si : P. 相似文献
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Absorption spectra of RbMnF3 in the 5500Å region were investigated in the temperature interval 4.2–77°K. Similar temperature dependence was observed for the exciton-magnon and the magnon-phonon sidebands. The position of the exciton lines does not vary as the temperature is increased. 相似文献
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C. P. Painuli B. P. Bahuguna B. D. Indu M. D. Tiwari 《International Journal of Theoretical Physics》1992,31(1):81-108
The theory of first-, second-, and third-order Raman scattering is investigated for isotopically disordered anharmonic crystals. The theory of time-dependent thermodynamic Zubarev Green's functions is adopted to obtain the Raman tensor, intensity of Raman lines, and differential cross sections of various orders of scatterings. It is observed that each class of scattering can be separated into diagonal and nondiagonal parts. The first-order and nondiagonal parts are absent in the case of chemically pure crystals. The diagonal parts are separated into anharmonic and interference terms. The interference terms arise due to the interactions of anharmonic phonons with the local phonons. The temperature and defect dependencies are discussed in detail along with the nature of continuous and line spectra. It is proposed that very high-power laser sources will reveal the third-order spectra, and that the resulting structure can be explained with the help of temperature-dependent one-, two-, and three-phonon density of states. 相似文献
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Glazkov VN Smirnov AI von Nidda HA Loidl A Uchinokura K Masuda T 《Physical review letters》2005,94(5):057205
The paramagnetic fraction surviving at the impurity-induced antiferromagnetic phase transition in the spin-Peierls magnet CuGeO3 is found to increase with an external magnetic field. This effect is explained by the competition of the Zeeman interaction and of the exchange interaction of local antiferromagnetic clusters formed on the spin-gap background near impurities. 相似文献
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The photoluminescence of Fe3+ in octahedral oxygen co-ordination has been observed in Fe3+- doped α-gallia. The energy of the emission is in good agreement with that predicted from measured spectral data for Cr3+ in α-gallia and the literature data for Cr3+ and Fe3+ in α-alumina. 相似文献
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Shijing Gong 《Physics letters. A》2009,373(42):3892-3896
The persistent spin helix discovered in intrinsic spin-orbit coupled systems previously is reexamined using the motion equations of Green's functions by considering the effect of extrinsic impurity-induced spin-orbit coupling. We find both the intrinsic and extrinsic spin-orbit couplings can increase the excitation energy of spin helix. They together can reduce drastically the lifetime of the spin helix, making it severely departure from the ideal infinite value. The effect of impurity density on spin helix is also analyzed. The results may be helpful to understand experimental measurements on spin helix. 相似文献
11.
X-ray induced luminescence has been observed in pure as well as Ni, Cu and Eu-doped LiNbO3. The emission spectrum for both, pure congruently grown and doped samples, consists of a well-defined band peaked at ≈425 nm. The shape and height of this band is also independent of the amount of radiation-induced coloring in the crystal. It has been concluded that the emission corresponds to an intrinsic and bulk recombination process. 相似文献
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Optical spectra (absorption, emission, excitation, decay) and dielectric relaxation were measured for divalent europium and partially for ytterbium in lanthanum fluoride crystals. Optical absorption of LaF3–Eu2+ contains not only asymmetric weakly structured band at 245 nm but also less intense bands at 330, 380 nm. Broadband Eu2+ emission at 600 nm appeared below 80 K with decay time 2.2 μs at 7.5 K. Emission at 600 nm is attributed to so-called anomalous luminescence. Bulk conductivity is directly proportional to absorption coefficient of Eu2+ bands. Dielectric relaxation peak of LaF3–EuF3 is attributed to rotation of dipoles Eu2+-anion vacancy. The long-wavelength absorption at 300–400 nm region are assigned to transitions from 4f7Eu2+ ground state to states of neighbouring fluorine vacancy. 相似文献
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Guifang Ju Yihua Hu Li Chen Xiaojuan Wang Zhongfei Mu Haoyi Wu Fengwen Kang 《Journal of luminescence》2012,132(3):717-721
A series of Bi3+/Eu3+ singly and doubly activated Ca4YO(BO3)3 phosphors were synthesized by solid-state reaction method. The structures and photoluminescent properties of the phosphors were investigated at room temperature. Under UV excitation Bi3+ and Eu3+ show a high light output. Ca4YO(BO3)3:Eu3+ has potential application as a phosphor for fluorescent lamps. The luminescence of Bi3+ and Eu3+ in Ca4YO(BO3)3 resembles more that in the rare earth oxides than that in borates. The free oxygen ion in the host lattice, which is not bonded to any boron ions seems to be responsible for that. In this host lattice energy migration between linear Eu3+ chains occurs. The emission of Bi3+ is completely quenched when Eu3+ is co-doped. A model was proposed to explain it. 相似文献
16.
M. E. Schillaci R. H. Heffner R. L. Hutson M. Leon D. W. Cooke A. Yaouanc S. A. Dodds P. M. Richards D. E. MacLaughlin C. Boekema 《Hyperfine Interactions》1984,17(1-4):351-354
We have measured the magnetic field dependence of the muon depolarization rate up to 5 kOe in AuGd (350 ppm), AgGd (340 ppm) and AgEr (300 ppm). A simple model which includes both dipolar and nearest-neighbor contact interactions between the muon and the magnetic impurity does not fit the data. An axial crystal-field interaction, arising from the electric field gradient induced by the muon at the site of the impurity, is found to dominate the Hamiltonian, and may have a large effect on the field dependence.Supported in part by the U.S. Department of Energy and the National Science Foundation.Work performed at Sandia National Laboratories supported by the U.S. Department of Energy under contract DE-AC04-76DP000789. 相似文献
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The variation in the parameters (width, position, intensity) of the fine structure lines in the C[6 A 1g → 4 A 1g , 4 E g(4 G)] and E[6 A 1g → 4 E g(4 D)] bands in RbMnF3 with temperature is studied in the temperature range 10–70 K. In the C band, two narrow (<6 cm?1) lines are are distinguished at distances of 77 and 80 cm?1 from the exciton line at T = 10 K. The other lines in the C band and all lines in the E band are more than 20 cm?1 wide. It is demonstrated that the narrow lines become allowed because of the spin-exchange interaction within a long-range magnetic order model and originate from the excitation of exciton-magnon bound states and that the other lines are made allowed by the exchange-vibronic mechanism within a short-range magnetic order model and originate from the excitation of bound states composed of an exciton, magnon, and oddparity phonon. The vibrational replicas of the main exciton-magnon-phonon lines are due to the quadratic vibronic interaction with odd-parity vibrations. Variations of the intensities and widths of the absorption lines with temperature indicate that these parameters are affected by relaxation and delocalization of the bound states. 相似文献
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L. Grigorjeva D. Millers K. Smits J. Grabis J. Fidelus W. ?ojkowski T. Chudoba K. Bienkowski 《Radiation measurements》2010,45(3-6):441-443
The luminescence properties of ZnO ceramics with grains 100–5000 nm sintered by different techniques from nanopowders were studied. The luminescence decay times were compared with that obtained for ZnO single crystal. The temperature dependence of non-exponential decay of defect luminescence (2.0–2.6 eV) was measured in wide time, intensity and temperature range. The luminescence decay kinetic at T ≤ 20 K shows the decay close to I(t) ~ t?1 dependence. At temperature region 50–250 K the decay kinetics is more complicate since the TSL was observed in this temperature region. It is shown that the luminescence properties of NP and ceramics strongly depend on defect distribution on grains surface and the volume/surface ratio determine the luminescence decay in ZnO nanostructures and ceramics. 相似文献