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Vol. 36, No. 5 (1987)

1987-03-05
CONTENT
ON THE NONLINEAR PROPERTIES OF THE PHOTO-MAGNETOELECTRIC EFFECT IN SEMICONDUCTORS
LIU ZHENG-RONG, LUO SHI-YU, SHAO MING-ZHU
1987, 36 (5): 547-554. doi: 10.7498/aps.36.547
Abstract +
The equation of continuity of the charge carriers through a semiconductor was reduced to a second order non-linear differential equation, by using the injection-leveldependent lifetime which was derived from Shockley-Read statistics. The general solution was found using two-parameters perturbation method. The PME short-circuit current Isc and the photoconductance ΔG in a semiconductor are calculated in the second order approximation. The nonlinear properties of the photomagnetoelectric effect in the case of large signal are disclosed, experimental results are better fitted by the theory.
ELECTRONIC STRUCTURES OF THE MIXED CHALCOGENIDE PAIRS IN Si
GU YI-MING, REN SHANG-YUAN
1987, 36 (5): 555-561. doi: 10.7498/aps.36.555
Abstract +
Using the Green's function method with a tight binding Hamiltonian, the electronic structures of the ground states of S0/Se0, S0/Te0 and Se0/Te0 mixed pairs in Si are investigated. Two A1 symmetrical states are introduced by the mixed pairs, the bonding A1 state is higher than the antibonding A1 state. The numerical results of the energy leveals of mixed pairs are obtained, which are in agreement with the experimental observations. It looks likely that the unidentified shallower energy leveals (S0/Se0 (X1), S0/Te0 (X1), Se0/Te0 (X1)…) are not introduced by the mixed pairs with other non-nearest positions. We note that the transfer direction of the s wavefuction between two different defect atoms in Si is reversed as compare with the ordinary diatomic molecule case. The physical reason is discussed.
STUDY ON THE COERCIVITY OF RF SPUTTERED IRON OXIDE THIN FILMS
LUO HUI-LIN, YU MEI, YOU GUANG-JIAN, ZHOU ZENG-JUN
1987, 36 (5): 562-569. doi: 10.7498/aps.36.562
Abstract +
The study on magnetic properties of RF sputtered iron oxide thin films was carried out systematically. More specifically, the temperature dependence (77-500 K) of the coercivity and the variation of coercivity with different iron oxide phases such as the as-sputtered Fe3O4, partially transformed Fe3O4/(γ-Fe2O3), and γ-Fe2O3, were investigated. Comparing the theoretical analyses with the experimental results, the contributions to the coercivity from shape anisotropy, magnetocrystalline anisotropy, and stress-induced magnetic anisotropy were obtained separately. And the first-order crystalline anisotropy constant K1 vs. temperature for Fe3O4 and γ-Fe2O3 films was derived from Ms(T) and Hc(T) over the temperature range of 100-500 K.
A STUDY OF SPIN WAVE IN Fe3Si AT LOW TEMPERATURE
P. v. BLANCKENHAGEN, TAO FANG, YAN QI-WEI, SHEN ZHI-GONG, LIN QUAN, LIN HONG
1987, 36 (5): 570-576. doi: 10.7498/aps.36.570
Abstract +
The dispersion relation of spin wave in Fe3Si at 14 K has been measured by inelastic coherent neutron scattering. The spin wave stiffness constant D0, which is obtained experimentally from quadratic dispersion of spin wave, equals 270 meV ?2. A calculation of effective exchange integral Jeff has been done in the frame of Heisenberg model. From the temperature dependence of magnetization, a spin wave stiffness constant Dm(0) can be derived also. There is an indication of the existence of Stoner excitations from a comparison of D0 and Dm(0). The temperature dependence of spin wave stiffness constant is also gaven.
BRILLOUIN SCATTERING FROM BCVIG SINGLE CRYSTALS
G. GüNTHERODT, R. MOCK, ZHANG PENG-XIANG, PANG YU-ZHANG
1987, 36 (5): 577-583. doi: 10.7498/aps.36.577
Abstract +
Magnon spectra were measured by means of Brillouin scattering from single crystals BCVIG (Bi3-2xCa2xFe5-xVxO12). We obtained a continuous band, including the bulk mag-non peak, which has been observed by Sandercock et al. in YIG, and Liu and Zhang et al. in Bi-YIG. The measured dispersion relation of the magnon band was analysed based on the theory of dipole-exchange spin waves. This measurement also show that the spin wave stiffness constant D is much larger than that of YIG and Bi-YIG. The reason of the lager D is discussed and its dependence on the incident laser power was studied.
A STUDY OF THE SPECTRAL CHARACTERISTICS OF YGG:Cr3+ CRYSTAL
CHEN JUN-DE, YANG SHI-JUN, YE LI-LI, LU SHI-PING, GAO WEN-BIN, WEN GEN-WANG
1987, 36 (5): 584-590. doi: 10.7498/aps.36.584
Abstract +
The spectral characteristics of YGG:Cr3+ crystal was investigated experimentally. The absorption spectrum at 300 K and the fluorescence spectrum at 10 K, 133 K, and 300 K are presented. The fluorescence life time, nonradiative transition propability and radiative quantum efficiency as the function of temperature are also presented. Based on the absorption spectrum and the fluorescence spectrum, with the perturbation of C3iS6 low symmetry field, the individual sub-staes resulting from the splitting of Cr3+ 2T1 state in the YGG host, and the location of R line due to 24A2→E zero phonon transition are determined.
SMALL-ANGLE X-RAY DIFFRACTION STUDY OF AMORPHOUS MULTILAYER AND SINGLE LAYER THIN FILMS
HUANG WEN-YONG, WANG CHANG-SUI, ZHOU GUI-EN, WU ZI-QIN, WU ZHI-QIANG, LU XIANG-DONG, LIU HONG-TU, JIN HUAI-CHENG
1987, 36 (5): 591-598. doi: 10.7498/aps.36.591
Abstract +
Small-angle X-ray diffraction study of amorphous a-Si:H/(a-SiNx:H) periodical multilayer thin films and some single layer films has been undertaken. A number of satellite peaks were found in the lower side of Bragg diffraction peaks of multilayer thin films with a less number of periods. A number of diffraction peaks were also found for the small-angle diffraction of single layer films. We have presented a simple formula for calculating the X-ray diffraction intensity of multilayer and single layer films. A satisfactory explaination of experimental results was obtained. Consequently, a simple method for measuring the total thickness of both multilayer and single layer thin films has been presented.
THE ELASTIC GREEN'S FUNCTION OF ANISOTROPIC CUBIC CRYSTALS AND ITS APPLICATIONS
YANG ZHENG-JU
1987, 36 (5): 599-612. doi: 10.7498/aps.36.599
Abstract +
The series expension of elastic Green's function of anisotropic cubic crystal is calculated and the expansion coefficients are given under the second order approximation. Applying the results to elastic dipole model, one obtains the expressions of elastic displacement field due to a symmetrical center and the interaction between two symmetrical centers. For strongly anisotropic cubic crystals such as K and Cu, it is surprising that the numerical results of the displacement field of the symmetrical center and the interaction between them are basically the same as those obtained by using lattice statics, which is based on the discrete native of the lattice, although the convergence is not very satisfactory. This seems to indicate that our analytical expression of the elastic Green's function leads to a simple and easy method, which can be used generally to describe some mechanical behaviour of cubic crystals correctly.
THE THEORY OF SUPERCONDUCTIVITY IN KONDO LATTICE
SU ZHAO-BING, LI TIE-CHENG, XU JI-HAI
1987, 36 (5): 613-622. doi: 10.7498/aps.36.613
Abstract +
S-wave and P-wave superconductivity in Kondo lattice is theoretically studied in connection with heavy-fermion superconductivity (HFS). The hybridization between f-electron and conduction electron is investigated consistently and the corresponding quantities have been calculated in detail in the generalized Nambu formalism. It is shown that if one thinks f-electrons are responsible for superconductivity, for S-wave paired state, the superconducting transition temperature is in agreement with that of Tachiki et al., but the specific heat jump is not, our result is more appropriate than theirs. For P-wave paired state, the HFSs described by a Kondo lattice model are essentially almost localized Fermi superfluids, with a small modification. The effects of impurities on S- and P-wave paired states have been studied in detail respectively, and the conditions of the appearence of gapless superconductivity have been obtained for each case .
ELECTRONIC SPECTRA AND MOBILITY EDGES IN ONE-DIMENSIONAL INCOMMENSURATE SYSTEM
ZHENG ZHAO-BO, ZHU KAI
1987, 36 (5): 623-629. doi: 10.7498/aps.36.623
Abstract +
Fine structures of electronic spectra of one-dimensional lattice with incommensurate potential Hn,n= 1.9*(cos(0.7n) + l/3*cos(1.4n))Hn,n-1=Hn,n+1= 1 are obtained. The precise positions of mobility edges are found by means of self-energy convergence criterion. Self-similarity in spectra and mobility edges are discussed.
COLLISION CROSS SECTIONS AND TRANSPORT COEFFICIENTS IN AN INDUCTIVELY COUPLED ARGON PLASMA
HUANG MAO, LIU KE-LING
1987, 36 (5): 630-639. doi: 10.7498/aps.36.630
Abstract +
Collision cross sections as well as electrical conductivity, thermal conductivity, diffusion coefficients and viscosity coefficients of an inductively coupled argon plasma are calculated. The results indicate that thermal conduction process plays an important role in energy transfer, while ambipolar diffusion leads to a much higher electron density in the cool plasma regions as compared with the value predicted by local thermal equilibrium. More significantly, both three body recombination and superelastic collision give rise to the creation of a large number of energetic electrons in the cool plasma regions. Such a deviation of electron velocity distribution from a Maxwellian may have a special significance for excitation mechanism of the plasma used as an emission spectroscopic source.
BRIEF REPORT
PHOTON COHERENT SCATTERING AT THE RELATIVELY SMALL MOMENTUM TRANSFER
FANG DU-FEI, YANG BAO-ZHUNG, LI YAO-QING, TANG XIAO-WEI
1987, 36 (5): 640-645. doi: 10.7498/aps.36.640
Abstract +
Using the radioactive gamma ray source 141Ce (Er = 145 keV) and Ge(Li) detector (FWHM = 2.21keV at 1.33 MeV), we have measured the cross sectipn of photon coherent scattering from Al, Fe, Cu and Pb over the range of momentum transfer x=1.2-5.0 ?-1. The theory of form-factor approximation resulting from relativistic Hartree-Fock (RHF) atomic model is found to be adequate in explaining the experimental results.
STUDY OF THE DEFECTS IN OXYGEN PLASMA IRRADIATED n/n+ Si
WANG FANG-PING, XU JIAN-GUO, SUN HENG-HUI
1987, 36 (5): 646-650. doi: 10.7498/aps.36.646
Abstract +
The defects in oxygen plasma irradiated Si have been studied. It is found that two kinds of defects E1(Ec-0.46 eV) and E2 (Ec-0.04 eV) are generated in the sample. The deep level optical spectroscopy reveals that defects E2 has a strong electron-phonon coupling, its Frank-Condon shift is 0.76 eV. For E1, the coupling is weaker, its Frank-Condon shift is 0.04 eV. The analysis shows that the phonon modes coupling to defects E1 and E2 is 28.7 meV and 20 meV respectively.
BR1LLOUIN SCATTERING FROM BISMUTH SUBSTITUTED IRON GARNETS
LIU YU-LONG, ZHANG PENG-XIANG, MO YU-JUN, TU AN
1987, 36 (5): 651-654. doi: 10.7498/aps.36.651
Abstract +
Brillouin scattering spectra of bismuth substituted iron garnets BixY3-xFe5O12 (x = 0, 0.14, 0.36, 0.54) were measured. The thermally excited bulk magnons were observed. Some magnetic parameters of these samples were determined according to the dispersion relation of the bulk magnons. We found that there is a dependance of the spin wave stiffness constant on bismuth contents, the higher the bismuth contents, the smaller the spin wave stiffness constant.
THE FINE STRUCTURES OF THE SECOND HARMONIC TIME RESOLVED SPECTRUM IN LASER PLASMAS
GU MIN, TAN WEI-HAN, LIN ZUN-QI, BI WU-JI, YU WEN-YAN, DENG XI-MING
1987, 36 (5): 655-659. doi: 10.7498/aps.36.655
Abstract +
This paper presents the time resolved spectrum with high temporal resolution (~10ps) and spectral resolution (~ 0.6?) of 2ω0 harmonic emission at 90°to the laser axis. It is shown experimentally that the primary peak and the secondary peak of 2ω0 harmonic are actually composed of many fine and bright fringes with the interval about 1.5 ~ 3? directly connected with atomic weight. Analysis and discussion on these are given.
THE INFLUENCE OF LASER FREQUENCY BANDWIDTH ON THE TIME AND SPACE STRUCTURES OF THE 2ω0 HARMONIC GENERATION
TAN WEI-HAN, LIN ZUN-QI, GU MIN, SHI A-YING, YU WEN-YAN, DENG XI-MING
1987, 36 (5): 660-667. doi: 10.7498/aps.36.660
Abstract +
Reported here are the 2ω0 harmonic space and time structures taken by streak camera in the direction of 90°with the laser optical axis. The evident differences, as shown between the broadband and narrowband laser shooting, are analyzed based on the theory of plasma soliton generation. The results obtained are consistent with the experiments on the whole.
RESEARCH ON THE STABILITY OF THE HIGH PRESSURE DISCHARGE EXCITED XeCl EXCIMER LASER
LOU QI-HONG
1987, 36 (5): 668-672. doi: 10.7498/aps.36.668
Abstract +
The stability of the high pressure discharge excited XeCl excimer laser are related to the concentration of halogen donor HC1. In this paper, a theoretical analysis of the equation for continuity of the electrons in the discharge plasma predicate that the duration of the uniform phase should vary as the inverse square root of the HC1 concentration. This prediction is in good agreement with experimental results obtained from a X-ray pre-ionized PFN pumped XeC1 excimer laser.
PRODUCTION OF F2+ CENTERS BY ELECTRON IRRADIATION AND THEIR FLUORESCENCE EMISSION
ZHANG TAO, WAN LIANG-FENG, RUAN YONG-FENG, GUO SHAO-ZHANG
1987, 36 (5): 673-678. doi: 10.7498/aps.36.673
Abstract +
LiF crystals were irradiated by electron beams at 77 K. F2+ centers were then produced in these crystals, the density of which reached as great as 1017 cm-3. The fluorescence emission characteristics of the F2+ centers were observed, and analysed theoretically.
STUDY THE PHASE TRANSITION FOR THE PTS SINGLE CRYSTAL AT LOW TEMPERATURE BY PHOTOACOUSTIC EFFECT
DU YING-LEI, WU BAI-MEI
1987, 36 (5): 679-683. doi: 10.7498/aps.36.679
Abstract +
The photoacoustic signal and phase angle have been measured for the single crystal of Polybis-(p-toluence sulfonate) of 2,4-(hexadiyne)-l,6-diol(PTS) in the temperature range of 175-225 K based on the photoacoustic effect (PAE.) The jump of photoacoustic signal and phase angle at 200 ±0.5 K was observed. We suggested that the jump can be attributed to the second order structural phase transition in PTS.
STUDIES ON THE CRYSTALLIZATION OF AMORPHOUS 3 BaO·3 B2O3·2GeO2
ZHANG JIN-PING, CHAI ZHANG, LIANG JING-KUI
1987, 36 (5): 684-690. doi: 10.7498/aps.36.684
Abstract +
3BaO·3B2O3·2GeO2 is a new compound in the ternary system BaO-B2O3-GeO2. Its crystallization process has been studied by means of thermoanalysis method. The temperature of crystallization decreases distinctly with decrease of the grain size. The activation energy of crystallization of the amorphous material with different grain size have been determined by means of the isothermal crystallization method or thermal peak shift method. The smaller the grain size is, the greater the activation energy of crystallization.