Vol. 32, No. 11 (1983)
1983-06-05
CONTENT
1983, 32 (11): 1361-1368.
doi: 10.7498/aps.32.1361
Abstract +
We have made direct observations of dislocation substructure in LiNbO3 and LiTaO3 single crystals decorated by gold particles by mean of transmission optical microscopy and ultra-microscopy. The three dimentional features of the subboundaries have been disclosed and the nature of subboundaries are determined with stereographic analysis, and quantitatively verified by Frank's formula.The analysis of dislocation networks and junctions of subboundaries shows that the Burgers vectors of dislocations in these crystals are , the smallest lattice vector;1/3, the next smallest lattice vector, and 1/3 , the short diagonal of therhombohedral cell.
1983, 32 (11): 1369-1375.
doi: 10.7498/aps.32.1369
Abstract +
In this paper, we studied the substitution of Fe3+ ions in BaFe12O19 crystal by Co2+-Ti4+ and Cu2+-Nb5+ ions. Two systems of single cry stals of BaFe12-2xCoxTixO19(with x=0, 0.04, 0.09, 0.13, 0.27, 0.68) and BaFe12-x(Nb1/3Cu2/3)xO19(with x = 0, 0.28, 0.44, 0.60) were grown from Bi2O3 melts. Magnetization a and anisotropy constant K1 of the above samples were measured in the temperature range of 100-300K. For the substitution with Co2+-Ti4+ ions, it was found that when x = 0.09 σ and K1 increased slightly with x at the beginning and decreased rapidly when x > 0.09 until K1→ O at x≈ 1.1. In the case of substitutions with Cu2+-Nb5+, the σ value was nearly the same in the studied compositions and showed a slightly increasing trend with increasing x; while K1 decreased monotonously with x. Our results were qualitatively discussed with the model of site occupation of substitution ions in the M-type hexagonal ferrite.
1983, 32 (11): 1376-1382.
doi: 10.7498/aps.32.1376
Abstract +
The effect of additive Al2O3 on both the formation of amorphous B2O3-0.7Li2O-0.7LiCl and it's ion conduction property have been studied. It has been found that rather large slab of amorphous material could be easily prepared by pouring directly the melt contained suitable amount of additive Al2O3 onto a copper plate at room temperature without using liquid nitrogen.The additive A12O3 decreases slightly the conductivity of amorphous B2O3-0.7Li2O-0.7LiCl but in high temperature range this effect is far less obvious because of the activation energy for the amorphous containing Al2O3 is slightly larger than that of pure one. It has been shown that Al2O3 = 0.03 is the optimum content which makes the preparation of amorphous more easily and dose not seriously influence the conductivity.
1983, 32 (11): 1383-1391.
doi: 10.7498/aps.32.1383
Abstract +
The field structure of resonance absorption and density profile steepening in laser plasmas is studied by means of a new analytical method. The resulting absorption coefficients can be expressed by elementary functions, and are in good agreement with numerical calculations. In addition, the analytic calculations for steady state, steepened density profile are also well consistent with the results obtained by using microwave plasma experiments and numerical simulation.
1983, 32 (11): 1392-1397.
doi: 10.7498/aps.32.1392
Abstract +
The second-order electron density fluctuation in homogeneous unmagnetized plasma is calculated by means of dynamical method. The third-order non-linear susceptibility resulting from interaction of three waves in plasma and the scattered power of K4=K1-K2+K3,ω4=ω1-ω2+ω3 is obtained. As compared with the normal non-coherent Thomson scattering, the scattered signal is very strong. So the coherent four-photon scattering can be taken as one of the important method in plasma diagnostics. It is showed that the result of reference [4] is a simplified form of the result obtained here.
1983, 32 (11): 1398-1406.
doi: 10.7498/aps.32.1398
Abstract +
The stability of a high-beta tokamak plasma having circular crosssection against the high-n ballooning modes is reconsidered. In the high-beta case, the poloidal magnetic field yields a rather strong driving term to the ballooning modes, leading to a substantial distortion of the structure of the second stability region. The various effects of the magnetic shear, pressure gradient and the poloidal magnetic field parameter on the eigenfunctions and the eigenvalues of these modes are calculated. The results obtained give a comprehensive indication in predicting the ideal MHD ballooning modes in circular tokamaks.
1983, 32 (11): 1407-1415.
doi: 10.7498/aps.32.1407
Abstract +
In this paper, a detailed analysis on the operating mechanism and parameter properties of free electron laser amplifier (FELA) in the case of small signal is presented. The results show that FELA is in essence the interaction between the electron beam and the fast cyclotron wave. The cyclotron resonance condition of electron motion in the uniform axial and periodic transverse static magnetic fields significantly influences the interaction process. We have calculated numerically the central operating frequency, band width, small signal gain and wave number of the amplified electromagnetic wave as functions of the parameters of the amplifier (such as the voltage and current density of the electron beam, the intensities of axial and transverse static magnetic field). The way to optimize the design of FELA is also suggested. It is possible to obtain a small signal gain of 10-2 cm-1 with enough band width in the millimeter and submillimeter range of weve length following a proper design.
1983, 32 (11): 1416-1425.
doi: 10.7498/aps.32.1416
Abstract +
In our treatment, crystals are considered as elastic continual, so that any strained vol-um element can be simulated by an elastic dipole. The effective moment of the dipole is found and classified into a permanent part and an induced part. The former depends upon the elastic property of the volum element and the surrounding matrix; while the latter defends upon the strain state of the medium. These two parts of the effective, moment make the medium aquires paraelastic and dielastic charateristies respectively.The displacement field produced by elastic dipole in an isotropic, unbounded, elastic continuum is given. Taking relaxation into account, we obtain the expression for interaction between elastic dipole and the strain field produced by other sources. This expression is simply the Kroner's formula with by some higher order terms added to it. In treating the problems of the interaction between the dislocation and a solute atom and that between two symmetrical centers, the results agree in general with the previous studies but with some higher order correction terms included.
1983, 32 (11): 1426-1434.
doi: 10.7498/aps.32.1426
Abstract +
If SU(2) potential Aμ, with Dμφ=?μφ+ Aμ×φ, can be expressed by n(xμ) with n ·n = 1 as Aμ= ?μn×n, we call it "deduced potential". Because Dμn = 0, it can be transformed into Abellian. Then, we find equivalent U/(l) potential and strength of field Fμv = Fμv ·n. This kind of Fμv (namely Ei and Bi) has the same specific properties and relations between E, B and n. Using this properties and relations, from the known strength of electric and magnetic field of monopole, we can construct a n = n(xμ) with n·n = 1. Then obtain the potential Aμ and its equivalent U(1) potential Cμ. In this way, we find a definite expression of potential for a moving monopole just like the Lienard-Wiechert potential for a moving charged particle. When monopole is at rest, the potential reduces to the famous Wu-Yang potential.
1983, 32 (11): 1435-1442.
doi: 10.7498/aps.32.1435
Abstract +
By using McMillan's method, the superconducting proximity effect between a nonsim-ple metal thin film with negative U centers and a thin film of BCS superconductor is analyzed theoretically. It is shown that the superconductivity of this kind of sandwich can be enhanced by this proximity effect. In order to raise Tc, it is desirable to investigate this kind of superconducting materials consisting of S-U multilayers.
BRIEF REPORT
1983, 32 (11): 1443-1448.
doi: 10.7498/aps.32.1443
Abstract +
The gadolinium-copper phase diagram has been compicted by X-ray diffraction and differential thermal analysis. The allotropic change in the GdCu6 phase was observed at 735℃.In this system there exist four intermetallic Compouds: GdCu, GdCu2, GdCu5 and GdCu6. The intermetallic compound GdCu5 melts congruently at 932℃. The intermetallic compounds GdCu, GdCu2 and GdCu6 are formed by peritectic reactions at 759℃, 870℃ and 884℃, respectively. Two eutectic reactions occur: at 32 at% Cu and 668℃, 92 at% Cu and 875℃. Neither Gd in Cu nor Cu in Gd Shows any detectable solid solubility.
1983, 32 (11): 1449-1454.
doi: 10.7498/aps.32.1449
Abstract +
The binary phase diagram of the neodymium-copper system has been determined by means of X-ray powder diffraction, differential, thermal analysis (DTA) and metallographic methoa.In this system there exist five intermetallic compounds: NdCu, NdCu2, NdCu4, NdCu5 and NdCu6. The intermetallic compounds NdCu2 and NdCu6 melt congruently at 830℃ and 962℃, and the intermetallic compounds NdCu, NdCu4 and NdCu5 are formed by peritectic reactions at 602℃, 853℃ and 916℃, respectively. Three eutectic reactions occur: at 33 at% Cu and 478℃, 74 at% Cu and 760℃, 91 at% Cu and 874℃. Neither Nd in Cu nor Cu in Nd shows any detectable solid solubility. The solid solubility between intermetallic compounds is undetectable.
1983, 32 (11): 1455-1459.
doi: 10.7498/aps.32.1455
Abstract +
The crystal structure and magnetic structure of hard magnetic alloy Mn1.074Al0.871C0.055 have been investigated by neutron diffraction technique. Mn1.074Al0.871C0.055 has body center tetragonal structure. The refinement of neutron diffraction data shows that 0.992 Mn and 0.008 C occupy (0,0,0) site and 0.082 Mn, 0.871 Al and 0.047 C occupy(1/2,1/2,1/2)site. The magnetic moments of manganese atoms in the different sites are alongc-axis pointing in opposite directions. In comparison of these results with that of binary alloy Mn1.09Al0.91, the significant improvement of magnetic and mechanical properties in ternary alloy Mn1.074Al0.871C0.055 can be explained.
1983, 32 (11): 1460-1466.
doi: 10.7498/aps.32.1460
Abstract +
For a semi-infinite crystal,the expression for wave field of X-ray reflection,Dh is de-rived by the retarded Green function G(r). For a crystal with finite thickness it can be solred using G(r) and advanced Green functions Ga as well.These results have been corn.pared with previous results obtained by using Riemann function or Fourier integral andit is found that they are in agreement quite well.
1983, 32 (11): 1467-1470.
doi: 10.7498/aps.32.1467
Abstract +
New data about photoemission spectra of silver on GaAs (110) cleavage surface have been found by measurement at hv=21.2eV, 40.8eV, and 1486.6eV. Some additional data of gold on GaAs are also obtained. The thickness of evaporated Ag and Au films used for measurement ranged from 0.1? to 1000?.A maximum in the functional relation between the intensity of UPS valence spectra and the thickness of film has been noted and discussed.
1983, 32 (11): 1471-1473.
doi: 10.7498/aps.32.1471
Abstract +
In solutions of fluorescent materials containing some suspended particles, an enhancement phenomenon has been observed. The effect is supposed to be caused by Rayleigh scattering and Mie structure resonance scattering from the particles.
1983, 32 (11): 1474-1478.
doi: 10.7498/aps.32.1474
Abstract +
The present note gives the results of computations of the electronic energy spectrum and local density of state of layered ultrathin coherent structures composed of two face-cen-tered-cubic metals under the tight-binding approximation with inclusion of only nearest neighbor interactions.
