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Volume 10 Issue 10
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Original Articles
Nonlocal Lie-Bäcklund Symmetries and Olver Symmetries of the KdV Equation
LOU Senyue, , HU Xingbiao,
Chin. Phys. Lett. 1993, 10 (10): 577-580 .  
Abstract   PDF(pc) (170KB) ( 476 )
Starting from a special nonlocal Lie Bäcklund symmetry of the KdV, mKdV. Potential mKdV and singularity manifold equation system, three sets of higher order nonlocal Olver symmetries are reobtained. The soliton solutions of these models can also be obtained from the finite Lie- Bäcklund transformations.
Anisotropic Magnetoresistive Sensors and Magnetometers Applying Alternating Bias Magnetic Field
ZOU Fengwu, HE Zhiyong, JIA Kechang*
Chin. Phys. Lett. 1993, 10 (10): 581-584 .  
Abstract   PDF(pc) (201KB) ( 466 )
Thin permalloy film with uniaxial anisotropy have been prepared by ion-beam sputtering method. Magnetic field sensors of this type film are composed of four magnetoresistors in Wheastone bridge connection. One may obtain sensitivity more than 10mV/Oe with 10-5 Oe resolution by suitable design of sensors parameters. A model based on single domain structure and resistance anisotropy effect explains the behavior of the sensors and a method has been developed to reduce the influence of offset voltage and hysteresis to minimum.

Wormholes with the Topology of R1 ⊗ S3 ⊗ Td in Higher Order Gravitational Theory
SHEN Yougen, CHENG Zongyi, SU Ruking
Chin. Phys. Lett. 1993, 10 (10): 585-587 .  
Abstract   PDF(pc) (113KB) ( 403 )
In this paper. we discuss the wormhole with the topology of R1 ⊗ S3 ⊗ Td in higher order gravitational theory with αR2+βRμvRμv term, and derive corresponding wormhole equations as well as their analytical solution.
Nuclear Gluon Density in the Constituent Quark Model
ZHU Wei, XU Zaixin
Chin. Phys. Lett. 1993, 10 (10): 588-590 .  
Abstract   PDF(pc) (144KB) ( 377 )
The nuclear gluon distribution is predicted using the constituent quark model. We point out that the nuclear shadowing and antishadowing depress nuclear gluon field when x < 0.08 and enhance it when 0.08 < x < 0.2.
Formation of Odd Numbered C-n (n > 50) Clusters in the Fusion of Fullerenes
ZHU Lei, WANG Shenyi, LI Yufen
Chin. Phys. Lett. 1993, 10 (10): 591-593 .  
Abstract   PDF(pc) (149KB) ( 551 )
We observed the phenomena of fusion of fullerenes by laser desorption of chemical adduct RnC60 (R=C6H5CH2) in negative ion channel. The unstable odd numbered C-n clusters (n>50) are readily produced under some experimental conditions, and this can be attributed to their structures possessing cross-section larger than that of the cage-like fullerenes.
Plasma-Loaded Cerenkov Free-Electron Laser
LING Genshen, CHEN Deming, LIU Yonggui, LI Chuanlu
Chin. Phys. Lett. 1993, 10 (10): 594-597 .  
Abstract   PDF(pc) (190KB) ( 455 )
The cylindrical plasma-loaded Cerenkov free-electron laser is studied by using fluid theory. It is shown that its working frequency and linear growth rate are higher than that of common Cerenkov free-electron laser, and for the same injection current, the linear growth rate of the system docs not decrease as the gap between the dielectric linear and the elcctron beam increases, but there is an optimum gap value corresponding to the maximum growth rate.
Surface-Enhanced Third-Order Nonlinear Optical Response of C60 Films on Roughed Glass Plate
LI Shijie, XU Xiaoping, LI Wenzhu, QIU Peihua, WANG Wenyao
Chin. Phys. Lett. 1993, 10 (10): 598-600 .  
Abstract   PDF(pc) (118KB) ( 413 )
The nonlineat third order optical susceptibility of C60 films on roughed glass plate has been studied by using a mode locked Nd : YAG laser emitting 8ps pulsed at 1.064μm of 0.3 J energy. The large | x ( 3 ) ( - 3ω . ω, ω, ω)I = 2 x10-8 esu for C60 films of 15 μm thickness has been observed, which is 103 larger than the value in the bulk C60. This is due to surface enhanced effect.
Optical and Acoustic Branches in the Vibrational Spectrum of a Diatomic Penrose Lattice
TIAN Decheng, LIU Zhengyou, JIANG Qing, WANG Lilong
Chin. Phys. Lett. 1993, 10 (10): 601-604 .  
Abstract   PDF(pc) (190KB) ( 443 )
Vibrational densities of states for a diatomic Penrose lattice are calculated. They show apparently acoustic and optical branches. The acoustic branches appear smooth and continuous, while the optical branches are peakrich and have some small gaps. Detailed analysis shows that the density of states in the acoustic branches is attributed to the phonons and the fracton-like excitations and that in the optical branches clue to some localized vibrational model.
Vacancy-Type Defects in Neutron-Irradiated Silicon
MENG Xiangti
Chin. Phys. Lett. 1993, 10 (10): 605-608 .  
Abstract   PDF(pc) (211KB) ( 413 )
Positron annihilation measurements show that the radiation defects and secondary defects in neutron-transmutation-doped (NTD) Si irradiated by two neutron doses can be removed at 600-650°C. The concentration and annealing behavior of V-type and V2 defects are related to the neutron doses. V4 appears at 150°C and 450°C - 550°C in NTD Si irradiated by higher neutron dose.
New Phases Formed During Nanocrystalline Titanium Preparation
QIN Yong, ZHU Yong, LI Zongquan
Chin. Phys. Lett. 1993, 10 (10): 609-611 .  
Abstract   PDF(pc) (219KB) ( 468 )
The nanocrystalline titanium samples, having a grain size of about 10nm, are prepared by direct current magnetron sputtering and subsequent in situ compaction. Two new phases are observed by means of transmission electron microscopy, one is a body-centered cubic structure with a lattice parameter of a=0.323nm, the other one is an orthorhombic structure with lattice parameters of a =0.303nm, b=0.391 nm and c =0.488nm. The formation of the two phases is also tentatively discussed.
Spin-Polarized Electronic Structure of MnBiAl
WANG Zuowei, HUANG Meichun
Chin. Phys. Lett. 1993, 10 (10): 612-615 .  
Abstract   PDF(pc) (188KB) ( 523 )
The self-consistent spin-polarized band-structure calculation of ferromagnetic compound MnBiAl in its low-temperature phase has been performed. In this paper the calculation results arc given. Comparison with the results of MnBi is performed in order to find the effect on electronic structure by doping with AI.
The η-Pairing Superconductivity in Spin-Density Wave Background
X. M. Qiu, Z. J. Wang
Chin. Phys. Lett. 1993, 10 (10): 616-619 .  
Abstract   PDF(pc) (162KB) ( 390 )
In this letter, we propose a modified attractive Hubbard model at half filling that can exhibit superconductivity through η-pairing mechanism in spin-density wave representation and derive a concise relationship between the energy disparity and the single-particle energy spectrum. This relationship, in the two limits of U, clearly shows that the system does not display superconductivity for very low doping concentration. but demonstrates superconductivity when the doping concentration exceeds a certain critical value. This conclusion is in qualitative agreement with the familiar experiments on high-Tc superconductivity.

Magnetic Properties and Crystallization of Amorphous Fe-Nd-B Alloys at Constant B Concentration
SHEN Baogen, YANG Linyuan, ZHAO Jiangao, GUO Huiqun
Chin. Phys. Lett. 1993, 10 (10): 620-622 .  
Abstract   PDF(pc) (179KB) ( 440 )
Magnetization, Curie temperature and crystallization temperature measurements for amorphous (Fe1-xNdx)100-yBy alloys with y=6, 18.5 and 25 have been made. Spontaneous magnetization shows a monotonic decrease with x, and the noncollinear spin structures have been proposed to explain the observed results. The composition dependence of Curie temperature is explained by the average molecular-field model. The substitution of small Nd for Fe is found to have a strong enhancement of the thermal stability in amorphous Fe-Nd-B alloys.
Reverse of Dumbbell Rotation in Garnet Bubble Films
SUN Huiyuan, NIE Xiangfu, TANG Guide, HAN Baoshan*
Chin. Phys. Lett. 1993, 10 (10): 623-626 .  
Abstract   PDF(pc) (219KB) ( 412 )
The bias field dependence of the rotation direction of the dumbbells, contracted from multi-branched domains, was experimentally studied. Moreover, it was found that the rotation direction of these dumbbells can be reversed by increasing the amplitude of the testing bias pulses with quite narrow width.
Phonon Spectra of a-SiNx : H/Si Heterostructures Observed by Brillouin Light Scattering
XIA Hua, ZHANG Wei, LI Zhifeng, QU Xuexuan, CHEN Kunji, ZHANG Xingkui
Chin. Phys. Lett. 1993, 10 (10): 627-629 .  
Abstract   PDF(pc) (168KB) ( 483 )
Low-frequency phonon spectra in a- SiNx : H/Si heterostructures have been observed by means of Brillouin light scattering. Measurement of the frequency shift on longitudinal and transverse acoustic phonons as well as on surface phonons enabled us to extract accurately two independent elastic moduli: c11 and c44 deduced from phase velocities of bulk acoustic modes and scattering wavevector, within effective medium approximation.
A Novel Ge Nanostructure Exhibiting Visible Photoluminescence
JIANG Jiangong, CHEN Kunji, HUANG Xinfan, FENG Duan, SUN Dayou
Chin. Phys. Lett. 1993, 10 (10): 630-633 .  
Abstract   PDF(pc) (204KB) ( 485 )
The a-Ge: H/a-SiNx :H multiquantum-well structures were prepared by a computercontrolled plasma enhanced chemical vapor deposition method and then crystallized by Ar+ laser annealing technique. When the Ge well-layer thickness was reduced to 30Å, the crystallized sample showed a room temperature photoluminescence with a peak at about 2.26eV. Meanwhile some significant characteristics of such a novel Ge nanostructure were also revealed by x-ray diffraction. Possible mechanisms of this visible PL phenomenon have been discussed.

Linear Electron-Phonon Interaction in Organic Spectral Hole-Burning Materials
TIAN Mingzhen, LUO Baozhu, LI Wenlian, HUANG Shihua, YU Jiaqi, YANG Kaihai*
Chin. Phys. Lett. 1993, 10 (10): 634-637 .  
Abstract   PDF(pc) (182KB) ( 438 )
The linear electron-phonon interaction in polymethylmethacrylate (PMMA) doped with electron donor zinc-tetraphenylbenzoporphyrin (ZnTPBP) and acceptor phydroxybenzaldhyde (PHBA), or p-aminoacetophenone (PAAP) was investigated by photon-gated spectral hole-burning (PHB). The aim is to study the factors that affect the linear electron-phonon coupling and the thermal stability of spectral holes in the organic film samples.
Optoelectronic Properties Modulated by Means of Change in Lattice Sites of Impurity in LiNbO3 Crystals
Chin. Phys. Lett. 1993, 10 (10): 638-640 .  
Abstract   PDF(pc) (153KB) ( 470 )
This paper discusses the actual possibility of altering artificially certain optoelectronic properties of LiNbO3 crystals by means of change in lattice site of a few Me3+ ions in the crystals. A new lattice site Cr3+ defect in Cr-doped LiNbO3 vapour transport equilibration has been displayed as a practical example.
18 articles