Table of contents

20 January 1998, Volume 7 Issue 1 Previous issue    Next issue

CLASSICAL AREAS OF PHENOMENOLOGY

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LIGHT TRACKS IN THE ANISOTROPIC OPTICAL FIBER WITH TWO TYPES OF PARABOLIC REFRACTIVE INDICES SHEN WEN-DA (沈文达), MAO LI-YU (毛立宇), GAO WEI (高炜), ZHU SHI-TONG (朱莳通) Acta Physica Sinica (Overseas Edition), 1998, 7 (1):  1-11.  DOI: 10.1088/1004-423X/7/1/001 Abstract ( 1275 )   PDF (214KB) ( 393 )   The light tracks in an anisotropic optical fiber are studied by the optical metric model. The ordinary and extraordinary light tracks are determined by solving the null geodesic equation. In the paraxial approximation the birefringence of the fiber is analyzed. The focusing and defocusing characte ristics of a light beam are described via the geodesic deviation equation

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BACKACTION EVADING MEASUREMENT AND QUANTUM STATE PREPARATION FOR PHONONS BY USING THE RAMAN-INDUCED KERR EFFECT CHAI JIN-HUA (柴金华), GUO GUANG-CAN (郭光灿) Acta Physica Sinica (Overseas Edition), 1998, 7 (1):  12-21.  DOI: 10.1088/1004-423X/7/1/002 Abstract ( 1252 )   PDF (245KB) ( 364 )   A scheme of quantum nondemolition measurement is proposed for probing the phonon inside a crystal by using the Raman-induced Kerr effect. The results of calculation show that under certain conditions either a backaction evading measurement or a quantum state preparation can be performed.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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DESTABILIZATION OF THE POLOIDAL ROTATION IN A MULTIPLE ION SPECIES TOKAMAK PLASMA LIU CAI-GEN (刘才根), QIAN SHANG-JIE (钱尚介) Acta Physica Sinica (Overseas Edition), 1998, 7 (1):  22-27.  DOI: 10.1088/1004-423X/7/1/003 Abstract ( 1216 )   PDF (175KB) ( 418 )   The destabilization of the poloidal rotation for the species of ions with the poloidally inhomogeneous sources or sinks is studied in multiple ion species tokamak plasmas. Based on the fluid equations, the evolution equation of the poloidal ion rotation speed is derived analytically. The magnitude of the inhomogeneous sources or sinks needed to destabilize the rotation is shown to be proportional to the ion density. It is suggested that the poloidal plasma rotation can be generated by destabilizing the rotation of the minority ions.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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BOUND POLARONS IN ASYMMETRIC QUANTUM WELLS IN AN ELECTRIC FIELD LIU ZI-XIN (刘自信), WENG YONG-GANG (翁永刚), SHI JUN-JIE (史俊杰), WANG ZHI-JIE (王志杰), PAN SHAO-HUA (潘少华) Acta Physica Sinica (Overseas Edition), 1998, 7 (1):  28-37.  DOI: 10.1088/1004-423X/7/1/004 Abstract ( 1198 )   PDF (263KB) ( 438 )   We have proposed the Hamiltonian of a polaron bound to a donor impurity in semiconductor quantum wells (QWs) in the presence of an electric field. The couplings of an electron with the confined bulk like longitudinal optical (L0) phonons, half-space L0 phonons and interface phonons are considered. In particular, the interaction of the impurity with the various phonon modes is also included. We have calculated the ionization energy of a bound polaron in Alxl Ga1-xl As/GaAs/Alxr Ga1-xr As asymmetric and symmetric QWs. Results are obtained as a function of the barrier height (or equivalently of Al concentration x),the well width, the electric field intensities and the position of impurity in the QWs. Our numerical calculations show clearly that the interaction between the impurity and the phonon field plays an important role in screening the Coulomb interaction. It is shown that for at hin well (＜12nm), the cumulative effects of the electron-phonon coupling and the impurity-phonon coupling can contribute appreciably to the donor ionization energy and polarizability.

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STRUCTURE AND MAGNETIC PROPERTIES OF NITRIDES R3Fe29-xCrxN4 HAN XIU-FENG (韩秀峰), ZAN YU-DE (昝玉德), WANG QI-YUAN (王启元), WANG JUN (王俊), YANG FU-MING (杨伏明), MA LONG (马龙) Acta Physica Sinica (Overseas Edition), 1998, 7 (1):  38-46.  DOI: 10.1088/1004-423X/7/1/005 Abstract ( 1347 )   PDF (210KB) ( 454 )   A systematic investigation of nitrides R3Fe29-xCrxN4(R=Y, Ce, Nd, Sm, Gd, Tb, and Dy) has been performed. The nitrogen concentration in the nitride R3Fe29-xCrxNy was determined to be y=4. Nitrogenation leads to a relative volume expansion of about 5.3%. The lattice constants and unit cell volume decrease with in creasing rare earth atomic number from Nd to Dy, reflecting the lanthanide contraction. In average, the increase of Curie temperature upon nitrogenation is about 200 K, compared with its parent compound. The nitrogenation also results in a remarkable improvement in the saturation magnetization and anisotropy fields for R3Fe29-xCrxN4 at 4.2 K and room temperature, comp ared with their parent compounds. A spin reorientation of Nd3Fe24.5 Cr4.5N4 occurs at around 368 K, which is 138 K higher than that of Nd3Fe24.5Cr4.5. Magnetohistory effects of R3Fe29-xCrxN4(R=Nd and Sm) are observed in a low field of 0.04 T. First order magneti zation process occurs in Sm3Fe24.0Cr5.0N4 in magnetic fields of around 3.0 T at 4.2 K. After nitrogenation the easy magnetization direction of Sm3Fe24.0Cr5.0 is changed from the easy cone structure to the uniaxial. The excellent intrinsic magnetic properties of Sm3Fe24.0Cr5.0N4 make this compound a hopeful candidate for new high performance permanent magnets.

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NONLINEAR MAGNETIZATION AND FREQUENCY CONVERSION OF MAGNETOSTATIC WAVES IN A FERROMAGNETIC SLAB WANG QI (王奇), LI CHUN-FANG (李春芳), BAO JIA-SHAN (鲍家善), I. Awai, A.D.Boardman Acta Physica Sinica (Overseas Edition), 1998, 7 (1):  47-60.  DOI: 10.1088/1004-423X/7/1/006 Abstract ( 1069 )   PDF (404KB) ( 437 )   The possibilities of the generation of second-order dc and second-harmonic magnetic fields excited by the magnetostatic surface wave (M SSW) and backward volume wave (MSBVW) in ferromagnetic films have been analyzed and discussed through the calculations of source terms in the equations satisfying the magnetostatic potentials. The results show that the nonlinear magnetization responses of the film to the MSSW can generate neither dc nor the second-har monic magnetic fields. And the responses to the MSBVW will not induce the dc field, but can excite second-harmonics under some conditions. The general expressions of third order nonlinear magnetization are also derived and discussed.

CROSS DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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STRESS ANALYSIS IN CUBIC BORON NITRIDE FILMS BY X-RAY DIFFRACTION USING sin2$\psi$  METHOD ZHANG XING-WANG (张兴旺), YUE JIN-SHUN (岳金顺), CHEN GUANG-HUA (陈光华), YAN HUI (严辉), LIU WEN-JUN (刘文君) Acta Physica Sinica (Overseas Edition), 1998, 7 (1):  61-67.  DOI: 10.1088/1004-423X/7/1/007 Abstract ( 1133 )   PDF (209KB) ( 361 )   The boron nitride (BN) films containing cubic boron nitride (c-BN) and hexagonal boron nitride (h-BN) were prepared by radio frequency a ssisted thermal filament chemical vapor deposition. The stress and strain in BN films were investigated by X-ray diffraction analysis using the sin2$\psi$ method. The results showed that both c-BN and h-BN in the same film have similar values of elastic strain, however, the compressive stress in c-BN is much greater than that in h-BN for the same film. Both stress and strain gradually decre ased with the increase of substrate temperature (Ts). The effective stress in the films calculated by the effective stress model increased with the increase of Ts. Furthermore, the dependence of effective stress in the films on Ts was also investigated.