Table of contents

20 August 1994, Volume 3 Issue 8 Previous issue    Next issue

CLASSICAL AREAS OF PHENOMENOLOGY

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LAMB WAVE MODES IN A TWO-LAYERED SOLID MEDIUM WITH A WEAK INTERFACE WANG YAO-JUN (王耀俊), NING WEI (宁伟), OU XIAN-HUA (欧贤华) Acta Physica Sinica (Overseas Edition), 1994, 3 (8):  561-566.  DOI: 10.1088/1004-423X/3/8/001 Abstract ( 1171 )   PDF (148KB) ( 509 )   Using the "spring" model for a weak interface between two solids, we derive the charac-teristic equation for the Lamb waves in a two-layered solid composite and make numerical computations for dispersion curves in an aluminum/copper structure with a rigid or slip interface. The influence of the shear stiffness of the interface on the low order Lamb wave modes is considered.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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DISSOLUTION OF IRON TO COPPER IN Fe60Cu40 ALLOY BY MECHANICAL ALLOYING AND SUBSEQUENT DECOMPOSITION YANG YUAN-ZHENG (杨元政), MA XUE-MING (马学鸣), WANG GEN-MIAO (王根苗), DONG YUAN-DA (董远达), ZHUANG YU-ZHI (庄育智) Acta Physica Sinica (Overseas Edition), 1994, 3 (8):  567-572.  DOI: 10.1088/1004-423X/3/8/002 Abstract ( 1280 )   PDF (171KB) ( 441 )   A metastable alloy with composition Fe60Cu40 can be prepared in single phase of a fcc structure by mechanical alloying, although Fe-Cu system is virtually immiscible in its equilibrium state at ambient temperature. The M$\ddot{\rm o}$ssbauer spectra of this supersaturated solid solution could be fitted by two subspectra whose hyperfine magnetic fields are 200 kOe and 250kOe. In this metastable alloy, the iron atoms at the interface are easy to form clusters characterized as $\alpha$-Fe at a temperature below 250℃, whereas the iron atoms in the body will cluster together at a higher temperature above 350℃ and behave as $\gamma$-Fe, and then transform to ferromagnetic bcc iron occurs.

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

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ANDERSON TRANSITION ZONE IN THE SOUKOULIS-ECONOMOU MODEL OF ONE-DIMENSIONAL INCOMMENSURATE SYSTEMS YANG FU-MIN (杨富民), SUN JIN-ZUO (孙金祚) Acta Physica Sinica (Overseas Edition), 1994, 3 (8):  573-582.  DOI: 10.1088/1004-423X/3/8/003 Abstract ( 1218 )   PDF (272KB) ( 320 )   Using numerical calculation method, we have studied the Anderson transition in the Soukoulis-Economou model of one-dimensional incommensurate systems. Our results in-dicate that the Anderson transition in this model should take place gradually, i.e., the transition from the extended state to the localized state should pass through a zone in which the intermediate state is located. We call it the Anderson transition zone of the Soukoulis-Economou model. This new conclusion differs from the traditional concept, which holds that the Anderson transition of the Soukoulis-Economou model occurs abruptly at the mobility edges of this model.

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SUPERCONDUCTING TRANSITION TEMPERATURES AND NORMAL-STATE ELECTRICAL RESISTIVITIES OF Tm1-xPrxBa2Cu3O7-$\delta$ CAO XIAO-WEN (曹效文) Acta Physica Sinica (Overseas Edition), 1994, 3 (8):  583-588.  DOI: 10.1088/1004-423X/3/8/004 Abstract ( 1126 )   PDF (145KB) ( 364 )   Superconducting transition temperature Tc and normal-state electrical resistivities $\rho$ of the Tm1-xPrxBa2Cu3O7-$\delta$ system have been measured. The results indicate that Tc remains constant for x = 0 to 0.08 before it drops steadily with higher x. Following the Abrikosov-Gor'kov model, a total suppression of superconductivity occurs at a critical Pr concentration xcr≈0.56. It is found for the first time, as far as we know, that the logarithmic resistivity at 270 K increases linearly with increasing x, yielding $\rho$ = $\rho$0eax. Judging from the relation between d$\rho$/dT and x, a metal to insulator transition occurs just beyond xcr.

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STUDY OF HALOGEN DOPING IN POLYCRYSTALLINE YBa2Cu3O7-$\delta$ ZHUANG RUI-FANG (庄瑞舫), XIE HUI (谢辉), JI HE-LIN (吉和林), JIN XIN (金新), QIN MENG-JUN (覃孟军), XU XIAO-NONG (徐小农), YAO XI-XIAN (姚希贤) Acta Physica Sinica (Overseas Edition), 1994, 3 (8):  589-594.  DOI: 10.1088/1004-423X/3/8/005 Abstract ( 1412 )   PDF (164KB) ( 398 )   This paper presents systematically the doping effects of halogens in YBa2Cu3O7-$\delta$ polycrystalline samples, with a series of concentrations of fluorine, chlorine, bromine or iodine. All samples were prepared by chemical method of citrate pyrolysis, which makes the halogen concentration in the samples more uniform. Samples doped with F have Tc as high as 94.5K, Cl, Br and I dopings also raise Tc to a certain extent. In addition, the influence of halogen doping on critical current density, morphology, constitution and so forth is discussed.

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STUDY OF PHOTON-TRAPPING PHENOMENON IN POROUS SILICON LAYER CHEN LIANG-YAO (陈良尧), HOU XIAO-YUAN (侯晓远), HUANG DA-MING (黄大鸣), ZHANG FU-LONG (张甫龙), FENG XING-WEI (冯星伟), YANG MIN (杨敏), SU YI (苏毅), QIAN YOU-HUA (钱佑华), WANG XUN (王迅) Acta Physica Sinica (Overseas Edition), 1994, 3 (8):  595-607.  DOI: 10.1088/1004-423X/3/8/006 Abstract ( 1583 )   PDF (399KB) ( 424 )   Porous silicon samples were prepared for optical studies by using the photoluminescence (PL), Raman scattering (RS), as well as the absolute reflectance and ellipsometry methods. Results show that the porous Si has low optic constants, and can trap the visible photons of more than 95%, but give no evidence of a strong interband transition existing in the vis-ible region. The Bruggeman effective-medium-approximation (EMA) and Lorentz oscillator models were used in data analyses. Calculations show that the layer dispersion effect may result in a red shift of the PL peak. The possible mechanism for the PL and Raman enhance-ment as well as the photon trap phenomenon was discussed, and was attributed mainly to the random multiple micro-reflections in the porous-Si layer having extremely large internal micro-Burfaces.

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THE INFLUENCE OF THE ADMIXING OF DIFFERENT MULTIPLETS ON THE SPIN MAGNETIC MOMENT AND FARADAY EFFECT OF HARE EARTH IONS IN GARNETS ZHANG GUO-YING (张国营), XU YOU (徐游), YANG JIE-HUI (杨杰慧) Acta Physica Sinica (Overseas Edition), 1994, 3 (8):  608-616.  DOI: 10.1088/1004-423X/3/8/007 Abstract ( 1091 )   PDF (245KB) ( 378 )   The influence of the admixing of the excited multiplets of the ground configuration with the ground multiplet on the spin magnetic moment of the crystal- field-and exchange-interaction-split ground state, the Faraday rotation and the magneto-optic coefficient induced by the rare earth ions in rare-earth-substituted garnets Y3-xRxFe5O12 (R=Ce and Pr) has been calculated in this paper. It is found that, in the case of Ce3+ ions, the admixing of the 4f1 2F7/2 multiplet with the 2F5/2 multiplet makes the spin magnetic moment of the crystal-field- and exchange-interaction-split ground state increase by 140% and the Faraday rotation increase by 180% at 633nm wavelength, and 150% at 1150nm at 294 K. In the case of Pr3+ ions, the admixing of the 4f2 3H5 multiplet with the 3H4 multiplet makes the spin magnetic moment of the crystal-field- and exchange-interaction-split ground state increase by 34% and the Faraday rotation increase by 59% at 294K. The admixing of different multiplets of the Ce3+ ions makes the ratio between the magneto-optic coefficients at 50 and 294K increase by 7% at 633nm wavelength and 15% at 1150nm.

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A MBE ON-LINE OPTICAL MODULATION PHOTOREFLECTANCE ANALYSIS SYSTEM HE YUAN-JIN (何元金), DONG YUE-MEI (董悦梅), DUAN XIAO-DONG (段晓东) Acta Physica Sinica (Overseas Edition), 1994, 3 (8):  617-622.  DOI: 10.1088/1004-423X/3/8/008 Abstract ( 1242 )   PDF (183KB) ( 406 )   An on-line optical modulation photoreflectance (PR) spectroscopy analysis system asso-cinted with the molecular beam epitaxy (MBE) system has been designed and established. This paper reports in detail the optical design, the experimental arrangement, and the adjust-ment of the system. GaAs film samples grown by MBE on Si-substrate have been measured with this on-line system. The results show that the on-line PR spectroscopy can characterize the quality of the as-grown film samples qualitatively and promptly.

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MONTE CARLO STUDIES OF RADIATION DAMAGE INDUCED BY FUSION DYNAMIC SIMULATION OF SPUTTERING SHAO QI-YUN (邵其鋆), PAN ZHENG-YING (潘正瑛), HUO YU-KUN (霍裕昆) Acta Physica Sinica (Overseas Edition), 1994, 3 (8):  623-629.  DOI: 10.1088/1004-423X/3/8/009 Abstract ( 1281 )   PDF (170KB) ( 422 )   In this paper, the sputtering caused by fusion of 4He particles in the first wall materials is investigated by using the dynamic Monte Carlo simulation, which is based on the binary collision approximation. The dependences of sputtering yields on the incident energy and angle, as well as the comparisons of results calculated using the Monte Carlo methed with results from experiments, are discussed. Energy spectrum and angular distributions of sputtered species, the depth of origin of the sputtered particles as well as range distributions of incident ions are given. From a comparison between the related experimental data and the calculated results with static and dynamic simulation it has been found that a better agreement is obtained for dynamic simulation.