• Title/Summary/Keyword: condensed matter physics

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Effects of laser polarization on hot electron emission in femtosecond laser-plasmas

  • Zhang, J.;Chen, L.M.;Teng, H.;Liang. T.J.;Zhao, L.Z.;Wei, Z.Y.
    • Proceedings of the Optical Society of Korea Conference
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    • 2001.02a
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    • pp.98-102
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    • 2001

  • Effects of laser polarization were studied on behaviors of fast electrons produced from an aluminum target irradiated by a solid target irradiated by obliquely incident laser pulses at Bx10$\^$15/ W/cm$^2$. Jet emission of outgoing fast electrons collimated in the polarization direction was observed for the s-polarized laser irradiation, whereas for the p-polarized irradiation, very directional emission of outgoing fast electrons was found close to the normal direction of the target. The behaviors of in-going fast electrons into the target for s- and p-polarized irradiation were also investigated by observing x-ray Bremsstrahlung radiation at the backside of the target.

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Atomic-scale Controlled Epitaxial Growth and Characterization of Oxide Thin Films

  • Yang, G.Z.;Lu, H.B.;Chen, F.;Zhao, T.;Chen, Z.H.
    • Proceedings of the Optical Society of Korea Conference
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    • 2001.02a
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    • pp.6-11
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    • 2001

  • More than ten kinds of oxide thin films and their heterostructure have been successfully fabricated on SrTiO$_3$(001) substrates by laser molecular beam epitaxy (laser MBE). Measurements of atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM) and X-ray small-angle reflectivity reveal that the surfaces and interfaces are atom-level-smooth. The unit cell layers and the lattice structure are perfect. The electrical and optical properties of BaTiO$_3$-x thin films and BaTiO$_3$/SrTiO$_3$ (BTO/STO) superlattices were examined. The all-perovskite oxide P-N junctions have been successfully fabricated and the better I-V curves were observed.

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Electrical resistivity and magnetization of Sr$_{1-x}K_xBiO_3$ superconductor in magnetic field: Observation of a reentrant superconducting resistive transition at low temperature

  • Kim, J.S.;Kim, D.C.;Joo, S.J.;Kim, G.T.;Lee, S.Y.;Khim, Z.G.;Bougerol-Chaillout, C.;Kazakov, S.M.;Pshirkov, J.S.;Antipov, E.V.;Park, Y.W.
    • 한국초전도학회:학술대회논문집
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    • v.9
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    • pp.210-213
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    • 1999

  • Magnetoresistance and magnetization of Sr$_{l-x}K_xBiO_3$ were both measured as functions of temperature and magnetic field. Resistivity goes to zero at T=10.1K and the overall superconducting transition behavior under applied magnetic fields is similar to that of other BiO based superconductors. Also, below T<5K we have observed the reappearance of finite resistivity with a power law temperature dependence( ${\rho}$ ${\sim}$T$^1$); the reentrant superconducting transition of resistivity. Contrary to the Josephson weak link effect in polycrystalline samples, which gives the depression of the superconducting state with increasing electrical current or magnetic field, the superconducting state for T<5K is resumed by applying a higher current or magnetic field. Magnetic susceptibility( ${\chi}$ ) of Sr$_{l-x}K_xBiO_3$ for T<5K also shows similar trends to that observed in transport measurements: increase of ${\chi}$ (paramagnetic-like behavior) at a low magnetic fields(B=50 Oe) and, the resumption of perfect diamagnetism at high fields.

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MAGNETISM OF NANOPHASE IRON PARTICLES LASER EVAPORATED IN A CONTROLLED OXYGEN ATMOSPHERE

  • Turkki, T.;Jonsson, B.J.;Strom, V.;Medelius, H.;El-Shall, M.S.;Rao, K.V.
    • Journal of the Korean Magnetics Society
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    • v.5 no.5
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    • pp.745-748
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    • 1995

  • Magnetic nanoparticles of iron and iron oxide have been prepared in a modified upward thermal diffusion cloud chamber using pulsed laser evaporation. SEM/TEM studies of these particles reveal a size distribution with a mean diameter of about $60\;{\AA}$. FTIR spectrum measurements are used to investigate the difference in oxidation level between nanoparticles prepared at different partial oxygen pressures. The complex magnetic behaviour of these particles was studied using DC- and AC-susceptibility measurements. All samples exhibit superparamagnetism with blocking temperatures ranging from 50 K to above room temperature. The coercivity fields as well as the dependence of the blocking temperature on measuring frequency have been studied. magnetic anisotropy constants are found to be one order of magnitude higher than is known for the bulk values. The mean particle size estimated from the magnetic data is found to be in perfect agreement with the TEM observations.

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