• 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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    • 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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    • 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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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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THE LOW TEMPERATURE DEPENDENCE OF MAGNETIZATION AND AC SUSCEPTIBILITY OF GLASSY $Fe_{91-x}Zr_{7}B_{2}Ni_{x}$ (x=0,5,10,15) ALLOYS

  • Strom, V.;Kim, K.S.;Jonsson, B.J.;Yu, S.C.;Inoue, A.;Rao, K.V.
    • Journal of the Korean Magnetics Society
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    • v.5 no.5
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    • pp.515-518
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    • 1995
  • We have studied the magnetization in fields up to 1T at 5K, the saturation magnetization dependence on temperature and the temperature dependence of AC-susceptibility at very low fields (5mOe to 50mOe) of glassy $Fe_{91-x}Zr_{7}B_{2}Ni_{x}$ (x = 0, 5, 10, 15) alloys. The temperature dependence of the magnetization follows the predictions of spin wave excitations with long wavelengths. At zero Ni concentration there is a clear competition between ferromagnetic and antiferromagnetic interactions giving rise to spin-glass behaviour. The addition of Ni drastically modifies the magnetic properties: the antiferromagnetic exchange coupling is reduced and finally disappears, the spin wave stiffness increases from 39.5 to $87.3\;meV{\AA}^{2}$ and To increases from 230 K to 478 K. We develop a simple model to quantify the competing interactions and to relate the antiferromagnetically coupled Fe moments to the Ni concentration. We find that the initial susceptibility increases with increasing Ni content along with a decrease of the temperature dependence.

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THE EFFECT OF SUBSTRATE TEMPERATURE ON GRAIN STRUCTURES AND MAGNETIC PROPERTIES OF Pd(Pt/Co/Pt) MODULATED MULTILAYERS

  • Xiao, Ying;Xu, Jun-Hao;Wittborn, Jesper;Yu, Seong-Cho;Rao, K.V.
    • Journal of the Korean Magnetics Society
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    • v.5 no.5
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    • pp.716-719
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    • 1995
  • Pd/(Pt/Co/Pt) modulated multilayer films have been deposited on various substrates with Pd/Pt buffer layers. Films grown at different temperatures have very distinct magnetic properties and surface microstructures. Atomic force(AFM) and scanning tunneling (STM) microscopies studies of these films reveal that films deposited at room temperature have small grain structures with an average grain size of about $140\;{\AA}$. However, much larger grains of about $1200\;{\AA}$ in size are observed in the films grown on buffer layers which were deposited at $500^{\circ}C$. These large grains are found to actually consist of smaller grains of about $170{\AA}$ in diameter. SQUID magnetic and Kerr hysteresis loop measurements indicate that multilayer films with large grains exhibit high magnetic coercivities of around 5 kOe. A subgrain growth model is proposed to understand the observed grain structures in the multilayers.

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A Study on the Research Data Management Methods for the Condensed Matter Physics (응집물질물리분야 연구데이터 관리 방안 연구)

  • Kim, Sungwook;Kim, Suntae
    • Journal of the Korean Society for information Management
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    • v.37 no.3
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    • pp.77-106
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    • 2020
  • In this study, we proposed a method to systematically manage research data in the field of condensed matter physics, which is the most active and interdisciplinary field. In the course of the research, a questionnaire was conducted for researchers in the field of condensed matter physics. The questionnaire was constructed based on the research data management tool Data Asset Framework (DAF) and the FAIR principle for data sharing and reuse. The current status of research data management in the field of aggregated material physics was collected from 14 researchers. The collected data consisted of data on the characteristics and basic information of researchers who answered the questionnaire, data preservation and management, and data sharing and access. By analyzing the collected questionnaire results, nine problems were drawn about the characteristics of research data in the field of aggregate material physics, data collection and production, data preservation and management, data sharing and access. In this study, suggestions were made to improve the problems derived from each aspect.