• 제목/요약/키워드: condensed matter physics

검색결과 56건 처리시간 0.025초

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.
    • 한국자기학회지
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    • 제5권5호
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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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An STM Study of $Na_{x}CoO_{2}(x=0.84)$ Surface

  • Huang, Song-Hsin;Lin, C.H.;Hsue, H.S.;Liu, Hsiang-Lin;Chou, F.C.;Pai, Woei Wu
    • 한국자기학회:학술대회 개요집
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    • 한국자기학회 2007년도 The 1st International Symposium on Advanced Magnetic Materials
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    • pp.298.1-298.1
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    • 2007
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Thermoelectric power and resistivity of the Sr$_{1-x}K_xBiO_3$ superconductor

  • Kim, D.C.;Kim, J.S.;Joo, S.J.;Bougerol-Chaillout, C.;Kazakov, S.M.;Pshirkov, J.S.;Antipov, E.V.;Park, Y.W.
    • 한국초전도학회:학술대회논문집
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    • 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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    • pp.229-232
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    • 1999
  • We have measured the temperature dependence of thermoelectric power (TEP) and resistivity for the Sr$_{1-x}K_xBiO_3$ superconductor (x=0.45-0.6). At T=10.2K, the resisitivity starts to increase from zero and a rather broad superconducting phase transition (${\Delta}$T ${\sim}$ 2.3K) is observed. TEP at room temperature has a small negative value ( S =-1.96${\mu}$V/K), characteristic of metallic-like TEP. The temperature dependence of TEP shows two distinct features. With decreasing temperature from room temperature, the absolute value of TEP decreases and the sign of TEP changes from negative to positive around 200k. Also, the negative slope of TEP(dS/dT) decreases substantially and becomes rather flat at around 160k, which is a feature already noted in Ba$_{1-x}K_xBiO_3$[1].

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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.
    • 한국자기학회지
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    • 제5권5호
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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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충격파와 연소 현상 하에서의 다중 물질 해석을 위한 Reactive Ghost Fluid 기법 개발 및 응용 (Shock compression of condensed matter using multi-material Reactive Ghost Fluid method : development and application)

  • 김기홍;여재익
    • 한국항공우주학회지
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    • 제37권6호
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    • pp.571-579
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    • 2009
  • 에너지 물질과 같이 연소 반응을 하는 압축성 물질을 해석하기 위하여 Hydro-SCCM (Shock Compression of Condensed Matter)이라는 에너지 물질과 비반응 물질을 포함한다중 물질 해석툴을 개발하였다. 고에너지 물질은 강한 충격파와 고온과 고압을 가진 물질경계면에서 높은 변형률을 발생시킨다. 이러한 큰 구배를 가진 현상을 해석하기 위하여 새로운 오일러리안 기법을 사용하였다. 본 논문에서는 현상을 해석하기 위한 수학적 방법과 해석결과를 소개하였다.

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

  • 김성욱;김선태
    • 정보관리학회지
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    • 제37권3호
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    • pp.77-106
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    • 2020
  • 본 연구에서는 학제 간 연구가 가장 활발하고 응용가능성이 가장 높은 응집물질물리분야의 연구데이터를 체계적으로 관리하기 위한 개선방안을 제안하였다. 이를 위해 연구데이터 관리 도구인 Data Asset Framework (DAF)와 데이터 공유 및 재사용을 위한 FAIR원칙을 바탕으로 설문 내용을 구성하여 14명의 연구자를 대상으로 응집물질물리분야의 연구데이터 관리 현황을 수집하였다. 수집된 데이터는 설문에 응답한 연구자의 특성 및 기초정보, 데이터 보존 및 관리, 데이터 공유 및 접근에 관한 데이터로 구성되었다. 수집된 설문결과를 분석하여 응집물질물리분야의 연구데이터 특징과 데이터 수집과 생산, 데이터 보존과 관리, 데이터 공유 및 접근에 대한 9가지 문제점을 도출하였으며, 각 측면에서 도출된 문제점에 대한 개선방안을 제언하였다.

Water Sorption/Desorption Kinetics and Convective Drying of Eucalyptus globulus Wood

  • AMER, Mahyoub;KABOUCHI, Bousselham;El ALAMI, Salah;AZIZE, Brahim;RAHOUTI, Mohamed;FAMIRI, Abderrahim;FIDAH, Abdelwahed
    • Journal of the Korean Wood Science and Technology
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    • 제47권5호
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    • pp.557-566
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    • 2019
  • Radial and tangential water diffusion in Eucalyptus globulus wood was investigated using three mature trees from a forest in Khemis Sahel (North Morocco). Absorption and desorption kinetics experiments were conducted at ambient temperature ($25^{\circ}C$) and $30^{\circ}C$, respectively, and a relative humidity of 60%. The diffusion coefficients in the two directions were determined under imposed hygrothermal conditions; they were greater in the radial direction for the absorption as well as desorption processes. Convective drying under load, preceded by reconditioning and followed up by balancing, revealed the drying conditions that corresponded to the appropriate drying schedules for E. globulus wood. This was verified by measuring the cracks and bowsbefore and after drying of boards.

Design of a High Temperature Oven for Measuring the Saturation Intensity of Samarium atom by using Two Wave Mixing

  • Ko, Kwang-Hoon;Moon, Hee-Jong;Park, Hyun-Min;Lee, Jong-Min;Lee, Won-Kyu;Lee, Jai-Hyung;Chang, Joon-Sung
    • Journal of the Optical Society of Korea
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    • 제4권2호
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    • pp.75-78
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    • 2000
  • We design a high temperature oven for measuring the saturation intensity of the transition line $4f^ 6/6s^{2 7}7F_0 ↔ 4f^6/6s6p $^1$P(J = 1)$ of the samarium atom. We first constructed a high temperature oven to generate the samarium vapor column and study the thermal characteristics of the oven. The oven is able to operate at a temperature up to about 1400 $^{\circ}C$ and the operation is tested by using several metals with high melting points. We describe two wave mixing experiment with the samarium vapor generated in the high temperature oven and obtain the saturation intensity by analyzing the first diffraction signal.