• Title/Summary/Keyword: High $T_c$ Superconductor

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Hall Effect of High $T_{c}$ superconductor $Y_{1}Ba_{2}Cu_{3}O_{7-\delta}$ Thin Film (고온초전도체 $Y_{1}Ba_{2}Cu_{3}O_{7-\delta}$ 박막의 Hall 효과)

  • 허재호;류제천;김형국;김장환
    • Journal of the Korean Magnetics Society
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    • v.4 no.1
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    • pp.44-47
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    • 1994
  • High $T_{c}$ superconducting $Y_{1}Ba_{2}Cu_{3}O_{7-\delta}$ thin film was grown up for c-axis orientation by epitaxial growth method on $LaAlO_{3}$ single crystal substrate. The crystal structures of this thin film were found to be c-axis orientation by X-ray diffraction patterns. Hall effect and resistivity measurements were made by van der Pauw method. Hall resistivity was calculated from the magnetoresistivity by considering thermomagnetic effect. The relation was $pH=p_{s}tan{\alpha}_{n}-QBT\frac{S_s}{K_s}$ The measured Hall resistivity and the calculated one are in good agreement each other.

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Numerical analysis of magnetization of HgBa$_2Ca_2Cu_3O_{8+{\delta}}$ superconductor (HgBa_2Ca_2Cu_3O_{8+{\delta}}$ 초전도체 자화의 수치적 해석)

  • Kim, Bong-Jun;Kim, Young-Cheol;Kim, Young-Jin;Back, Sang-Min
    • 한국초전도학회:학술대회논문집
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    • v.9
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    • pp.218-221
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    • 1999
  • Magnetization measurements have been carried out on grain aligned Hg-1223 with the applied field parallel to the c-axis. The temperature dependence of the lower critical field H$_{cl}$(T) was determined by considering the effect of the surface barrier on the magnetization. H$_{cl}$(T) have been determined .from magnetic hysteresis loops within the framework of the modified Kim-Anderson critical-state model, where the surface barrier and the lower critical field are explicitly considered. At high temperature, H$_{cl}$(T) is identified as H$_p$(T). This results are agreed with the theory of Bean-Livinston surface barriers.

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EPR Study of the High $T_c$ Superconductor $YBa_2$$Cu_3$$O_{7-y}$ Doped with Palladium or Zinc

  • Hag Chun Kim;Hyunsoo So;Ho Keun Lee
    • Bulletin of the Korean Chemical Society
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    • v.12 no.5
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    • pp.499-504
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    • 1991
  • EPR spectra of the high $T_c$ superconductor $YBa_2Cu_3O_{7-y}$ (YBCO) doped with $Pd^{2+} or Zn^{2+}$ have been measured at several temperatures and dopant concentrations. The spectral intensity of $YBa_2({Cu_{1-x}}{Pd_x})_3O_{7-y}$ is proportional to the dopant concentration. The behavior of $YBa_2(Cu_{1-x}Zn_x)_3O_{7-y}$ is quite different: the spectral intensity remains almost constant up to x=0.10 and then increases rapidly above x=0.10. The results are interpreted in terms of localized and antiferromagnetically spin-paired d holes in both CuO chain and planes. The $Pd_{2+}$ ion substitutes on the CuO chain consisting of "CuOCu dimers", and a $Cu_{2+}$ ion with an unpaired spin is gene rated for each $Pd_{2+}$ ion substituted. On the other hand, $Zn_{2+}$ substitutes on the CuO planes, and all or most of the spins in the two-dimensional plane manage to pair up in the region of low dopant concentration. When the dopant concentration exceeds a certain limit, it becomes more difficult for the spins to find partners, and the number of unpaired spins increases rapidly with increasing dopant concentration. The $Zn_{2+}$ ion is more effective than the $Pd_{2+}$ ion in suppressing the superconductivity of YBCO. This is attributed to the fact that $Zn_{2+}$ substitutes on the CuO planes which are mainly responsible for the superconductivity, while $Pd_{2+}$ substitutes on the CuO chain which is of secondary importance in the superconductivity.

Brief Review on Iron-based Superconductors: are There Clues for Unconventional Superconductivity?

  • Oh, Hyung-Ju;Moon, Ji-Soo;Shin, Dong-Han;Moon, Chang-Youn;Choi, Hyoung-Joon
    • Progress in Superconductivity
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    • v.13 no.2
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    • pp.65-84
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    • 2011
  • Study of superconductivity in layered iron-based materials was initiated in 2006 by Hosono's group, and boosted in 2008 by the superconducting transition temperature, $T_c$, of 26 K in $LaFeAsO_{1-X}F_X$. Since then, enormous researches have been done on the materials, with $T_c$ reaching as high as 55 K. Here, we review briefly experimental and theoretical results on atomic and electronic structures and magnetic and superconducting properties of FeAs-based superconductors and related compounds. We seek for clues for unconventional superconductivity in the materials.

A study on the magnetic and optical properties of high $T_c$ superconductor (고온 초전도체의 자기적, 광학적 성질에 관한 연구)

  • 김채옥;김재욱;김의훈
    • Electrical & Electronic Materials
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    • v.5 no.3
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    • pp.271-277
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    • 1992
  • X-선 회절 분석 및 적외선 투과율 측정은 실온에서 수행되었다. 또한 $Y_{1-x}$Nd$_{x}$Ba$_{2}$Cu$_{3}$O$_{7-y}$고온초전도체의 자기 임계전류밀도와 저항은 각각 30K와 80-140K 범위의 온도에서 조사되었다. 시료들은 고상 반응법에 의해서 제조되었다. 시료들의 결정구조는 X-선 회절무늬로 부터 모두 직방정계임이 판명되었다. 한편 x의 양이 증가함에 따라서 전이온도 T$_{c}$는 88K 근처의 값을 가지며 x의 양이 증가함에 따라 약간 감소하였다. 적외선 투과율 측정에서 날카로운 peak들은 472.23-618.87$cm^{-1}$ / 범위에 있었다. 이것은 특이할 정도로의 low-lying plasmalike edge와 낮은 에너지의 전자적인 여기가 존재함을 나타내는 것이다. 자기임계 전류밀도는 $10^{2}$~$10^{3}$A/$cm^{2}$ 범위에 있었다.있었다.

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Microstructure and Electrical Properties of (YNdSm)-Ba-Cu-O High Tc Composite Superconductors by Zone Melting Process (존멜팅법으로 제조한 (YNdSm)-Ba-Cu-O계 고온복합초전도체의 미세구조 및 전기적 특성)

  • Kim, So-Jung;Lee, Sang-Heon
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.29 no.2
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    • pp.110-113
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    • 2016
  • (YNdSm)-Ba-Cu-O system high Tc composite superconductors were directionally grown by zone melting process, having large temperature gradient, in air atmosphere. Cylindrical green rods of $(YNdSm)_{1.8}Ba_{2.4}Cu_{3.4}O_x$ [(YNS)1.8]composite oxides by CIP (cold isostatic pressing) method using rubber mold were fabricated. The microstructure and superconducting properties were investigated by XRD, TEM and SQUID magnetometer. The size of nonsuperconducting $(YNdSm)_2BaCuO_5$ inclusions of the melt-textured (YNS)1.8 sample with $CeO_2$ additive were remarkably reduced and uniformly distributed within the superconducting (YNS)1.8 matrix. (YNS)1.8 samples, with / without $CeO_2$ additive, showed an onset $T_c{\geq}90K$ and sharp superconducting transition. The critical current density $J_c$ value of the (YNdSm)1.8 superconductor with $CeO_2$ additive were 840 A, $1.2{\times}104A/cm^2$ in 77 K, 0 Tesla by direct current transport method.

Preparation and Characterization of Epitaxial $YBa_2Cu_3O_{7-\delta}$ Thin Films for Fabrication of High-$T_{c}$ Superconducting Microwave Devices (마이크로파 소자 응용을 위한 고온초전도 $YBa_2Cu_3O_{7-\delta}$ 에피택셜 박막의 제조 및 특성분석)

  • 강광용;한석길;김제하;이상렬
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1995.05a
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    • pp.26-30
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    • 1995
  • We describe the preparation and characterization of epitaxial thin films made with high temperature superconductor, $YBa_2Cu_3O_{7-\delta}$. The influence of processing parameters for YBCO thin films on MgO substrates in-situ grown by the pulsed laser deposition, including parameters of a laser beam energy, oxygen pressure, substrate temperature, target-substrate dis-tance is discussed. The characteristics of YBCO thin films were analyzed by using XRD, R-T measurement, AFM, crosssectional TEM, and RBS. For examples of microwave device applications, The fabrication and characterization of the microstrip lowpass filter and bandpass filter are also presented.

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The Effect of Processing Parameters on HTS Tube Characteristics

  • Jung, Sengho;Jang, Guneik;Ha, Dongwoo;Sung, Taehyun
    • Transactions on Electrical and Electronic Materials
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    • v.5 no.2
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    • pp.55-60
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    • 2004
  • High-temperature Superconductor(HTS) tubes were fabricated in terms of different chemical compositions and various SrSO$_4$additions by centrifugal forming method. For powder melting by induction the optimum range of melting temperatures and preheating temperature were 1050$^{\circ}C$, 1100$^{\circ}C$ and 550$^{\circ}C$ for 30 min, respectively. The mould rotating speed was 1000 rpm. A tube was annealed at 840$^{\circ}C$ for 72 hours in oxygen atmosphere. The plates like grains more than 20 $\mu\textrm{m}$ were well developed along the rotating direction of mould regardless of initial chemical compositions and the amounts of SrSO$_4$in Bi2212. The specimen with Bi2212 composition exhibited T$\_$c/ of 83 K, while the specimens fabricated with other compositions are lower than 60 K. The measured I$\_$c/ and J$\_$c/ at 77 K(B = 0 T) in Bi2212 with 7 % SrSO$_4$ composition were about 680 A and 380 A/$\textrm{cm}^2$.

형상에 따른 초전도 튜브의 전기적 특성변화

  • Jang, G.E.;Park, C.W.;Ha, D.W.;Seung, T.H.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.07a
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    • pp.527-530
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    • 2004
  • High-temperature Superconductor(HTS) tubes were fabricated in term of different diameter, length and thickness by centrigugal forming method. For powder melting by induction the optimum range of melting temperatures and preheating temperature were $1050^{\circ}C{\sim}1100^{\circ}C\;amd\;550^{\circ}C$ for 30min, respectively. The mould renting speed was 1000rpm. A tube was annealed at $840^{\circ}C$ for 72hours in oxygen atmosphere. The plate-like grains were well developed along the renting direction and typical grain size was about more than $40{\mu}m$. It was found that Ic values increased with increasing the tube diameter while the Ic decreased with increasing tube thickness. Also Ic decreased with increasing the tube length. The measured Ic in $50mm{\times}70mm{\times}25mm$ tube was about 896Amp.

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Superconductivity of High $T_c$ Superconductor $(Y_{1-x}Eu_x)Ba_2Cu_3O_{7-{\delta}}$ (고온초전도체 $(Y_{1-x}Eu_x)Ba_2Cu_3O_{7-{\delta}}$의 초전도성)

  • Chung Won Yang;Kweon Jung Ohk;Cho Eun Kyung;Kim Keyung Nam;Han, Sang Mok
    • Journal of the Korean Chemical Society
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    • v.36 no.1
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    • pp.16-23
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    • 1992
  • High $T_c$, superconductor $(Y_{1-x}Eu_x)Ba_2Cu_3O_{7-{\delta}}$ (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared and the physical properties were observed. XRD analysis showed that the structures of all the specimen were orthorhombic and the lattice parameters a, b and c increased with the increasing x value. Electrical resistivity and magnetization measurements revealed that pure high $T_c$, superconducting phases were formed at above 90 K. The critical temperatures increased with increasing the amount of Eu. From the measurement of magnetization and the size of the grains using SEM micrographs, volume diamagnetic susceptibilities for each specimen were calculated. These values decreased with the increasing x value. The composition of Ba in the lattice site decreased as the concentration of Eu increased, and this was confirmed by EPMA. It was found out that the volume diamagnetic susceptibility of each specimen was directly influenced by the composition of Ba in the lattice site.

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