• Title/Summary/Keyword: ${\Delta}SR$

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Crystal Structure and Electrical Transport Characteristics of ${La_{1-x}}{Sr_x}{MnO_{3-{\delta}}}$(0.19$\leq$x$\leq$0.31) Thin Films (${La_{1-x}}{Sr_x}{MnO_{3-{\delta}}}$(0.19$\leq$x$\leq$0.31) 박막의 결정구조 및 전기전도 특성)

  • Heo, H.;Lim, S.J.;Cho, N-H.
    • Korean Journal of Materials Research
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    • v.10 no.6
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    • pp.437-444
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    • 2000

  • We investigated the effect of substrate temperature, chemical composition and post-deposition heat-treatment on the crystal structure and electrical transport of $La_{1-x}Sr_xMnO_{3-{\delta}}$(0.19${\leq}x{\leq}$0.31) thin films. As-prepared $La_{1-x}Sr_xMnO_{3-{\delta}}$ films grown at $500^{\circ}C$ by sputter techniques were found to have the pseudo-tetragonal system(a/c=0.97) and a highly preferential <001> orientation. The films were changed to be of the cubic system by post-deposition annealing at around $900^{\circ}C$. A main target of $La_{0.67}Sr_{0.33}MnO_3$ as well as auxliary targets of $La_{0.3}Sr_{0.7}MnO_3$ ceramics were co-sputtered to control the chemical composition of the film. The Sr content(x) of the film ranged from 0.19 to 0.31, depending on the number of the auxiliary target. When x increased from 0.19 to 0.31, the electrical resistivity of the film decreased and the transition temperature between metal and semiconductor shifted to higher temperature. With a magnetic field of 0.18 T, the magneto-resistance ratio (MR(%) = (${\rho}_o-{\rho}_H/{\rho}_H$) of the $La_{0.69}Sr_{0.31}MnO_3$ thin film was about 390%.

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Microstructure and Superconducting Properties of Ag-$Bi_{1.84}Pb_{0.34}Sr_{1.91}Ca_{2.03}Cu_{3.06}O_{10+{\delta}}$ Composites (Ag-$Bi_{1.84}Pb_{0.34}Sr_{1.91}Ca_{2.03}Cu_{3.06}O_{10+{\delta}}$ 복합체의 미세구조와 초전도특성)

  • 이민수
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.52 no.6
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    • pp.249-256
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    • 2003

  • Samples with the nominal composition, Ag-$Bi_{1.84}Pb_{0.34}Sr_{1.91}Ca_{2.03}Cu_{3.06}O_{10+{\delta}}$ high $T_{c}$ superconductors containing Ag as an additive were fabricated by a solid-state reaction method. Samples with Ag of 10 wt%, 30 wt%, and 50 wt% each were sintered at $860^{\circ}C$~$870^{\circ}C$ for 24 hours. The structural characteristics, the microstructures and the critical temperature with respect to the each samples were investigated by XRD, four-prove methode, SEM and EDS respectively. The $T_{c}\;^{zero}$ of the sample with the 50 wt% Ag additive at the surface showed 94 K.

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B과 Sr동위원소를 이용한 지하수 수질 특성 연구

  • Go Gyeong-Seok;Yeom Byeong-U;Ha Gyu-Cheol;Ryu Jong-Sik;Go Dong-Chan;Bae Gwang-Ok
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2006.04a
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    • pp.328-332
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    • 2006

  • 본 연구는 농경활동이 활발한 만경강 하천부지에서 지하수의 수리지질 및 수리지화학적 특성을 고찰하고 B과 Sr 동위원소를 이용하여 지하수 수질 변화에 영향을 미치는 요인을 알아보고자 하였다. 연구 결과 만경강 하천부지는 지표로부터 실트질 모래층, 자갈모래층, 풍화대로 크게 3등분되며 투수성은 모래자갈층에서 가장 좋고 그 다음으로 풍화대, 실트질 모래층 순이었다. 화학성분 검층과 ${\delta}^{11}B,\;^{87}Sr/^{86}Sr$ 동위원소 분석결과 지하수 조성은 해수와 농업 활동에 의한 영향을 크게 받는 것으로 나타났다. 화학성분 검층 결과 해수 영향은 하천과 도로제방 사이 중간정도 까지인 것으로 사료되었으며 ${\delta}^{11}B$ 분석 결과 자갈모래층과 풍화대 지하수는 해수의 영향을 받는 것이 확인되었다. 본 연구지역 지하수는 지층 특성에 의한 영향으로 천층지하수는 토지이용에 따른 농업활동의 영향을 받으며 지표하 10m 이하의 지하수는 해수의 영향을 받는 것으로 사료되었다.

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Magnetic properties and magnetocaloric effect of Sr-doped Pr0.7Ca0.3MnO3 compounds

  • Yen, Pham Duc Huyen;Dung, Nguyen Thi;Thanh, Tran Dang;Yu, Seong-Cho
    • Current Applied Physics
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    • v.18 no.11
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    • pp.1280-1288
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    • 2018

  • In this work, we pointed out that Sr substitution for Ca leads to modify the magnetic and magnetocaloric properties of $Pr_{0.7}Ca_{0.3-x}Sr_xMnO_3$ compounds. Analyzing temperature dependence of magnetization, M(T), proves that the Curie temperature ($T_C$) increased with increasing Sr content (x); $T_C$ value is found to be 130-260 K for x = 0.0-0.3, respectively. Using the phenomenological model and M(T,H) data measured at several applied magnetic field, the magnetocaloric effect of $Pr_{0.7}Ca_{0.3-x}Sr_xMnO_3$ compounds has been investigated through their temperature and magnetic field dependences of magnetic entropy change ${\Delta}S_m$(T,H) and the change of the specific heat change ${\Delta}C_P$(T,H). Under an applied magnetic field change of 10 kOe, the maximum value of $-{\Delta}S_m$ is found to be about $3J/kg{\cdot}K$, and the maximum and minimum values of ${\Delta}C_P$(T) calculated to be about ${\pm}60J/kg{\cdot}K$ for x = 0.3 sample. Additionally, the critical behaviors of $Pr_{0.7}Ca_{0.3-x}Sr_xMnO_3$ compounds around their $T_C$ have been also analyzed. Results suggested a coexistence of the ferromagnetic short- and long-range interactions in samples. Moreover, Sr-doping favors establishing the short-range interactions.

  • https://doi.org/10.1016/j.cap.2018.07.006 인용 KSCI