2002 Fiscal Year Final Research Report Summary
Search for a novel double honeycomb lattice superconductor
| Project/Area Number |
13640347
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | Tohoku University |
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Principal Investigator |
SHAMOTO Shin-ichi Tohoku University, Graduate School of Engineering, Associate Professor, 大学院・工学系研究科, 助教授 (90235698)
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| Co-Investigator(Kenkyū-buntansha) |
KAJITANI Tsuyoshi Tohoku University, Graduate School of Engineering, Professor, 大学院・工学系研究科, 教授 (80134039)
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| Project Period (FY) |
2001 – 2002
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| Keywords | Double honeycomb lattice / Superconducting / Material search / HfNCl |
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| Research Abstract |
We have synthesized double honeycomb lattice superconductors, such as Li_xZrNCl (T_c=15 K), Li_xNBr (T_c=13 K), and Na_xHfNCl (T_c=20-23 K) under ambient pressure. By synthesizing large amount of sample, we have succeeded to determine these structural parameters by Rietveld analysis using neutron powder diffraction data one by one. As a result, we found the close relationship between the transfer integral estimated by Harrison approximation and the superconducting transition temperature T_c in these compounds. This is partially because Na_xHfNCl has large Debye temperature in spite of the large mass of a Hf atom, I.e., stiff lattice. It basically suggests that the longer bond distance between the nearest neighbor transition metal atoms are, the higher T_c is. Based on this finding, we have selected YOCl, TaON, and CeSI as high-T_c candidates of double honeycomb lattice superconductors. Our simple estimation predicts that Na_xYOCl would have a T_c of 30 K. After we successfully sysnthesized Li_xYOCl powder sample in DRI-LAB glove box under an atmosphere of less than 1 ppm moisture, we found it was an insulator with curious temperature dependence of magnetization. This is the first discovery of a double honeycomb lattice insulator. It proves that Na_xHfNCl locates close to an insulator region in our transfer integral phase diagram. This result suggests that Li_xYOCl sample might be a high-T_c superconductor under pressure.
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Research Products
(18 results)
