| Project/Area Number |
06650001
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Applied materials science/Crystal engineering
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| Research Institution | Tohoku University |
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Principal Investigator |
NOJI Takashi Tohoku University, Assistant Researcher, 工学部, 助手 (50180740)
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| Project Period (FY) |
1994 – 1995
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1995: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1994: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Keywords | Pb-based cuprate / Single crystal / High-Tc superconductivity / Anisotropy / Irreversibility field / Polymerized complex method / Second peak / 高温超伝導 / 超伝導転移温度 |
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| Research Abstract |
We have investigated Pb-based cuprates Pb_2Sr_2A_<n-1>Cu_<n+1>O_<2n+4+delta> (A : rare earth elements and alkaline earths), so-called Pb32 (n-1) n phases.
1. We have investigated the effects of extra oxygen for polycrystalline samples of the Pb-3201 phase, prepared by the polymerized complex method. It has been found that the extra oxygen supplies the CuO_2 sheets with hole carriers.
2. We have grown Pb_2Sr_2Y_<1-x>Ca_xCu_3O_8 single crystals of the Pb-3212 phase with 0*x*0.5 by means of the flux method. The anisotropic parameter gamma=(m_c^<**>/m_<ab>^<**>)^<1/2> has been found to increase with decreasing x, namely, with decreasing hole concentration. The irreversibility field H_<irr> and the anomalous second peak in the magnetization curves have been studied from the magnetization measurements for these single crystals. In the high temperature regime near T_<c'> not only H_<irr> but also the second peak field H_p at each reduced temperature t=T/T_c are roughly proportional to gamma^<-2>. For crystals of larger gamma values, H_<irr> in high magnetic fields in the low temperature regime is due to two-dimensional vortex-lattice melting.
3. We have tried to prepare a bulk sample of the Pb-3223 phase by the modified polymerized complex method. However, the Pb-3223 phase has not been produced in spite of a lot of efforts. At sintering temperature above 700ﾟC,the Pb-3212 phase is produced, while Ca_2PbO_4 is produced below 700ﾟC.
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