Growth and anisotropic superconducting properties of Nd2–xCexCu04–y single crystals
Growth and anisotropic superconducting properties of Nd2–xCexCu04–y single crystals
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DOI：
10.1038/338635a0
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发表时间：
1989-04
期刊：
影响因子：
64.8
通讯作者：
Y. Hidaka;M. Suzuki
中科院分区：
文献类型：
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作者：
Y. Hidaka;M. Suzuki
最近在Ln_（2-x）CexCuO_（4-y）体系中发现了电子掺杂的氧化铜超导体，其中Ln为Pr，Nd或Sn ~（1，2）。本文报道了Nd_（2-x）Ce_xCuO_（4-y）单晶的生长及其各向异性超导性能的测量。Nd_（1.84）Ce_（0.16）CuO_（4-y）在22.5K时出现了明显的超导转变。电阻率表现出金属温度依赖性平行和垂直于基面。施加垂直于基面的磁场会导致电阻转变曲线向较低温度平行移动，与传统的II型超导体一样，但与空穴掺杂的氧化铜超导体不同。从严格定义的上临界磁场估计的金斯堡-朗道相干长度是70.2在基面和3.4沿着c轴，显示各向异性因子为21。该值远大于La 2-xSrxCuO 4-y中的值，尽管它们具有明显的结构相似性。从空穴掺杂系统的晶体学差异和随之而来的电子性质的变化可能提供线索的Cu-O平面中的高温超导体的微观配对机制的作用。
ELECTRON-DOPED copper oxide superconductors have recently been discovered in the system Ln2–xCexCuO4–y, where Ln is Pr, Nd or Sin1,2. Here we report the growth of single crystals of Nd2–xCexCuO4–y, and measurements of their anisotropic superconducting properties. A sharp superconducting transition is observed at 22.5 K in Nd1.84Ce0.16CuO4–y. The resistivity shows a metallic temperature dependence both parallel and perpendicular to the basal plane. Applying a magnetic field perpendicular to the basal plane causes a parallel shift of the resistive transition curve to lower temperatures, as in conventional type II superconductors but unlike the hole-doped copper oxide superconductors. The Ginzburg–Landau coherence lengths estimated from the resistively defined upper critical magnetic field are 70.2 Å in the basal plane and 3.4 Å along the c axis, showing an anisotropy factor of 21. This value is much larger than that in La2–xSrxCuO4–ydespite their apparent structural similarities. Crystallographic differences from the hole-doped systems and the concomitant changes in electronic properties may offer clues to the role of the Cu–O planes in the microscopic pairing mechanism of high-temperature superconductors.