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Very high upper critical fields of F-doped Fe-based layered superconductors NdO0.88F0.12FeAs and CeO0.88F0.12FeAs 总被引:1,自引:0,他引:1
Dan Wu Zheng Li ShaoKui Su Jing Dong Gang Li WanZheng Hu Ping Zheng GenFu Chen JianLin Luo NanLin Wang 《中国科学G辑(英文版)》2008,51(6):715-718
Using the solid state reaction method, we have synthesized the polycrystalline F-doped NdO0.88F0.12FeAs and CeO0.88F0.12FeAs with the superconducting transition temperatures at about 48 and 40 K, respectively. To obtain the upper critical field
H
c2 of Nd(Ce)O0.88F0.12FeAs samples, we measured the electrical resistivity under magnetic field up to 14 T. Based on the Werthamer-Helfand-Hohenberg
(WHH) relation together with the H
c2(T) curves in a relatively high field, we estimated that these superconductors have a rather high upper critical field of about
115 T for Nd-based and 107 T for Ce-based samples, indicating the similarities between these ReO1−x
F
x
FeAs (Re = rare earth element) superconductors and high T
c cuprate superconductors.
Recommended by Prof. Nie Yuxin, Executive Editor of Science in China Series G-Physics, Mechanics & Astronomy
Supported by the National Basic Research Program of China (973 Program)(Grant No. 2006CB9213001) and the National Natural
Science Foundation of China (Grant No. 10774181) 相似文献
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Doping Mn into(Li_(1-x)Fe_x)OHFe_(1-y)Se superconducting crystals via ion-exchange and ion-release/introduction syntheses 下载免费PDF全文
We report the success in introducing Mn into(Li_(1-_x)Fe_x)OHFe_(1-y) Se superconducting crystals by applying two different hydrothermal routes, ion e_xchange(1-step) and ion release/introduction(2-step). The micro-region _x-ray diffraction and energy dispersive _x-ray spectroscopy analyses indicate that Mn has been doped into the lattice, and its content in the 1-step fabricated sample is higher than that in the 2-step one. Magnetic susceptibility and electric transport properties reveal that Mn doping influences little on the superconducting transition, regardless of 1-step or 2-step routes. By contrast, the characteristic temperature T*, at which the negative Hall coefficient reaches its minimum, is significantly reduced by Mn doping.This implies that the hole carriers contribution is obviously modified, and hence the hole band might have no direct relationship with the superconductivity in(Li_(1-_x)Fe_x)OHFe_(1-y) Se superconductors. Our present hydrothermal methods of ion e_xchange and ion release/introduction provide an efficient way for elements substitution/doping into(Li_(1-_x)Fe_x)OHFe_(1-y) Se superconductors, which will promote the in-depth investigations on the role of multiple electron and hole bands and their interplay with the high-temperature superconductivity in the FeSe-based superconductors. 相似文献
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低能氩离子束轰击并后退火处理的离子束表面改性,会影响高温超导薄膜的表面结构和超导特性,但是其中的深刻微观机理不清楚.本文通过连续改变离子束轰击时间,系统研究了离子束表面改性对于超导膜结构和临界电流密度的影响.通过扫描电子显微镜、X射线衍射、J_(c-scanning)测试表征样品的结构特性和超导特性,并得出内应变、氧空位缺陷等参量.研究表明,经过表面改性的钇钡铜氧(YBa_2Cu_3O_(7-δ),YBCO)薄膜,随轰击时间增加表面形貌会变得更加均匀致密,a轴晶粒消失,并且临界电流密度有了显著的提高.由化学键收缩配对模型分析得出,临界电流密度的提高与薄膜内应变增大和引发的局部YBCO结构中Cu—O键收缩有关. 相似文献
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Floating-zone growth and property characterizations of high-quality La2-хSrхCuO4 superconductor crystals 下载免费PDF全文
We have grown underdoped(x=0.11,0.12) and optimally doped(x=0.16) La2 x SrxCuO4 single crystals by the traveling-solvent floating-zone technique.In order to prepare good quality cuprate crystals,we have made much effort to optimize the preparation procedures.For example,we haveadopted the sol-gel route to prepare a highly fine and homogeneous La2xSrxCuO4 precursor powder for fabricating a very dense ceramic feed rod used for the floating-zone growth,and we have also used quite a slow growth rate.The high quality of the grown crystals has been verified by double-crystal x-ray rocking curves,with the full-width-at-half-maximum being only 113-150 arcseconds,which are the best data reported so far for La2xSrxCuO4 crystals.The superconducting critical temperatures of the grown crystals are 30,31 and 38.5 K for x=0.11,0.12 and 0.16 samples,respectively,according to magnetic measurements. 相似文献
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K.Y. Kok B. Goldsmith N.B. Saidin 《Journal of magnetism and magnetic materials》2010,322(24):3876-3881
Permalloy (Ni80Fe20)/Cu multilayered nanowires (NWs) were electrodeposited using a template directed method from sulfate baths via pulse potential technique. Microstructures and compositions of the nanowires were characterized using various microscopy and spectroscopy techniques. To synthesize compositionally uniform nanowires with high efficiency, new sulfate baths with a high content of Ni2+ were developed. The effects of deposition potential and concentration of metal ions were optimized to reduce composition inhomogeneity and incorporation of copper in the permalloy layers. Composition of the NiFe layers was found to be close to 20 at% Fe with a maximum of 5 at% Cu. TEM analysis indicated that individual nanowires exhibit distinct and coherent layering structure with rough and wavy interfaces. A synthesized single nanowire was also AC dielectrophoretically assembled across the microfabricated gold electrodes for subsequent magnetoresistance measurements. 相似文献
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Bing Li Yunlong Xu Jun Chen Guorong Chen Chongjun Zhao Xiuzhen Qian Meng Wang 《Applied Surface Science》2009,256(1):235-238
A facile approach to the formation of Ag/PPy composite film, through the reaction of Ag+ and pyrrole monomer, was developed with the help of synergistic effect of NH3·H2O on this reaction. Black or gray Ag/PPy film precipitated on the insert wall of the vessel within 0.5 h with this new method. The Ag/PPy composite film has good conductivity (sheet resistance: 0.28 Ω/square) and superhydrophility (contact angle of water, CAW 0°). Mechanism involved in the reaction rate acceleration was briefly discussed. 相似文献