Relationship between superconductivity and crystal structure in NbB2+x
Relationship between superconductivity and crystal structure in NbB2+x
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DOI：
10.1016/j.stam.2005.11.015
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发表时间：
2006-01
影响因子：
5.5
通讯作者：
H. Takagiwa;E. Nishibori;Noriko Okada;Masaki Takata;M. Sakata;J. Akimitsu
中科院分区：
文献类型：
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作者：
H. Takagiwa;E. Nishibori;Noriko Okada;Masaki Takata;M. Sakata;J. Akimitsu
我们对非化学计量NbB 2+ x超导体进行了磁化率测量和精确的晶体结构分析，揭示了温度与晶体结构之间的关系。通过磁化率测量，发现tc随x的增加从2.2 K增加到5.8 K。利用三种不同波长的同步加速器x射线粉末衍射数据，用Rietveld精化法精确测定了晶体结构，包括化学成分和晶格常数。我们发现原子间Nb-B的距离随着温度的增加而增加。基于Rietveld细化的最大熵方法揭示了NbB 2+ x的电荷密度。我们发现不同成分和不同温度的NbB 2+ x在Nb位和B层的电子数是不同的。
We have performed magnetic susceptibility measurements and precise crystal structure analysis of the nonstoichiometric NbB 2+ x superconductor to reveal the relationship between T c and crystal structure. From magnetic susceptibility measurements, it was found that T c increases from 2.2 to 5.8 K with x. The crystal structures including both chemical compositions and lattice constants were precisely determined by Rietveld refinement using synchrotron X-ray powder diffraction data with three different wavelengths. We found that interatomic Nb–B distance increases with T c. The charge density of NbB 2+ x was revealed by the maximum entropy method based on Rietveld refinement. We find the difference in the number of electrons in the Nb site and B layer for NbB 2+ x with different compositions and T c.