K(x)Fe(2-y)Se(2-z)S(z)体系磁性和超导电性之间的关联和相互作用研究

In addition to the cooper-oxides, the family of the iron-based superconductors discovered in 2008 is the second family of high-Tc superconductors. The iron-based superconductors provide new thinking and striving directions for the mechanism study in high-Tc superconductivity and the synthesis of novel superconductors. Among them, the iron chalcogenides has generated much interest because the parent compound FeSe possesses the simplest crystal structure of FeSe4 layers and has no toxic arsenic element. The coexisten and interplay between superconductivity and magnetism is a hotspot in the study of iron-based superconductors and is usually related to the pairing mechanism of superconductivity. In this project,we choose the K(x)Fe(2-y)Se(2-z)S(z)(0<z<2) system as study object, in which system superconductivity is found coexistenting with ferromagentism and antiferromagnetism. By applying high pressure and annealing in high magentice field, we plan to study the intrinsic relevance and interaction between magnetism and superconductivity in iron chalcogenides through investigating the pressure effect and anneal effect on superconductivity and magnetic properties of this system.

2008年发现的铁基超导体是除铜氧化物外又一类高温超导材料，为高温超导机理研究和新型超导体合成提供了新的思路和方向。其中FeSe具有铁基超导体系最简单的结构，同时不含毒性元素砷，因此铁硒体系受到了人们的广泛关注。在铁基高温超导研究中，磁性和超导的共存和竞争一直是个热点问题，同时也被认为很可能和铁基超导的配对机制紧密相关。本项目计划选取新型铁硒超导材料K(x)Fe(2-y)Se(2-z)S(z)（0<z<2）这一反铁磁、铁磁和超导共存的体系作为研究对象，利用高压和强磁场等极端条件，通过测量不同的压力和磁场退火条件对体系磁性和超导电性的影响，来研究该体系磁性和超导之间的关联和相互作用问题。

反铁磁和超导电性的共存和竞争现象是Fe-Se基超导材料中的一个重要的研究领域。我们利用自助溶剂方法合成了Rb(0.81)Fe(1.72)Se(2), Cs(0.81)Fe(1.72)Se(2), K(x)Fe(2-y)Se(2), K(x)Fe(2-y)Se(1.6)S(0.4)等单晶,Co和Cu掺杂的Fe(1+y)Fe(0.6)Se(0.4)系列单晶，Fe(1+y-x)Co(x)Te(x=0,0.01,0.04,0.07,0.09,0.11)系列单晶，和FeTe(1-x)Sb(x)(x=0,0.05,0.07,0.08,0.1)系列单晶样品，对多个Fe-Se基超导材料单晶体系进行了深入而系统的研究。借助结构，磁性，电阻，比热，扫描显微镜，电子自旋顺磁共振图谱等方面的考察，通过利用高压和强磁场等极端条件，分析不同掺杂和退火条件对磁性和超导电性的影响，研究了该体系磁性和超导之间的关联和相互作用，取得了一些有意义的成果，在相关领域的国际期刊发表多篇文章。