Magnetic Correlations in Superconducting Iron Arsenides

超导砷化铁的磁关联

• 批准号: EP/G067457/1
• 负责人: Andrew Boothroyd
• 金额: $ 17.36万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FG067457%2F1
• 关键词: Magnetic; Correlations; Superconducting; Iron; Arsenides

Since February 2008 a new family of superconductors has been developed based on a series of compounds containing layers of iron and arsenic atoms or alternatively iron and selenium atoms. These compounds exhibit superconductivity (i.e. they lose all their electrical resistance) at relatively high temperatures (at up to 56 K as at November 2008). The current thinking is that the mechanism of superconductivity is not the same as that found in simple elements and compounds, such as lead and magnesium diboride, in which the vibrations of the crystal lattice cause the electrons to lower their energy by binding into pairs which can move through the crystal without resistance. Rather, the new iron arsenide and selenide superconductors exist in close proximity to magnetic phases, which suggests that magnetic interactions might be responsible for superconductivity.The purpose of the proposed work is to investigate the relationship between superconductivity and magnetism in selected members of the iron arsenide family of compounds. So far, all compounds found with a particular structural arrangement of iron and arsenic atoms have been successfully turned into superconductors through control of their electron count, even though there is considerable variation in the crystal structures. This is achieved by making small variations in the chemical composition through substitutions, e.g. by replacing some of the iron toms by cobalt. This chemical flexibility potentially makes it possible to tune the physical behaviour of the materials in many different ways, which may be exploited to perform systematic experiments to study the interplay between magnetism and superconductivity. The applicants have recently contributed new compositions to this field, such as LiFeAs and NaFeAs, and are well placed to embark on a systematic investigation of the magnetic and superconducting properties of these materials. In this project a graduate student will perform a series of studies using a range of neutron and X-ray scattering techniques to gain access to the fundamental magnetic behaviour on an atomic scale. The particular focus will be on the use of neutron spectroscopy to probe the magnetic dynamics in the non-superconducting compounds close in composition to the superconductors, and to probe the nature of the superconducting energy gap in the superconducting members. The proposed studies at the ISIS, ILL and Diamond facilities will build on the very recent work by the applicants in this field and will provide a coherent research programme for a graduate student who will gain experience of chemical synthesis, physical property measurements and extensive use of Central Facilities.

自2008年2月以来，基于一系列含有铁和砷原子层或铁和硒原子层的化合物，一个新的超导体家族已经被开发出来。这些化合物在相对较高的温度下（2008年11月高达56 K）表现出超导性（即它们失去了所有的电阻）。目前的想法是，超导的机制与在简单元素和化合物（如铅和二硼化镁）中发现的机制不同，在这些元素和化合物中，晶格的振动导致电子结合成成对，从而降低了它们的能量，从而可以在晶体中无阻力地移动。相反，新的砷化铁和硒化铁超导体存在于磁相附近，这表明磁相互作用可能是超导性的原因。本文的目的是研究砷化铁化合物家族中某些成员的超导性和磁性之间的关系。到目前为止，通过控制铁和砷原子的电子数，所有具有特定结构排列的化合物都已成功地转化为超导体，尽管晶体结构存在相当大的差异。这是通过取代使化学成分发生微小变化来实现的，例如用钴代替一些铁原子。这种化学柔韧性有可能以许多不同的方式调整材料的物理行为，这可能被用来进行系统的实验来研究磁性和超导性之间的相互作用。申请人最近在这一领域贡献了新的组合物，如LiFeAs和nafea，并且很好地开始对这些材料的磁性和超导特性进行系统的研究。在这个项目中，研究生将使用一系列中子和x射线散射技术进行一系列研究，以获得原子尺度上的基本磁性行为。特别的重点将是利用中子光谱学来探测在组成上接近超导体的非超导化合物中的磁动力学，并探测超导成员中超导能隙的性质。在ISIS， ILL和Diamond设施的拟议研究将建立在申请人在该领域的最新工作的基础上，并将为研究生提供一个连贯的研究计划，该研究生将获得化学合成，物理性质测量和广泛使用中央设施的经验。