螺旋铁磁金属钬一维纳米结构的构筑及其超导近邻效应研究

Dramatic advances have been seen in designing and building structures that combine the zero-resistance supercurrents of superconductors with the spin alignment of ferromagnets. The long range spin-polarized supercurrents, as a controllable source of spin states, hold tantalizing promise for spintronics, an emerging field that exploits electrons’ spin degrees of freedom for electronic devices. Experimental research and theory analysis indicated that the realization of long range spin-polarized supercurrents in ferromagnet is based on the magnetic inhomogeneity at superconductor-ferromagnet interface and size effect. However, due to the lack of sufficient experimental data and information on the ferromagnetic nanowires, whether the long-range spin-polarized supercurrents can be detected in nanowires and the influence of size effect on the superconductor proximity effect still remains an open question. The concial magnetic structure makes Ho a better system to the study of long-ranged proximity effect and spin-polarized supercurrents. In this project, we attempt to study the long-range proximity effect and spin-polarized supercurrents in Ho-based one dimentional nanostructures. The aim of this proposed research project is to synthesize the Ho one dimentional nanostructures by electrodepositing method, to study the influence of the preparation conditions on the size, crystal quality, crystal boundary, orientation of the nanowires, to investigate the magnetic property and magnet structure of the nanowire, to unveil the magnetic inhomogeneity in nanowire, to prepare the quasi-one-dimensional superconductor-ferromagnet heterostructures by focused ion beam (FIB) method. With the detailed studies of quantum transport of the heterostructures, the information of interplay between superconductivity and ferromagnetism, especially the influence of the size of nanowire, microstructure and magnetic inhomogeneity at the superconductor-ferromagnet interface will be get. Meanwhile, the long-range spin-polarized supercurrents and other novel quantum phenomenon with the result of interplay between different quantum states in the nanowires will be also explored. The proposed work is expected to shed new light on the nature of quantum phenomenon in low-dimensional metallic nanowires, and providing chance of exploring new quantum devices based on the long-range spin-polarized supercurrents.

一维铁磁体中的长程自旋极化超导电流在量子器件领域具有诱人的应用前景。引入磁不均匀性和尺寸效应是实现长程自旋极化超导电流的关键。然而在具有本征非共线磁结构的一维体系中，磁不均匀性以及尺寸效应对超导近邻效应的影响规律尚不明确。本项目拟以具有螺旋磁结构的金属钬(Ho)为研究对象，采用电化学沉积法制备Ho一维纳米结构，研究制备条件对尺寸、结晶质量和择优取向的影响规律，阐明样品的生长机制，实现金属Ho的可控制备；利用洛伦兹电镜，研究Ho一维体系的磁性和磁结构，明确Ho的磁不均匀性及影响因素；研究金属钬尺寸、微观结构、本征磁不均匀性和异质结界面处磁不均匀性对超导近邻效应的影响，探索长程自旋极化超导电流以及其他新奇的量子现象。本研究将加深对一维体系微观磁结构、超导近邻效应等量子现象的认识，并为基于自旋极化超导电流的量子器件的研究提供重要的实验基础及理论依据。

螺旋铁磁金属钬是一种理想的本征磁不均匀性材料，是进行超导近邻效应研究的理想材料，然而，由于受金属钬纳米材料制备困难的限制，目前金属钬一维纳米材料的制备、微观结构、磁性和超导近邻效应相关研究较少，本项目采用了多种方法制备金属钬纳米材料，同时通过Fe、Co强磁性元素掺杂改善磁性能，明确了加工测试过程中钬纳米材料的抗氧化性，构筑了超导/铁磁异质结，研究了电输运特性，研究结果为低维量子器件研究提供材料基础和实验依据。.开发了电沉积法、化学气相沉积以及熔炼-快淬法结合FIB加工制备金属钬纳米材料的三种制备方法，获得金属钬纳米线、纳米片、棒、条带、钬氧化物多孔薄膜样品，并探索了不同制备方法的制备工艺以及不同形貌样品的生长机制，研究了材料生长过程中的结构变化规律，表征了不同尺寸、不同微观结构样品的磁性和磁结构，分析了微观结构与磁性和磁结构的关联，利用FeSe超导体作为超导相构筑超导/铁磁异质结，以期可以在金属钬材料中诱导出超导近邻效应，研究了电输运特性。研究基本完成了计划书的各项内容。.科研成果产出：发表学术论文5篇，另有2篇相关文章正在准备中。申请国家发明专利2项，还有两项正在准备中。.人才培养：在本项目的资助下，培养本科生6名，达到预期目标。