Half-metallic ferromagnets: materials fundamentals for next-generation spintronics

半金属铁磁体：下一代自旋电子学的材料基础

基本信息

批准号：
EP/K03278X/1
负责人：
Vlado Lazarov
金额：
$ 72.48万
依托单位：
University of York
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2013
资助国家：
英国
起止时间：
2013 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FK03278X%2F1
关键词：
Half metallic ferromagnets materials fundamentals

项目摘要

Semiconductors (such as silicon) underpin so many aspects of modern life, through electronics and data processing for the WWW, telecoms, medicine, transport, etc., that it is hard to overstate their importance. However, silicon chip technology is approaching hard physical limits and alternatives are needed. One radical approach is spintronics, where the both the "spin" and charge of electrons are used for data storage and processing. Spin is a fundamental property of electrons related to magnetism: in a magnetic field, a spin prefers to align in one of two ways, along or against the field. Full utilisation of spin would enable revolutionary new chip designs, which are fast, energy-efficient and fully integrate data storage with logic. We will study half-metallic ferromagnetic (HMF) materials. HMFs are a class of materials discovered theoretically in the 1980s which combine the properties of a semiconductor and a ferromagnetic metal. Only one of the two electron spin alignments can easily move inside an HMF - they are "100% spin-polarised". They should hence be ideal materials for use in spintronics. However, despite major research efforts to make HMF devices, in most cases HMFs do not outperform ordinary magnetic materials (which are typically 30-40% spin-polarised). There is no clear understanding of why this is the case, which prevents the potential of HMFs being unlocked for advanced spintronics. We propose to solve this outstanding problem with a comprehensive and rigorous study of HMFs in the physical form which is actually used in devices, i.e. in thin-films on an oxide or semiconductor substrate. We will combine our expertise in four areas: (1) production of high quality thin films of HMFs, (2) characterisation of magnetic thin films down to the atomic level, (3) accurate theoretical description of these materials, and (4) fabrication of HMF spintronic devices. This will enable us to study holistically the most likely culprits for weakened HMF performance, namely temperature, defects and the HMF /substrate interface. Spin-polarisation collapses as an HMF heats up, and this cut-off, for a practical device, must be well above room temperature. We will measure this explicitly and model it with state-of-the-art theory developed recently in Warwick. Residual defects in the thin films can destroy spin polarisation and we will both understand these via atomic-scale imaging / modelling and adjust our thin film growth to minimise them. Finally, there must always be an interface between the HMF and its substrate, which also influences the spin polarisation and functional performance. We will image and model the interfaces, and again adjust our growth to optimise them. Atomic-scale imaging and analysis is possible using cutting-edge aberration-corrected electron microscopes (York and Warwick each have such a microscope, with complementary capabilities). Finally, this fundamental work will be correlated with the functional performance of the HMFs in prototypical spintronic devices. We will be able to fabricate devices, using established designs, and subsequently measure the atomic-scale interfaces and defects on the actual device structure. This unique combination of capabilities ranging from first-principles theory to device performance will enable the first comprehensive and rigorous study of half-metallicity in real thin film structures. Our goals are to understand in a fundamental way the limitations of HMFs in real structures, to guide future HMF device design, and also develop the highest possible room temperature spin polarisation in HMF thin films. Between York and Warwick, we have growth expertise in three different classes of HMF material (transition metal pnictides, magnetite and Heusler alloys) which will enable us both to produce a generalised understanding of HMFs and find the best materials for ultra-high spin polarisation films.

半导体（例如硅）通过万维网、电信、医学、运输等的电子和数据处理支撑着现代生活的许多方面，其重要性怎么强调都不为过。然而，硅芯片技术正在接近物理极限，需要替代方案。一种激进的方法是自旋电子学，其中电子的“自旋”和电荷都用于数据存储和处理。自旋是与磁性相关的电子的基本属性：在磁场中，自旋更喜欢以两种方式之一排列：沿着磁场或逆着磁场。充分利用自旋将实现革命性的新芯片设计，这种设计速度快、节能且将数据存储与逻辑完全集成。我们将研究半金属铁磁（HMF）材料。 HMF 是 20 世纪 80 年代理论上发现的一类材料，它结合了半导体和铁磁金属的特性。两个电子自旋排列中只有一个可以轻松地在 HMF 内移动 - 它们是“100% 自旋极化”。因此，它们应该是用于自旋电子学的理想材料。然而，尽管在制造 HMF 器件方面进行了大量研究，但在大多数情况下，HMF 的性能并不优于普通磁性材料（通常为 30-40% 自旋极化）。目前尚不清楚为什么会出现这种情况，这阻碍了 HMF 在先进自旋电子学方面的潜力的发挥。我们建议通过对实际用于器件（即氧化物或半导体衬底上的薄膜）的物理形式的 HMF 进行全面而严格的研究来解决这一突出问题。我们将结合我们在四个领域的专业知识：(1) 高质量 HMF 薄膜的生产，(2) 磁性薄膜的原子级表征，(3) 这些材料的准确理论描述，以及 (4) 制造HMF自旋电子器件。这将使我们能够全面研究 HMF 性能减弱的最可能的原因，即温度、缺陷和 HMF/基材界面。随着 HMF 升温，自旋极化会崩溃，对于实际器件来说，这种截止温度必须远高于室温。我们将明确地测量这一点，并用沃里克最近开发的最先进的理论对其进行建模。薄膜中的残余缺陷会破坏自旋极化，我们将通过原子级成像/建模来了解这些缺陷，并调整薄膜生长以将其最小化。最后，HMF 与其基底之间必须始终存在界面，这也会影响自旋极化和功能性能。我们将对界面进行成像和建模，并再次调整我们的增长以优化它们。使用尖端的像差校正电子显微镜可以进行原子尺度的成像和分析（约克和沃里克各有这样的显微镜，并且具有互补的功能）。最后，这项基础工作将与原型自旋电子器件中 HMF 的功能性能相关。我们将能够使用既定的设计来制造设备，并随后测量实际设备结构上的原子级界面和缺陷。这种从第一原理理论到器件性能的独特能力组合将使对真实薄膜结构中的半金属性的首次全面而严格的研究成为可能。我们的目标是从根本上了解 HMF 在实际结构中的局限性，指导未来的 HMF 器件设计，并在 HMF 薄膜中开发尽可能高的室温自旋极化。约克和沃里克之间，我们在三种不同类别的 HMF 材料（过渡金属磷化物、磁铁矿和 Heusler 合金）方面拥有丰富的专业知识，这将使我们能够对 HMF 产生普遍的了解，并找到用于超高自旋极化薄膜的最佳材料。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Enhanced magnetoelectric effect in M-type hexaferrites by Co substitution into trigonal bi-pyramidal sites

Co取代三角双锥位点增强M型六角铁氧体的磁电效应

DOI：
10.1063/1.5017683
发表时间：
2018-02-20
期刊：
Applied Physics Letters
影响因子：
4
作者：
J. Beevers;C. Love;V. Lazarov;S. Cavill;H. Izadkhah;C. Vittoria;R. Fan;G. Laan;S. Dhesi
通讯作者：
S. Dhesi