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

• 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

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）基于现代生活的许多方面，通过www，电信，医学，运输等的电子和数据处理，以至于很难夸大其重要性。但是，硅芯片技术正在接近艰苦的物理限制，需要替代方案。一种激进的方法是Spintronics，其中“自旋”和电子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特性：在磁场中，旋转更喜欢以两种方式对齐，沿着或对抗该场。旋转的全面利用将使革命性的新芯片设计能够快速，节能，并将数据存储与逻辑完全整合在一起。我们将研究半金属铁磁（HMF）材料。 HMF是一类在1980年代理论上发现的材料，它们结合了半导体和铁磁金属的特性。两个电子自旋对齐中只有一个可以很容易地在HMF内移动 - 它们是“ 100％自旋偏振”。因此，它们应该是用于旋转的理想材料。但是，尽管进行了HMF设备进行了重大研究，但在大多数情况下，HMF并未超过普通磁性材料（通常是30-40％的自旋极化）。尚无清楚的了解为什么是这种情况，这阻止了HMF被解锁的高级旋转基质的潜力。我们建议通过以物理形式对HMF进行全面而严格的研究来解决这个杰出的问题，该研究实际上在设备中使用，即在氧化物或半导体底物上的薄膜中使用。我们将在四个领域结合我们的专业知识：（1）生产HMF的高质量薄膜，（2）将磁性薄膜的表征降低到原子水平，（3）这些材料的准确理论描述，以及（4）HMF Spintronic设备的制造。这将使我们能够整体研究HMF性能削弱的最可能的罪魁祸首，即温度，缺陷和HMF /底物界面。自旋极化会随着HMF的加热而崩溃，对于实用设备，这种截止值必须远高于室温。我们将明确地衡量这一问题，并用最近在沃里克开发的最新理论对其进行建模。薄膜中的残留缺陷可以破坏自旋极化，我们将通过原子尺度成像 /建模来理解它们，并调整薄膜的生长以最大程度地减少它们。最后，HMF及其底物之间必须始终有一个接口，这也会影响自旋极化和功能性能。我们将图像和建模界面，然后再次调整我们的增长以优化它们。使用尖端的异常校正电子显微镜（约克和沃里克都具有如此的显微镜，具有互补功能），可以使用原子尺度的成像和分析。最后，这项基本工作将与HMFS在典型的Spintronic设备中的功能性能相关。我们将能够使用已建立的设计来制造设备，然后在实际设备结构上测量原子尺度接口和缺陷。从第一原理理论到设备性能，这种功能的独特组合将使对真实薄膜结构中的半金属性进行首次全面而严格的研究。我们的目标是以一种基本的方式理解实际结构中HMF的局限性，指导未来的HMF设备设计，并在HMF薄膜中发展最高的室温旋转极化。在约克和沃里克之间，我们在三种不同类别的HMF材料（过渡金属pnictides，Magnitite和Heusler合金）中拥有增长专业知识，这将使我们俩都能对HMF产生广泛的了解，并为超高旋转极化膜找到最佳的材料。

项目成果

Correlation between spin transport signal and Heusler/semiconductor interface quality in lateral spin-valve devices

横向自旋阀器件中自旋输运信号与 Heusler/半导体界面质量之间的相关性

• DOI: 10.1103/physrevb.98.115304
• 发表时间: 2018
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Achinuq B

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

• DOI: 10.1063/1.5017683
• 发表时间: 2018-02-19
• 期刊: APPLIED PHYSICS LETTERS
• 影响因子: 4
• 作者: Beevers, J. E.;Love, C. J.;Dhesi, S. S.
• 通讯作者: Dhesi, S. S.

Spin pumping in magnetic trilayer structures with an MgO barrier.

• DOI: 10.1038/srep35582
• 发表时间: 2016-10-18
• 期刊: Scientific reports
• 影响因子: 4.6
• 作者: Baker AA;Figueroa AI;Pingstone D;Lazarov VK;van der Laan G;Hesjedal T
• 通讯作者: Hesjedal T

Correlated electron diffraction and energy-dispersive X-ray for automated microstructure analysis

用于自动微观结构分析的相关电子衍射和能量色散 X 射线

• DOI: 10.1016/j.commatsci.2023.112336
• 发表时间: 2023
• 期刊: Computational Materials Science
• 影响因子: 3.3
• 作者: Duran E

Heusler alloys for spintronic devices: review on recent development and future perspectives.

• DOI: 10.1080/14686996.2020.1812364
• 发表时间: 2021-03-29
• 期刊: Science and technology of advanced materials
• 影响因子: 5.5
• 作者: Elphick K;Frost W;Samiepour M;Kubota T;Takanashi K;Sukegawa H;Mitani S;Hirohata A
• 通讯作者: Hirohata A