Half metal oxides: In search for 100% spin polarised materials

半%20金属%20氧化物：%20In%20search%20for%20100%%20spin%20极化%20材料

• 批准号: EP/K013114/1
• 负责人: Vlado Lazarov
• 金额: $ 12.58万
• 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%2FK013114%2F1
• 关键词: Half; metal; oxides; search; 100

Spintronics is a rapidly developing field that utilises the electron's spin in addition to its charge to create new devices combining logic, data storage and sensor applications. The huge potential of spintronics has stimulated a wide range of research from spin transport, spin injection/accumulation and spin manipulation to device fabrication such as spin valves and magnetic tunnel junctions. One of the main challenges in the spintronics field is to find/create highly spin polarised materials that are compatible (lattice match, conductivity match, thermodynamically stable, high Curie temperature (Tc), etc.) with CMOS technology. In this proposal magnetite (Fe3O4) is proposed as the optimum highly spin polarised material for spintronics and by understanding the material at the atomic level seeks to solve the challenges in its implementation.Conventional 3d ferromagnetic metals and their alloys are only 30-40% spin polarised at the Fermi level, thus material systems with better spin polarisation are essential for the next generation of spintronic devices. The existence of 100% spin polarised materials at the Fermi level has been predicted by density functional theory (DFT). Such 100% spin polarised materials, also termed half-metals, have one of the spin channels metallic while the other spin channel is insulating. A rather large number of materials including oxides (Fe3O4, CrO2, manganites), pnictides, chalcogenides, and Heusler alloys have been predicted to be half-metallic. Among these materials magnetite (Tc=855 K) is of special interest since: (i) it has a Tc in excess of 500K, the threshold temperature for device applications; (ii) it has an excellent lattice match with MgO and MgAl2O4, the two most important oxides for spintronic applications; (iii) it can form atomically sharp interfaces with relevant semiconductors (SC) such as GaAs, GaN and SiC; and (iv) its layered structure will allow interface atomic engineering at magnetite/oxide and, magnetite/SC heterojunctions. It is worth noting that no other SP materials have these properties. For example, CrO2 has Tc below 500K and Heusler/SC junctions are not abrupt due to the high annealing temperature required for Heuslers to fully order into a L21 structure that is half-metallic. In order to incorporate magnetite in device structure, growth of thin films of magnetite and heterostructures of magnetite with suitable oxides, metals and semiconductors (SC) is required.The two main challenges to overcome for successful application of Fe3O4 are: 1) growth of thin films with control of stoichiometry and structural defects; it is well known that defects such as antiphase domain boundaries (APBs) can completely determine the functionality of magnetite films, thus controlling the APBs nature and density is highly important;2) engineering the interfaces between magnetite/oxide barriers and magnetite/SC; spin transport across interfaces critically depends on the interfaces' atomic structure.These are the two crucial steps to understand the structural basis of spin-related phenomena in the magnetite films as well as some of technologically important magnetite/oxide and magnetite/SC interfaces. This knowledge would provide a path and guide for the engineering of spintronic devices based on Fe3O4. In order to achieve this goal, the direct correlation of the films' functionality and their atomic structure, in this application I propose a joint experimental and theoretical study on the growth of half-metal magnetite oxide films and the atomic and electronic structure of the film, APBs and magnetite/oxide and magnetite/SC interfaces which are of interest for spintronic devices. Film growth will be done by Molecular Beam Epitaxy, spin polarised calculations will be performed by DFT, and High Resolution Transmission Electron Microscopy, High Angle Annular Dark Field Imaging and Electron Energy Loss Spectroscopy will be used to fully characterise these systems on atomic scale.

SpinTronics是一个快速发展的领域，除了电荷外，还利用电子旋转来创建结合逻辑，数据存储和传感器应用的新设备。 Spintronics的巨大潜力刺激了从自旋传输，自旋注射/积累和自旋操作到装置制造（例如自旋阀和磁性隧道连接）的广泛研究。 Spintronics领域的主要挑战之一是与CMOS技术找到/创建高度自旋极化材料（晶格匹配，电导率匹配，热力学稳定，高咖喱温度（TC）等）。 In this proposal magnetite (Fe3O4) is proposed as the optimum highly spin polarised material for spintronics and by understanding the material at the atomic level seeks to solve the challenges in its implementation.Conventional 3d ferromagnetic metals and their alloys are only 30-40% spin polarised at the Fermi level, thus material systems with better spin polarisation are essential for the next generation of spintronic devices.通过密度功能理论（DFT）预测了在费米水平上的100％自旋极化材料的存在。这种100％自旋极化材料（也称为半金属）具有金属旋转通道之一，而另一个自旋通道则是绝缘的。预计已经有大量材料（Fe3O4，CRO2，锰），Pnictides，Chalcogenides和Heusler Alloys为半金属。在这些材料中，磁铁矿（TC = 855 K）具有特殊的兴趣，因为：（i）它的TC超过500K，是设备应用的阈值温度； （ii）它与MGO和MGAL2O4具有出色的晶格匹配，这是两种用于旋转型应用的最重要的氧化物； （iii）它可以与相关的半导体（SC）（例如GAAS，GAN和SIC）形成原子上锐利的界面； （iv）其分层结构将允许在磁铁矿/氧化物和磁铁矿/SC杂音处的界面原子工程。值得注意的是，没有其他SP材料具有这些特性。例如，CRO2的TC低于500K，由于Heusler所需的高退火温度使Heuslers完全订购成半金属的L21结构，因此Heusler/SC连接并不突然。为了将磁铁矿掺入设备结构中，需要磁铁矿的薄膜和磁铁矿的异质结构，具有合适的氧化物，金属和半导体（SC）。成功应用Fe3O4的两个主要挑战是：1）薄膜的生长，具有薄膜的生长；众所周知，诸如反相结构域边界（APB）之类的缺陷可以完全确定磁铁矿膜的功能，因此控制APBS性质和密度非常重要； 2）在磁铁矿/氧化物屏障和磁铁矿/SC之间进行工程界面；跨接口的自旋转运在界面上取决于界面的原子结构。这是了解磁铁矿膜中自旋相关现象的结构基础的两个关键步骤，以及一些技术上重要的磁铁矿/氧化物/氧化物和磁铁矿/SC界面。这些知识将为基于FE3O4的Spintronic设备的工程提供道路和指南。为了实现这一目标，膜功能及其原子结构的直接相关性，在此应用中，我提出了一项关于半金属磁铁矿氧化物膜的生长以及膜的原子和电子结构的联合实验和理论研究，APBS和APBS和磁铁球/氧化物/氧化物和磁铁/磁铁/sc interfacts的原子和电子结构感兴趣，这对旋转器件感兴趣。膜的生长将通过分子束外延，自旋极化计算将通过DFT进行，高分辨率透射电子显微镜，高角度环形暗场成像和电子能量损耗光谱将用于在原子量表上充分表征这些系统。

项目成果

Atomic study of Fe3O4/SrTiO3 Interface

• DOI: 10.1017/s143192761500728x
• 发表时间: 2015-08
• 期刊: Microscopy and Microanalysis
• 影响因子: 2.8
• 作者: D. Gilks;D. Kepaptsoglou;K. McKenna;L. Lari;Q. Ramasse;K. Matsuzaki;T. Susaki;V. Lazarov

Atomic and electronic structure of twin growth defects in magnetite.

• DOI: 10.1038/srep20943
• 发表时间: 2016-02-15
• 期刊: Scientific reports
• 影响因子: 4.6
• 作者: Gilks D;Nedelkoski Z;Lari L;Kuerbanjiang B;Matsuzaki K;Susaki T;Kepaptsoglou D;Ramasse Q;Evans R;McKenna K;Lazarov VK
• 通讯作者: Lazarov VK

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

Polar Spinel-Perovskite Interfaces: an atomistic study of Fe3O4(111)/SrTiO3(111) structure and functionality.

• DOI: 10.1038/srep29724
• 发表时间: 2016-07-14
• 期刊: Scientific reports
• 影响因子: 4.6
• 作者: Gilks D;McKenna KP;Nedelkoski Z;Kuerbanjiang B;Matsuzaki K;Susaki T;Lari L;Kepaptsoglou D;Ramasse Q;Tear S;Lazarov VK
• 通讯作者: Lazarov VK

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.