Growth and characterisation of frustrated kagome ferromagnet thin films

受挫戈薇铁磁体薄膜的生长和表征

• 批准号: 2597145
• 金额: --
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2597145
• 关键词: Growth; characterisation; frustrated; kagome; ferromagnet

The layered kagome ferromagnet Fe3Sn2 has massive Dirac fermions and frustrated magnetism that shows skyrmions at room temperature. Magnetic skyrmions are small (nm to 100s of nm in size), stable (protected by their non-trivial topology) and easily moved (they respond to spin torques at low current densities). As such they are appealing candidates for the representation of data in new forms of spintronic data storage and logic devices that will be non-volatile, consume little energy, and permit novel compute-in-memory architectures suitable for both Boolean and neuromorphic computation. So far Fe3Sn2 has only been studied in bulk form, but thin films are required for spintronic devices. It has recently been shown that the related compound FeSn can be grown as an epitaxial thin film on (111) SrTiO3. Since both compounds have the same kagome places of Fe with a very close lattice constant, we expect that we could grow Fe3Sn2 on SrTiO3. In this project we will develop the means to grow thin films of Fe3Sn2 in the state-of-the-art Royce Institute multi-chamber deposition system at Leeds, characterise the films using world-leading electron microscopy in the Bragg Centre, and study their electron transport and magnetic properties, especially those related to skyrmions. A particular feature of this project is that we can grow the magnetic metal layer epitaxially on the surface of an oxide heterostructure, each grown in a specialised chamber of the growth system and transferred under UHV. This should ensure the highest quality growth of the critical interfaces in the stack, which we shall confirm using high resolution TEM of cross-section specimens. The epitaxial oxide growth means that it will also be possible to include other oxide materials in the heterostructure such as water-soluble Sr3Al2O6, which can be used to form a sacrificial layer to allow the thin film to be floated off for study by means of transmission experiments. As well as providing plan-view samples for TEM characterisation within this project, such samples will also be useful for magnetic imaging by means of Lorentz or soft x-ray microscopy through our network of collaborators, e.g. at the University of Glasgow and Paul Scherrer Institute. The combination of an exotic electronic structure with spin textures with non-trivial real-space topology is expected to lead to new insights into magnetotransport phenomena governed by the Berry phase, such as the topological Hall effect. Applying gate voltages will allow us to probe transport below, at, and above the Dirac point. Meanwhile, the fact that skyrmions are stabilised by frustration, rather than the more usual means of a chiral Dzyaloshinskii-Moriya interaction means that the skyrmion chirality is in principle switchable, providing a bistable state variable for the representation of digital data.

层状戈薇铁磁体 Fe3Sn2 具有大量狄拉克费米子和在室温下显示斯格明子的受挫磁性。磁性斯格明子体积小（尺寸为纳米到数百纳米）、稳定（受到其非凡拓扑的保护）并且易于移动（它们在低电流密度下响应自旋扭矩）。因此，它们是新型自旋电子数据存储和逻辑设备中数据表示的有吸引力的候选者，这些设备将是非易失性的，消耗很少的能量，并允许适用于布尔和神经形态计算的新型内存计算架构。到目前为止，Fe3Sn2 仅以块体形式进行研究，但自旋电子器件需要薄膜。最近的研究表明，相关化合物 FeSn 可以在 (111) SrTiO3 上生长为外延薄膜。由于这两种化合物具有相同的 Fe 位置且晶格常数非常接近，因此我们期望可以在 SrTiO3 上生长 Fe3Sn2。在这个项目中，我们将开发在利兹最先进的罗伊斯研究所多室沉积系统中生长 Fe3Sn2 薄膜的方法，在布拉格中心使用世界领先的电子显微镜表征薄膜，并研究它们的性能。电子传输和磁特性，特别是与斯格明子相关的特性。该项目的一个特点是，我们可以在氧化物异质结构的表面上外延生长磁性金属层，每个层都在生长系统的专用室中生长并在特高压下转移。这应确保堆叠中关键界面的最高质量生长，我们将使用横截面样本的高分辨率 TEM 来确认这一点。外延氧化物生长意味着异质结构中还可以包含其他氧化物材料，例如水溶性Sr3Al2O6，它可用于形成牺牲层，使薄膜能够浮出以通过透射的方式进行研究实验。除了在该项目中提供用于 TEM 表征的平面视图样本外，此类样本还可以通过我们的合作者网络（例如，通过洛伦兹或软 X 射线显微镜进行磁成像）。格拉斯哥大学和保罗谢勒研究所。奇异的电子结构与自旋纹理和非平凡的实空间拓扑的结合预计将带来对贝里相控制的磁输运现象的新见解，例如拓扑霍尔效应。施加栅极电压将使我们能够探测狄拉克点下方、处和上方的传输。同时，斯格明子通过挫败而不是更常见的手性 Dzyaloshinskii-Moriya 相互作用来稳定，这一事实意味着斯格明子手性原则上是可切换的，为数字数据的表示提供了双稳态变量。