Understanding and developing spin-based emitters for improved far-infrared radiation sources

光与厚度小于人类头发宽度1/5000的磁性/非磁性金属超薄薄膜相互作用的独特方式最近被证明提供了一种产生新型辐射源的途径，其波长覆盖从中红外到远红外的广泛范围。这种发射覆盖了太赫兹区域，位于电磁波谱的微波和红外波长之间；一个难以覆盖的波长范围，但在各种各样的应用中具有巨大的潜力。例如，太赫兹辐射由于其非电离特性，对机场安检人员特别有用，也可用于查看爆炸物、毒品和灰尘颗粒等材料的光谱指纹。众所周知，界面的原子特性对许多技术上重要的设备的功能至关重要，例如自旋-扭矩转移磁性随机存取存储器（STT-MRAM），硬盘驱动器中使用的传感器和介质以及新的人工多铁性材料。这个项目的重点是发展对超薄磁性结构的发射过程如何取决于材料性质的急需的理解。通过了解排放过程的基本机制，我们将能够展示商业上可行的排放者。更具体地说，第一个发射器将实现在不需要外部磁场的情况下运行，克服目前这种要求对主动发射区域和输出能量的限制。太赫兹辐射也为研究基于自旋的设备提供了一种目前尚未开发的方法。在理解材料特性和太赫兹发射之间的关系中获得的知识将被证明在为下一代数据存储设备开发的自旋电子设备的设计中是无价的。总体目标是开发太赫兹辐射源，这将对未来的一些应用领域产生影响，特别是在观察材料的光谱指纹以检测危险气体和粉尘颗粒时，这些气体和粉尘颗粒在采矿业等领域引起严重的健康和安全问题。因此，开发充分理解的自旋基发射器将对英国的经济成功产生直接影响，使太赫兹辐射和自旋基设备的新应用得以开发，从而促进社会的技术进步。

The unique way that light interacts with magnetic/non-magnetic metal ultra-thin films with thicknesses less than 1/5000th the width of a human hair has recently been shown to offer a route to producing novel sources of radiation with wavelengths that cover a wide range stretching from the mid- to far- infrared. This emission covers the THz region that lies between the microwave and the infra-red wavelengths of the electromagnetic spectrum; a wavelength range that remains difficult to cover, but has an enormous potential for a diverse range of applications. For example, THz radiation is particularly useful for security screening of people at airports due to its non-ionising properties, as well as for looking at the spectral fingerprints of materials including explosives, drugs and dust particles. The atomic properties of interfaces are well known to be critical to the functionality of many technologically important devices, examples include spin-torque transfer magnetic random-access memory (STT-MRAM), the sensors and media used in hard disk drives and new, artificial multiferroics. This project is focused on developing much needed understanding of how the emission process from ultra-thin magnetic structures depends on the material properties. By gaining understanding of how the underlying mechanisms are responsible for the emission process we will be able to demonstrate commercially-viable emitters. More specifically, the first emitters will be realised that operate without the need for an external magnetic field, overcoming the limitation this requirement currently imposes on the active emitting area and output energy. THz radiation also provides a currently untapped approach to investigating spin-based devices. The knowledge gained in understanding the relationship between material properties and THz emission will prove invaluable in the design of spintronic devices being developed for the next generation of data storage devices. The overall goal is the development of sources of THz radiation that will have impact in a number of future application areas, in particular when looking at the spectral fingerprints of materials for detecting dangerous gases and dust particles which present serious health and safety concerns in areas such as the mining industry. Hence, the development of well-understood spin-based emitters would have a direct impact on UK economic success by enabling the development of new applications of THz radiation and spin-based devices that will add to the technological advancement of society.