Artificial Spin Ice for Rewritable Magnonics

该项目的关键物理概念是，磁性自旋波，或其量子磁子，可以作为信息载体，并被操纵进行信息处理和计算。传统的计算机依赖于物理移动的粒子(电子)，并且大量的能量被电子传输引起的欧姆损耗和加热浪费，这两者都在逻辑器件内，特别是在分离的逻辑和存储介质之间。如果目前的趋势继续下去，到2040年，计算将消耗全球能源生产的三分之一，因此提高计算能效是一个关键挑战。由于磁铁可以在不交换任何物理粒子的情况下将信息从一个设备传输到另一个设备，并且具有固有的被动数据存储功能，因此从原则上讲，磁铁的能效比标准电子设备高出几个数量级--这是帮助全球能源危机的一种有前途的方法。磁体用于存储设备，因为它们被动地保留写入其中的信息(非易失性)。该项目将能够创建纳米磁铁的耦合阵列，可以被视为存储器和处理器，在那里可以随意写入和重新编程新的电路。我们实现这一点的能力利用了我们开发的一种名为全光磁开关(AOMS)的技术，允许使用像蓝光播放器这样的低功率激光控制写入阵列中的任何单个纳米磁铁，加上世界领先的专业技术，利用纳米磁阵列进行自旋波信息处理-包括世界上第一次在一系列相互作用的纳米磁铁中演示磁性神经形态计算。每个铁磁纳米岛存储固定的平均磁化强度，但磁矩不是完全静态的，而是在微波(GHz)范围内以特征共振频率围绕平均方向前进。对于单个纳米磁铁，其频率由其大小和形状控制，就像缩短吉他弦改变音符一样。耦合的纳米磁体阵列具有不同的光谱指纹，这些指纹可以用于读出状态。磁子共振对每个岛的磁性结构也高度敏感，我们最近的一项突破利用这一点来制备双稳态涡旋和宏观自旋岛，与传统的全宏观自旋系统相比，它显示出更大的功能磁子灵活性。从模拟中已经很好地建立了阵列的精确微观状态控制磁子的共振频率，并且我们可以实现用于逻辑功能的开关和晶体管类型的器件，其中磁状态控制特定频率的磁子是否可以通过。该项目旨在集成不同的功能元件，并探索磁学元件和电路的原型。它是高度冒险的，要实现完全的磁学计算，还有许多实验挑战需要克服。例如，一种称为衰减的过程会导致行进自旋波随时间和距离迅速衰减。这给在信息丢失之前完成全部计算带来了挑战，也代表了能量低效的来源--尽管它可以使用我们的方案也起作用的共振驻波磁子来避免。虽然在大型阵列中测量这些“驻波”磁子很简单，但在纳米设备结构中检测移动磁子是最先进的能力的边缘。在这个项目中，我们的目标是开发和扩展这些能力，以我们的专业知识为基础，建立对不同磁晶状态之间耦合、同步、传输和损耗的基本物理理解，并提供一个富有成效的场地来探索新的计算体系结构。

The key physical concept of this project is that magnetic spin-waves, or their quanta magnons, can act as information carriers and be manipulated for information processing & computation. Conventional computers rely on physically moving particles (electrons), and vast amounts of energy are wasted by ohmic loss and heating induced by electronic transit, both within the logic devices and particularly between the separate logic and storage media. If current trends continue, computation will consume one third of global energy production by 2040, and consequently increasing computational energy efficiency is a critical challenge. Because magnets can transfer information from one device to the next without the exchange of any physical particles and have intrinsic passive data storage, 'magnonics' is in principle orders of magnitude more energy efficient than standard electronics & a promising route to aiding the global energy crisis.Magnets are used in memory devices as they passively retain information written into them (non-volatile). This project will enable creation of coupled arrays of nanomagnets that can be viewed as both memory and processor where novel circuits can be written and reprogrammed at will. Our ability to accomplish this exploits a technique which we have developed called All-Optical Magnetic Switching (AOMS), allowing controlled writing of any individual nanomagnet in the array with a low-power laser like a Blu-Ray player, plus world-leading expertise harnessing nanomagnetic arrays for spin-wave information processing - including world-first demonstration of magnonic neuromorphic computation in an array of interacting nanomagnets.Each ferromagnetic nanoisland stores a fixed average magnetization, but the magnetic moment is not completely static, instead precessing around the average direction at characteristic resonant frequencies in the microwave (GHz) range. For a single nanomagnet, the frequency is controlled by its size and shape in the same way that shortening a guitar string changes the note. Coupled arrays of nanomagnets have distinct spectral fingerprints and these can be used for readout of states. The magnonic resonances are also highly sensitive to the magnetic texture of each island, and one of our recent breakthroughs exploits this to prepare bistable vortex & macrospin islands exhibiting far greater functional magnonic flexibility versus conventional all-macrospin systems.It is already well established from simulations that the exact microstate of the array controls the resonant frequency of the magnons and that we can realise switches and transistor type devices for logic functions where the magnetic state controls whether magnons of a specific frequency can pass through or not. This project aims to integrate different functional elements and explore prototype magnonic components and circuits. It is highly adventurous, and there are many experimental challenges to overcome to realise fully magnonic computation. For example, a process called damping causes travelling spin waves to attenuate rapidly with both time and distance. This presents a challenge in terms of completing the full computation before information is lost, as well as representing a source of energy inefficiency - though it can be avoided using resonant 'standing wave' magnons with which our scheme also functions. Although it is straightforward to measure these 'standing wave' magnons in a large array, detecting travelling magnons in nanoscale device structures is at the edge of state-of-the-art capabilities. In this project we aim to develop and expand these capabilities, building on our expertise and establish fundamental understanding of the physics of coupling, synchronization, transmission, and loss between different magnonic crystal states, and deliver a fruitful playground to explore novel computation architectures.