Artificial Spin Ice for Rewritable Magnonics

该项目的关键物理概念是磁自旋波或其量子磁振子可以作为信息载体并被操纵用于信息处理和计算。传统的计算机依赖于物理上移动的粒子（电子），并且大量的能量被逻辑设备内以及特别是单独的逻辑和存储介质之间的电子传输引起的欧姆损耗和加热浪费。如果目前的趋势继续下去，到2040年，计算将消耗全球能源产量的三分之一，因此提高计算能源效率是一个关键挑战。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，因此“磁效应”在原则上比标准电子产品更节能几个数量级&这是一条帮助解决全球能源危机的有希望的途径。磁铁用于存储设备，因为它们被动地保留写入其中的信息（非易失性）。该项目将使纳米磁体耦合阵列的创建成为可能，这些纳米磁体可以被视为存储器和处理器，其中可以随意写入和重新编程新电路。我们实现这一目标的能力利用了我们开发的一种称为全光磁开关（AOMS）的技术，允许用低功率激光器（如蓝光播放器）控制阵列中任何单个纳米磁体的写入，加上世界领先的专业知识，利用纳米磁性阵列进行自旋波信息处理-包括世界-在相互作用的纳米磁体阵列中的磁振子神经形态计算的第一个演示。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）范围内的特征谐振频率处围绕平均方向进动。对于单个纳米磁体，频率由其大小和形状控制，就像缩短吉他弦改变音符一样。纳米磁体的耦合阵列具有不同的光谱指纹，并且这些可以用于读出状态。磁振子共振对每个岛的磁性结构也非常敏感，我们最近的一项突破就是利用这一点来制备具有更大功能的磁振子灵活性的涡旋和宏自旋岛，从模拟中已经很好地建立了阵列的精确微观状态控制磁振子的谐振频率，并且我们可以实现开关和晶体管。磁状态控制特定频率的磁振子是否能通过的逻辑功能器件。本项目旨在整合不同的功能元件，并探索原型磁振子组件和电路。这是非常冒险的，并且有许多实验挑战需要克服以实现完全的磁振子计算。例如，一个被称为阻尼的过程会使行进中的自旋波随着时间和距离迅速衰减。这在信息丢失之前完成完整计算方面提出了一个挑战，以及代表能量效率低下的来源-尽管它可以使用谐振“驻波”磁振子来避免，我们的方案也可以使用。虽然在大型阵列中测量这些“驻波”磁振子是简单的，但检测纳米级器件结构中的旅行磁振子是最先进的能力。在这个项目中，我们的目标是开发和扩展这些能力，建立在我们的专业知识和建立不同的磁振子晶体状态之间的耦合，同步，传输和损耗的物理学的基本理解，并提供一个富有成效的操场，探索新的计算架构。

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.