Chemical control of spin-phonon coupling and magnetisation dynamics

采用自下而上的方法制造新技术可以在提高能源效率的同时减小设备尺寸。一个例子是使用分子进行二进制数据存储，它要求数据在具有经济冷却要求的温度下不易失性；一个常用的基准是液氮的温度（77 K）。最近，我们通过将dysprosocenium单分子磁体（SMM）中的分子记忆温度从14 K提高到60 K，实现了一个阶梯变化（Goodwin, Ortu, Reta， Chilton和Mills， Nature, 2017, 548, 439）。分子电子自旋与其环境的相互作用（自旋-声子耦合）是SMM性能的一个关键限制特征，因为它会导致磁弛豫和磁信息的损失。为了实现基于分子的高密度数据存储，必须控制自旋声子耦合。我们最近开发了一种计算自旋-声子耦合的计算方法，并利用它来证明高温下镝中的磁弛豫是由于局部分子振动引起的，其中四种振动模式特别重要。该项目将采用我们的计算方法来开发控制smm中自旋声子耦合的一般策略，从而有针对性地设计在更高温度下显示磁记忆的smm，从而为基于分子的高密度数据存储提供技术上可行的候选材料。目标是：(i)了解分子结构如何影响振动谱（ii）了解分子结构如何调节自旋-声子耦合（iii）确定改进smms的设计标准。这些目标将通过以下方式实现：(i)采用密度泛函理论计算假设分子来编目结构-振动关系（ii）采用我们的自旋-声子耦合方法来确定磁松弛如何受到影响本项目与EPSRC“物理科学”和“量子技术”研究主题直接相关，特别是“新量子技术的量子物理学”和“功能材料的纳米级设计”的“物理学大挑战”，以及“具有目标特性的扩展结构的定向组装”的“化学科学与工程大挑战”。

Manufacturing new technologies with bottom-up approaches could lead to reductions in device size with increased energy efficiency. An example is the use of molecules for binary data storage, which requires data to be non-volatile at temperatures achievable with economical cooling requirements; a common benchmark is the temperature of liquid nitrogen (77 K). We have recently made a step-change by raising the temperature at which molecular memory can be observed from 14 K to 60 K in a dysprosocenium single-molecule magnet (SMM) (Goodwin, Ortu, Reta, Chilton and Mills, Nature, 2017, 548, 439). Interaction of the molecular electronic spin with its environment (spin-phonon coupling) is a critically limiting feature for SMM performance, as it leads to magnetic relaxation and the loss of magnetic information. To realise molecule-based high-density data storage, we must control the spin-phonon coupling.We recently developed a computational method for calculating spin-phonon coupling and employed it to show that magnetic relaxation in dysprosocenium at high temperatures is due to localised molecular vibrations, with four vibrational modes being particularly important. This project will employ our computational method to develop general strategies for controlling the spin-phonon coupling in SMMs, leading to targeted design of SMMs displaying magnetic memory at higher temperatures, and thus delivering technologically viable candidates for molecule-based high-density data storage.The objectives are:(i) to understand how molecular structure influences vibrational spectrum (ii) to understand how spin-phonon coupling can be modulated by molecular structure(iii) to determine design criteria for improved SMMsThese objectives will be achieved by:(i) employing density-functional theory calculations on hypothetical molecules to catalogue structure-vibration relationship(ii) employing our spin-phonon coupling method to determine how magnetic relaxation is influenced by vibrational profileThis project is directly relevant to the EPSRC "Physical Sciences" and "Quantum Technologies" research themes, specifically to the "Physics grand challenge(s)" of "Quantum Physics for New Quantum Technologies" and "Nanoscale Design of Functional Materials", and the "Chemical sciences and engineering grand challenge" of "Directed Assembly of Extended Structures with Targeted Properties".