Chemical control of spin-phonon coupling and magnetisation dynamics

用自下而上的方法制造新技术可以减少设备尺寸，提高能源效率。一个例子是使用分子进行二进制数据存储，这要求数据在经济的冷却要求下达到的温度下是非易失性的；一个常见的基准是液氮温度(77K)。我们最近做出了一项阶段性改变，将在失调单分子磁体(SMM)中观察到分子记忆的温度从14K提高到60K(Goodwin，Ortu，Reta，Chilton and 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性能的关键限制特征，因为它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，我们必须控制自旋-声子耦合。我们最近发展了一种计算自旋-声子耦合的方法，并用它来证明高温下的磁弛豫是由于分子的局域振动所致，其中四个振动模式尤为重要。这个项目将使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，目标是：(I)了解分子结构如何影响振动光谱(Ii)了解自旋-声子耦合如何被分子结构调制(Iii)确定改进的SMMS的设计标准这些目标将通过以下方式实现：(I)使用假设分子的密度泛函理论计算来分类结构-振动关系(Ii)使用我们的自旋-声子耦合方法来确定磁弛豫如何受振动轮廓的影响本项目与EPSRC的“物理科学”和“量子技术”研究主题直接相关，具体到《面向新量子技术的量子物理》和《功能材料的纳米尺度设计》的《物理宏伟挑战(S)》，以及《定向组装具有靶向性质的扩展结构》的《化学科学与工程宏伟挑战》。

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".