Femtosecond Coherences in Single-Molecule Magnets

单分子磁体中的飞秒相干性

• 批准号: EP/V010573/1
• 负责人: Johan Johansson
• 金额: $ 113.53万
• 依托单位: University of Edinburgh
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FV010573%2F1
• 关键词: Femtosecond; Coherences; Single; Molecule; Magnets

New materials and technologies for data storage are urgently needed to keep up with projected data use in applications of big data and artificial intelligence. More efficient devices will also reduce the energy consumption associated with running data servers worldwide. Magnetic materials have always been used for data storage and are projected to keep their importance for large-scale data storage facilities. The magnetic poles represent binary "one" and "zero", and writing data corresponds to reversing the pole direction. Optical control of the poles is desirable because it will allow for orders of magnitude faster reversal rates using femtosecond lasers, which is a timescale not accessible with electronics. In response to this growing problem, the field of ultrafast magnetism (i.e. controlled changes in magnetisation occurring on the femtosecond timescale) has developed rapidly since the initial discoveries enabling all-optical magnetisation reversal using femtosecond laser pulses. So far these results have been limited to solid-state magnetic materials. To reduce the size of information centres in hard drives, and therefore increase the data storage density, single-molecule magnets (SMMs) are promising candidates because of their nanometre size. However, to date, the interaction of femtosecond laser pulses with SMMs has not been explored. Here, we will investigate this interaction by building a research programme combining synthesis, ultrafast spectroscopies and advanced computational modelling. Specifically, we will study Mn(III)-based coordination compounds, which are characterised by a partial population of antibonding orbitals. This leads to a geometrical distortion via the Jahn-Teller (JT) effect, which in turn gives a preferred spatial direction of the magnetisation. In a proof-of-principle study [Liedy et al, Nature Chemistry, 12, 452 - 458 (2020)], we showed that by optically redistributing the population of antibonding orbitals, a fast change in the anisotropy of the molecule takes place via the formation of a vibrational wavepacket. Since the geometry is intimately related to the magnetic anisotropy of these molecules, the collective motion associated with the wavepacket opens up possibilities to control magnetisation on the femtosecond timescale. We also found that we could tune the dynamics of the wavepacket by using molecular design, which implies that there is a synthetic route towards achieving fast and efficient magnetisation control in SMMs. These initial findings are very promising. However, a detailed understanding of the dynamics and the exact nature of the coupling between the electronic and nuclear degrees of freedom remains unclear. The aim of this proposal is to explore new ways to manipulate paramagnetic coordination compounds by creating femtosecond coherent vibrational wavepackets along the JT axis to enable optical control of the magnetic anisotropy. Specifically, we will explore a range of Mn(III)-based complexes by varying the geometry of the JT axis. We will increase the structural complexity of the molecules being studied, from monomeric model systems to exchange-coupled dimers. We will measure the wavepacket motion using transient absorption spectroscopy, ultrafast electron diffraction and X-ray free-electron lasers. Changes to the magnetic anisotropy will be measured using femtosecond magneto-optical spectroscopy. At the conclusion of the project, we will have developed an understanding of how light can be used to control the magnetisation of Mn coordination compounds and what structural factors are important for achieving efficient changes to the magnetic anisotropy using femtosecond coherent wavepackets. This will enable non-thermal control of the magnetisation, which in turn can lead to the underpinning technology in future low-energy, ultrafast and ultradense magnetic storage devices.

在大数据和人工智能的应用中，迫切需要进行数据存储的新材料和技术。更有效的设备还将减少与全球运行数据服务器相关的能源消耗。磁性材料一直用于数据存储，并预计将其对大规模数据存储设施的重要性保持重要性。磁极代表二进制“一个”和“零”，写入数据对应于逆转极方向。需要对极点进行光学控制，因为它将使用飞秒激光器使用飞秒激光器的逆转速率更快，这是电子设备无法访问的时间尺度。为了应对这个日益增长的问题，自从最初发现的最初发现能够使用飞秒激光脉冲的最初发现，实现了全光磁逆转，超快磁性领域（即发生在飞秒时间尺度上的磁化的控制变化）已迅速发展。到目前为止，这些结果仅限于固态磁性材料。为了减少硬盘驱动器中信息中心的大小，因此增加了数据存储密度，由于其纳米尺寸，单分子磁铁（SMM）是有希望的候选人。但是，迄今为止，尚未探索飞秒激光脉冲与SMM的相互作用。在这里，我们将通过构建合成，超快光谱和高级计算建模的研究计划来研究这种相互作用。具体而言，我们将研究基于MN（III）的配位化合物，其特征在于部分抗抗轨道。这通过Jahn-Teller（JT）效应导致几何变形，从而给出了磁化的首选空间方向。在一项原始研究[Liedy等人，自然化学，12，452-458（2020）]中，我们表明，通过光学地重新分布抗体轨道的群体，分子各向异性的快速变化是通过振动波动小包的形成而发生的。由于几何形状与这些分子的磁各向异性密切相关，因此与波袋相关的集体运动为控制飞秒时间尺度上的磁化而开辟了可能性。我们还发现，我们可以使用分子设计来调整波袋的动力学，这意味着在SMMS中有一种合成的途径，可以实现快速有效的磁化控制。这些初步发现非常有前途。但是，对电子和核自由度之间耦合的动态和确切性质的详细理解尚不清楚。该提案的目的是探索通过沿JT轴创建飞秒连贯的振动波袋来操纵顺磁配位化合物的新方法，以实现磁各向异性的光学控制。具体而言，我们将通过改变JT轴的几何形状来探索一系列基于MN（III）的复合物。从单体模型系统到交换耦合二聚体，我们将增加所研究分子的结构复杂性。我们将使用瞬态吸收光谱，超快电子衍射和X射线自由电子激光器测量波袋运动。磁各向异性的变化将使用飞秒磁光光谱法测量。在项目的结论中，我们将了解如何使用光来控制Mn配位化合物的磁化以及哪些结构因子使用飞秒相干波袋对磁各向异性的有效变化很重要。这将实现对磁化的非热控制，这又可以导致未来低能，超快和超高磁性存储设备的基础技术。

项目成果

Transient magneto-optical spectrum of photoexcited electrons in the van der Waals ferromagnet Cr 2 Ge 2 Te 6

范德华铁磁体 Cr 2 Ge 2 Te 6 中光激发电子的瞬态磁光光谱

• DOI: 10.1103/physrevb.107.174432
• 发表时间: 2023
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Sutcliffe E

A Femtosecond Magnetic Circular Dichroism Spectrometer

飞秒磁圆二色性光谱仪

• DOI: 10.48550/arxiv.2107.10729
• 发表时间: 2021
• 作者: Sutcliffe J

A femtosecond magnetic circular dichroism spectrometer.

飞秒磁性圆二色性光谱仪。

• DOI: 10.1063/5.0064460
• 发表时间: 2021
• 期刊: The Review of scientific instruments
• 作者: Sutcliffe J

Towards understanding and controlling ultrafast dynamics in molecular photomagnets

• DOI: 10.1016/j.ccr.2023.215346
• 发表时间: 2023
• 期刊: Coordination Chemistry Reviews
• 影响因子: 20.6
• 作者: T. Penfold;J. Johansson;Julien Eng

Towards panchromatic Fe( ii ) NHC sensitizers via HOMO inversion

通过HOMO反转研究全色Fe(ii)NHC敏化剂

• DOI: 10.1039/d2qi01903e
• 发表时间: 2023
• 期刊: Inorganic Chemistry Frontiers
• 影响因子: 7
• 作者: Marri A