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.

迫切需要用于数据存储的新材料和技术，以跟上大数据和人工智能应用中预计的数据使用。更高效的设备还将减少与全球数据服务器运行相关的能耗。磁性材料一直被用于数据存储，并预计将保持其对大规模数据存储设施的重要性。磁极表示二进制的“一”和“零”，并且写入数据对应于反转磁极方向。极点的光学控制是期望的，因为它将允许使用飞秒激光器的数量级更快的反转速率，这是电子设备无法达到的时间尺度。为了解决这个日益严重的问题，自最初发现使用飞秒激光脉冲实现全光学磁化反转以来，超快磁性（即在飞秒时间尺度上发生的磁化强度的受控变化）领域迅速发展。到目前为止，这些结果仅限于固态磁性材料。为了减小硬盘中信息中心的尺寸，从而提高数据存储密度，单分子磁体（SMM）由于其纳米尺寸而成为有希望的候选者。然而，到目前为止，飞秒激光脉冲与SMM的相互作用尚未被探索。在这里，我们将通过建立一个结合合成，超快光谱和先进的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Mn（III）为基础的配位化合物，其特征在于由反键轨道的部分人口。这导致通过Jahn-Teller（JT）效应的几何失真，这又给出了磁化的优选空间方向。在一项原理验证研究中[Liedy et al，Nature Chemistry，12，452 - 458（2020）]，我们表明，通过光学重新分布反键轨道的数量，通过形成振动波包，分子的各向异性发生快速变化。由于几何形状与这些分子的磁各向异性密切相关，因此与波包相关的集体运动开辟了在飞秒时间尺度上控制磁化的可能性。我们还发现，我们可以通过使用分子设计来调整波包的动力学，这意味着在SMM中实现快速有效的磁化控制有一条合成路线。这些初步发现非常有希望。然而，对电子和核自由度之间耦合的动力学和确切性质的详细理解仍然不清楚。该提案的目的是探索新的方法来操纵顺磁配位化合物，通过创建飞秒相干振动波包沿着JT轴，使光学控制的磁各向异性。具体而言，我们将探索一系列Mn（III）为基础的配合物通过改变JT轴的几何形状。我们将增加所研究的分子的结构复杂性，从单体模型系统到交换偶联二聚体。我们将使用瞬态吸收光谱，超快电子衍射和X射线自由电子激光测量波包运动。将使用飞秒磁光光谱测量磁各向异性的变化。在项目结束时，我们将了解光如何用于控制Mn配位化合物的磁化强度，以及什么结构因素对于使用飞秒相干波包实现磁各向异性的有效变化很重要。这将实现磁化的非热控制，这反过来又可以导致未来低能量，超快和超密度磁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 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

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