The 2022 magneto-optics roadmap
The 2022 magneto-optics roadmap
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DOI：
10.1088/1361-6463/ac8da0
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发表时间：
2022-08
期刊：
影响因子：
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通讯作者：
A. Kimel;A. Zvezdin;Sangeeta Sharma;S. Shallcross;Nuno Alves de Sousa;A. García-Martín;G. Salvan
中科院分区：
文献类型：
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作者：
A. Kimel;A. Zvezdin;Sangeeta Sharma;S. Shallcross;Nuno Alves de Sousa;A. García-Martín;G. Salvan
磁光（MO）效应，即。一个半世纪前就发现了磁性样品反射或透射时光强度或偏振的磁感应变化。最初，他们在揭示电磁学和量子力学的基础知识方面发挥了至关重要的作用。然而，直到 20 世纪 60 年代，由于缺乏合适、可靠且易于操作的光源，MO 方法的更广泛相关性和广泛使用仍然相当有限。激光技术的出现和其他新型光源的出现导致了 MO 测量技术和应用的巨大扩展，这种扩展一直持续到今天（参见第 1 节）。这里汇总的路线图文章旨在以相当简洁的形式对许多最相关的最新发展、进展和新兴研究方向进行有意义的调查，以便读者可以轻松地获得有关这个非常动态的研究领域的重要概述。虽然光源技术和其他实验发展对于当今磁光的建立至关重要，但进步还依赖于从量子力学角度对 MO 效应不断增长的理论理解（参见第 2 节），以及使用电磁理论和建模方法（参见第 3 节），以便能够对更加复杂的材料、超材料和器件几何形状进行定量可靠的预测。第 4 节（MOKE 光谱）、第 5 节（高阶 MOKE 效应）、第 6 节（MOKE 显微镜）、第 8 节（高灵敏度 MOKE）、第 9 节（广义 MO 椭圆光度法）和第 20 节（二维材料中的 Cotton-Mouton 效应）介绍了已建立的 MO 方法的最新进展，特别是 MO Kerr 效应 (MOKE) 的利用。此外，MO效应现在正在光谱范围内进行研究和利用，它们最初看起来完全陌生，如同步加速器辐射X射线（参见第14节关于三维磁表征和第16节关于携带轨道角动量的光束），以及最近的太赫兹（THz）范围（参见第18节关于THz MOKE和第19节关于用于电子顺磁共振检测的太赫兹椭圆光度术）。当与飞秒激光脉冲结合时，磁光还以独特的方式展示了它的优势（参见第 10 节关于超快 MOKE 和第 15 节关于使用 X 射线自由电子激光器的磁光），促进了时间分辨 MO 光谱的非常活跃的领域，可以研究非平衡光激发载流子的自旋弛豫、铁磁序的瞬态修改和光致动态相变等现象。纳米科学和纳米技术的最新进展与在纳米尺度上可靠地制造材料和功能结构所取得的令人印象深刻的能力密切相关，现在可以利用由纳米尺度的光与物质相互作用引起的强烈增强的MO效应（参见关于磁等离子体的第12节和关于MO超表面的第13节）。 MO 效应也是强大的磁表征技术的核心，例如用于研究自旋波的布里渊光散射和时间分辨泵浦探针测量（参见第 7 节）、它们与声波的相互作用（参见第 11 节）以及基于金刚石氮空位中心的超灵敏磁场传感应用（参见第 17 节）。尽管我们尽了最大努力准确地描述磁光领域并公正地对待其所有新颖的发展和多样性，但该研究领域是如此广泛和活跃，以至于在决定此类文章中包含哪些内容时仍然存在很大的自由度，这反过来又意味着某些领域可能无法在这里得到充分的体现。然而，我们认为，这篇 2022 年磁光路线图文章由 20 个部分组成，每个部分均由该领域的专家撰写，仅用两页纸讨论了一个特定主题，准确地反映了该研究领域当今的状况。相应地，它应该为现代磁光新兴研究方向提供有价值的参考和指南，并阐明该研究领域在可预见的未来可能采取的方向。
Magneto-optical (MO) effects, viz. magnetically induced changes in light intensity or polarization upon reflection from or transmission through a magnetic sample, were discovered over a century and a half ago. Initially they played a crucially relevant role in unveiling the fundamentals of electromagnetism and quantum mechanics. A more broad-based relevance and wide-spread use of MO methods, however, remained quite limited until the 1960s due to a lack of suitable, reliable and easy-to-operate light sources. The advent of Laser technology and the availability of other novel light sources led to an enormous expansion of MO measurement techniques and applications that continues to this day (see section 1). The here-assembled roadmap article is intended to provide a meaningful survey over many of the most relevant recent developments, advances, and emerging research directions in a rather condensed form, so that readers can easily access a significant overview about this very dynamic research field. While light source technology and other experimental developments were crucial in the establishment of today’s magneto-optics, progress also relies on an ever-increasing theoretical understanding of MO effects from a quantum mechanical perspective (see section 2), as well as using electromagnetic theory and modelling approaches (see section 3) to enable quantitatively reliable predictions for ever more complex materials, metamaterials, and device geometries. The latest advances in established MO methodologies and especially the utilization of the MO Kerr effect (MOKE) are presented in sections 4 (MOKE spectroscopy), 5 (higher order MOKE effects), 6 (MOKE microscopy), 8 (high sensitivity MOKE), 9 (generalized MO ellipsometry), and 20 (Cotton–Mouton effect in two-dimensional materials). In addition, MO effects are now being investigated and utilized in spectral ranges, to which they originally seemed completely foreign, as those of synchrotron radiation x-rays (see section 14 on three-dimensional magnetic characterization and section 16 on light beams carrying orbital angular momentum) and, very recently, the terahertz (THz) regime (see section 18 on THz MOKE and section 19 on THz ellipsometry for electron paramagnetic resonance detection). Magneto-optics also demonstrates its strength in a unique way when combined with femtosecond laser pulses (see section 10 on ultrafast MOKE and section 15 on magneto-optics using x-ray free electron lasers), facilitating the very active field of time-resolved MO spectroscopy that enables investigations of phenomena like spin relaxation of non-equilibrium photoexcited carriers, transient modifications of ferromagnetic order, and photo-induced dynamic phase transitions, to name a few. Recent progress in nanoscience and nanotechnology, which is intimately linked to the achieved impressive ability to reliably fabricate materials and functional structures at the nanoscale, now enables the exploitation of strongly enhanced MO effects induced by light–matter interaction at the nanoscale (see section 12 on magnetoplasmonics and section 13 on MO metasurfaces). MO effects are also at the very heart of powerful magnetic characterization techniques like Brillouin light scattering and time-resolved pump-probe measurements for the study of spin waves (see section 7), their interactions with acoustic waves (see section 11), and ultra-sensitive magnetic field sensing applications based on nitrogen-vacancy centres in diamond (see section 17). Despite our best attempt to represent the field of magneto-optics accurately and do justice to all its novel developments and its diversity, the research area is so extensive and active that there remains great latitude in deciding what to include in an article of this sort, which in turn means that some areas might not be adequately represented here. However, we feel that the 20 sections that form this 2022 magneto-optics roadmap article, each written by experts in the field and addressing a specific subject on only two pages, provide an accurate snapshot of where this research field stands today. Correspondingly, it should act as a valuable reference point and guideline for emerging research directions in modern magneto-optics, as well as illustrate the directions this research field might take in the foreseeable future.