Alexey Kimel, Anatoly Zvezdin, Sangeeta Sharma, Samuel Shallcross, Nuno de Sousa, Antonio García-Martín, Georgeta Salvan, Jaroslav Hamrle, Ondřej Stejskal, Jeffrey McCord, Silvia Tacchi, Giovanni Carlotti, Pietro Gambardella, Gian Salis, Markus Münzenberg, Martin Schultze, Vasily Temnov, Igor V Bychkov, Leonid N Kotov, Nicolò Maccaferri, Daria Ignatyeva, Vladimir Belotelov, Claire Donnelly, Aurelio Hierro Rodriguez, Iwao Matsuda, Thierry Ruchon, Mauro Fanciulli, Maurizio Sacchi, Chunhui Rita Du, Hailong Wang, N Peter Armitage, Mathias Schubert, Vanya Darakchieva, Bilu Liu, Ziyang Huang, Baofu Ding, Andreas Berger, Paolo Vavassori, Radboud University [Nijmegen], A. M. Prokhorov General Physics Institute (GPI), Russian Academy of Sciences [Moscow] (RAS), Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (MBI), Donostia International Physics Center (DIPC), University of the Basque Country/Euskal Herriko Unibertsitatea (UPV/EHU), IMN-Instituto de Micro y Nanotecnología (CNM-CSIC), Isaac Newton 8, PTM, 28760 Tres Cantos, Madrid, Spain, Institute of Physics, University of Technology Chemnitz, Chemnitz University of Technology / Technische Universität Chemnitz, Institute of Physics of Charles University, Faculty of Mathematics and Physics, Charles University [Prague] (CU), Institut für Materialwissenschaft Universität Kiel, Università degli Studi di Perugia = University of Perugia (UNIPG), Department of Materials [ETH Zürich] (D-MATL), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), IBM Research [Zurich], Institut für Physik [Greifswald], Ernst-Moritz-Arndt-Universität Greifswald, Graz University of Technology [Graz] (TU Graz), Laboratoire des Solides Irradiés (LSI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Chelyabinsk State University, Syktyvkar State University, Syktywkar State University, Umeå University, Physics and Materials Science Research Unit, University of Luxembourg, University of Luxembourg [Luxembourg], Russian Quantum Center, Faculty of Physics, Lomonosov Moscow State University, Lomonosov Moscow State University (MSU), Max Planck Institute for Chemical Physics of Solids (CPfS), Max-Planck-Gesellschaft, Departamento de Fisica, Universidad de Oviedo, 33006 Oviedo, Spain, Universidad de Oviedo [Oviedo], Nanomaterials and Nanotechnology Research Center (CINN), Universidad de Oviedo [Oviedo]-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581, Japan, Laboratoire Interactions, Dynamiques et Lasers (ex SPAM) (LIDyl), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Attophysique (ATTO), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Laboratoire Interactions, Dynamiques et Lasers (ex SPAM) (LIDyl), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique des Matériaux et des Surfaces (LPMS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-CY Cergy Paris Université (CY), Croissance et propriétés de systèmes hybrides en couches minces (INSP-E8), Institut des Nanosciences de Paris (INSP), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), University of California [San Diego] (UC San Diego), University of California (UC), Center for Memory and Recording Research, University of California (UC)-University of California (UC), Johns Hopkins University (JHU), University of Nebraska–Lincoln, University of Nebraska System, Department of Physics, Chemistry and Biology, Linköping University, Lund University [Lund], Shenzhen Key Laboratory on Power Battery Safety and Shenzhen Geim Graphene Center, Tsinghua University [Beijing] (THU), Shenzhen Institute of Advanced Technology [Shenzhen] (SIAT), Chinese Academy of Sciences [Beijing] (CAS), CIC NanoGUNE BRTA, Ikerbasque - Basque Foundation for Science, ANR-21-CE30-0037,HELIMAG,Dichroisme hélicoïdal de structures magnétiques(2021), Dutch Research Council, Russian Science Foundation, German Research Foundation, Agencia Estatal de Investigación (España), Ministerio de Ciencia, Innovación y Universidades (España), Czech Science Foundation, Collaborative Research Centre CRC 1261 (Germany), Ministero dell'Istruzione, dell'Università e della Ricerca, National Centres of Competence in Research (Switzerland), Swiss National Science Foundation, European Commission, Agence Nationale de la Recherche (France), Fonds National de la Recherche Luxembourg, Swedish Research Council, Ministry of Science and Higher Education of the Russian Federation, Max Planck Society, Japan Synchrotron Radiation Research Institute, University of Tokyo, Université Paris-Saclay, Air Force Office of Scientific Research (US), National Science Foundation (US), Energy Frontier Research Centers (US), Swedish Foundation for Strategic Research, Linköping University, and National Natural Science Foundation of China
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., Journal of Physics D: Applied Physics, 55 (46), ISSN:0022-3727, ISSN:1361-6463