Abstract 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.
more »
« less
Light-Directed Organization of Polymer Materials from Photoreactive Formulations
This perspective presents a recently developed approach to organize polymer and polymer composite materials through a new form of light-directed organization of photoreactive polymeric media. Under suitable conditions, such media will interact with light, in a mutual dynamic process, that results in the spontaneous organization of both the input light field and, importantly, the polymer media. New material structures can be created in free-radical-initiated media, polymer blends and polymer–solvent mixtures, as well as possibly more complex, multicomponent formulations. An overview of the underlying principles and chemical phenomena and exemplary material structures are presented. Materials produced using this new processing approach can be used as functional coatings, textured surfaces, and membranes, as well as a host of other applications via selection of polymer composition. Key open questions and areas for further inquiry and advancement are presented. Coupling the dynamics of light pattern formation processes to photoreactive matter is a promising new approach to the organization of materials for a range of critical applications and reveals interesting nonlinear dynamic phenomena in the organization of materials.
more »
« less
- Award ID(s):
- 1751621
- NSF-PAR ID:
- 10251673
- Date Published:
- Journal Name:
- Chemistry of materials
- Volume:
- 32
- Issue:
- 7
- ISSN:
- 1520-5002
- Page Range / eLocation ID:
- 2673
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
more » « less
Abstract Memory technologies and applications implemented fully or partially using emerging 2D materials have attracted increasing interest in the research community in recent years. Their unique characteristics provide new possibilities for highly integrated circuits with superior performances and low power consumption, as well as special functionalities. Here, an overview of progress in 2D‐material‐based memory technologies and applications on the circuit level is presented. In the material growth and fabrication aspects, the advantages and disadvantages of various methods for producing large‐scale 2D memory devices are discussed. Reports on 2D‐material‐based integrated memory circuits, from conventional dynamic random‐access memory, static random‐access memory, and flash memory arrays, to emerging memristive crossbar structures, all the way to 3D monolithic stacking architecture, are systematically reviewed. Comparisons between experimental implementations and theoretical estimations for different integration architectures are given in terms of the critical parameters in 2D memory devices. Attempts to use 2D memory arrays for in‐memory computing applications, mostly on logic‐in‐memory and neuromorphic computing, are summarized here. Finally, challenges that impede the large‐scale applications of 2D‐material‐based memory are reviewed, and perspectives on possible approaches toward a more reliable system‐level fabrication are also given, hopefully shedding some light on future research.
-
Hydrogels are soft water-rich materials with physical properties that can be easily tuned by modifying their network structure. For instance, increasing or decreasing the cross-linking density has a profound effect on their water absorption capabilities and mechanical strength. These physical changes are showcased in a new experiment for organic chemistry and polymer science teaching laboratories based on the practical green synthesis and characterization of lactose methacrylate derived hydrogels. Lactose, a disaccharide derived from dairy waste byproducts, is functionalized with photoreactive methacrylate groups using methacrylic anhydride. The resulting mixture is subsequently photoirradiated to generate a cross-linked hydrogel. Structure–property relationships are assessed through comparative studies of three hydrogels of varying compositions. Compression tests and swelling studies in different aqueous environments offer a guided-inquiry experience. Students determine a relationship between cross-linking density and the physical properties of the hydrogels. This experiment highlights the valorization of biomass and multiple green chemistry principles including use of renewable feedstocks, atom economy, energy efficiency, waste prevention, and water as a benign solvent. Learning outcomes for an organic chemistry laboratory course include introduction to disaccharide and cross-linked polymer structures, observable physical change dependency with cross-linking density, and laboratory methods for evaluating water absorption capacities. Objectives aligned with a polymer course are incorporating mechanical compression instrumentation, mechanistic understanding of light-induced free radical polymerizations, and an appreciation for the application of hydrogels to commercial products. Overall, the translation of a current literature publication to an inexpensive and versatile experiment engages students in a modern example of sustainable polymer chemistry.more » « less
-
more » « less
Abstract Shape‐morphing magnetic soft materials, composed of magnetic particles in a soft polymer matrix, can transform shape reversibly, remotely, and rapidly, finding diverse applications in actuators, soft robotics, and biomedical devices. To achieve on‐demand and sophisticated shape morphing, the manufacture of structures with complex geometry and magnetization distribution is highly desired. Here, a magnetic dynamic polymer (MDP) composite composed of hard‐magnetic microparticles in a dynamic polymer network with thermally responsive reversible linkages, which permits functionalities including targeted welding for magnetic‐assisted assembly, magnetization reprogramming, and permanent structural reconfiguration, is reported. These functions not only provide highly desirable structural and material programmability and reprogrammability but also enable the manufacturing of functional soft architected materials such as 3D kirigami with complex magnetization distribution. The welding of magnetic‐assisted modular assembly can be further combined with magnetization reprogramming and permanent reshaping capabilities for programmable and reconfigurable architectures and morphing structures. The reported MDP are anticipated to provide a new paradigm for the design and manufacture of future multifunctional assemblies and reconfigurable morphing architectures and devices.
-
Fibers are valuable to biomedical applications. Used as sutures or meshes, there is an increased dual need to provide functionality such as drug delivery. Porosity represents a high surface area to volume architecture. Coaxial fibers with porous and non-porous layers offer a new design framework for fiber design that can resolve dual needs of mechanical robustness with transport phenomena. Using preferential solubility of a polymer in supercritical CO2, we develop a new architecture using biocompatible polymers based on porous core-sheath fiber fabrication technique. Polycaprolactone was selected as the CO2 miscible phase and Poly(butyrate adipate terephthalate)(PBAT) as the immiscible phase. The mechanical performance of the fibers was investigated using quasi static and dynamic loading. SEM images indicate no physical detachment of the two polymer surface after CO2 exposure indicating a successful amalgamation of polymers at the boundary of core and sheath. PCL as a sheath and as a core showed an increase of 650% and 468% in tensile strength compared to pristine PCL and PBAT. Introduction of porosity on the surface of coaxial fiber fPCL(cPBAT) further enhanced the yield strength increases by 40%. Dynamic mechanical analysis was used to analyze the viscoelastic properties of the fibers. The storage and loss modulus for coaxial fibers shows superior modulus throughout the glassy, glass transition and rubbery region as compared to the pristine PCL and PBAT, showing enhancement in both the elastic and viscous response of the material. The results indicate a new approach that is free of volatile organic solvents to manipulate the architecture of the cross-section of the electrospun fiber and tailor mechanical properties to the required application.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acs.chemmater.9b05373
