A. F. Kravets

Bio: A. F. Kravets is an academic researcher from Royal Institute of Technology. The author has contributed to research in topics: Ferromagnetic resonance & Ferromagnetism. The author has an hindex of 13, co-authored 42 publications receiving 583 citations. Previous affiliations of A. F. Kravets include National Academy of Sciences of Ukraine.

Ferromagnetic resonance in granular thin films

Abstract: A theoretical analysis has been done of the effects of granule size, shape, orientation, and concentration and the temperature effects on the ferromagnetic resonance (FMR) field Hr in granular thin films. The granular CoxAg1−x thin films with 0.2 fp. For the Co–Ag system, persistence of a considerable SPM fraction is revealed by the superconducting quantum interference device data up to the highest f, and the effect at f=fp consists in a discontinuous jump of the Hr(f) slope. Otherwise, the FMR data for granular Fe–SiO2 films reveal a discontinuous jump in H...

Correlation between the magnetorefractive effect, giant magnetoresistance, and optical properties of Co-Ag granular magnetic films

Abstract: Giant magnetoresistance (GMR), optical properties, and the infrared magnetorefractive effect (MRE) are studied in reflection for granular films of composition ${\mathrm{Co}}_{x}{\mathrm{Ag}}_{1\ensuremath{-}x}$ with x ranging from 01 to 07 From ellipsometry measurements it is shown that it is necessary to take into account finite-size effects in order to successfully model the optical data demonstrating the importance of the microstructure to the MRE The ellipsometry data enable the variation in optical properties with Co concentration to be determined and incorporated into a model of the MRE The MRE itself is calculated with a frequency- and spin-dependent conductivity Both the experimental and theoretical analyses reveal a correlation between GMR and the MRE demonstrating the feasibility of using the MRE as a contactless method for measuring the GMR and for extracting fundamental spin-dependent scattering parameters

Temperature-controlled interlayer exchange coupling in strong/weak ferromagnetic multilayers : A thermomagnetic Curie switch

Abstract: We investigate interlayer exchange coupling based on driving a strong/weak/strong ferromagnetic trilayer through the Curie point of the weakly ferromagnetic spacer, with exchange coupling between the strongly ferromagnetic outer layers that can be switched on and off, or varied continuously in magnitude by controlling the temperature of the material. We use Ni-Cu alloys of varied composition as the spacer material and model the effects of proximity-induced magnetism and the interlayer exchange coupling through the spacer from first principles, taking into account not only thermal spin disorder but also the dependence of the atomic moment of Ni on the nearest-neighbor concentration of the nonmagnetic Cu. We propose and demonstrate a gradient-composition spacer, with a lower Ni concentration at the interfaces, for greatly improved effective-exchange uniformity and significantly improved thermomagnetic switching in the structure. The reported multilayer materials can form the base for a variety of magnetic devices, such as sensors, oscillators, and memory elements based on thermomagnetic Curie switching.

Plasmonic Surface Lattice Resonances: A Review of Properties and Applications

Abstract: When metal nanoparticles are arranged in an ordered array, they may scatter light to produce diffracted waves. If one of the diffracted waves then propagates in the plane of the array, it may couple the localized plasmon resonances associated with individual nanoparticles together, leading to an exciting phenomenon, the drastic narrowing of plasmon resonances, down to 1–2 nm in spectral width. This presents a dramatic improvement compared to a typical single particle resonance line width of >80 nm. The very high quality factors of these diffractively coupled plasmon resonances, often referred to as plasmonic surface lattice resonances, and related effects have made this topic a very active and exciting field for fundamental research, and increasingly, these resonances have been investigated for their potential in the development of practical devices for communications, optoelectronics, photovoltaics, data storage, biosensing, and other applications. In the present review article, we describe the basic phy...

Nearly total absorption of light and heat generation by plasmonic metamaterials

Abstract: We theoretically and numerically study the absorption effect and the heat generation in plasmonic metamaterials under light radiation at their plasmonic resonance. Three different types of structures, all possessing high-performance absorption for visible lights, are investigated. The main aim of this work is to present an intuitive and original understanding of the high-performance absorption effects. From the macroscopic electromagnetic point of view, the effective-medium approach is used to describe the absorption effects of the plasmonic metamaterials. On the other hand, the field distributions and heat generation effects in such plasmonic nanostructures are investigated, which also provides a satisfactory qualitative description of such absorption behavior based upon the microscopic perspective.

Plasmonic and metamaterial structures as electromagnetic absorbers

Abstract: Electromagnetic absorbers have drawn increasing attention in many areas. A series of plasmonic and metamaterial structures can work as efficient narrowband absorbers due to the excitation of plasmonic or photonic resonances, providing a great potential for applications in designing selective thermal emitters, biosensing, etc. In other applications such as solar-energy harvesting and photonic detection, the bandwidth of light absorbers is required to be quite broad. Under such a background, a variety of mechanisms of broadband/multiband absorption have been proposed, such as mixing multiple resonances together, exciting phase resonances, slowing down light by anisotropic metamaterials, employing high loss materials and so on.

Plasmonic and Metamaterial Structures as Electromagnetic Absorbers

Abstract: Electromagnetic absorbers have drawn increasing attention in many areas. A series of plasmonic and metamaterial structures can work as efficient narrow band absorbers due to the excitation of plasmonic or photonic resonances, providing a great potential for applications in designing selective thermal emitters, bio-sensing, etc. In other applications such as solar energy harvesting and photonic detection, the bandwidth of light absorbers is required to be quite broad. Under such a background, a variety of mechanisms of broadband/multiband absorption have been proposed, such as mixing multiple resonances together, exciting phase resonances, slowing down light by anisotropic metamaterials, employing high loss materials and so on.

Gradient metasurfaces: a review of fundamentals and applications.

Abstract: In the wake of intense research on metamaterials the two-dimensional analogue, known as metasurfaces, has attracted progressively increasing attention in recent years due to the ease of fabrication and smaller insertion losses, while enabling an unprecedented control over spatial distributions of transmitted and reflected optical fields. Metasurfaces represent optically thin planar arrays of resonant subwavelength elements that can be arranged in a strictly or quasi periodic fashion, or even in an aperiodic manner, depending on targeted optical wavefronts to be molded with their help. This paper reviews a broad subclass of metasurfaces, viz. gradient metasurfaces, which are devised to exhibit spatially varying optical responses resulting in spatially varying amplitudes, phases and polarizations of scattered fields. Starting with introducing the concept of gradient metasurfaces, we present classification of different metasurfaces from the viewpoint of their responses, differentiating electrical-dipole, geometric, reflective and Huygens' metasurfaces. The fundamental building blocks essential for the realization of metasurfaces are then discussed in order to elucidate the underlying physics of various physical realizations of both plasmonic and purely dielectric metasurfaces. We then overview the main applications of gradient metasurfaces, including waveplates, flat lenses, spiral phase plates, broadband absorbers, color printing, holograms, polarimeters and surface wave couplers. The review is terminated with a short section on recently developed nonlinear metasurfaces, followed by the outlook presenting our view on possible future developments and perspectives for future applications.