Search Results (150)

Multilayer thin films composed of cobalt (Co), carbon (C), and chromium (Cr) possess promising electromagnetic properties, yet the combined Co–C–Cr system remains underexplored, particularly regarding its performance as a microwave absorber. Existing research has primarily focused on binary Co–C or Co–Cr compositions, leaving a critical knowledge gap in understanding how ternary multilayer architectures influence electromagnetic behavior. This study addresses this gap by investigating the structure, phase composition, and microwave absorption performance of Co–C–Cr multilayer coatings fabricated via magnetron sputtering onto porous silicon substrates. This study compares four-layer and eight-layer configurations to assess how multilayer architecture affects impedance matching, reflection coefficients, and absorption characteristics within the 8.2–12.4 GHz frequency range. Structural analyses using X-ray diffraction and transmission electron microscopy confirm the coexistence of amorphous and nanocrystalline phases, which enhance absorption through dielectric and magnetic loss mechanisms. Both experimental and simulated results show that increasing the number of layers improves impedance gradients and broadens the operational bandwidth. The eight-layer coatings demonstrate a more uniform absorption response, while four-layer structures exhibit sharper resonant minima. These findings advance the understanding of ternary multilayer systems and contribute to the development of frequency-selective surfaces and broadband microwave shielding materials. Full article

Magneto-plasmonic structures have been a subject of tremendous attention of researchers in recent decades as they provide unique approaches regarding the efficient control of optical, magneto-optical, and nonlinear-optical effects. Among others, magneto-plasmonic crystals (MPCs) have become one of the most studied structures, known for their high-quality tunable resonant optical properties. Here, we present the results of experimental and numerical studies on the functional magneto-optical (MO) response of planar 1D plasmonic crystals composed of Co/Au stripes of submicron period on the surface of a 3 μm thick rare-earth garnet layer. The experimental and numerical studies confirm that the wavelength–angular spectra of such structures contain a set of tunable resonant features in their optical and magneto-optical response, associated with the excitation of (i) surface plasmon polaritons at the Co/Au grating–garnet interface, as well as (ii) waveguide (WG) modes propagating in the garnet slab. A comparison of the MO effects in the transversal and longitudinal magnetization of the plasmonic structures is presented. We show that the most efficient Fano-type MPC magneto-optical response is realized for the WG modes of the first order for the longitudinal magnetization of the structure. Further perspectives regarding the optimization of this type of plasmonic crystal are discussed. Full article

The poor magnetic and magneto-optical properties of BiFeO₃, along with its significant lattice mismatch with silicon, have limited its application in silicon-based integrated magneto-optical devices. In this study, co-doping with Sr²⁺ and Ti⁴⁺ ions effectively transformed the trigonal structure of BiFeO₃ into a cubic phase, thereby reducing the lattice mismatch with silicon to 2.8%. High-quality, highly oriented, silicon-based cubic Sr,Ti:BiFeO₃ thin films were successfully fabricated using radio frequency magnetron sputtering. Due to the induced lattice distortion, the characteristic periodic spiral spin antiferromagnetic structure of BiFeO₃ was suppressed, resulting in a significant enhancement of the saturation magnetization of cubic Bi_0.5Sr_0.5Fe_0.5Ti_0.5O₃ (48.0 emu/cm³), compared to that of pristine BiFeO₃ (5.0 emu/cm³). Furthermore, the incorporation of Sr²⁺ and Ti⁴⁺ ions eliminated the birefringence effect inherent in trigonal BiFeO₃, thereby inducing a pronounced magneto-optical effect in the cubic Sr,Ti:BiFeO₃ thin film. The magnetic circular dichroic ellipticity (ψ_F) of Bi_0.5Sr_0.5Fe_0.5Ti_0.5O₃ reached an impressive 2300 degrees/cm. Full article

Nickel (Ni) ultrathin films exhibit phase-dependent electrical, magnetic, and optical characteristics that are significantly influenced by deposition methods. However, these films are inherently prone to rapid oxidation, with the oxidation rate dependent on substrate, temperature, and deposition parameters. The focus of this research is to investigate the temporal oxidation of RF-sputtered Ni ultrathin films on Corning glass under ambient atmospheric conditions and its impact on their structural, surface, and optical characteristics. Controlled film thicknesses were achieved through precise manipulation of deposition parameters, enabling the analysis of oxidation-induced modifications. Atomic force microscopy (AFM) revealed that films with high structural integrity and surface uniformity are exhibiting roughness values (Rq) from 0.679 to 4.379 nm of corresponding thicknesses ranging from 4 to 85 nm. Scanning electron microscopy (SEM) validated the formation of Ni grains interspersed with NiO phases, facilitating SPR-like effects. UV-visible spectroscopy is demonstrating thickness-dependent spectral (plasmonic peak) shifts. Finite Difference Time Domain (FDTD) simulations corroborate the observed thickness-dependent optical absorbance and the resultant shifts in the absorbance-induced plasmonic peak position and bandgap. Increased NiO presence primarily drives the enhancement of electromagnetic (EM) field localization and the direct impact on power absorption efficiency, which are modulated by the tunability of the plasmonic peak position. Our work demonstrates that controlled fabrication conditions and optimal film thickness selection allow for accurate manipulation of the Ni oxidation process, significantly altering their optical properties. This enables the tailoring of these Ni films for applications in transparent conductive electrodes (TCEs), magneto-optic (MO) devices, spintronics, wear-resistant coatings, microelectronics, and photonics. Full article

Pulse wave velocity (PWV) has been recognised as the gold standard for assessing arterial stiffness and a relevant indicator in diagnosing cardiovascular disease. Conventional approaches can be affected by factors such as the size of the probe, its positioning on the skin with the appropriate angle and magnitude of the incident force, or influenced by optical properties. Aiming at improving the assessment of PWV parameter, an important cardiovascular risk marker, the present study introduces a new arterial pulse wave measurement technique based on measurements of the impedance phase characteristics of giant magneto-impedance (GMI) sensors submitted to slight magnetic field variations caused by the displacement of a small magnetic marker placed on the patient’s skin, whose movement is coordinated by the local pressure wave. The proposed method eliminates the necessity of using probes with mechanical amplification, enhancing spatial resolution and usability in hard-to-reach anatomical regions through a contactless device unaffected by optical parameters. The obtained experimental results indicate the potential of the developed measurement system in measuring arterial pulse waveform and PWV. Full article

A kind of magnetoplasmonic resonators is numerically designed with hexagonally arrayed Au/bismuth iron garnet (BIG) bilayer nanodiscks on Au thin film layers. Multi-physics coupling calculation on their magnetoplasmonic resonance features suggest that there exists a strong resonant coupling between the surface plasmon excited by the hexagonal grating and the waveguide modes induced by Au-BIG-Au, which can significantly enhance the transverse magneto-optical Kerr effect. Interestingly, a new type of circular oscillating can be induced in the optical-transparent BIG layers as the thickness of BIG layers is between 2 nm and 22 nm. This circular oscillating exhibits a distinct thickness-dependent feature, which can be attributed to the near field interference of the excited localized plasmon resonance between the two interfaces formed by the middle BIG nanodiscs in the top Au nanodisks and the bottom Au thin film layers according to the simulation. These unique magnetoplasmonic features endow this kind of magnetoplasmonic resonators with a greatly enhanced refractive index sensing property, with a calculated figure of merit (FOM) value of up to 7527 RIU⁻¹. Full article

Liquid crystals based on dispersions of two-dimensional (2D) materials have recently been developed for light modulation, exhibiting superior performances compared to conventional organic liquid crystals in a variety of prototypical applications, including coloration, solar-blind communications and blue-light fluoresce. Among the diverse family of 2D liquid crystals, vermiculite-based liquid crystals stand out with advantages in low cost, ease of mass production and environmental sustainability, owing to the high natural abundance of the material. Here, we demonstrated magnetic-field tunable optics with 2D vermiculite dispersions prepared through a facile ‘exchange and redispersion’ method. By exploiting the intrinsic ion-exchange capability of clay minerals, we observed a significantly enhanced magneto-birefringence of the vermiculite dispersion upon replacing the native cations with magnetic ions, manifesting in a doubled Cotton–Mouton coefficient, representing the highest value among previous reports. Magnetization measurements reveal that there is a remarkable magnetic anisotropy in Fe ion-exchanged vermiculite samples in contrast to the isotropic magnetism of pristine vermiculite, which accounts for the observed enhancement of magneto-birefringence. Our findings demonstrate that ion exchange can serve as a simple and effective strategy to modulate the physical and chemical properties of 2D materials’ dispersions, thereby opening avenues for broader and more diverse applications. Full article

Based on modern concepts of the nonlinear percolation mechanisms of electrical and magnetic properties in granular metal–dielectric nanocomposites, the authors present for the first time a comparative analysis of their own results of a comprehensive study of nonlinear electromagnetic properties in two nanocomposite systems: metal–dielectric Co_x(MgF₂)_100−x and alloy–dielectric (CoFeZr)_x(MgF₂)_100−x, obtained by ion-beam sputtering of composite targets in a wide range of different compositions. For the first time, the features of the influence of atomic composition and structural-phase transitions on nonlinear magnetoresistive, magnetic, and magneto-optical properties in two systems are presented in comparison, one of which, Co_x(MgF₂)_100−x, showed soft magnetic properties, and the second, (CoFeZr)_x(MgF₂)_100−x, hard magnetic properties, during the transition from the superparamagnetic to the ferromagnetic state. Moreover, for the first time, the concentration dependences of the oscillating fine structure of XANES K-absorption edges of Co atoms in the first system and Co and Fe atoms in the second system are presented, which undergo changes at the percolation thresholds in each of the two systems and thus confirm the nonlinear nature of the electromagnetic properties changes in each of the two systems at the atomic level. Full article

Magneto-optic surface plasmon resonances (MOSPRs) rely on the interaction of magnetic fields with surface plasmon polaritons (SPP) to modulate plasmonic bands with magnetic fields and enhance magneto-optical activity. In the present work, a study on the magnetoplasmonic behavior of Ag/Fe bilayers is carried out by VIS-NIR spectroscopy and backed with SQUID measurements, determining the thickness-dependent magnetization of thin-film samples. The MOSPR sensing properties of Ag/Fe planar bilayers are simulated using Berreman’s matrix formalism, from which an optimized structure composed of 15 nm of Ag and 12.5 nm of Fe is obtained. The selected structure is fabricated and characterized for refractive index (RI) sensitivity, reaching 4946 RIU⁻¹ and returning an effective enhancement of refractometric sensitivity after magneto-optical modulation. A new optimized and cobalt-free magnetoplasmonic Ag/Fe bilayer structure is studied, fabricated, and characterized for the first time towards refractometric sensing, to the best of our knowledge. This configuration exhibits potential for enhancing refractometric sensitivity via magneto-optical modulation, thus paving the way towards a simpler, more accessible, and safe type of RI sensor with potential applications in chemical sensors and biosensors. Full article

In this paper, we investigate the optical absorption and luminescence spectra of rare-earth garnets activated by the terbium (Tb³⁺) ion, as well as their magneto-optical properties. Crystals of terbium gallium garnet (TbGaG) and terbium aluminum garnet (TbAlG) are considered. The focus is on the physical and optical properties and structural features of the energy levels of rare-earth ions in the crystal field of garnets. This work highlights the importance of studying intraconfigurational 4f-4f and interconfigurational 4f-5d transitions, as well as the influence of the crystal field on the magnetic and optical properties of materials. Integrated methods are used, including absorption spectroscopy, luminescence and magneto-optical studies, which allows us to obtain detailed information on the excited states of rare-earth ions. The experimental results show the presence of significant Zeeman shifts, as well as anisotropy of the absorption and luminescence spectra, depending on the orientation of the crystal lattice and the external magnetic field. This work contributes to our understanding of the mechanisms of light absorption and emission in rare-earth garnets, which may facilitate the development of new optoelectronic devices based on them. Full article

Lanthanides have seen rapid growth in the pharmaceutical and biomedical field, thus necessitating the development of hybrid metal–organic materials capable of exerting defined biological activities. Ternary hybrid lanthanide compounds were synthesized through reaction systems of Ln(III) (Ln = La, Nd, Eu) involving the antioxidant flavonoid chrysin (Chr) and 1,10-phenanhtroline (phen) under solvothermal conditions, thus leading to pure crystalline materials. The so-derived compounds were characterized physicochemically in the solid state through analytical (elemental analysis), spectroscopic (FT-IR, UV-visible, luminescence, ESI-MS, circular dichroism, ¹⁵¹Eu Mössbauer), magnetic susceptibility, and X-ray crystallographic techniques. The analytical and spectroscopic data corroborate the 3D structure of the mononuclear complex assemblies and are in line with theoretical calculations (Bond Valence Sum and Hirshfeld analysis), with their luminescence suggesting quenching on the flavonoid-phen electronic signature. Magnetic susceptibility data suggest potential correlations, which could be envisioned, supporting future functional sensors. At the biological level, the title compounds were investigated for their (a) ability to interact with bovine serum albumin and (b) antibacterial efficacy against Gram(−) (E. coli) and Gram(+) (S. aureus) bacteria, collectively revealing distinctly configured biological profiles and suggesting analogous applications in cellular (patho)physiologies. Full article

AuCo alloys are promising materials due to their magnetic, magneto-optical and magneto-plasmonic properties. These two metals are characterized by having zero mutual solubility at room temperature, significant differences in their physical and mechanical parameters and positive enthalpy of mixing. In the form of bulk samples, AuCo alloys can be synthesized by high-pressure torsion. In this study, the influence of the thermal conditions of high-pressure torsion synthesis and subsequent annealing procedures on the phase composition, magnetic domain structure and bulk magnetic properties of non-equilibrium AuCo alloys are investigated. Magnetic atomic force microscopy revealed the presence of a different magnetic domain structure in the AuCo alloys after high-pressure torsion synthesis at −193 and 23 °C. Specifically, in the AuCo alloy synthesized after 10 revolutions at 23 °C, a stripe domain structure was formed, whereas, after cryo-deformation, blurred low-contrast domain walls prevailed in the allow. The regularities of the magnetic domain structure were compared with the magnetic response of the bulk sample obtained by vibrating sample magnetometry. It was found that the saturation magnetization was slightly higher for the alloy synthesized at 23 °C, while the coercive force was higher for the AuCo alloy synthesized at −193 °C. Thermal treatment of these alloys leads to an increase in coercivity which doubles and reaches a plateau after annealing at 310 °C after cryo-deformation. Full article

Thin (~50 nm thick) BaM hexaferrite (BaFe₁₂O₁₉) films were grown on (1–102) and (0001) cut α-Al₂O₃ (sapphire) substrates via laser molecular beam epitaxy using a one- or two-stage growth protocol. The advantages of a two-stage protocol are shown. The surface morphology, structural and magnetic properties of films were studied using atomic force microscopy, reflected high-energy electron diffraction, three-dimensional X-ray diffraction reciprocal space mapping, powder X-ray diffraction, magneto-optical, and magnetometric methods. Annealed BaFe₁₂O₁₉/Al₂O₃ (1–102) structures consist of close-packed islands epitaxially bonded to the substrate. The hexagonal crystallographic axis and the easy axis (EA) of the magnetization of the films are deflected from the normal to the film by an angle of φ~60°. The films exhibit magnetic hysteresis loops for both in-plane H_in-plane and out-of-plane H_out-of-plane magnetic fields. The shape of M_out-of-plane(H_in-plane) and M_in-plane(H_in-plane) hysteresis loops strongly depends on the azimuth θ of the H_{in plane}, confirming the tilted orientation of the EA. The M_out-of-plane(H_out-of-plane) magnetization curves are caused by the reversible rotation of magnetization and irreversible magnetization jumps associated with the appearance and motion of domain walls. In the absence of a magnetic field, the magnetization is oriented at an angle close to φ. Full article

The giant magnetoresistance effect in two-dimensional (2D) magnetic materials has sparked substantial interest in various fields; including sensing; data storage; electronics; and spintronics. Their unique 2D layered structures allow for the manifestation of distinctive physical properties and precise performance regulation under different conditions. In this review, we present an overview of this rapidly developing research area. Firstly, these 2D magnetic materials are catalogued according to magnetic coupling types. Then, several vital effects in 2D magnets are highlighted together with theoretical investigation, such as magnetic circular dichroism, magneto-optical Kerr effect, and anomalous Hall effect. After that, we forecast the potential applications of 2D magnetic materials for spintronic devices. Lastly, research advances in the attracting magnons, skyrmions and other spin textures in 2D magnets are discussed. Full article

The interaction between light and the magnetization of a material is called the magneto–optical effect. It was used in magneto–optical recording such as MO disks and has been applied to optical isolators etc. with the development of optical communications. The magneto–optical properties of magnetic garnets and their applications are briefly reviewed in this article. In the first half, after a brief overview of the phenomenology of the magneto–optical effect, the effects of element substitution on properties such as Faraday rotation and optical absorbance of magnetic garnets are shown. In the second half, some interesting applications such as imaging technologies and other novel applications using the magneto–optical effect of magnetic garnets are also introduced. Full article