Nanowires made of FexCoyCu _(100-x-y) and FexNiyCu _(100-x-y) alloys have been investigated. Specific features of the formation of these structures by template synthesis are studied. Elemental analysis of the nanowires grown at successively increasing voltages revealed a significant decrease in the amount of copper, as well as a change in the ratio of the main magnetic elements. X-ray diffraction analysis showed that FeCoCu is a three-component solid solution, whereas FeNiCu contains three phases of solid solutions: FeCu with a Cu content up to 80

Polyvinylidene fluoride (PVDF) has gained attention as a promising material for tissue engineering due to its biocompatibility and piezoelectricity. However, achieving proper cell adhesion to PVDF surfaces remains a challenge. This study focuses on the preparation and characterization of PVDF-based substrates, including PVDF thin films and nanocomposites incorporating CoFe2O4 magnetic nanoparticles. Helium plasma treatment is employed to modify the surface properties of these substrates. The plasma treatment induces significant changes in the topography of the PVDF-based nanocomposites. The roughness values of the samples increase from 2-3 nm to 14-17 nm after 90 s of plasma treatment, leading to enhanced hydrophilicity with an average contact angle below 60 degrees. Importantly, the helium plasma treatment preserves the magnetic and structural properties of the substrates, suggesting the retention of their magnetoelectric properties and, thus treated composites hold potential for remote stem cell activation. We provide evidence of cytocompatibility and improved adhesive properties of plasma-treated substrates using human mesenchymal stem cell cultures.

The use of multiparametric optimization of an unknown discrete function in the development of applied solutions for physical systems is considered. Such optimization is practically implemented in real time using modern data transfer protocols at high speed with continuously increasing computing power. Optimization of the sensitivity of a modern magnetic sensor based on high-frequency magnetoimpedance in ferromagnetic microwires is studied as an applied problem. Iterative methods of a global maximum search—successive approximation and particle swarm algorithms—have been used for this optimization. The output signal of the sensor depends non-linearly on both the internal magnetic properties of the microwire and the excitation mode, which requires a certain calibration to establish optimal excitation parameters. Using an automated installation, sensor output signals for various excitation parameters and external magnetic fields were measured. The results of the search for the global maximum of sensor sensitivity by the successive approximation method and the particle swarm algorithm were presented. It was established that the particle swarm algorithm turned out to be more effective and precise than the successive approximation method.. With various excitation parameters, the particle swarm algorithm always determined the maximum sensitivity of the sensor when varying the three basic parameters of the excitation signal: frequency, amplitude, and the constant component. The results obtained will be applied in the development of highly sensitive intelligent magnetic sensors and systems based on them.

The magnetic and optical properties of gold-coated nickel nanotubes obtained by template synthesis have been studied. A change in the relative intensity of an optical beam passing through a solution of nanotubes in a magnetic field perpendicular and parallel to the beam propagation shows the possibility of orienting nanotubes along the magnetic field. The results provide an assessment of the applicability of such nanotubes in combined photothermal and magnetomechanical anticancer therapy.

Nanoparticles represent a class of highly adaptable nanostructures with a remarkable surface -to -volume ratio, allowing for the precise tuning of their shape to influence their properties. Moreover, their surfaces can be functionalized with organic or inorganic materials, thereby tailoring their performance and introducing specific functionalities. Iron oxide nanoparticles including Fe 3 O 4 and spinel Co ferrites emerge as promising candidates for medical applications due to their notable biocompatibility and appropriate magnetic properties. Their potential in cancer therapy primarily hinges on localized cancer cell heating, which can be remotely triggered by an external AC magnetic field (magnetic hyperthermia). Additional heating induced by light excitation can reduce the required particle dosages during such treatments. The optical characteristics of iron oxide nanoparticles within the wavelength range of biological transparency open up exciting prospects for utilizing these structures in adjuvant thermal therapies. In this study, we demonstrate the results of synthesis and study of magnetic and optical properties of iron oxide nanoparticles coated with organic materials. Notably, CoFe 2 O 4 nanoparticles coated with dihydrocaffeic acid demonstrated the coefficient of heat efficiency conversion close to 100 % under 810 nm laser excitation. They also demonstrated the magnetization curves characterized by minimal hysteresis and remanent magnetization typical of superparamagnetic behavior of iron oxide nanoparticles. This suggests their potential for combined magnetic and optical hyperthermia.

Soft magnetic materials with high magnetic susceptibility in response to the influence of alternating magnetic fields, generate an inductive electric voltage in the receiving coil, the spectrum of which contains higher harmonics. This is due to the nonlinear dependence of magnetization on the magnetic field, and the amplitudes of higher harmonics make a significant contribution to the overall signal if an external field leads to magnetic saturation. Magnetic susceptibility and saturation field are largely determined by magnetoelastic interactions in amorphous ferromagnets, respectively, the amplitudes of higher harmonics should depend on external mechanical stresses. In this work, we study the processes of magnetization reversal in amorphous microwires of two compositions: Co71Fe5B11Si10Cr3 and Co66.6Fe4.28B11.51Si14.48Ni1.44Mo1.69 under the action of external tensile stresses. For the first composition, mechanical stresses exceeding a certain limit (higher than 350 MPa) lead to the transformation of the magnetic hysteresis from a bistable type to an inclined one. In this case, a sharp change of the harmonic spectrum is observed. In microwires of the second composition with an initially inclined loop, external stresses cause a monotonous increase in the slope of the hysteresis loop (a decrease in susceptibility). In this case, the amplitudes of higher harmonics change significantly at low stresses, lower than 100 MPa. The results were obtained by magnetization reversal of microwire samples using a system of flat coils, which demonstrates the potential of using these materials as wireless sensors of mechanical stresses with remote reading.

Arrays of iron nanowires (NWs) obtained by template-assisted electrodeposition constitute a promising composite material characterized by a combination of high magnetization in the filler and perpendicular magnetic anisotropy. The properties of these composites arise from the interplay between the behavior of individual NWs and their magnetostatic interactions. In this study, we investigated NW arrays with identical wire diameters but varying spatial arrangements. Major hysteresis loops were studied under various field directions relative to the NW axis. Key parameters such as the slope of the magnetization curve, saturation magnetization, and coercive force were quantified. Additionally, FORC (First Order Reversal Curve) measurements were conducted with the field oriented longitudinally with respect to the NW, offering insights into the inhomogeneity of the demagnetizing field influenced by the NW array's configuration. In the sample with the highest NW density, we observed isotropic behavior of the effective demagnetizing field, and we proposed an explanation for this phenomenon using the effective media approach. Micromagnetic simulations revealed that the magnetic behavior of individual NWs with a 100 nm diameter can be described as an interchange between volumes characterized by vortex and uniform magnetization patterns. Calculations of the demagnetizing field using the effective medium model demonstrated excellent agreement with experimental data across arrays featuring different NW densities. Remarkably, the quantitative consistency of coercive field values obtained from micromagnetic simulations and experimental measurements in the range of angles from 0 degrees to 45 degrees for the studied samples underscores the structural homogeneity of the obtained NWs.

A study of the temperature behavior of high-frequency magnetoimpedance (MI) in amorphous microcircuits in a glass shell up to the Curie temperature T C has been carried out. Samples from the alloy Co 27.4 Fe 5 B 12.26 Si 12.26 Ni 43.08 with a low Curie temperature (T C ~48 o C) and negative magnetostriction were used. Near T C , the impedance curves retain their characteristic behavior for materials with circular anisotropy, but the sensitivity of MI with respect to the field decreases sharply. The change in impedance with temperature becomes significant only in the presence of an external magnetic field. With an increase in temperature from room temperature to T C , the relative change in impedance can reach 140-275% in the frequency range 0.1-0.9 GHz and a magnetic field of ~10 Oe. Taking into account the location of T C in an almost important temperature region, the results obtained are interesting for the development of miniature temperature sensors, including contactless embedded sensors. Keywords: amorphous alloys, MI-effect, circular anisotropy, spin-orientation transition.

The development of magnetic field sensors for biomedical applications faces the challenge of maintaining the required detection sensitivity limit and overall design improvement in order to allow low-cost fabrication methods and flexibility of usage outside of special environments (e.g., shielding rooms). The feasibility of magnetic field sensors for applications such as magnetocardiography, magnetotomography, magnetomyography, and magnetoneurography has been successfully demonstrated; however, they are still not widely used in clinical practice due to a set of stringent requirements. In this chapter we discuss a number of room-temperature magnetic field sensors including giant magnetoresistive, fluxgate, and giant magnetoimpedance. The presentation is subdivided into two main categories: (1) measuring a magnetic field produced by human organs, (2) detecting magnetically labeled bio-molecules. The requirement of point-of-care diagnostics is to provide bioanalysis on a cellular or molecular level. Subsequently, important points are mobility, the speedy obtaining of results and low cost of fabrication.

The research on the solar cell structure based on various inorganic, organic and hybrid type of perovskite absorbing materials is increasing due to their legion features. Various inorganic titanium (Ti) based double perovskite absorbing materials like, Cs2TiCl6, Cs2TiBr6, and Cs2TiI6 are examined. Cs2TiBr6 is chosen to be the most promising absorbing layer material alternative suitable for a stable environmentally friendly solar cell application due to its larger spectrum response and tunable band gap than the other promising absorbing materials. The primary objective of this work aims for investigating the functioning of Cs2TiBr6 with various inorganic charge transport materials under simulated conditions using the simulation software, SCAPS-1D (a Solar Cell Capacitance Simulator), Solar Cell Capacitance Simulator, and its functioning is evaluated by varying the interface defect density, thickness, defect density, etc. of various layer materials of the solar cell device. The basic input parameters, like electron-affinity, thickness, band-gap, charge mobility, permittivity, and defect density, of different layer materials are used in the simulation software to accomplish the modelling of the novel structure of solar cell device. A highly efficient environmentally friendly perovskite solar cell structure is the focus of this numerical research. Analysis results are compared with the existing data for substantiation. Finally, one planar inverted, high performance device structure, Glass/MoO3/Cs2TiBr6/SnO2/Au, is evolved, which is a promising eco-friendly device that can be used for making solar panels without any toxic consequences. The short circuit current density, the open circuit voltage, power conversion efficiency, and the fill-factor of this innovative inverted solar cell structure are observed to be 16.589 mA/cm2, 1.1 V, 15.68 %, and 85.76 %, which are significantly better parameters than those previously reported.

Проведено исследование температурного поведения высокочастотного магнитоимпеданса (МИ) в аморфных микропроводах в стеклянной оболочке вплоть до температуры Кюри TC. Использовались образцы из сплава Co27.4Fe5B12.26Si12.26Ni43.08 с низкой температурой Кюри (TC~48oC) и отрицательной магнитострикцией. Вблизи TC кривые импеданса сохраняют характерное поведение для материалов с циркулярной анизотропией, но чувствительность МИ по отношению к полю резко снижается. Изменение импеданса с температурой становится значительным только в присутствие внешнего магнитного поля. При повышении температуры от комнатной до TC относительное изменение импеданса может достигать 140-275% в области частот 0.1-0.9 GHz и магнитном поле ~10 Oe. С учетом нахождения TC в практически важной температурной области, полученные результаты интересны для разработки миниатюрных температурных сенсоров, в том числе бесконтактных встраиваемых сенсоров. Ключевые слова: аморфные сплавы, МИ-эффект, циркулярная анизотропия, спин-ориентационный переход.

The structural, magnetic, and optical properties of mesoscale particles in the form of Au/Fe/Au layered disks and Ni@Au nanotubes have been studied. The disks were produced by electron-beam lithography followed by deposition of functional layers. Ni nanotubes were obtained by template synthesis using electrochemical deposition into pores of ion track membranes. They were removed from the templates and the resulting powders were covered with gold by chemical modification. Ferromagnetic structures coated with plasmonic metals demonstrate a high photothermal conversion efficiency in the region of plasmon resonance. Together with their magnetic properties, such as the vortex magnetic state, these structures are promising for biomedical applications.

Nanotechnology is rapidly gaining prominence across various fields, ranging from medicine to military applications. Considered as the forefront of innovation, nanotechnology holds immense potential for military use, with a multitude of applications on the horizon. The deployment of miniaturized military systems would offer a substantial strategic advantage against adversaries. Examples include miniature drones or swarms of artificial bees, which enhance battlespace awareness and situational visibility. Moreover, employing miniaturized AI-equipped bots at the frontline provides a comprehensive understanding of evolving battlefields. As nanotechnology progresses, it will unlock the development of a new class of lethal weapons, reshaping the geopolitical landscape. It is imperative for the world to acknowledge and embrace the advanced capabilities of nanotechnology, integrating them into contemporary warfare strategies.

Heterostructural nanowires with alternating copper and nickel layers were obtained by matrix synthesis, then were cut into cylindrical magnetic nanoparticles of calibrated sizes. For their use in medicine, the tasks of their separation (overcoming agglomeration) and spatial orientation for targeted drug delivery and hyperthermia, respectively, were solved.

In this paper, the structural and magnetic properties of layered nanowires (NWs) made of alternating layers of nickel and copper were investigated. NW arrays were obtained by matrix synthesis. The nickel layers had a fixed thickness of 400 nm, and the thickness of the copper layers varied from 25 to 300 nm. The magnetic characteristics of such NWs were studied in two states: in a matrix (integral magnetic characteristics determined using vibrating sample magnetometry) and for individual NW (local magnetization visualized using MFM). For NWs in the matrix, the hysteresis loops measured for the two directions of the magnetic field become identical when the thickness of the Cu layer increases to 300 nm, which is due to the weakening of the dipole interaction between the Ni layers. The coercive force (190 Oe) and the residual magnetization (0.32 Ms) in the parallel direction of the field are maximal for the thickness of the Cu layer equal to 100 nm, which corresponds to the diameter of NWs and the distance between them. The MFM method was used to study samples with Cu layer thicknesses of 300 nm. It is demonstrated step by step how the application of an external magnetic field leads to remagnetization. An intermediate antiparallel distribution of magnetization in neighboring layers is revealed. The magnitude of the coercive force for an agglomerate of two or three NWs varies between 40-50 Oe, but the magnetization switching field turns out to be about 160 Oe, which is comparable to the coercive force for an array of NWs of this type (180-190 Oe). This demonstrates the role of the NWs' dipole interaction in the matrix.

The study focuses on examining the impact of shell-induced stresses on the magnetic characteristics of Fe-based microwires encased in glass, with particular attention given to the critical fabrication parameters employed in the microwire production process utilizing the Taylor-Ulitovsky method. We systematically investigate how internal stresses affect magnetization reversal behaviors in both glass-coated and uncoated Fe77.5Si7.5B15 microwires through experimental analysis and compare these effects with those resulting from stress-annealing procedures. The simulation of stress distribution caused by the solidification process is based on thermo viscoelasticity theory considering a non-constant glass transition temperature. The analysis also includes the knowledge of the initial parameters of the microwires during the manufacturing.

The magnetic properties of layered nanowires (NWs) composed of alternating nickel and copper layers were studied. In such structures, magnetic properties are governed by several factors, such as the aspect ratio of alternating layers, the dipole interaction between neighboring layers within a single NW, and the interaction of neighboring NWs. NW arrays were formed by matrix synthesis. Nickel layers had a fixed thickness of 400 nm, and the thickness of copper layers varied from 25 to 300 nm. The magnetic characteristics of such NWs were studied in two states: in a matrix (integral magnetic characteristics determined by vibrating sample magnetometry) and for individual NWs (local magnetization visualized by magnetic force microscopy (MFM)). For NWs in a matrix, the hysteresis loops measured for two magnetic field directions became identical when the thickness of a Cu layer increased to 300 nm due to the weakening of dipole interaction between Ni layers inside NWs and the growing role of dipole interaction between neighboring NWs. In this case, the residual magnetization grew after a field parallel to the matrix plane was applied. The samples with a Cu layer thickness of 300 nm were studied by MFM. It was step-by-step demonstrated how the application of an external magnetic field led to magnetization reversal. Magnetization reversal in a pair of NWs was revealed to occur in two stages like in a two-phase system with two characteristic fields: H c1 = 40–50 Oe for the formation of a pair with the opposite magnetization direction and H c2 =160 Oe for complete magnetization reversal. The latter value was close to the coercive force for an array of NWs in a matrix.

•Photothermal conversion coefficient of CoFe2O4 nanoparticles coated with dihydrocaffeic acid can be as high as 97 %•Organic coating slightly decreases pristine iron oxide nanoparticles photothermal performance.•Coating of CoFe2O4 and Fe3O4 nanoparticles by citric & dihydrocaffeic acids lowers cytotoxicity.•Electric polarizabilities of iron oxide nanoparticles and their gold hybrids are similar in near IR.

Heterostructural nanowires with alternating layers of copper and nickel are obtained by matrix synthesis and then cut into cylindrical magnetic nanoparticles of calibrated sizes. Problems of separating layers (overcoming agglomeration) for their use in medicine and their spatial orientation for targeted drug delivery and treating hyperthermia, respectively, are solved.

The temperature behavior of high-frequency magnetoimpedance (MI) in amorphous microwires in a glass sheath has been studied in the temperature range up to the Curie temperature T C . Two alloy samples with compositions of Co 27.4 Fe 5 B 12.26 Si 12.26 Ni 43.08 ( T C ≈ 48°C) and Co 64.82 Fe 3.9 B 10.2 Si 12 Cr 9 Mo 0.08 ( T C ≈ 61°C) with different signs of magnetostriction constant λ s and with different types of magnetic anisotropy were used. For the first alloy sample, λ s < 0, which leads to circular anisotropy. For the second alloy sample, λ s > 0, and easy axis anisotropy is formed along the wire axis. A substantial decrease in the impedance is observed at elevated frequencies with an increase in the temperature in microwires with easy axis anisotropy, regardless of the application of a magnetic field, while the change in the impedance in wires with circular anisotropy is more substantial in the presence of an external field. Moreover, the change in the impedance with an increase in the temperature from room temperature to T C can reach 200–300% in the frequency range of 0.5–0.9 GHz in a magnetic field of about 10 Oe. These results may be of interest for the development of miniature temperature sensors.