In this study, the influence of Cu addition on the morphology, elemental composition, structure, and magnetic properties of FeCoNi nanowires is investigated. FeCoNiCu nanowires were electrodeposited at various cathodic potentials in polycarbonate membranes with a pore diameter of 80 nm and a channel length of 6 μm. Electrochemical analysis indicates easier reduction in Cu-containing systems, yet associated with charge-transfer limitations. The samples exhibit homogeneous elemental distributions, except at the nanowire ends in samples deposited at lower potentials, where Cu-rich regions are observed. Increasing the cathodic potential leads to an increase in Ni content, accompanied by a simultaneous decrease in the content of the other elements. Cu incorporation results in grain refinement and increased defect density, but does not affect the crystallographic texture; the polycrystalline fcc phase retains preferred growth directions along [111] and [220] at lower and higher potentials, respectively. The Cu-containing samples exhibit significantly higher coercivity and squareness, along with lower saturation magnetization, compared to Cu-free samples. These changes are attributed to increased defect density and dilution of the magnetic matrix due to the addition of diamagnetic Cu, respectively. However, the evolution of these parameters within the Cu-containing series is governed primarily by dipolar interactions. The weak angular dependence of coercivity and Cu-dependent switching field distribution indicate a complex magnetization reversal process arising from competing interactions, with dipolar coupling playing a dominant role in FeCoNiCu nanowires. These systems predominantly exhibit a single-domain structure, with a slight vortex-like domain formation at the nanowire ends.

Progress in artificial intelligence requires the development of new types of devices, such as artificial neural networks. Magnetic nanowires made of permalloy can be ideal materials for their production. The presented experimental and theoretical investigations of the FeNi nanowire matrix are the first stage of studies aimed at designing artificial neural networks. FeNi nanowires with a diameter of 40 nm were synthesized in alumina membranes by electrodeposition at potentials ranging from -1.0 V to -1.3 V vs. Ag/AgCl. Increasing voltage caused changes in the chemical composition of nanowires with a gradual increase in Ni content. Nanowires obtained at lower potentials showed an anomalous character of co-deposition. The elemental content influenced the phase composition. At higher potentials, Ni-rich alloys with fcc structure dominated (with Ni hcp phase), at a potential of -1.05 V vs. Ag/AgCl the FeNi3 phase was identified with a lattice parameter a = 0.355 nm, while at the lowest potential FeNi phase appeared. The samples demonstrated a preferred growth direction that varied with the chemical composition. All samples showed magnetic anisotropy with an easy axis along the nanowires. Low coercivity and squareness with high saturation magnetization were observed for the samples exhibiting permalloy composition. Micromagnetic simulations of nanowires with permalloy composition revealed the magnetization reversal mechanism, which proceeded through the nucleation and propagation of vortex domain walls. Analysis of the demagnetizing field distribution confirmed strong magnetostatic interactions between nanowires in the array and the important role of the vortex domain walls in reducing the demagnetization field value.

FeCoNi nanowires (NWs) with different diameters (40-120 nm) and lengths (1.5-6 mu m) were electrodeposited in the polycarbonate membranes. Magnetic measurements confirmed anisotropy along the NW axis. Changes in the nanowire geometry resulted in increased coercivity and squareness for smaller diameters. Studies of the magnetization reversal mechanism showed a non-monotonic coercivity variation as a function of angle, pointing out the initial vortex domain wall propagation that transformed into a transverse or coherent rotation at angles closer to the hard direction. FORC analysis confirmed that the nanowire diameter is the main factor determining magnetostatic interaction between nanowires and indicated a non-interacting system in the case of a small diameter NW matrix. Magnetic imaging of the sample using Lorentz microscopy did not reveal domain walls, which together with FORC results, implies a single-domain structure of nanowires. Therefore, the obtained nanowires meet the criteria required for 3D racetrack memory applications.

This study focused on investigations of FeCo and FeNi nanowires prepared by template-assisted electrodeposition in polycarbonate membranes. Nanowires with a diameter of 100 nm and length of 6 µm were grown at different cathodic potentials and electrolyte compositions. Scanning electron microscopy images revealed densely packed arrays of continuous nanowires with smooth surfaces without visible porosity, regardless of the applied potential. Chemical analysis of nanowires pointed out weak sensitivity of chemical composition on the electrodeposition potential in the case of FeCo nanowires, in contrast to FeNi nanowires, where the increase of the cathodic potential resulted in higher Ni content. X-ray diffraction studies showed polycrystalline structure for all samples indicating B2 phase (Pm-3m) with isotropic growth of FeCo nanowires and FeNi3 phase with a preferential growth along [111] direction in the case of FeNi nanowires. The peak broadening suggests a fine crystalline structure for both FeCo and FeNi materials with average crystallite sizes below 20 nm. Magnetic studies indicated an easy axis of magnetization parallel to the nanowire axis for all FeCo nanowires and potential-dependent anisotropy for FeNi nanowires. The present studies thus suggested the feasibility of producing segmented nanowires based on FeNi alloys, while poor chemical sensitivity to the applied potential was observed for the FeCo system.

Yttrium iron garnet (YIG) is a ferrimagnetic material which found applications in magnetics, electronics and optics. For those applications, a monocrystalline structure is often required. Although effective methods to grow large YIG single crystals exist, fabricating such structures in a powder form can be challenging. Here, we show a simple procedure to obtain large quantities of monocrystalline Y _3 Fe _5 O _12 particles based on the precipitation synthesis. The average size of the single crystals was evaluated to be 149(6) nm. The morphology of the particles was analysed using SEM, TEM, DLS and nitrogen adsorption techniques. The material was tested for its structural properties with the use of XRD and electron diffraction methods. The chemical composition was investigated using FTIR, EDS and Raman spectroscopy. Finally, the thermal characteristics were analysed using TGA, while magnetic properties were tested with the use of the SQUID magnetometry. The obtained results are in good agreement with the theoretical values.

FeCoNi alloyed nanowires with diameters of 40 nm and 100 nm and a length of 6 mu m were electrodeposited in the polycarbonate membranes at constant cathodic potentials ranging from -1.0 to -1.8 V. The increase in cathodic potential caused an increase in Ni content with a simultaneous decrease in Fe and Co concentrations. The samples showed an fcc structure (with a small hcp fraction observed in one sample) with a preferred growth along [111] direction, which changed to a [220] texture at higher deposition potentials. With the increase in Ni content, a shortening of the lattice parameters and an increase in the crystallite size were observed. Various chemical compositions resulted in the modification of the magnetic properties of nanowires. The magnetization saturation value increased with increasing cathodic potential for both types of nanowires. However, coercivity and squareness rose for samples with a diameter of 40 nm and fell down for 100 nm diameter nanowires. This specific behavior was explained based on dipolar interactions, which can be neglected in 40 nm diameter nanowires, due to the low membrane porosity.

In the current work, we report on the synthesizing of a series of novel nanocomposite materials obtained by functionalizing the SBA-15 silica matrix with anchored iron phosphonate molecules and the following thermal treatment. The obtained results reveal the formation of a unique amorphic layer of Fe-based compounds on the surface of silica walls of SBA-15 channels as a result of the organic groups’ decomposition after moderate thermal treatment. Due to their unique structure, represented in an active Fe-containing amorphous coating spread over a large surface area, these materials are of great interest for their potential applications in fields such as catalysis, adsorption, and non-linear optics. The obtained materials remain amorphous, preserving the SBA-15 mesoporous structure up to temperatures of approximately 800 °C, after which the partial melting of the silica backbone is observed with the simultaneous formation of nanocrystals inside the newly-formed glassy mass. All obtained materials were characterized using such techniques as thermogravimetry, transmission and scanning electron microscopy combined with energy dispersive x-ray spectroscopy mapping, Raman spectroscopy, N 2 sorption analysis, x-ray diffraction, x-ray photoelectron spectroscopy, Mössbauer spectroscopy, and SQUID measurements.

The effect of annealing on the crystal structure and magnetic properties of Co95Ru5 alloy nanowires electrodeposited in anodic alumina membrane (AAM) has been investigated. Cobalt ruthenium alloy nanowires were annealed at temperatures ranging from 300 degrees C to 700 degrees C. Scanning electron microscopy showed that the nanowires have an average diameter (o) of 55 nm and an approximate length of 15 & mu;m. From X-ray diffraction studies, we found that the alloy nanowires crystalize in the hcp structure, with the c-axis tending to be perpendicular to the main axis of the wires. As shown in the hysteresis loop measurements, the cobalt ruthenium alloy nanowires exhibit magnetic anisotropy with an easy axis in the direction parallel to the wire axis. Changes in saturation magnetization, squareness (Mr/Ms) and coercivity were analyzed as a function of annealing temperature (Ta). The coercivity measured parallel to the wire axis was the highest before the annealing process and varied non-monotonically during the thermal treatment, reaching the highest value at the temperature of 600 degrees C. The maximum (Mr/Ms) ratio attained in this study was 0.62, but during heating, it decreased monotonically to 0.35. It was found that the magnetic properties of the nanowire arrays were strongly dependent on the thermal treatment.

Cylindrical ferromagnetic nanowires are of particular interest in nanomaterials science due to various manufacturing methods and a wide range of applications in nanotechnology, with special attention given to those with diameters less than the single domain limit. In the current study, the simulations of magnetic properties of isolated iron nanowires with a diameter of 5 nm and various aspect ratios, as well as two types of arrays of such nanowires (with hexagonal and square arrangement), were performed using atomistic spin model. In the case of a single nanowire, change of coercive field for different applied field directions with aspect ratio was discussed. It was shown that the evolution of the magnetization reversal mechanism from coherent rotation to domain wall propagation appears with increasing length of single nanowire. For the arrays of cylindrical nanostructures, it was revealed that different number of nearest neighbors for each nanostructure in square and hexagonal arrays have an influence on their magnetostatic interactions, which are the most significant for shortest interwire distances. The corresponding spin configurations during the remagnetization process showed the appearance of intermediate magnetization states (when a part of wires is magnetized parallel and part antiparallel to the field direction), connected with Barkhausen effect, which influence the observed hysteresis curves.

In this research, we focused on studies of the influence of Cu addition on the structure and magnetic properties of FeCu-alloyed and Fe/Cu-multilayered nanowires electrodeposited into polycarbonate membranes. It was observed that Cu addition prevents oxidation of overdeposited caps, compared to the surface of membranes filled with pure Fe, which immediately becomes covered with an oxide layer in the air. TEM studies revealed the polycrystalline structure of the multilayered NWs and confirmed that the wires were composed of alternating Fe and Cu layers. Magnetic studies performed using a SQUID magnetometer indicated a magnetic anisotropy with an easy axis along the nanowires. The increase in the Cu concentration in alloyed nanowires from 10% to 30%, resulted in an increase in both coercivity and squareness by about 30%. In the case of multilayered nanowires, significant reduction in squareness and non-monotonic changes in coercivity with the increase in Cu layer thickness were observed.

Materials based on Ni-Co-Fe alloys, due to their excellent magnetic properties, attract great attention in nanotechnology, especially as candidates for high-density magnetic recording media and other applications from spintronic to consumer electronics. In this study, Ni-Co-Fe nanocrystalline coatings were electrodeposited from citrate-sulfate baths with the Ni2+:Co2+:Fe2+ ion concentration ratios equal to 15:1:1, 15:2:1, and 15:4:1. The effect of the composition of the bath on the morphology, microstructure, chemical composition, microhardness, and magnetic properties of the coatings was examined. Scanning (SEM) and transmission (TEM) electron microscopy, X-ray diffractometry (XRD), and energy dispersive X-ray spectroscopy (EDS) were used to study surface morphology, microstructure, chemical, and phase composition. Isothermal cross-sections of the Ni-Co-Fe ternary equilibrium system for the temperature of 50 °C and 600 °C were generated using the FactSage package. Magnetic properties were analyzed by a superconducting quantum interference device magnetometer (SQUID). All the coatings were composed of a single phase being face-centered cubic (fcc) solid solution. They were characterized by a smooth surface with globular morphology and a nanocrystalline structure of grain diameter below 30 nm. It was determined that Ni-Co-Fe coatings exhibit high hardness above 4.2 GPa. The measurements of hysteresis loops showed a significant value of magnetization saturation and small coercivity. The microstructure and properties of the obtained nanocrystalline coatings are interesting in terms of their future use in micromechanical devices (MEMS).

We studied the morphology, structure, and magnetic properties of Fe nanowires that were electrodeposited as a function of the electrolyte temperature. The nucleation mechanism followed instantaneous growth. At low temperatures, we observed an increase of the total charge reduced into the templates, thus suggesting a significant increase in the degree of pore filling. Scanning electron microscopy images revealed smooth nanowires without any characteristic features that would differentiate their morphology as a function of the electrolyte temperature. X-ray photoelectron spectroscopy studies indicated the presence of a polycarbonate coating that covered the nanowires and protected them against oxidation. The X-ray diffraction measurements showed peaks coming from the polycrystalline Fe bcc structure without any traces of the oxide phases. The crystallite size decreased with an increasing electrolyte temperature. The transmission electron microscopy measurements proved the fine-crystalline structure and revealed elongated crystallite shapes with a columnar arrangement along the nanowire. Mössbauer studies indicated a deviation in the magnetization vector from the normal direction, which agrees with the SQUID measurements. An increase in the electrolyte temperature caused a rise in the out of the membrane plane coercivity. The studies showed the oxidation resistance of the Fe nanowires deposited at elevated electrolyte temperatures.

In this study, nc-TiO 2 /Ni–Fe composite coatings, and Ni–Fe alloys as equivalents to their matrices, were obtained from citrate-sulphate baths in the electrodeposition process using direct current and pulse current conditions. The aim of the study was to examine the effects of TiO 2 nanoparticles and current conditions on the chemical composition, surface morphology, microstructure, microhardness and magnetic properties of the electrodeposited coatings. The results show that the concentration of Fe in Ni–Fe alloys is related to the current conditions and is higher in the case of pulse current electrodeposition, while such a relationship was not observed for composites. The reinforcement of composites with TiO 2 nanoparticles results in a more developed surface topography with many nodule-like structures. Composites and equivalent alloys deposited in pulse current are characterized by a finer grain size than those obtained in direct current. TiO 2 nanoparticles and their agglomerates, several tens of nanometres in size, are distributed randomly in the Ni–Fe matrix of composites deposited in both current conditions used. Incorporation of a high volume fraction of nc-TiO 2 , exceeding over a dozen percent, and decreasing the nanograin size in nc-TiO 2 /Ni–Fe composites electrodeposited under pulse current conditions, allow a higher hardness to be achieved than in their counterparts obtained using direct current. Magnetic measurements showed ferromagnetic ordering of pristine TiO 2 nanoparticles, however, the introduction of TiO 2 nanoparticles into the Ni–Fe matrix resulted in a decrease in coercivity and saturation magnetization. Graphic Abstract

CoRu nanowire arrays (NWs) were fabricated by DC electrodeposition into hexagonally ordered alumina pores. A homogeneous magnetic field, parallel to the membrane plane, was applied during the deposition to control the wire growth. The largest magnetic field (of 0.6 T) strongly affected the morphology of the CoRu alloy nanowires, which became continuous with smooth lateral surfaces. The increasing magnetic field caused a rise of nanowire lengths and Co concentration in NWs. X-ray diffraction studies showed a hexagonal structure of nanowires. It was found that cobalt ruthenium alloy nanowires exhibit magnetic anisotropy with easy axis in a direction parallel to the wire axis. The changes in the microstructure led to an increase of anisotropy energy and drop of the coercivity.

In this study, we analysed Fe/Cr multilayers that had been modified by Bi, In, and Pb surfactants. Their structure, morphology and interface roughness were investigated using low-energy electron diffraction, Auger electron spectroscopy (AES), X-ray reflectivity and conversion electron Mossbauer spectroscopy (CEMS). The magnetic and magnetotransport properties of the multilayers were studied by measuring the Kerr effect and four-point magnetoresistance, respectively. We observed that the Bi surfactant caused a slight interface smoothening while the introduction of In and Pb surfactants had a negative influence on the epitaxial growth of Fe and Cr, which were associated with an increase of interface roughness. These changes did not destroy the layer continuity, which was confirmed by AES measurements. The magnetic measurements revealed an antiferromagnetic coupling of the Fe layers for the as-deposited sample as well as for the Bi and Pb-modified multilayers and its partial reduction for the In-modified sample. We observed that the increase of interface roughness that had originated from atom intermixing resulted in a reduction of the giant magnetoresistance. In these investigations in which CEMS studies were used, we were able to distinguish between the interface roughness that was caused by atom intermixing and interface corrugation. (C) 2020 Elsevier B.V. All rights reserved.

The paper is devoted to the study of microstructural and magnetic properties of the Fe-based amorphous ribbons after interference pulsed laser heating. The ternary amorphous alloy FeSiB, as well as the multi-component alloys FeCuSiB and FeCuNbSiB, was subjected to laser pulses to induce crystallization in many microislands simultaneously. Structure and properties changes occurred in laser-heated dots. Detailed TEM analysis from a single dot shows the presence of FeSi(α) nanocrystals in the amorphous matrix. The FeSiB alloy is characterized after conventional crystallization by a dendritic structure; however, the alloys with copper as well copper and niobium additions are characterized by the formation of equiaxed crystals in the amorphous matrix. Amorphous alloys before and after the laser heating are soft magnetic; however, conventional crystallization leads to a deterioration of the soft magnetic properties of the material.

Preliminary studies on the sediments collected from water meters of Krakow water supply system were performed in the cooperation with the Municipal Water Supply and Sewage.Creation and deposition of sediments on the measuring devices installed in the water supply system is a serious technological and economical problem for water companies, defectively operating for this reason water meters must be replaced.It is evident that knowledge of the chemical and phase composition of sediments is an important step towards resolving the problem of impurities in water supply systems.Four different samples of sediments, coming from water meters, were investigated using the proton-induced X-ray emission, the X-ray diffraction, the Fourier transform infrared and Raman spectroscopy.The X-ray methods revealed presence of amorphous and fine-crystalline phases as well as high content of iron-based compounds.As a crystalline phase, the most frequently appeared: goethite, lepidocrocite, iron oxides (hematite, maghemite, magnetite), calcium carbonate, and quartz.In one of the samples, the nanocrystalline phase was found and identified as hydrous iron oxyhydroxide ferrihydrite.Vibrational spectroscopy methods confirmed the composition of crystalline phases as well as enabled to estimate the abundance of amorphous phase in samples.

The influence of Q-switched pulsed Nd:YAG laser interference heating parameters on microstructure and magnetic properties of amorphous Fe80Si11B9 alloy was examined. Different laser pulse energy and a variable number of consecutive pulses were used. Results were compared with amorphous and conventionally annealed ribbons. Microstructural analysis, using light, scanning and transmission electron microscopy, was complemented by results of AFM and Mössbauer spectroscopy, as well as measurements of magnetic properties (vibrating sample magnetometer). Periodically distributed crystallized micro-areas, ~10 μm in diameter, in the amorphous matrix were produced by the laser treatment. Laser heating produced nanograin crystalline structure in the amorphous matrix. While after the conventional annealing – dendritic structure was observed. The magnetic hysteresis loop measurement showed that laser heating had no significant influence on soft magnetic properties. Magnetization measurements showed that the as-cast ribbon and laser light irradiated samples are magnetically soft materials. The results lead to the conclusion that the dots corresponding to the laser modified regions exhibit a perpendicular magnetic anisotropy. Magnetic force microscopy showed expanded magnetic structure in laser heated microareas, while the amorphous matrix did not give any magnetic signal.

We studied changes of morphology and magnetic properties of Co/Cu multilayered nanowires, electrodeposited in polycarbonate membranes, as a function of Cu layer thickness. The morphology and structure of wire assemblies with an average diameter of 200 nm and length of 10 mu m, investigated by X-ray diffraction and scanning electron microscopy techniques, revealed polycrystalline structure of Cu and Co layers with smooth lateral surface of nanowires. Overdeposited nanowires created caps which showed flower-like dendrites with shape changing as a function of Cu thickness and electrodeposition parameters. Chemical composition of Co and Cu nanowires analysed by energy dispersive spectroscopy and proton induced X-ray emission showed Cu nanowires free from Co atoms while in Co nanowires, Cu contamination with concentration below 10% was observed. The oxidation traces observed in single-component Cu nanowires did not appear in multilayered nanowires. Magnetic measurements indicated easy axis of magnetization in membrane plane for nanowires with Cu thickness smaller than 20 nm, whereas for larger Cu thicknesses isotropic orientation of magnetization was observed. The presence of Cu atoms in single-component Co nanowires resulted in the appearance of magnetic anisotropy with easy axis along nanowire axis and the increase of coercivity value.

Paper describes the results of Fe80Si11B9 amorphous ribbon investigation after pulsed laser interference heating and conventional annealing. As a result of interference heating periodically placed laser heated microareas were obtained. Structure characterisation by scanning and transmission electron microscopy showed in case of laser heated samples presence of crystalline nanostructure in amorphous matrix. Microscopy observations showed significant difference in material structure after laser heating - nanograin structure, and material after annealing - dendritic structure. Magnetic force microscopy investigation showed expanded magnetic structure in laser heated microareas, while amorphous matrix did not give magnetic signal. Change of magnetic properties was examined by magnetic hysteresis loop measurement, which showed that the laser heating did not have a significant influence on soft magnetic properties.