NiFe nanocrystalline films were formed onto Au film via pulsed electrolyte deposition with variable time of relaxation between the sequential pulses. Analysis of anomalous non-liner changes in the NiFe film structure showed the implementation of three mechanisms, resulting in "layer-by-layer", "layer-plus-island", or "island" growth. The change of the interpulse relaxation time provides the possibility to realize all three different mechanisms. The grown NiFe films may have different morphology. The ultrathin NiFe films have nanosized grains and exhibit high uniformity of structure, the films may be also combined of less that 10 nm nanoscale grains and their conglomerates, typically, about 50 nm in size, and, additionally, the film structure, consisting of isolated magnetic islands can be realized. The phenomenological explanation of the different mechanisms was obtained using atomic-force-microscopy (AFM) approach. It has been demonstrated that the growth mechanism can be controlled by nanocrystallites conglomeration, which is accelerated with increasing the relaxation time. The origin of the conglomeration process is mainly associated with high surface energy of nanosized grains.

A pure ferrite and epoxy samples as well as the epoxy/ferrite composites with different 20 wt.%, 30 wt.%, 40 wt.%, and 50 wt.% weight ferrite contents have been prepared by the chemical co-precipitation method. AC-conductivity and dielectric properties such as the dielectric constant and dielectric loss of the prepared samples have been studied. The obtained results showed that the samples had a semiconductor behavior. The dielectric constant of the composites has been calculated theoretically using several models. For the composite sample that contains 20 wt.% of ferrites, these models give satisfactory compliance, while for the composite samples with a higher percentage of nanofillers, more than 30 wt.% theoretical results do not coincide with experimental data. The investigated polymer has very low conductivity, so this type of polymer can be useful for high-frequency applications, which can reduce the losses caused by eddy current. Thus, the prepared samples are promising materials for practical use as elements of microwave devices.Nanomaterials 2020, 10, 492 2 of 16 Nanotechnology can be an excellent tool in the study, preparation, research, and use of new perspective materials, as well as in solving the problem of particles sizes in the range of 1-100 nm, where unusual phenomena allow new applications [2][3][4]. Tiny nanoparticles with diameters of some nanometers usually look like molecules. Therefore, the atomic and electronic structures of such small nanoparticles possess different features, certainly not the same as those of the bulk materials. The size-dependent abilities of nanoparticles include electronic, magnetic, optical, and chemical substance characteristics. Nanoparticles can be crystalline or amorphous [5].Nanosized ferrites could be prepared by many methods, including mechanized milling, ultrasonic cavitation method, radio rate of recurrence plasma, hydrothermal technique, reverse micelle method, sol-gel technique, citrate precursor, and co-precipitation technique [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. It is advisable to possess a synthesis method that allows for governor on the nanoparticle dimension and produces nanoparticles having a significant size distribution [2]. The chemical substance co-precipitation method is the most excellent ideal for the formation of nanoparticles due to its ease and much-improved handle over the crystallite dimension and other qualities of the components [22]. Also, lately, magnetic composites comprising magnetic materials alongside polymers comprise a new era of multifunctional components that mix the properties from the constituents; these components are known as magneto-polymeric components [23].The characteristics of ferrites are highly susceptible to methodical handling, sintering conditions, and impurity. Nickel-zinc ferrite is one of the first widely used ferrite produced for an open range of applications that recognizes to high saturation magnetization, high resistance, high Curie temperature, high chemical stability, low coerciv...

Nanostructured NiFe film was obtained on silicon with a thin gold sublayer via pulsed electrodeposition and annealed at a temperature from 100 to 400 °C in order to study the effect of heat treatment on the surface microstructure and mechanical properties. High-resolution atomic force microscopy made it possible to trace stepwise evolving microstructure under the influence of heat treatment. It was found that NiFe film grains undergo coalescence twice—at ~100 and ~300 °C—in the process of a gradual increase in grain size. The mechanical properties of the Au/NiFe nanostructured system have been investigated by nanoindentation at two various indentation depths, 10 and 50 nm. The results showed the opposite effect of heat treatment on the mechanical properties in the near-surface layer and in the material volume. Surface homogenization in combination with oxidation activation leads to abnormal strengthening and hardening-up of the near-surface layer. At the same time, a nonlinear decrease in hardness and Young’s modulus with increasing temperature of heat treatment characterizes the internal volume of nanostructured NiFe. An explanation of this phenomenon was found in the complex effect of changing the ratio of grain volume/grain boundaries and increasing the concentration of thermally activated diffuse gold atoms from the sublayer to the NiFe film.

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The paper describes preparation features of functional composites based on ferrites, such as “Ba(Fe1−xGax)12O19/epoxy,” and the results of studying their systems; namely, the correlation between structure, magnetic properties and electromagnetic absorption characteristics. We demonstrated the strong mutual influence of the chemical compositions of magnetic fillers (Ba(Fe1−xGax)12O19 0.01 < x < 0.1 solid solutions), and the main magnetic (coercivity, magnetization, anisotropy field and the first anisotropy constant) and microwave (resonant frequency and amplitude) characteristics of functional composites with 30 wt.% of hexaferrite. The paper presents a correlation between the chemical compositions of composites and amplitude–frequency characteristics. Increase of Ga-content from x = 0 to 0.1 in Ba(Fe1−xGax)12O19/epoxy composites leads to increase of the resonant frequency from 51 to 54 GHz and absorption amplitude from −1.5 to −10.5 dB/mm. The ability to control the electromagnetic properties in these types of composites opens great prospects for their practical applications due to high absorption efficiency, and lower cost in comparison with pure ceramics oxides.