A magnetite -diatomite nanocomposite (MDM) adsorbent was synthesized using the coprecipitation method, wherein a magnetite precursor was intercalated into diatomite clay minerals sourced from the Ethiopian Rift Valley. Fourier -transform infrared spectroscopy (FTIR), Xray diffraction (XRD), scanning electron microscopy energy dispersive x-ray (SEM-EDX), Brunauer-Emmett-Teller (BET) and magnetometry measurements were used to look into the structure and magnetic properties of the adsorbent. Batch experiments were conducted to study the remarkable Cd (II) adsorption capacity of MDM and the ease of separating the used adsorbent with a bar magnet. The most important adsorption parameters, namely, initial pH, adsorbent dose (g), initial (Cd (II) concentration (mg), and contact time (min), were optimized using BoxBehnken design (BBD). The MDM has shown exceptional Cd (II) removal under optimum conditions, with a maximum adsorption capacity of 31.4 mg/g from aqueous solution. Based on the results of isotherm and kinetic studies, the Temkin and pseudo -second -order models were found to provide the most accurate fit for adsorption equilibrium when compared to the alternative models. The thermodynamic studies, under standard conditions revealed that, Cd (II) uptake is exothermic and spontaneous. The finding of this study confirms that the MDM adsorbent is easily reusable, extractable from the solution using an external magnet, and capable of recovering around 80 % of Cd (II) when HNO 3 is used as a desorbing agent. The study demonstrates a costeffective and environmentally friendly approach to remediate Cd (II) pollution in wastewater. Furthermore, the superior Cd (II) adsorption capacity, combined with the ease of separating using a bar magnet and high reusability, highlights the potential of this novel adsorbent as a sustainable and efficient solution for addressing Cd (II) contamination in various wastewater treatment applications.Thereby contributing significantly to advancements in the field of heavy metal removal from aqueous solutions.

A number of solid solutions based on BaFe12-xTixO19 M-type barium hexaferrite doped with titanium cations up to x = 2.00 were obtained using conventional ceramic technology. The phase composition, crystal structure and unit cell parameters were refined by the Rietveld method using powder X-ray diffraction data up to T = 900 K. It was found that all the compositions have a magnetoplumbite structure satisfactorily described by P6(3)/mmc space group (No. 194). With increasing temperature and doping concentration, the unit cell parameters increase almost monotonically. The minimum volume of V similar to 696.72 angstrom(3) was determined for the composition with x = 1.00 at T = 100 K, while the maximum value of V similar to 714.00 angstrom(3) is observed for the composition with x = 2.00 at T = 900 K. The mechanism of occupation nonequivalent crystallographic positions with titanium cations is established. The spin-glass component of the magnetic phase state is fixed. The T-dif temperature of the difference between the ZFC-FC curves decreases with an increase in the concentration of titanium cations and the magnetic field from similar to 237.2 K to similar to 44.5 K, while the T-inf inflection temperature of the ZFC curve increases from similar to 21.0 K to similar to 23.8 K. With an increase in the doping concentration, both the D-av average and D-max maximum clusters grow up to similar to 100 nm. As the magnetic field increases above the critical value, the spin-glass component disappears. For compositions with x > 1.00, the magnetization is not saturated in fields up to 6 T. Along with the formation of the spin-glass component, doping with titanium cations for barium hexaferrite lowers the T-C Curie temperature down to T similar to 600 K. The M-s spontaneous and M-r remanent magnetizations, as well as the B-c coercivity, decrease with increasing doping concentration almost monotonically, while the latter has an inflection point at x = 1.00. The minimum values of spontaneous and remanent magnetization, as well as coercivity, are observed for the composition with x = 2.00 and amount to M-s similar to 17.7 emu/g, M-r similar to 1.9 emu/g, and B-c similar to 3.9 x 10(-3) T, respectively. An interpretation of the magnetic state of the doped BaFe12-xTixO19 barium hexaferrite is given taking into account the mechanism of occupation nonequivalent crystallographic positions with titanium cations. (C) 2020 Elsevier B.V. All rights reserved.

The dielectric and magnetic properties of ceramics based on barium titanate and solid solutions of barium strontium titanate doped with iron and gadolinium ions at concentrations below 5 mol.% have been investigated. It is shown that these ceramics exhibit paramagnetic behavior in a wide temperature range from 10 to 300 K and their dielectric and magnetic properties are strongly influenced by the doping.

We present results of experimental studies of high-field magnetoresistance of Co–SiO 2 , Co–LiNbO 3 , CoNbTa–SiO 2 nanocomposites with metal volume fraction close to the percolation threshold. The nanocomposite films were deposited onto a glass-ceramic substrate by ion-beam sputtering at the growth temperature not exceeding 80°C. Magnetization was measured using a superconducting quantum interference device (SQUID) magnetometer in the temperature range of 4.2–300 K. Out-of-plane magnetoresistance was measured in a pulsed magnetic field up to 20 T in the temperature range of 4.2–300 K with the pulse duration of 11–12 ms. In addition to negative magnetoresistance, a linear positive contribution to magnetoresistance was observed in high magnetic fields for nanocomposites with the composition close to the percolation threshold. This effect was explained by the influence of the Zeeman effect on the tunnel barrier height. It is shown that the unconventional anisotropy of magnetoresistance of Co–LiNbO 3 is associated with the peculiarities of its microstructure.

A layer-by-layer sputtering method was used to fabricate nanostructures (ZnO/C)(25) composed of zinc oxide and carbon alternating layers, with a total multilayer thickness of 146 nm and 153 nm. At low temperatures, the multilayers show signatures of local ferromagnetic order: magnetic hysteresis, weak magnetization and the characteristic shape of the thermomagnetic curve. In-plane and out-of-plane magnetoresistance (MR) was measured in a pulsed magnetic field up to 20 T in the temperature range of 15-300 K. At T <= 20 K, MR changed its sign from negative in low magnetic fields to positive in moderate fields, and then back to negative in high magnetic fields. At T >= 80 K, MR was negative in the full range of magnetic fields studied. The unusual MR behavior can be associated with the influence of the Zeeman effect on the Fermi level position in the case of 2D variable hopping conduction along the interfaces, scattering on magnetic heterogeneities and the effect of magnetic blockade.

Abstract A number of solid solutions based on BaFe12-xTixO19 M-type barium hexaferrite doped with titanium cations up to x = 2.00 were obtained using conventional ceramic technology. The phase composition, crystal structure and unit cell parameters were refined by the Rietveld method using powder X-ray diffraction data up to T = 900 K. It was found that all the compositions have a magnetoplumbite structure satisfactorily described by P63/mmc space group (No. 194). With increasing temperature and doping concentration, the unit cell parameters increase almost monotonically. The minimum volume of V ~ 696.72 A3 was determined for the composition with x = 1.00 at T= 100 K, while the maximum value of V ~ 714.00 A3 is observed for the composition with x = 2.00 at T= 900 K. The mechanism of occupation nonequivalent crystallographic positions with titanium cations is established. The spin-glass component of the magnetic phase state is fixed. The Tdif temperature of the difference between the ZFC-FC curves decreases with an increase in the concentration of titanium cations and the magnetic field from ~ 237.2 K to ~ 44.5 K, while the Tinf inflection temperature of the ZFC curve increases from ~ 21.0 K to ~ 23.8 K. With an increase in the doping concentration, both the Dav average and Dmax maximum clusters grow up to ~ 100 nm. As the magnetic field increases above the critical value, the spin-glass component disappears. For compositions with x \u003e 1.00, the magnetization is not saturated in fields up to 6 T. Along with the formation of the spin-glass component, doping with titanium cations for barium hexaferrite lowers the TC Curie temperature down to T ~ 600 K. The Ms spontaneous and Mr remanent magnetizations, as well as the Bc coercivity, decrease with increasing doping concentration almost monotonically, while the latter has an inflection point at x = 1.00. The minimum values of spontaneous and remanent magnetization, as well as coercivity, are observed for the composition with x = 2.00 and amount to Ms ~ 17.7 emu/g, Mr ~ 1.9 emu/g, and Bc ~ 3.9*10-3 T, respectively. An interpretation of the magnetic state of the doped BaFe12-xTixO19 barium hexaferrite is given taking into account the mechanism of occupation nonequivalent crystallographic positions with titanium cations.

This review is devoted to an analysis of the electrical resistance, the magnetoresistance, and the anomalous Hall effect in magnetic “ferromagnetic metal–insulator” nanocomposites at a metal content near the percolation threshold and the memristive properties of the capacitor structures based on these nanocomposites. A high content (up to 10 22 cm –3 ) of dispersed atoms in intergranular gaps leads to a logarithmic temperature dependence of the electrical resistance, a positive contribution to the magnetoresistance, the appearance of tunneling anomalous Hall effect, and a multifilament mechanism of resistive switching (which causes an adaptive character of memristor nanocomposites with dispersed atoms).

ZnO- and C-based heterostructures were fabricated by the layer-by-layer deposition technique using the ion-beam sputtering process. Structure, electrical and magnetic properties of fabricated heterostructures are discussed. The two-phase (ZnO and C) films are evolved into a multilayer structure, consisting of amorphous carbon and crystalline ZnO layers when the bilayer thickness increases. When carbon is added to ZnO, its electrical resistivity reduces. The conduction mechanism changes from the variable-range hopping in a narrow energy band to the nearest neighbors hopping in ZnO-C films with a thickness of h < 150 nm. The temperature dependence of conductivity changes from the Arrhenius-like to logarithmic law, indicating that the strong charge localization turns into a weak one when the film thickness is about 150 nm. The negative magnetoresistance of up to 1%was detected at 77 K. The film ferromagnetism at the temperature of 10 K was not found.

Magnetic Heusler alloys X 2 BZ (where X and B are 3 d elements and Z belongs to the sp group) exhibit diverse magnetic and structural properties, which are important for designing multifunctional smart materials. Electronic band structure calculations demonstrate that, if the valence of element B is higher than that of element X, such alloys (so-called inverse Heusler alloys) can behave differently as compared to traditional Heusler alloys. The growth, the crystal structure, and the magnetic properties of thin films of a new Mn 2 FeSi Heusler alloy deposited under various conditions (including various substrates and annealing temperatures) are studied in this work. A temperature-induced structural transition into a low-magnetization martensitic phase and a thermally stable austenitic phase are detected. A magnetic field of 500 Oe applied to some samples at a temperature of 380 K is found to cause a large exchange bias (about 1 kOe) at T = 10 K. The influence of the type of substrate and the annealing temperature on the magnetic and structural properties of the films is discussed.

The magnetic and magneto-optical properties of (Со40Fe40B20)x(SiO2)100x nanocomposites with x = 30–72 at % are studied. The results reveal the inhomogeneous structure of the nanocomposites, which exhibit both large granules and small particles that make independent contributions of different nature to the magnetic properties of the materials. Specific features of the coercive force near the percolation threshold indicate superferromagnetic ordering in the composites at low temperatures.

We explore whether it is possible to enhance the magnetocaloric effect (MCE) in layered systems, where a refrigerant (weak ferromagnet) is sandwiched by strong ferromagnets, by magnetizing the spacer with the effective field that results from its exchange coupling to the surroundings. Temperature variation around the Curie point of the spacer (TC) leads to a change in interlayer coupling between strongly ferromagnetic surroundings, which manifests in increasing the switching field and/or the coercivity of the softer from the surroundings. In order to verify the hypothesis above, we have prepared layered stacks of Py(10 nm)/Gd(x nm)/Co90Fe10(7 nm)/Ir20Mn80(15 nm) (Py = Ni80Fe20 is permalloy) with the Gd spacer in thickness varied from x = 20 nm to x = 5 nm. In this system we clarified how the magnetization switching in the Py layer was sensitive to temperature varied in the range between 300 K and 50 K. We have found that strong enough exchange between the Py and Gd layers emerges only at low temperatures (T < 100 K) which are far from TC. This feature provides an understanding of the observed magnetocaloric properties of the system under study.

Titanium substituted BaFe12-xTixO19 (x <= 1) barium hexaferrites have been synthesized using the solid phase method. The phase purity and the crystal structure of the obtained solid solutions have been studied by X-ray diffraction. It was found that the unit cell parameters change a non-monotonically. The a parameter has a maximum of 5.896 angstrom at x = 0.25 and then it decreases almost linearly down to 5.886 angstrom at x = 1. The c parameter almost linearly increases from 23.216 angstrom up to 23.282 angstrom with x increasing. It has been discovered that titanium cations are located in the following positions: 4fIV tetrahedral and octahedral 4f(VI) and 12k ones. Results of the Mossbauer and Raman spectrometry confirm the established substitution mechanism. The homogeneous ferrimagnetic ordering is detected by magnetic measurements down to similar to 35 K. Below this temperature the noncollinear magnetic structure is formed as a result of Fe2+ cations change in the spin state from high to low configuration. Magnetization for all the samples is saturated at room temperature in fields of similar to 1 T. The saturation magnetization decreases from similar to 70.6 emu/g for x = 0.25 to similar to 56.7 emu/g for x = 1. The real part of the dielectric constant has value of similar to 0.2 for all the samples and gradually decreases at heating from room temperature up to similar to 500 K, after which it begins to increase sharply. The dielectric loss tangent has a maximum in the region of similar to 500 K and reaches a value of similar to 0.25 at a frequency of 10(4) Hz. With increasing the substitution level, the dielectric constant and the dielectric loss of all the samples increase.

Magnetostructural transition was observed in Ni-Mn-In-Cr Heusler alloy with help of Magnetic Force Microscopy (MFM). The crystal structure of a sample and characteristic temperatures of the phase transition were controlled by roentgenostructural phase analysis and magnetometry, respectively. It appeared prominently important to prepare the surface of the sample until the nanometer level of surface roughness. Magnetic study performed with scanning probe microscope revealed existence of magnetic domains, which were spread across the surface evenly. Further studies revealed that intensity of magnetic signal decreases as fading out of the contrast of the MFM images. It was found that location of domains shifted after the heating/cooling cycle above Curie temperature for the studied alloy. Location of new domain walls appeared correlating with surface scrapings and defects, whilst it became independent from those after heating until just 70°C. The mechanism behind the observed transition is proposed.