Papers by Keyword: Magnetic Properties

Abstract: The investigation addresses the structure of a Co-based alloy and its magnetic properties. The major applications of these materials are in the development of different sensors, which require materials with high permeability. The structure evolution processes need to be explored to clarify the main parameters determining the time-temperature stability. In the present paper, a nanocrystallization behavior of Co₆₇Fe₄Cr₇Si₈B₁₄ amorphous alloy manufactured in the form of a ribbon was studied using X-ray diffraction and sample vibromagnetometry methods. The structure evolution induced by the 30min isothermal annealing at a temperature range of 450 - 700 °C was studied by the X-ray diffraction method, and crystallization with hcp-Co, fcc-Co, and Co₂B nanophases was revealed depending on the annealing temperature. According to thermomagnetic measurements, the nanocrystallization process corresponds to a three-stage crystallization model. The crystallization onset temperature of the amorphous alloy was observed to be to equal540 °C. The Curie point and saturation magnetization of the as-quenched alloy were defined as 305 °C and 76 Am²/kg, respectively.

Abstract: In this work, we successfully synthesized a magnetic nanocomposite material (Fe₃O₄@ZnO/TiO₂) with an iron oxide core and a zinc oxide/TiO₂ shell (Fe₃O₄@ZnO/TiO₂). The purpose of this study was to characterize the Crystal Structure, Morphology, and Magnetic Properties of Magnetic Nanocomposites with Iron Oxide Core and Zinc Oxide/Titanium Oxide Shell. The crystal structure of the sample was analyzed using X-ray diffraction, which identified three distinct phases: Fe₃O₄, ZnO, and TiO₂. These phases respectively exhibited cubic spinel, hexagonal wurtzite, and tetragonal crystal structures. Transmission Electron Microscopy (TEM) characterization confirmed that the sample had a magnetic core–shell structure, with superparamagnetic properties and excellent stability owing to its spinel cubic structure, which is the primary magnetic material structure of the sample. The successful formation of the Fe₃O₄@ZnO/TiO₂ nanocomposite represents a significant advancement in the synthesis of materials. This could serve as a basis for further investigations into magnetic materials, opening up possibilities for their application across diverse fields.

Abstract: The aim of this research is to identify the crystal structure, surface area, and magnetic properties of The Mn_0.25Fe_2.75O₄-rGO (reduced Graphene Oxide) nanocomposites (NCs). The synthesis of Mn_0.25Fe_2.75O₄-rGO nanocomposites used the co-precipitation method. The rGO was obtained from the chemical reduction of GO by hydrazine hydrate as the reduction agent. The ratio between Mn_0.25Fe_2.75O₄ nanoparticles and rGO was 1:1 that ultrasonicated at 200 Hz for an hour. The IR spectra of NCs from the FTIR instrument showed that the absorption band around 580 cm^-1 and 1622 cm^-1 corresponds to the stretching mode of Fe-O and C=C respectively. According to X-Ray Diffraction (XRD) pattern analysis, peak of Mn_0.25Fe_2.75O₄ was detected on 2θ at 30.1°, 35.5°, 53.5°, 57.1°, 62.7° and the peak of rGO phases was amorphous that detected on 2θ between 17º and 30º. The XRD pattern analysis and FTIR spectra have proved the completion of NC’s synthesis. The crystallite size was between 10.3 nm by Scherer's formula. The Specific Surface Area showed that the surface area of the nanocomposites was 100.61 m²/g and the Molecular cross-sectional area was 0.162 nm² by BET Theory. The Magnetic properties show that the NCs were Superparamagnetic material that has a saturation magnetization of 9.34 emu/g. The material has many potentials to be explored by the researcher around the world.

Abstract: Nanoscale mixed ferrites with a spinel structure are highly versatile materials widely employed across diverse fields, including engineering, biomedicine, and ecology. This study explores the influence of pH on the structure, morphology, electrophysical, and mechanical properties of CuFe₂O₄ spinel, synthesized using the sol-gel self-combustion method. The investigation reveals that the pH level significantly impacts the structure formation, even at the gel formation stage, thereby shaping the subsequent structure and properties of the synthesized ferrite. X-ray diffraction (XRD) analysis demonstrates that the dominant phase (>90%) corresponds to the cubic spinel phase with the chemical formula CuFe₂O₄, belonging to the Fd3m space group. Notably, the pH of the reaction medium exerts a profound influence on the distribution of iron and copper ions within the octahedral and tetrahedral sublattices of the spinel structure. This variation in cationic distribution manifests in notable changes in the synthesized ferrite's magnetic, mechanical, and degradation properties. Furthermore, the study delves into the impact of the synthesized CuFe₂O₄ spinel as a photocatalyst for degrading organic dyes through the photo-Fenton process. It demonstrates that degradation efficiency is closely related to the ferrite's band gap width and particle size. This study aimed to determine how the pH of the reaction medium impacts the structure, morphology, optical, mechanical, and magnetic characteristics of the nanosized ferrites being synthesized. Furthermore, the synthesized materials were evaluated for their photocatalytic abilities in degrading organic dyes in water. The ferrite powders showcased remarkable dye degradation capabilities via the photo-Fenton process. Degradation efficiency largely hinged on the band gap width and the size of the particles. The most notable outcome was achieved with sample P1, which had particle sizes averaging 12.14 nm. By unraveling the complex relationship between pH, structure, and properties, this research enhances our understanding of the design and optimization of nanoscale mixed ferrites.

Abstract: We developed a new 1-12-type magnetic material of (Sm,Zr)(Fe,Co)_11.3Ti_0.7 composition that exhibits magnetic properties superior to Nd-Fe-B magnets. In the new 1-12 magnets, the amorphous alloys of above composition show a change in XRD pattern with increasing of heat treatment temperature from a single 1-9 phase to 1-9 and 1-12 mixed phases, and finally to a single 1-12 phase, and the magnetic properties also change accordingly. In this study, we established a method for calculating the formation ratio of the 1-12 phase in the samples from the peak shift of the diffraction peaks of the 1-12 phase base on the peaks of the 1-9 phase. As a result, it was revealed that the formation ratio of the 1-12 phase in the samples, whose XRD pattern of 1-9 and 1-12 mixed phase, has a wide distribution, ranging from about 20 to 80 %. With the development of the phase transition from 1-9 to 1-12 phases, the lattice constant a of 1-12 phase increases, and inversely the lattice constant c of 1-12 phase decreases. Furthermore, it was revealed that the formation ratio of the 1-12 phase was about 83 % for the sample indicating the maximum coercivity H_c = 5.46 kOe.

Abstract: Structure, morphology, and magnetic properties of perovskite La_0.7Sr_0.2Ba_0.1Mn_1-xCr_xO₃ (x = 0; 0.03; 0.05; 0.07 and 0.1) synthesized via sol-gel method have been studied. X-ray diffraction studies confirm the Rhombohedral structure with R-3c space groups for all samples. The magnetization measurements clearly show that magnetization decreases with increasing Cr substitution concentration. The partial substitution of Cr³⁺ in the Mn site weakens the ferromagnetic double exchange interaction of the Mn³⁺–O–Mn⁴⁺ bond. It is caused by the emergence of the Cr³⁺–O–Cr³⁺ antiferromagnetic interaction. As known, the structural parameters affect the magnetic properties of perovskite manganese materials in the double exchange interaction. As the Cr³⁺ concentration increases, the average Mn-O bond length also increases, and the average Mn-O-Mn bond angle decreases, which dramatically weakens the Mn³⁺–O–Mn⁴⁺ double exchange interaction.

Abstract: The effects of Ga substitution at Mn site on electroresistance behaviour of La_0.85Ag_0.15MnO₃ compound prepared by solid-state reaction method were investigated. X-ray diffraction (XRD) measurement were recorded at room temperature and refined by employing Rietveld techniques. Ferromagnetic to paramagnetic transitions behaviour have been observed from ac susceptibility results. Resistivity-temperature curve with different applied currents of 1 mA and 5 mA showed metal-insulator, MI transition temperature, T_MI decreased with increased of the applied currents. The increased in applied current caused the maximum resistivity around T_MI to be decreased for both samples indicated increased in charge carrier density which resulting in drop of resistivity, hence, enhanced double exchange mechanism. The electroresistance (ER) effects have been investigated. The result showed that the ER effect increases when Ga is substituted.

Abstract: This study includes the preparation of the ferrite nanoparticles Cu_xCe_0.3-XNi_0.7Fe₂O₄ (where: x = 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) using the sol-gel (auto combustion) method, and citric acid was used as a fuel for combustion. The results of the tests conducted by X-ray diffraction (XRD), emitting-field scanning electron microscopy (FE-SEM), energy-dispersive X-ray analyzer (EDX), and Vibration Sample Magnetic Device (VSM) showed that the compound has a face-centered cubic structure, and the lattice constant is increased with increasing Cu ion. On the other hand, the compound has apparent porosity and spherical particles, and there are no other elements other than those participating in the preparation of the compound, which means that it is of high purity. The prepared compound possesses excellent magnetic properties due to the narrowness of the magnetic hysteresis ring. The gas sensing system found that the compound has good sensitivity to H₂S gas.

Abstract: The magnetization process at elevated frequencies (up to 15 kHz) of ring-shaped binary Fe₈₁Ga₁₉ alloy was studied. Frequency and magnetic field dependences of coercive field and remanent induction were analyzed. Hysteresis loops and initial permeability were studied at low (200 Hz) and high (15 kHz) frequencies. The same measurements were made for FeGaRE alloys to establish the effect of rare-earth elements on dynamic magnetic properties.

Abstract: The need to recycle and develop valuable materials from waste, and use them in various applications have become increasingly important in recent decades. Printer toner waste is one of the most polluting electronic waste due to the toxic nature of the material content in it. Despite the toxicity of the material in the toner powder, it contains iron oxide that can be extracted and recycled to make a beneficial material. Therefore, this study aims to investigate a facile and effective method to extract iron oxide from printer toner waste powder. Magnetic separation and oxidation processes were used as a method for extraction and phase conversion. The structural transformation was investigated using X-ray diffraction, microstructural observation using scanning electron microscope whereas static magnetic characteristics were investigates using vibrating sample magnetometer. The results from XRD spectra show that printer toner wastes that have been subjected to magnetic separation process and chemical treatment, even without any heat treatment process, have produced a single phase magnetite. Through the process of heat treatment on the sample, phase transformation from magnetite to hematite occurs, in which a single phase of hematite is obtained at a temperature of 1400 °C. The saturation magnetization of the sample also showed a reduction where the sample before undergoing the heat treatment process had a saturated magnetization value of 18.81 emu/g. Meanwhile, after heat treatment, the saturation magnetization value decreased to 0.42 emu/g. These results are in line with the phase transformation shown where magnetite has high ferrimagnetic characteristics, whereas hematite is basically antiferromagnetic at room temperature. However, the saturation magnetization that has been obtained in hematite shows a little difference to that of commercially sold hematite. This proves that iron oxide extracted from printer toner waste has a high potential as an alternative to existing commercial iron oxide in producing high performance magnetic materials.