Papers by Keyword: Ferromagnetic

Abstract: In this research, different types of Mg-Zn based intermetallics that appear in the Mg-Zn alloy system were synthesized by conventional casting route. Consequently, the structural, mechanical, electrical, and magnetic properties of these Mg-Zn intermetallics were thoroughly studied. Every casting underwent a trivial loss of Mg by oxidation which resulted in slightly higher weight percentages of Zn. X-ray Diffraction (XRD) analysis confirmed the coexistence of several intermetallics in each sample. The morphology of the samples was studied under Optical and Field Emission Scanning Electron Microscopes and the phases were identified by Energy Dispersive Spectroscopy (EDS). Differential Scanning Calorimetry (DSC) analysis further confirmed many of the available phases found. Mainly five intermetallics i.e., Mg₅₁Zn₂₀, MgZn, Mg₄Zn₇, MgZn₂ and Mg₂Zn₁₁ were observed in the structures. The cast sample which is rich in Mg₂Zn₁₁ showed the highest compressive strength (122.6 MPa) and electrical conductivity of 10.47 S/m. From Vibrating Sample Magnetometry (VSM) analysis it was found that three of the samples are soft ferromagnets whereas only the samples abundant in MgZn₂ content showed paramagnetic behavior with maximum magnetization of 0.66 emu/gm.

Abstract: Anisotropy of a powder ferromagnetic product can be created by focusing separate particles in the direction of a certain crystallographic axis in a magnetic field. By fitting modes of electromagnetic field it is possible to regulate the intensity of clusters movement and powder particles, as well as to destroy clusters up to the separate particles. At the increase of constant magnetic field induction up to a certain value, typical for every material, the intensification of processes of secondary aggregation and formation of anisotropic layer structure takes place. A design model of magneto-vibrational state of finely divided powder suggested in the article enables to calculate the parameters of electromagnetic field, which provide optimal characteristics of a powder product. It has been shown that, at a certain ratio of parameters of electromagnetic field in a dispersive ferromagnetic medium, a chain system is formed. The chains are focused along magnetic-field lines and execute a vibration in a variable inhomogeneous magnetic field, according to the law of a string with fixed ends.

Abstract: In this paper, the magnetization reversal of sphere-shaped ferromagnetic nanoparticles has been investigated by means of micromagnetic simulation. Some ferromagnetic particles such as Cobalt, Iron, Nickel, and Permalloy were modeled with size variation from 50 nm to 100 nm. The discretization of the ferromagnetic model was used a cell size of 2.5×2.5×2.5 nm³ considering the exchange length (l_ex) of the materials. The quasi-static magnetic field was induced into the nanosphere to observe the magnetization response under time dependence. It is found that the coercivity values are decreased as the sphere size increased, which was conformed the experimental results. It is also observed that the domain structure of a single particle in remanent and ground-state condition are identical. Therefore, the specific understanding of magnetization process and domain structures in ferromagnetic nanoparticles could be an important step in the development of nanopatterned magnetic memory storage.

Abstract: The structural, elastic and anisotropic properties for rare earth manganites compound YMnO3 in ferromagnetic state with hexagonal structure, have been investigated using the ab initio calculations based on the density functional theory, this calculations were based on the full potential linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA). The agreement of the DFT (FP-LAPW) calculations including internal atomic relaxations, with the experimental data is very good. Other relevant quantities such as elastic constants, shear modulus, Young’s modulus, Poisson’s ratio, anisotropy factors, sound velocity, and Debye temperature have been calculated and discussed.

Abstract: Nowadays, the magneto-ellipsometry technique is considered as a promising tool for studying nanostructures. It leads to a great demand of both designing set-ups for conducting experiments and developing approaches to data processing. The later one is a problem in framework of in situ analysis as it would be useful to have an approach to data analysis which is reliable, quick and reasonably easy. This work continues our previous study of layered nanostructures by means of magneto-ellipsometry technique and logically generalizes the approach to magneto-ellipsometry data analysis for the multi-layered model use. As a result, the algorithm with detailed description of necessary formulae is presented.

Abstract: Magnetoelectric (1−x) BNT−x CFO nanoparticulate thin films with (x = 0, 0.1, 0.2, 0.3) were fabricated by a chemical solution deposition technique. The X-ray diffraction shows that no other secondary phases are observed. Transmission electron microscope (TEM) revels that CFO nanoparticles were well distributed in matrix of BNT. The nanocomposite films exhibit both good magnetic and ferroelectric properties at room temperature (R-T), as well as enhanced magnetoelectric coupling. The composite with x = 0.2, showed the large value of ME voltage coefficient (α_E ) ~ 163 mV/cmOe. These ME composites provide a great opportunity as potential lead free systems for ME devices.

Abstract: Yttrium iron garnet (YIG) powdered ceramic powders were synthesized as bulk quantity by traditional solid state synthesis method by the use of yttrium oxide and iron oxide powders. Finely grinded powders were then calcinated for various temperatures such as 900, 1200 ^oC for 3 hours and 1400^oC for 6 hours respectively after making multiple grindings to obtain homogeneity. The calcinated powders were then subjected to phase purity by the use of powder X-ray analysis. As it is clear evident from the samples that the powdered samples were of single phase in nature and that it is clear evident from the nature of the sample which transforms to green in colour from the traditional red iron based oxides. The bonding nature was further ascertained by the used of Fourier transform infrared spectrometer (FTIR) analysis. Thermal stability and phase formation was confirmed through thermal analysis. The thermo-magnetization curve reveals the curie temperature of the sample which is in good agreemement with that of the reported values. Magnetization versus magnetic field curve was obtained which showed increase in magnetization due to the pure phase formation. These preliminary results suggest that the YIG powders could be made in to ceramic pellets for the use of tunable filters in the areas of microwave oscillators.

Abstract: The electrical properties of anisotropic materials based on microwires in extremely high frequency (EHF) range were researched. The frequency dependence of the transmission coefficient of electromagnetic wave for materials based on FeCoBSi microwires in parallel and orthogonal ordering of conductors relative to the polarization of incident radiation are shown. Angular dependence of the transmission coefficient for these samples at different of frequencies are presented. It was shown, that samples of ordered structure based on microwires with a repetition period 1 mm provides changing transmission coefficient from 35% to 60% in the range of 38-56 GHz.

Abstract: In order to improve the structural and ferromagnetic property of BiFeO₃, the effects of Ho³⁺ doping is systematically investigated. Pure BiFeO₃ and Ho-doped BiFeO₃ thin films are fabricated by sol-gel method, and the phase structure, morphology, crystalline structure, ferromagnetic are characterized by XRD, SEM, Raman spectra and VSM, respectively. The XRD patterns of the samples indicate that all the compounds crystallize in rhombohedral distorted perovskite structure with space group R₃c and the Ho substitution can suppress the intrinsic formation of the miscellaneous phase. The SEM proves that along with the increasing of Ho concentration, the surface roughness of BiFeO₃ is decreased due to the reduction of defects in the preparation. From the Raman spectroscopy, it is found that the peak intensity of 8 modes in Bi_1-xHo_xFeO₃ are increased and the modes shift to higher wave number. Besides, the VSM results show that the ferromagnetic of the samples is enhanced with increasing of Ho concentration. When x=0.1, Ms is improved to be 4.8emu/g. The results can prove that the Ho³⁺ doping can reduce the volatilization of Bi³⁺, decrease the concentration of oxygen vacancies and improve the room-temperature ferromagnetic of BiFeO_3.

Abstract: Several machine components including a part of electrical circuit box, an electrical motor and an automotive part were common ferromagnetic materials used under the magnetic fields. In the general, their friction had occurred in the magnetized materials during operation. The friction coefficient of the sample under magnetic fields was different from the sample without magnetic field treatment. Its friction coefficient had correlation with wear behavior of specimens. The wear protection procedures for the ferromagnetic parts during operation are recognized different from others without magnetization. Its friction coefficient was thus used to measure the wear characteristics with a ball on disc friction tester. The microstructure of wear trace and debris was investigated by scanning electron microscope. From the results, the magnetic fields affected the change of friction coefficient. The friction coefficient was decreased with an increasing magnetic intensity. This was because the wear debris was induced and thus decreased the adhesive wear mode during friction test.