Papers by Keyword: Soft Magnetic

Abstract: Although magnetic nanoparticles have been widely studied, limited research has compared different ferrite types and synthesis routes for use in hyperthermia-based bioactive glass applications. This study aims to synthesize magnetic materials from two types of ferrites: magnesium ferrite (MgFe₂O₄) and zinc ferrite (ZnFe₂O₄). These ferrite nanoparticles were synthesized using two distinct methods; the conventional solid-state reaction and the co-precipitation method in order to identify the optimal synthesis route and the most suitable type of magnetic material for hyperthermia treatment. The data demonstrated that MgFe₂O₄ powder with synthesis by using the solid-state method consistently presented higher value of magnetic properties compared to those synthesized by co-precipitation method under higher calcination temperature. Moreover, ZnFe₂O₄ powder was found to be unsuitable for use as a precursor in hyperthermia treatment because of its structure typically leads to antiferromagnetic or superparamagnetic behavior. The effect of MgFe₂O₄ containing in bioactive glass was investigated. The oxide precursors of bioactive glass were mixed with varying amounts of MgFe₂O₄ and subsequently melted to form glass at 1400 °C. The phase formation presented SiO₂ was the dominant phase and coexisted with Na₂CO₃, MgSiO₃, Fe₃O₄, Na₂Ca (PO₄)₂SiO₄, Ca₂SiO₄, and Na₄Ca₄Si₆O₁₈. However, the MgFe₂O₄ phase was not observed in all of glass-ceramic samples. This may be due to MgFe₂O₄ decomposed during the high-temperature melting process at 1400 °C. Nevertheless, these magnetic bioactive glass ceramic samples exhibited magnetic properties, which were attributed primarily to the presence of Fe₃O₄.

Abstract: This work presents a systematic study of the effects of current pulsation on soft magnetic properties and giant magnetoimpedance (GMI) of nickel-iron (NiFe) coatings electrodeposited on copper wires. The specimens were prepared by the electrodeposition technique with controlled bath compositions and varied applied current waveforms. The microstructural and chemical investigations indicate that current pulsation with 50% duty cycle and 50 Hz frequency provides significantly smoother coating surface of uniform nodules, with comparable Fe content but different phase composition, as compared to the direct current condition. The vibrating sample magnetometer evidently shows that the deposits prepared with a pulsed current exhibit relatively small coercivity, below 4 Oe. Using the four-point probe technique, the MI ratio of the pulse deposits is found to reach a significantly high value above 2,000% with decent sensitivity. The benefits of current pulsation in improving the characteristics of NiFe deposits, and correspondingly the alloys’ soft magnetic properties and MI effects are demonstrated.

Abstract: In this work, magnetic force microscopy (MFM) tips coated with a nickel thin-film were prepared and characterized for applications in the measurement of the magnetic write field. Nickel films with various thicknesses in a range of 20 – 80 nm were deposited on silicon substrates and silicon atomic force microscopy (AFM) tips by electron beam evaporation. Film surface morphologies and magnetic properties of the coated nickel films were investigated by using AFM and vibrating sample magnetometry (VSM). The rms roughness increased with the film thickness and was in a range between 0.1 and 0.3 nm. VSM results revealed that the mean coercive field of the nickel films was 20 Oe and there was an increase in the coercivity as the film thickness increased. In addition, the prepared MFM tips were evaluated for the tip response to the dc and ac magnetic field generated from perpendicular write heads. It was found that the MFM tip had the best response to the write field when coated with 60 nm thick nickel film. The coating thickness over 60 nm was inapplicable due to the cantilever bending caused by the film stress.

Abstract: Recent advance and application about Fe-based amorphous nanocrystalline alloy have been reviewed, the latest achievement of static stress annealing, continuous moving stress annealing, and magnetic field annealing for the alloy discussed, and future tendency of Fe-based amorphous nanocrystalline prospected in the paper.

Abstract: nanocomposite [(Co_91.5Zr_8.5)- or CZN films has been prepared by reactive co-sputter deposition method. Nitrogen content plays key role to tune soft magnetic properties. Experimental observation shows that, non-magnetic nitrogen content enhances magnetization and reduces coercivity. The nanostructure is composed of Co nanoclusters embedded in CoN/ZrN matrix, revealed by high resolution transmission electron microscope study. The d-spacing of single Co nanocluster was found to be ~0.22nm corresponding to (002) phase of Cobalt. X-ray diffraction result is in agreement with cubic (400) and (622) phase of CoZr. High electrical resistivity ρ_s~108μΩ-cm attained corresponding to 16% N₂ content films. Hysteresis loop squareness depends on film thickness and coercivity squareness (S^*)~0.84, obtained for ~250nm film thickness. A correlated composite nanostructure evolution is responsible for nitrogen induced magnetization and, suggests that film properties can tuned by controlling nitrogen content, in CoN/ZrN composite matrix.

Abstract: The formation of quaternary 76Ni17Fe5Cu2Cr (wt. %) alloy by mechanical alloying is investigated. The elemental powders of Ni, Fe, Cu and Cr where milled in argon atmosphere in a planetary ball mill for time up to 20 h. Formation of the alloy was checked by X-ray diffraction studies. It is found that the rapid formation of the alloy lead to the rapid establishment of an equilibrium between the welding and fracture process during milling, leading to a constant particle size distribution over a big range of milling time. The morphology of the powders, studied by scanning electron microscopy (SEM) confirms the rapid increase in size. The particle size distribution and the flowability of the powders are also analyzed as a function of milling time. Enhanced magnetization was found for the milled samples, compared to a cast alloy.

Abstract: The Hipernik alloy (50Ni50Fe wt. %) was obtained by mechanical alloying. The milling was performed in argon atmosphere, with a ball/powder mass ration of 8:1 for times ranging from 2 up to 20h. The alloy formation was studied by X-ray diffraction. The obtained structure is face cantered cubic, indicating the extension of the γ domain for the Ni-Fe alloys by mechanical alloying. The mean crystallite size was calculated with the Williamson – Hall method. Using scanning electron microscopy (SEM) the morphology and the chemical homogeneity of the powders was analysed. The technological properties of the powders as particle size distribution and flowability are determined as a function of the milling time. The magnetic behaviour of the samples was studied by magnetic measurements under high magnetic fields.

Abstract: In the paper, we will present experimental results on the Fe73.5CuNb3Si13.5B9 ferromagnetic resonance (FMR) line width as a function of annealing conditions, as well as the annealing-temperature dependence of the crystallite size, coercive force, and the magnetic anisotropy field. We shall show the interrelationship of these quantities, demonstrate that these parameters are all traceable to the nanoparticle crystallization, and indicate how they can be examined by extending the random anisotropy theory. To obtain quantitative parameters of random magnetic anisotropy we investigate the magnetization curves approaching saturation. This technique allows one to quantitatively determine the local magnetic anisotropy field (Ha) and magnetic anisotropy correlation radius (Rc), as well as to estimate the averaged magnetic anisotropy field (L) and ferromagnetic correlation radius (RL).

Abstract: Data on the random magnetic anisotropy and exchange correlation length in soft magnetic nanocrystalline Fe79Zr10N11 films were obtained using a calculation technique in frame of the random magnetic anisotropy model. The calculations are performed using approach magnetization to saturation curves. The local magnetic anisotropy fields (Ha), and magnetic anisotropy correlation radii (Rс) reduced to =(A/K)1/2 were determined for the films annealed at 475 and 6000 C for 0.5, 1, 2, and 3 h. The correlation Hc ~(Rc/)3 for the all annealed films was found.

Abstract: Magnetic properties of nanostructured materials are affected by the microstructures such as grain size (or particle size), internal strain and crystal structure. Thus, it is necessary to study the synthesis of nanostructured materials to make significant improvements in their magnetic properties. In this study, nanostructured Fe-20at.%Co and Fe-50at.%Co alloy powders were prepared by hydrogen reduction from the two oxide powder mixtures, Fe2O3 and Co3O4. Furthermore, the effect of microstructure on the magnetic properties of hydrogen reduced Fe-Co alloy powders was examined using XRD, SEM, TEM, and VSM.