Significant Increase In Saturation Magnetization Research Articles

3D Printing Soft Magnet: Binder Study for Vat Photopolymerization of Ferrosilicon Magnetic Composites.

Liquid Crystal Display (LCD) masking is a 3D printing technique that can produce soft magnetic composite parts to high resolution and complexity for robotics and energy electronics applications. This additive manufacturing technique has the potential to produce larger, lighter-weight, more efficient, and more durable parts for automotive and mechanical applications. This study conducted a binder study to create a low-viscosity and stiff binder capable of loading at least 60 v/v% Fe-6.5 wt%Si particles. Percolation Theory was applied to anticipate the magnetic interaction of suspended particles. A series of binders were formulated, with adjustments to diluent ratios. The behavior of the binders was assessed by studying their rheological properties, conversion rates, and mechanical properties. A post-cure study was conducted across various energy settings using UV, thermal, and a combination of both energy sources to find the combination that provided the best mechanical properties. As a result, 64 v/v% Fe-6.5 wt%Si loading was achieved and cured using UV light of 405 nm wavelength. Vibrating Sample Spectroscopy (VSM) was used to characterize the composite's magnetic behavior, and a significant increase in saturation magnetization and negligible change in coercivity was observed when the added load exceeded the percolation threshold.

Impact of Cu2+ cations substitution on structural, morphological, optical and magnetic properties of Co1-xCuxFe2O4 nanoparticles synthesized by a facile hydrothermal approach

Spinel ferrites have received extended discussions among different ceramic magnetic nanoparticles due to dependence of its physiochemical properties on the fabrication processes and composition. In this context, copper doped cobalt ferrites (Co1-xCuxFe2O4) with different Cu2+ doping content (i.e., 0.0 ≤ x ≤ 0.4) were successfully fabricated via hydrothermal method. The impact of exchanging divalent cobalt (Co2+) cations by divalent copper (Cu2+) cations on structure-magneto-optic characteristics of Co1-xCuxFe2O4 ceramic magnetic nanoparticles was studied. The spinel single cubic phase of prepared samples with the signature of CuO phase for x ≥ 0.2 was proved by powder X-ray diffraction (XRD) and infrared spectroscopy (IRS) studies. The particle size distribution depending on the Cu2+ doping content was studied by means of XRD and Transmission electron microscopy (TEM) analysis. The particle size is in the range between 11 and 16 nm. The metal-oxygen vibrational modes and the Force constant of spinel structure bonds were investigated using IRS analysis. The optical analysis in the ultraviolet–visible spectrum region by UV–Vis spectroscopy indicates that the optical energy gap of Co1-xCuxFe2O4 nanoparticles range from 1.77 to 2.2 eV. The specific surface area and optical energy gap values of Co1-xCuxFe2O4, demonstrates the possibility of using this compound effectively in water purification processes. The scanning electron microscopy (SEM) and (TEM) analysis confirmed the nano-sized spherical-shaped particle morphology of our investigated nanoparticles. A significant increase in saturation magnetization from 79 to 106 (emu/g) was observed with increase in Cu2+ content from 0.0 to 0.4. Substitution of Co2+ ions in cobalt ferrite lattice structure with Cu2+ ions allow variations in their nanocrystals size, optical energy gap and magnetic characteristics, which has great benefit in using these compounds in many potential applications.

Cubic Anisotropic Co- and Zn-Substituted Ferrite Nanoparticles as Multimodal Magnetic Agents.

The use of magnetic nanoparticles as theranostic agents for the detection and treatment of cancer diseases has been extensively analyzed in the last few years. In this work, cubic-shaped cobalt and zinc-doped iron oxide nanoparticles with edge lengths in the range from 28 to 94 nm are proposed as negative contrast agents for magnetic resonance imaging and to generate localized heat by magnetic hyperthermia, obtaining high values of transverse relaxation coefficients and specific adsorption rates. The applied magnetic fields presented suitable characteristics for the potential validation of the results into the clinical practice in all cases. Pure iron oxide and cobalt- and zinc-substituted ferrites have been structurally and magnetically characterized, observing magnetite as the predominant phase and weak ferrimagnetic behavior at room temperature, with saturation values even larger than those of bulk magnetite. The coercive force increased due to the incorporation of cobalt ions, while zinc substitution promotes a significant increase in saturation magnetization. After their transfer to aqueous solution, those particles showing the best properties were chosen for evaluation in in vitro cell models, exhibiting high critical cytotoxic concentrations and high internalization degrees in several cell lines. The magnetic behavior of the nanocubes after their successful cell internalization was analyzed, detecting negligible variations on their magnetic hysteresis loops and a significant decrease in the specific adsorption rate values.

Investigation of negative magnetization and impedance spectroscopy of Sm-substituted gadolinium iron garnets

Samarium substituted gadolinium iron garnet samples were synthesized in pure-phase form by solid-state chemical reaction method. The lattice constant increases (12.4624 Å to 12.5211 Å) with Sm-concentration. Magnetization measurements show an increase in ferrimagnetic (FIM) transition temperature (TC = 567 K to 575 K) and a decrease in magnetic compensation temperature (Tcomp = 286 K to 70 K) upon Sm-substitution. In addition to magnetic compensation, an interesting negative magnetization under field-cooled condition is achieved for a sample with x = 2.0, and it has been explained in terms of enhanced magnetic anisotropy due to Sm-substitution. A significant increase in saturation magnetization is attained at room temperature by Sm-substitution. Frequency dependence of complex impedance shows relaxation behavior and the relaxation frequency follows the Arrhenius power-law, along with an anomaly around FIM TC. Such anomaly is ascribed to magneto-electric coupling.

Non-isothermal Primary Crystallization Kinetics of the Amorphous Fe85.3B11P3Cu0.7 Alloy

In the present research, the primary crystallization kinetics of the amorphous Fe85.3B11P3Cu0.7 alloy was analyzed using non-isothermal DSC measurements. The average and local activation energies, Ea, were determined by different isokinetic and isoconversional methods. The results obtained for activation energy in this research, show that due to the complexity of the primary crystallization process in this alloy, isoconversional methods are more suitable than the isokinetic ones. The Avrami exponents lie between about 1 and 2 in a wide temperature range of 370˂T≤410˚C. This indicates that one dimensional growth of nuclei with a decreasing rate of nucleation is the main mechanism during non-isothermal primary crystallization process of the amorphous Fe85.3B11P3Cu0.7 alloy which is a new finding for this alloy. Study of magnetic properties in the amorphous and nanocrystalline states revealed that annealing the amorphous ribbons at 440˚C for 10 minutes gives rise to a significant increase in saturation magnetization, Ms, i.e. from 144 in as-spun to 201 emu/g in annealed states. This amount of Ms makes this material a good candidate for different applications, especially in transformer cores.

Effect of Cu2+ substitution on structural, magnetic and dielectric properties of cobalt ferrite with its enhanced antimicrobial property

Cu2+ substituted cobalt ferrite represented chemically as Co1−xCuxFe2O4 (x = 0.00, 0.05, 0.10, 0.15, 0.20 and 0.25) was prepared by the sol–gel assisted auto-combustion process using malic acid as a complexing agent. The auto-combusted sample was investigated using thermal analyzer, and accordingly, thermal treatments were given to the samples. The concentration of metal ions present was estimated using ICP-AES technique. Evaluation of transmission electron microscopy and scanning electron microscopy results indicate the homogenous distribution of particles along with agglomeration. X-ray photoelectron spectroscopy studies confirm the existence of elements in their respective oxidation states. Raman and Infrared spectroscopy were employed to shed light on the vibrational modes of the spinel ferrites. Magnetic properties determined from vibrating sample magnetometer at 50 K shows a significant increase in saturation magnetization (Ms) and coercivity (Hc) as compared to 300 K. While, the substitution of Cu2+ ions showed a marginal decrease in Ms and Hc at individual temperatures. The drop in Curie temperature (Tc) with Cu2+ content indicates the weakening in the strength of the overall A–B super-exchange interaction. The dielectric properties have been determined as a function of frequency and temperature. Antimicrobial tests performed, indicated that the Cu2+ content in CoFe2O4 significantly influenced the activity against both Gram-positive and Gram-negative pathogenic microbes.

Exploring the pathways for enhancing the hard magnetic properties of binary Al-55at.%Mn Heusler alloy through mechanical alloying

This work reports enhancing the hard magnetic properties of a binary ferromagnetic Heusler alloy based on Mn-Al system through mechanical milling. We report the processing induced evolution of magnetic properties for two sets of alloys, both having the same stoichiometric composition of Al-55at.%Mn with one of them containing high temperature ε phase while the other consisting of only metastable ferromagnetic τ phase. No effect of milling on the magnetic properties of ε phase could be detected due to its nonmagnetic nature. However, subsequent annealing at 350°C for 30min after milling results in structural change and exhibits magnetic response. The phase transitions were found to depend on prior milling history. The highest saturation magnetization and coercivity were obtained for 4h milled sample that is annealed at 350°C for 30min with values of 23emu/g and 5.2 KOe, respectively. In the case of samples with initial microstructure consisting of grains of only metastable τ phase, no decomposition could be observed when milled for a period up to 9h. Additionally, it was observed that after 3h of milling, the saturation magnetization value reduces to 24emu/g and coercivity increases to 5.2 KOe from an initial values of 116emu/g and 0.98KOe respectively. Further milling causes a decrease in both the values. Annealing of the 3h milled powder at 350°C for 30min, resulted in a slight decrease in coercivity (Hc=4.9 KOe) while a significant increase in saturation magnetization (34emu/g) value could be observed. Experimental results suggest that magnetization reversal is domain nucleation controlled and that the nonmagnetic phases (β+γ2) present can act as the pinning sites.

Magnetic and thermal properties of amorphous TbFeCo alloy films

Amorphous TbFeCo material with perpendicular magnetic anisotropy is currently attracting more attention for potential applications in spintronic devices and logic memories. We systematically investigate magnetic, structural, thermal, optical and electrical properties of TbFeCo alloy films. It shows out-of-plane easy axis of the films turns into in-plane orientation after annealing. Significant increase in saturation magnetization in the temperature range between 400 and 450°C is revealed by thermomagnetic measurements. The occurrence of crystallization and oxidation at high temperatures is confirmed by X-ray diffraction measurements. Pronounced changes in optical reflectance and sheet resistance are observed with temperature, in line with structural relaxation and change. The activation barriers for crystallization and oxidation are determined to be 1.01eV and 0.83eV, respectively, for FeCo-rich and Tb-rich samples. Better thermal stability against crystallization and oxidation is demonstrated in the FeCo-rich sample than the Tb-rich type. Our results provide some useful information for the alloy used in device fabrication.

Recycling of Iron Sintered Wastes Into Nanoparticles Barium Hexaferrite and Zinc-Ferrite Glass-Ceramics

About 25 % of iron oxides in the sintering process are wastes. In this paper, sintered waste (SW) was used as a source of iron oxides to prepare both hard and soft magnetic glass-ceramics via a melting-quenching technique. About 71 % by wt. of sintered waste was used for preparing soft magnetic glass-ceramics, while ∼46 % was used for preparing hard magnetic glass-ceramics. The comparison between ferrimagnetic glass-ceramics prepared from pure chemicals and that from sintered waste before and after heat treatment was studied. X-ray diffraction shows crystallization of both hematite and Zn-ferrite phases in sintered waste while pure Zn-ferrite or Ba-hexaferrite phases were crystallized in soft magnetic and hard magnetic glass-ceramics, prepared from sintered waste, respectively. Transmission electron microscopy determined the crystalliza- tion of nano-particles ∼20 nm and <15 nm for soft and hard magnetic glass-ceramics respectively. Vibrating scanning magnetometry revealed a significant increase in saturation magnetization from ∼26 emu/g for sintered waste to ∼44 emu/g in soft magnetic glass ceramics while it decreased to ∼12 emu/g for hard magnetic glass-ceramics.

Facile approach to suppress γ-Fe2O3 to α-Fe2O3 phase transition beyond 600 °C in Fe3O4 nanoparticles

Magnetic iron oxide nanoparticles on a zeolite template have been synthesized using wet chemical approach. The average particle size initially decreases from 8.5 to 6 nm (increasing zeolite concentration from 0 to 75 mg) but increases to 11 nm for higher zeolite concentration (100 mg). Room temperature magnetization curves show an initial decrease in saturation magnetization from 62 to 42 emu per gram due to decrease in particle size as well as increase in contribution from nonmagnetic zeolite template. Further increase in zeolite concentration to 100 mg results in a significant increase in saturation magnetization from 42 to 51 emu per gram. Calorimetric studies show a continuous enhancement in γ-Fe2O3 to α-Fe2O3 phase transition temperature from 590 to 715 °C by increasing the zeolite concentration from 0 to 75 gm. The exothermic peak corresponding to the γ-Fe2O3 to α-Fe2O3 phase transition has been completely suppressed for nanoparticles prepared in presence of 100 mg of zeolite. Mössbauer spectra of as-synthesized nanoparticles show an increase of superparamagnetic components from 7 to 36% corresponding to increase in zeolite concentration from 0 to 100 mg. Mössbauer spectra of pure Fe3O4 nanoparticles annealed at 500 °C shows formation of pure α-Fe2O3 phase and Mössbauer spectra of particles prepared in presence of 25 mg shows only 18% of α-Fe2O3 phase after annealing at 550 °C. Further increase in zeolite concentration to 50 and 75 mg (annealed at 550 °C) leads to pure γ-Fe2O3. Annealing of Fe3O4 nanoparticles prepared in the presence of 100 mg of zeolite at 650 °C shows formation of only 8% α-Fe2O3 phase. Our results show an easy and effective method to enhance the thermal stability of magnetic iron oxide nanoparticles making it suitable for high temperature applications.

Laser assisted crystallization of ferromagnetic amorphous ribbons: A multimodal characterization and thermal model study

This paper focuses on laser-based de-vitrification of amorphous soft magnetic Fe-Si-B ribbons and its consequent influence on the magnetic properties. Laser processing resulted in a finer scale of crystallites due to rapid heating and cooling during laser annealing compared to conventional furnace annealing process. A significant increase in saturation magnetization is observed for laser-annealed ribbons compared to both as-received and furnace annealed samples coupled with an increase in coercivity compared to the as received samples. The combined effect of thermal histories and stresses developed during laser annealing results in the formation of nano-crystalline phase along the laser track. The phase evolution is studied by micro-XRD and TEM analysis. Solute partitioning and compositional variation within the phases are obtained by Local Electrode Atom probe analysis. The evolution of microstructure is rationalized using a Finite Element based heat transfer multi-physics model.

Structural and size dependent magnetic properties of single phase nanostructured gadolinium-iron-garnet under high magnetic field of 32 tesla

Here we report the single phase nanostructured Gd3Fe5O12 garnets with different grain sizes (bulk, 75, 47, 35, and 22 nm) were prepared by ball milling for various milling times. Both the average grain size and the lattice parameter were estimated from the x-ray diffraction line broadening. The F57e Mössbauer spectra were recorded at 300 and 77 K for the samples with different grain sizes clearly evidenced the formation of Fe2+ ions induced by milling and the content of Fe2+ increases with milling time. At 4.2 K, a significant increase in saturation magnetization (+11%) has been observed for the 47 nm particles. The magnetization is strongly applied field dependent and no saturation effect is observed even at fields as high as of 320 kOe. The results presented here have been explained in terms of the key role played by the Fe2+ ions.