Particle Magnetic Properties Research Articles

Spin effects from Four Bosons EM

Electromagnetism is the theory of electric charge and spin. Our study is on a spin-valued four bosons electromag- netism. An EM under the charge exchange {+, 0, −} intermediated by four bosons {AμI } ≡ {Aμ, Uμ, V ± μ } where Aμ means the usual photon, Uμ a massive photon, V ± μ charged photons. EM should express electric charge and spin together. Understand from first principles on the spin role in the electric and magnetic properties of particles. Theoretically, the spin is a space-time physical entity derived from Lorentz group. Phenomenologically, it appears as a vectorial entity inserted in the magnetic moment and electric dipole. A theoretical closure between them is expected. A spin-valued four bosons EM is constituted by introducing Lorentz group Lie Algebra valued fields. Consider the quadruplet fields as A I μ = A I μ,κλ(Σκλ)αβ where (Σκλ)αβ is the Lorentz generator. It provides spin as an intrinsec entity compatible with relativity and group theory. Similarly to the non-abelian gauge theory, where Aμa = Aμata, one incorporates the spin valued field through a Lie algebra. From first principles. Electric charge and spin are unified under a constructivist Lagrangian. Spin effects arestudied through equations of motion and Bianchi identities. Enlarging the EM for interactions beyond electric charge. Four types are derived. Usual electric charge interaction, neutral interaction, electric charge and spin, neutral and spin. A formalism is expressed. The spin valued performance is related through a Lagrangian. Spin interactions are derived. The magnetic moment and electric dipole are expressed by vectors S~ and ~s respectivity. They are able to couple spin with granular and collective fields strengths. Developing interacting terms constitutive as B~ · S~, E~ · ~s, ~e · S~ and so on. Faraday interaction between magnetic field and photon is reproduced from first principles.

Fully Integrated Microfluidic Device for Magnetic Bead Manipulation to Assist Rapid Reaction and Cleaning.

Methods to manipulate magnetic beads are essential factors to determine the efficiency and dimension of an in vitro diagnostic system. Currently, using movable permanent magnets and planar electromagnets is still the major approach to achieve magnetic bead control, causing significant constraint in the miniaturization of in vitro diagnostic systems. Here, we propose techniques to construct a fully integrated microfluidic device that can conduct automatic magnetic bead manipulation as well as rapid chemical reaction and cleaning in a minimized dimension similar to a USB disk. The device combines the precision control of multiple electromagnetic coils with the compactness of microfluidic channels, leading to one of the smallest automatic magnetic bead manipulation systems that can complete several major magnetic bead-based operation steps such as sample injection, reaction, cleaning, and collection. The influencing factors such as coil driving parameters, surface treatment of the microchannels, and properties of magnetic particles have also been investigated to optimize the device performance. The device can drive mixtures of Fe3O4 microparticles and polymer magnetic beads (PMBs) with a weight ratio of 1:1 at a maximum speed of 0.5 cm·s-1 and reduce the time for DNA binding and dissociation reactions from 20 min to only 48 s. This device has significantly advanced the conventional manipulation methods of magnetic beads and has demonstrated the possibility to construct an automatic and ultraminiaturized in vitro diagnostic system that may facilitate portable or even wearable chemical analysis.

Magnetic spirals: an innovative approach for enhancing the separation of ferro- and para-magnetic particles

ABSTRACT Spirals are one of the most widely used beneficiation equipment in mineral processing industry. The prerequisite to improve spirals' performance is to understand the forces that affect valuable and gangue minerals' separation. This paper investigates how magnetic properties of particles can be used to achieve a sharper separation of magnetic and non-magnetic particles in spirals. To this end, separation behavior of a synthetic mixed magnetite and quartz particles in the presence and absence of magnetic field was investigated via analyzing variations in the forces that affect particles’ separation in a spiral. Changes in Zero force line were considered as the reference point in the studies. In this regard an innovative magnetic-spiral was designed and fabricated. A magnetic force was added to separation process of the selected spiral. This, increased fine particles grade and recovery up to 8.5% and 7.5% respectively.

Preparation of flake-shaped Fe-based nanocrystalline soft magnetic alloy particles subjected to plastic deformation

ABSTRACT Fe-based nanocrystalline alloy powder prepared by ball-milling is a potential candidate as a soft magnetic composite (SMC). Since the magnetic properties of particles having a random geometry arising from brittle fracture deteriorate by the presence of a demagnetising field, plastically deformed flake-shaped powders, exhibiting better magnetic properties on account of the suppression of any demagnetising field, are desirable. Microstructure such as grain size, lattice distortion and the distribution of dislocations, are affected by ball-milling treatment which changes the magnetic properties. In this study, Fe-based nanocrystalline alloy sheets are ball-milled with lubricant oil as a process control agent (PCA) and the microstructure of the particles investigated. The PCA effectively suppresses the brittle fracture of the alloy sheet during the ball-milling treatment and plastically deformed flake-shaped particles are then successfully obtained. Transmission electron microscopy reveals that there were few lattice defects in the α-Fe grain of the alloy, which indicated that almost only grain-boundary-mediated processes such as GB diffusion/sliding/migration and grain rotation dominate the deformation mechanism. However, Williamson–Hall analysis based on synchrotron radiation exhibits a slope indicating micro-strain in the α-Fe grains. It is found that the plastic deformation induced by the ball-milling treatment forms a microstructure having lattice distortion but containing few lattice defects. It is considered that a slight growth of the existing grains, which can be induced by thermal treatment, can achieve a strain- and dislocation-free microstructure, which is desirable for soft magnetic alloys.

Electroless copper plating obtained by Selective Metallisation using a Magnetic Field (SMMF)

Lithography is the most commonly used method for the selective metallisation of non-conductive surfaces in the manufacture of electronic devices such as printed circuit boards and antennae. However, when used in subtractive mode, lithography results in the generation of large amounts of organic solvent and metal containing waste and requires high initial capital investment. For these reasons, additive methods of selective metallisation are being widely investigated. In this work, a novel additive approach of Selective Metallisation using a Magnetic Field (SMMF) was studied. This method uses a magnetic catalyst to initiate the electroless plating process. Magnetic catalyst particles composed of magnetite-silicon dioxide-silver were synthesised by a wet-chemical procedure. Their composition was analysed by scanning electron microscopy and energy dispersive X-ray spectroscopy and the phase formation was confirmed by X-ray diffractometry. Catalytic activity towards formaldehyde oxidation and the magnetic properties of particles were confirmed by cyclic voltammetry and vibrating sample magnetometry, respectively. The results showed that the particles can be used as a catalyst for electroless copper plating and are attracted by the magnetic field. The pattern of deposition of the magnetic catalyst is defined by the magnetic field. Two different configurations of magnet and substrate were used to deposit the catalyst dispersion onto the substrate surface. In both cases, the particles were attracted by the magnetic field and deposited exclusively where the magnetic field was applied. Subsequent electroless copper plating also only occurred at these areas. Parallel lines of electroless copper were obtained. The effect of the magnetic field on magnetic catalyst deposition and subsequent electroless plating was studied and key process-specific defects were identified.

Synthesis of Magnetite Fe3O4 from Laterite Iron Rock as Microwave Absorber Material

Synthesis of magnetite from laterite iron rock material was successfully introduced as microwave absorber material. In this research, magnetite has been made from laterite iron rock, Tanah Laut, South Kalimantan, Indonesia to be laterite iron sand was achieved by a simple method. Magnetite with paint coating is applied to steel grade A type AH36. The sample was characterized by an X-ray fluorescence spectrometer (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM) to investigated element composition, crystal structure, the morphology of particles, hysteresis loops of the magnetic sample, respectively. Based on the experiment, the magnetic particle properties have saturated magnetization of 120 emu g−1 and the coercive force of 0.05 T. VNA to investigate the absorption characteristics of microwaves in a frequency range between 8-12 GHz. The results showed that the reflection loss of magnetite is higher than uncoated steel samples. The sample has a maximum reflection loss value of −14.4 dB at 8 GHz with a sample thickness of 4 mm.

Spin-Valued Four Bosons Electrodynamics

Electromagnetism is based on electric charge and spin. The study here corresponds to understand on spin effects at a vectorial electrodynamics. Its scenario is a non-linear abelian electromagnetism where the electric charge is transmitted through a four bosons quadruplet, constituted by the usual photon, massive photon and charged massive photons. These four bosons intermediate the charge exchange ΔQ = 0, ±1.The spin is introduced at first principles. A spintronics Lagrangian for four vector fields is performed. Considering that spin is a space-time physical entity derived from Lorentz Group, these vector fields are associated to Lorentz Group, as Lie algebra valued. Similarly to non-abelian gauge theories where Aμ≡ Aμ,ata, one introduces the relationship Aμ≡ Aμ,κλΣκλ where (Σκλ)αβ is the Lorentz Group generator. Thus, based on three fundamentals which are light invariance, electric charge conservation law and vector fields Lie algebra valued through Lorentz Group generators, one derives a spin-valued four vectorial electrodynamics. It is given by the fields quadruplet Aμ1 ≡ {Aμ, Uμ, Vμ±} where Aμ means the usual photon, Uμ a massive photon and Vμ± massive charged photons. Two novelties appear. The first one is that, new terms are developed into usual four bosons electromagnetism. They contribute to Lagrangian, equations of motion, Noether theorem. The second one is that the equations of motion derive a renormalizable spin coupling with the electric and magnetic fields.There is a spin-1 electrodynamics to be investigated. A neutral electromagnetism is mandatory to be analyzed. Something beyond dipole, quadrupole and so on. Understand the role of spin in the electrical and magnetic properties of particles. A spin vectorial expression S--> is obtained. It adds EM interactions not depending on electric charge and with spin interactions through electric dipole and magnetic moments.

EDTA-functionalized magnetic chitosan oligosaccharide and carboxymethyl cellulose nanocomposite: Synthesis, characterization, and Pb(II) adsorption performance

A novel ethylenediaminetetraacetic acid (EDTA)-functionalized magnetic chitosan oligosaccharide and carboxymethyl cellulose (Fe3O4@CMCCOS-EDTA) nanocomposite adsorbent was successfully fabricated for Pb(II) adsorption. The adsorbent was characterized by Fourier transform infrared, and X-ray photoelectron spectroscopy was used to confirm successful EDTA modification and Pb(II) adsorption. Scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometer, and thermogravimetric analysis were used to study the morphology and properties of magnetic particles. EDTA modification considerably improved the capacity of the adsorbent. The batch adsorption experiment results indicated that the pseudo-second-order (PSO) model and the Langmuir isotherm model reliably described the adsorption behavior. The maximum adsorption capacity (qm) for monolayer chemical adsorption was calculated to be 432.34 mg/g at the pH of 5 and temperature of 308 K. Notably, Fe3O4@CMCCOS-EDTA exhibited a high Pb(II) removal rate of ~100% using an initial metal ion solution of 100 mg/L and 200 mg/L.

The role of faceting and elongation on the magnetic anisotropy of magnetite Fe3O4 nanocrystals

Fe3O4 nanoparticles are one of the most promising candidates for biomedical applications such as magnetic hyperthermia and theranostics due to their bio-compatibility, structural stability and good magnetic properties. However, much is unknown about the nanoscale origins of the observed magnetic properties of particles due to the dominance of surface and finite size effects. Here we have developed an atomistic spin model of elongated magnetite nanocrystals to specifically address the role of faceting and elongation on the magnetic shape anisotropy. We find that for faceted particles simple analytical formulae overestimate the magnetic shape anisotropy and that the underlying cubic anisotropy makes a significant contribution to the energy barrier for moderately elongated particles. Our results enable a better estimation of the effective magnetic anisotropy of highly crystalline magnetite nanoparticles and is a step towards quantitative prediction of the heating effects of magnetic nanoparticles.

Magnetic properties of micro-particles with different shapes and postures in the high precision particles detection

Although some established electromagnetic particle detectors have been used to detect and distinguish micro-particles in different fields, the adopted particle equivalent model leads to large detection error because that ignores the difference of the magnetic perturbations induced by particles with different shapes and postures. To improve the development of high-precision electromagnetic micro-particle detectors, the magnetic models of particles with different shapes and postures are established. The distribution of magnetic flux density and the magnetic energy change caused by particles are calculated. The theoretical and experimental results illustrate that the change of magnetic energy caused by spherical particles is much lower than that caused by ellipsoidal and flaky particles of the same volume, meanwhile, with the increase of the rotation angle of ellipsoidal and flaky particles, the variation of magnetic energy decreases significantly. Based on the results, precise particle equivalent functions considering the magnetic properties of particles are proposed.

Magnetic Properties of Soft Magnetic Alloys 5BDSR and 82K3HSR

The paper explores the size and morphology of microparticles of soft magnetic alloys 5BDSR and 82K3HSR and nanoparticles first obtained from these alloys using pulsed laser ablation in gas. The magnetic properties of particles are studied depending on their size, composition and production method.

Исследование магнитных свойств частиц магнитомягких сплавов 5БДСР и 82К3ХСР

Исследование магнитных свойств частиц магнитомягких сплавов 5БДСР и 82К3ХСР

Influence of Organic Ligands on the Surface Oxidation State and Magnetic Properties of Iron Oxide Particles

Abstract For the application of iron oxide nanoparticles from thermal decomposition approaches as contrast agents in magnetic resonance imaging (MRI), their initial hydrophobic ligands have to be replaced by hydrophilic ones. This exchange can influence the surface oxidation state and the magnetic properties of the particles. Here, the effect of the anchor group of three organic ligands, citric acid and two catechols, dihydrocaffeic acid and its nitrated derivative nitro dihydrocaffeic acid on iron oxide nanoparticles is evaluated. The oleate ligands of Fe3O4/γ-Fe2O3 nanoparticles prepared by the thermal decomposition of iron oleate were exchanged against the hydrophilic ligands. X-ray absorption spectroscopy, especially X-ray magnetic circular dichroism (XMCD) measurements in the total electron yield (TEY) mode was used to investigate local magnetic and electronic properties of the particles’ surface region before and after the ligand exchange. XMCD was combined with charge transfer multiplet calculations which provide information on the contributions of Fe2+ and Fe3+ at different lattice sites, i.e. either in tetrahedral or octahedral environment. The obtained data demonstrate that nitro hydrocaffeic acid leads to least reduction of the magnetizability of the surface region of the iron oxide nanoparticles compared to the two other ligands. For all hydrophilic samples, the proportion of Fe3+ ions in octahedral sites increases at the expense of the Fe2+ in octahedral sites whereas the percentage of Fe3+ in tetrahedral sites hardly changes. These observations suggest that an oxidation process took place, but a selective decrease of the Fe2+ ions in octahedral sites ions due to surface dissolution processes is unlikely. The citrate ligand has the least oxidative effect, whereas the degree of oxidation was similar for both catechol ligands regardless of the nitro group. Twenty-four hours of incubation in isotonic saline has nearly no influences on the magnetic properties of the nanoparticles, the least on those with the nitrated hydrocaffeic acid ligand.

Antibody-free detection of infectious bacteria using quantum dots-based barcode assay

Staphylococcus aureus, methicillin-resistant Staphylococcus aureus and Klebsiella pneumoniae are the most representative bacteria causing infectious diseases. Due to the increased application of antibiotics, the bacterial resistance is growing causing severe complications. Therefore, a sensitive determination of these pathogens is crucial for effective treatment.The aim of this study was to design an effective method for multiplex detection of Staphylococcus aureus, methicillin-resistant Staphylococcus aureus and Klebsiella pneumoniae taking advantage from properties of magnetic particles as well as fluorescent nanoparticles (quantum dots). The method was able to detect as low concentrations of bacteria as 102 CFU/mL using the bacteria-specific genes (fnbA, mecA and wcaG).

Effect of Cu2+ substitution on structural and magnetic properties of Ni–Zn ferrite nanopowders

In this study copper substituted nickel–zinc ferrite powders with the general composition Ni0.6−xCuxZn0.4Fe2O4 (x = 0, 0.05, 0.1, 0.15, 0.2, and 0.25) were prepared via auto-combustion sol–gel method. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy, Mossbauer spectroscopy, vibrating sample magnetometer (VSM) and superconducting quantum interference device analysis were carried out in order to characterize the structural and magnetic properties of particles. The XRD results confirmed the formation of single phase spinel ferrite particles for all of the samples. The results of FTIR analysis indicated that the there are two main frequency bands, namely, the high frequency band observed at ~577 cm−1 and the low frequency band observed at ~450 cm−1. These two bands correspond to the intrinsic vibrations of tetrahedral and octahedral Fe3+–O2− complexes, respectively, and are the characteristics of all the ferrite materials. The size of particles was around 80–800 nm. The VSM results revealed that with an increase in the amount of copper in ferrites, the saturation magnetization increased. Saturation magnetization increased to 97 emu/g for x = 0.05 at room temperature and increased to 261 emu/g for x = 0 and 0.05 at 2 K. The results indicated that the powder is suitable for the application in multilayer chip inductor due to its low temperature sinterability and good magnetic properties.

Label-Free Microfluidic Manipulation of Particles and Cells in Magnetic Liquids.

Manipulating particles and cells in magnetic liquids through so-called "negative magnetophoresis" is a new research field. It has resulted in label-free and low-cost manipulation techniques in microfluidic systems and many exciting applications. It is the goal of this review to introduce the fundamental principles of negative magnetophoresis and its recent applications in microfluidic manipulation of particles and cells. We will first discuss the theoretical background of three commonly used specificities of manipulation in magnetic liquids, which include the size, density and magnetic property of particles and cells. We will then review and compare the media used in negative magnetophoresis, which include paramagnetic salt solutions and ferrofluids. Afterwards, we will focus on reviewing existing microfluidic applications of negative magnetophoresis, including separation, focusing, trapping and concentration of particles and cells, determination of cell density, measurement of particles' magnetic susceptibility, and others. We will also examine the need for developing biocompatible magnetic liquids for live cell manipulation and analysis, and its recent progress. Finally, we will conclude this review with a brief outlook for this exciting research field.

Optimizing and modeling of effective parameters on the structural and magnetic properties of Fe3O4 nanoparticles synthesized by coprecipitation technique using response surface methodology

In present work, the Fe3O4 magnetic nanoparticles were successfully synthesized by coprecipitation method. In order to study the effects of influential factors on the structural and magnetic properties of particles, the experimental runs were designed using response surface methodology (RSM) based on central composite design (CCD), while the reaction temperature, Fe2+/Fe3+ cation ratio, and pH of reaction were defined as effective factors on the two responses include the amounts of crystallinity degree and saturation magnetization (Ms). The investigation of structural, magnetic, and microstructural properties of particles were carried out by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses. As a result, the predictive quadratic models were fitted on the both responses while the R2 values were more than 0.97 for both models. The highest amounts of both responses (crystallinity degree: 88.07% and Ms: 65.801emu/g) are presented when the reaction temperature, cation ratio, and pH amounts are equal to 90°C, 0.60, and 10.5, respectively. Finally, the TEM results show the particles with size of about 10nm and narrow size distribution.

On the Magnetic Analysis of External Magnetic Field Annealing of Co 2 -W Hexagonal Shape Particles

W-type hexaferrite particles with composition of SrCo2−x (NiZnMg) x/3Fe16 O 27 (x = 0–0.5) were synthesized by a chemical co-precipitation method. The effect of substitution on the structural and magnetic properties of particles was characterized by X-ray diffraction (XRD), Fourier-transformed infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), vibrating sample magnetometer (VSM), and B-H tracer. The synthesized particles were applied under a high magnetic field of 1 T by employing a super high-capacity magnetizer and normal compression stress. The XRD patterns confirmed the existence of hexagonal W-type single phase. The FE-SEM micrographs demonstrate the nucleation of hexagonal particles along with the close view of aspect ratio of hexagonal platelet. The elemental composition estimated from the EDX analysis was in good agreement with the nominal composition. Hysteresis loops for all samples were measured at a room temperature up to a maximum applied field of 24 kOe. The results revealed that with an increase in substitutional cation contents, the values of saturation magnetization decreased from 60.6 to 11.6 emu/g, and the values of coercivity increased from 2255 to 5107 Oe. The B-H curves of field annealed bulk ferrites also display the similar trend.

Extreme neutron stars from Extended Theories of Gravity

We discuss neutron stars with strong magnetic mean fields in the framework of Extended Theories of Gravity. In particular, we take into account models derived from f(R) and f(\U0001d4a2) extensions of General Relativity where functions of the Ricci curvature invariant R and the Gauss-Bonnet invariant \U0001d4a2 are respectively considered. Dense matter in magnetic mean field, generated by magnetic properties of particles, is described by assuming a model with three meson fields and baryons octet. As result, the considerable increasing of maximal mass of neutron stars can be achieved by cubic corrections in f(R) gravity. In principle, massive stars with M > 4M☉ can be obtained. On the other hand, stable stars with highstrangeness fraction (with central densities ρc ∼ 1.5–2.0 GeV/fm3) are possible considering quadratic corrections of f(\U0001d4a2) gravity. The magnetic field strength in the star center is of order 6–8 × 1018 G. In general, we can say that other branches of massive neutron stars are possible considering the extra pressure contributions coming from gravity extensions. Such a feature can constitute both a probe for alternative theories and a way out to address anomalous self-gravitating compact systems.

Novel methods for in situ characterization of individual micro- and nanoscale magnetic particles

Abstract