Comparative Analysis Of Magnetic Properties Research Articles

Magnetic Properties of GaAs/NiFe Coaxial Core-Shell Structures.

Uniform nanogranular NiFe layers with Ni contents of 65%, 80%, and 100% have been electroplated in the potentiostatic deposition mode on both planar substrates and arrays of nanowires prepared by the anodization of GaAs substrates. The fabricated planar and coaxial core-shell ferromagnetic structures have been investigated by means of scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). To determine the perspectives for applications, a comparative analysis of magnetic properties, in terms of the saturation and remanence moment, the squareness ratio, and the coercivity, was performed for structures with different Ni contents.

Clinical and Experimental Substantiation of the Possibility of Using a 25G Tip to a Permanent Magnet to Remove Intraocular Foreign Bodies

Purpose: to develop, experimentally study and evaluate in the clinic the effectiveness of using a 25G handpiece to a permanent operating magnet for IOFB removal.Materials and methods. In the work, we analyzed the results of an experimental study and clinical application of 25 G handpieces. In the experimental part of it, a comparative analysis of magnetic properties was carried out: the force of attraction, strength and topography of the magnetic fields of a standard 25-mm handpiece by V.V. Volkov and 25G caliber handpieces (30, 35, 40, 45 mm long) for a permanent eye magnet. In the clinical part of the work, we analyzed the results of surgical treatment of 57 patients of the ophthalmology clinic with type C OGI (according to the ISOT classification) with localization in the posterior segment of the eye. The mechanism of injury, the area and depth of injury, intraoperative and postoperative complications were analyzed, and the advantages of IOFB removal by a combined method using a 25G tip to a permanent magnet were evaluated.Results. According to the results of our experimental studies, it was revealed: the force of the 25G handpieces is sufficient to fix foreign bodies weighing up to 11 (for a 45 mm handpiece), and the minimum distance at which the magnetic field begins to act around the handpieces is at least 8 mm (data for the longest handpiece 45 mm). A pronounced decrease in the magnetic field strength at the tip surface at a distance of up to 2 mm was revealed. At the stage of using the 25G handpiece in the clinic, when assessing the OTG mechanism, the injuries were distributed as follows: household injury — 47 %, industrial injury — 27 %, road traffic accident — 13 %, combat injury — 13 %. Removal of IOFB was carried out in two versions: transvitreal and combined. IOFB was removed using a 25G permanent eye magnet tip and using a 25G vitreous forceps. During the operation, the following methods of removing IOFB were used: tweezers-tweezers, magnet-tweezers, magnet-magnet. Intraoperatively, in 7 % of cases, there was a slip and fall of IOFB to the fundus. In all cases, an increase in visual acuity was obtained, and in most cases, visual acuity at the time of discharge from the hospital was in the range from 0.05 to 0.1.Conclusion. Removal of magnetic IOFB using a 25 G tip to a permanent magnet allows reliable fixation of IOFB, significantly reduces the risks of intraoperative complications and shortens the duration of surgery.

A comparative analysis of magnetic properties and microstructure of high coercivity Sm(CoCuFe)5 quasi-binary alloys in the framework of fractal geometry

The results of the micro- and nanostructures investigation of Sm(CoCuFe)5 alloys by means of scanning electron and atomic force microscopy are presented. It was shown that sequential high- and low-temperature heat treatments lead to the formation of a homogeneous microstructure with nanoscale compositional heterogeneities. Such a structure provides a coercive filed of up to 32 kOe. The coercivity and remanent magnetization of the samples in the temperature range from 300 to 700 K linearly decrease. The predominant coercivity mechanism in these materials is pinning on nanoscale inhomogeneities with an increased copper concentration. The fractal dimension of the surface of the Sm(CoCuFe)5 alloy metallographic specimen was determined at different stages of heat treatments. The comparative analysis of magnetic properties and microstructure in the framework of fractal geometry was carried out.

Novel method for the production of copper(II) formates, their thermal, spectral and magnetic properties

A new method for the synthesis of various types of copper(II) formates with Cu(NO3)2∙3H2O and formic acid, orthorhombic (α) and monoclinic (β) modifications of anhydrous copper(II) formate, as well as Cu(HCOO)2∙2H2O and Cu(HCOO)2∙4H2O. The identity of the obtained compounds was confirmed by X-ray phase analysis, optical microscopy and thermogravimetry methods. It was shown that Cu(HCOO)2∙4H2O can be used as a precursor for producing copper powders with particle size of the order of 150 nm. The results of investigation of vibration and absorption spectra of α and β modifications of anhydrous copper(II) formate are presented. Their magnetic behavior in the temperature interval 2–300 K was estimated, and comparative analysis of magnetic properties was carried out. First-principle calculations of electronic band structure for anhydrous α and β modifications were performed. The results obtained correspond to experimentally observed structural instability of β-Cu(HCOO)2, fundamental absorption edge enhancement during transition from α to β modification, and low-temperature ferromagnetic ordering in α-Cu(HCOO)2. Simulation for β modification is indicative of antiferromagnetic ordering of magnetic moments inside chains formed by copper-oxygen octahedra.

Magnetism of Bi2Se3 thin films with Eu-rich flat inclusions

We report the results of experimental and theoretical studies of Eu-doped Bi2Se3 thin films with extremely inhomogeneous distribution of magnetic component. The obtained electron microscopy images suggest that Eu atoms are concentrated within platelet-like nanoinclusions. The number of inclusions grows with the increase in Eu content, x. Moreover, at relatively high x values, the stacks of platelets (inclusions located one under another) become rather frequent. A comparative analysis of magnetic properties of the films under study reveals no pronounced changes of their temperature dependence with the increase in x, which, however, leads to the decrease in the average magnetic moment per Eu atom. A theoretical analysis of different mechanisms contributing to a possible magnetic ordering in the Eu-doped films demonstrates that at small distances (i.e. within a platelet) a dominant contribution is related to the RKKY interaction via electrons in the bulk, while the ordering at inter-platelet distances is governed by magnetic dipole–dipole interaction. The latter implies the antiferromagnetic ordering within the stacks of platelets explaining a drop of per Eu atom. We employ the model of a metallic spin glass to estimate the transition temperature, characterising the interaction within the ensemble of randomly distributed magnetic platelets. This estimate gives satisfactory agreement with the experiment, even if we take into account a finite film thickness, thus, neglecting the interaction anisotropy and including only the antiferromagnetism related to the stacking. While the overall contribution of interface Dirac electrons is damped in the systems under study, we argue that the obtained results can be used for the investigation of ultrathin films with analogous impurity profile, where this contribution should be clearly pronounced.

Soft magnetic materials for sensor applications in the high frequency range

The increase in the number of materials for research and extending the list of their applications requires a parallel optimization of the methods of characterization. Microwave magnetoimpedance (MI) in low magnetic fields was proposed for the characterization of the axial magnetization process in different materials. Characterization of the same parameter using different techniques becomes increasingly required. Here we describe our experience in the comparative analysis of magnetic properties, giant magnetoimpedance, ferromagnetic resonance (FMR), and low field MI of CuBe/Fe19Co17Ni64 electroplated and (Co0.94Fe0.06)72.5Si12.5B15 in-water solidified amorphous wires. Microwave studies were conducted using specially designed installation on the basis of Rohde & Schwarz ZVA-67 Vector Network Analyzer for two lengths of the wire of 3 and 6 mm. FMR was also measured using classic cavity perturbation technique. The analysis of the results allows us to observe evolution of the intensity of two absorption peaks and conclude the corresponding to MI and FMR features.

DC bias immune nanocrystalline magnetic cores made of Fe73Nb3Cu1B7Si16 ribbon with induced transverse magnetic anisotropy.

The comparative analysis of magnetic properties of cut cores made of nanocrystalline Fe73Nb3Cu1B7Si16 alloy ribbon and cores made of the same ribbon with preliminary tension-induced transverse magnetic anisotropy was carried out. The possibility of improving magnetic properties of cut cores, decreasing loss, and increasing DC bias immunity of reversible magnetic permeability is presented. The influence of induced magnetic anisotropy on DC bias immunity of reversible magnetic permeability was investigated. The advantages and disadvantages of new cores (made of ribbon heated under tensile stress) over cut ones were determined.

Size effects in the magnetic properties of ε-Fe2O3 nanoparticles

We report the results of comparative analysis of magnetic properties of the systems based on ε-Fe2O3, nanoparticles with different average sizes (from ∼3 to 9 nm) and dispersions. The experimental data for nanoparticles higher than 6–8 nm in size are consistent with the available data, specifically, the transition to the magnetically ordered state occurs at a temperature of ∼500 K and the anomalies of magnetic properties observed in the range of 80–150 K correspond to the magnetic transition. At the same time, Mőssbauer and ferromagnetic resonance spectroscopy data as well as the results of static magnetic measurements show that at room temperature all the investigated samples contain ε-Fe2O3 particles that exhibit the superparamagnetic behavior. It was established that the magnetic properties of nanoparticles significantly change with a decrease in their size to ∼6 nm. According to high-resolution electron microscopy and Mőssbauer spectroscopy data, the particle structure can be attributed to the ε–modification of trivalent iron oxide; meanwhile, the temperature of the magnetic order onset in these particles is increased, the well-known magnetic transition in the range of 80–150 K does not occur, the crystallographic magnetic anisotropy constant is significantly reduced, and the surface magnetic anisotropy plays a decisive role. This is apparently due to redistribution of cations over crystallographic positions with decreasing particle size, which was established using Mössbauer spectra. As the particle size is decreased and the fraction of surface atoms is increased, the contribution of an additional magnetic subsystem formed in a shell of particles smaller than ∼4 nm becomes significant, which manifests itself in the static magnetic measurements as paramagnetic contribution.

Soft magnetic properties of nanocrystalline Fe73B7Si16Nb3Cu1 alloy after rapid heating under tensile stress.

Amorphous Fe73B7Si16Nb3Cu1 ribbon was crystallized rapidly by electric current heating under simultaneously applied tensile stress along the ribbon axis. As a result, strong transverse magnetic anisotropy was induced in the ribbon. Dynamic magnetic properties of the ribbons rapidly heated either under the tensile stress or without tensile stress were measured using toroidal cores. Optimal electric current heating regime that provides maximum improvement of the initial magnetic permeability and core loss was determined. Tensile stress increase from 0 to 180 MPa was shown to result in the decrease of the initial magnetic permeability down to 400 and core loss at frequencies from 0.4 to 200 kHz. Comparative analysis of magnetic properties of the cut core (with non-magnetic gap) and the cores heated under tensile stress was carried out. The magnetic properties of the latter cores are advantageous for manufacturing the reactors and linear chokes of switch-mode power supplies.

A comparative analysis of magnetic properties in rocks: Five active submarine volcanoes in the western Pacific

We studied the petrophysical and magnetic properties of dredged rocks that compose the edifices of five active submarine volcanoes in the Pacific Ocean, viz., the Fukujin, Esmeralda, Kovachi, and Simbo at island arcs, and Ile des Cendres in a marginal sea. We measured the standard petrophysical and magnetic characteristics and performed three kinds of thermomagnetic analysis as well as an electron-probe analysis. Comparative analysis of magnetic properties in rocks showed that they are strongly differentiated by the value of natural remanent magnetization and of magnetic susceptibility. The greatest values are shown by the Esmeralda aphyric basaltic andesites, the lowest occur in the Ile des Cendres xenoliths. The principal carriers of magnetization in the rocks are grains of unaltered and/or oxidized titanomagnetite with varying domain structures. All the samples are magnetically isotropic.

Comparative analysis of magnetic properties of the basalts collected in the Red Sea and other rift zones

The magnetic properties of basalts collected from the young rift zone of the Red Sea are studied in detail. Special features revealed in the magnetic behavior of the samples testify to a complex character of the evolution of the Red Sea rift zone. The magnetic characteristics of basalts from the Red Sea rift zone and other rift zones are compared. The reasons for high values of the natural remanent magnetization I n and Konigsberger factor Q n obtained for the Red Sea basalts are clarified.