Formation Of Magnetic Structure Research Articles

Magnetic ordering in granular system

The conditions of the formation of different magnetic structures with ferromagnetic (FM) and antiferromagnetic (AFM) ordering in granular materials containing a subsystem of ferromagnetic granules are considered within the phenomenological approach. It is supposed that the magnetostatic field and the exchange interaction between conduction electrons and magnetic ions are responsible for the formation of magnetic structure.

Thickness dependence of magnetic properties of granular thin films with interacting particles

The effect of film thickness on magnetic properties of Cu80Co20 granular alloy was studied. It was observed that the susceptibility peak temperature, TM, strongly increases with the film thickness, t, for t<100 nm. The long-range nature of this effect points to magnetic dipole interaction as responsible mechanism. This dependence of TM can be explained within the framework of Dormann’s theory of dipolar interaction between magnetic particles. The coercive field has different thickness dependence and it is related to formation of magnetic domain structure of Co particles in the granular alloy.

Hall effect and magnetic viscosity phenomena in κ-(BEDT-TTF)2Cu[N(CN)2]X (X=Cl, Br)

Hall effect studies have been performed in the compounds \ensuremath{\kappa}-(BEDT-TTF${)}_{2}$Cu[N(CN${)}_{2}$]X, where X=Cl and Br and BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene, in the temperature range 100 to 10 K. Hall constant has been found to be temperature independent in the Br salt down to 55 K and equal to +2\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}8}$ ${\mathrm{m}}^{3}$/C. In the Cl salt the Hall constant is equal to +1.4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}7}$ ${\mathrm{m}}^{3}$/C at 100 K and increases on cooling down to 70 K almost parallel to the resistance increase. Below \ensuremath{\sim}70 and \ensuremath{\sim}55 K in the Cl and Br, respectively, the magnetic field change has been found to produce long-term sample resistance relaxation. The relaxation phenomena change dramatically with temperature, reaching the maximum above magnetic ordering temperature in the Cl salt at 30 K, and then sharply dropping in magnitude in the magnetically ordered state. A similar relaxation is observed in the Br salt. These effects are considered to be due to the magnetic domain structure formation in the antiferromagnetically ordered state. Essential changes of the domain wall dynamics, appearing in the Br salt at 25 K, evidence the presence of the second magnetic transition in the Br salt, quite similar to the Cl salt. By studying the anisotropy of the relaxation phenomena within highly conducting plane in the Cl compound it is shown that domain walls are lying parallel to the a direction. A possible origin of the magnetic order in the salts is discussed.

Plasma Spraying of Magnetite Coatings for M.W. Applications

The possibilities of arc - plasma spray deposition of polycrystalline ferromagnetic coating are investigated. Powder sintered microwave absorbing ferrite materials were deposited by arc-plasma jet on polycrystalline substrates. By varying the distance between plasma torch and substrates and the spray duration, coatings with different thickness and porosity were obtained. The coatings characteristics were studied by optical, SEM and XRD methods. The mechanism of the magnetic structure formation was controlled by Mossbauer spectroscopy. The microwave absorption at 9.4 GHz, measured using a standard waveguide equipment was found to be 26%.

Low‐temperature Magnetic Properties of Terbium Orthoferrite Single Crystals

AbstractSpontaneous and by an external magnetic field induced magnetic phase transitions in TbFeO3 have been experimentally studied. Precision investigations of velocities of transmission and attenuation of sound wave were made, the processes of formation and rearrangement of magnetic structure examined and its change under the influence of external magnetic field explored. This has been made possible by the development of methods of controlled growth of rare‐earth orthoferrites resulting in the formation of high‐quality single crystals of required size with reproducible physical properties. The measurements were taken in the temperature range from 0.45 to 8.0 K. From the threshold Geld values a Ha  T phase diagram for TbFeO3 has been plotted.

Time and temperature dependence of nanocrystalline structure formation in a Finemet-type amorphous alloy

The magnetic softness and nanocrystalline structure formation of Fe 73.5Cu 1Nb 3Si 13.5B 9 Finemet alloy as a function of annealing temperature (500–600°C) and annealing time (5 s - 3 h) were investigated by means of magnetic measurements, DSC and X-ray diffractometry. Annealed at 550°C the grain size, the solute silicon content of α-Fe grains and the improvement in magnetic softness saturates as a function of time. The deterioration of the magnetic softness after annealing at 575°C is attributed to the Fe 3Si compound which segregates from the α-Fe solid solution, giving a third intermediate peak on the well-known double-peaked DSC diagram. The crystallization products appearing after annealing at 600°C destroy the intergranular magnetic coupling and give rise to a magnetic hardening.

The nearby 2-solar mass BOK globule LBN 11 - Sub-sonic molecular clumps in a magnetic environment

A multiwavelength study of the nearby small Bok globule LBN 11 is performed in order to investigate the relationship between embedded magnetic fields, cloud structure, and star formation. Optical polarimetry of background stars is used to characterize and trace the embedded magnetic field direction. High-dispersion CO isotopic mapping is employed to determine the radial density distribution of the gas, measure cloud rotation, and identify individual gas clumps. CS and SO mapping revealed dense cores within the (C-13)O clumps. Analysis of coadded IRAS images reveal the cloud to be free of current or recent star formation: there are no IR point sources of sufficient flux or proper colors to signify young stars associated with the cloud. The molecular line maps show the cloud to be extremely clumpy. Clumps are found to range in size from 0.2 pc for the largest CO clump to about 0.04 pc for the smallest CS feature. It is concluded that, at least in the envelope of the cloud, the magnetic field and the CO clumps are coupled.

Preparation of substituted barium ferrite powders

Pure and (Co, Ti)-substituted Ba ferrites, produced by the citration process with the initial Fe to Ba ratio equal to 11.2, have been studied. The substitution x in Ba(Co, Ti) x Fe 12- x O 19 has been varied from 0 to 1.1. The mechanism of the magnetic structure formation has been controlled by Mössbauer and infrared spectroscopy combined with magnetic susceptibility measurements. The substitution x = 0.5 showed promising properties for magnetic recording applications.

Influence of metamagnetic transition on the vortex phase in antiferromagnetic superconductors

Abstract The metamagnetic (or spin-flop) transition which is experimentally observed in certain antiferromagnetic superconductors results in the formation of magnetic domain structure if the demagnetization factor of the sample is nonzero. It is demonstrated that such structure leads to the modulation of vortex lattice density which is maximal in the domains of spin-flop phase. The structure of a vortex with a ferrimagnetic domain near its core is also investigated. The results of calculations show that under appropriate conditions the interplay between superconductivity and metamagnetism makes the formation of peculiar two-quanta vortices energetically favourable.

Magnetic Transitions in Perovskites Ca(Mn3−xCux)Mn4012

en

Effect of vibration on the process of magnetic structure formation in powdered materials

Effect of vibration on the process of magnetic structure formation in powdered materials

Magnetic properties of the CrSxTe1−x (x = 0−0.2) solid solutions

AbstractOn the basis of X‐ray, magnetic and neutron diffraction measurements the range of solubility in the CrSxTe1−x (x = 0−0.2) system has been established and the magnetic phase diagram of the system has been plotted. The decrease of magnetization at low temperature and the additional reflections in the neutron diffraction patterns are associated with the formation of noncollinear magnetic structure which is characterized by the antiferromagnetic component of the magnetic moments. This component has the orthorhombic unit cell with \documentclass{article}\pagestyle{empty}\begin{document}$ a_M = \sqrt {3a_0 } $\end{document}, bM = a0, cM = c0. The character of the exchange interactions giving rise to this magnetic structure is discussed.