Papers by Keyword: Magnetisation

Abstract: The interlayer coupling in Co/Ge/Co trilayer films has been experimentally studied by the SQUID magnetometry and electron magnetic resonance. It has been found that the interlayer coupling is temperature-dependent. The values of the exchange constants have been determined.

Abstract: Structure and magnetic properties of non-stoichiometric rare earth intermetallic compounds TbNi2Mnx and DyNi2Mnx x have been studied. It was found that for the compositions with x ≤ 1 the alloys retain the single-phase cubic structure despite the fact that the rare earth-to-3d metal ratio changes from 1:2 to 1:3. Magnetic measurements revealed that the Mn alloying leads to a substantial growth of the Curie temperature with a maximum at x ~ 0.5. At low temperatures the magnetization reversal of the Mn-containing samples is characterized by a considerable hysteresis caused by pinning of narrow domain walls by the structure defects. The observed experimental data are discussed within the assumption on a local distortion of the crystal electric field and the formation of a non-collinear magnetic structure of the rare earth sublattice.

Abstract: Weak magnetic ZnFe2O4 nanoparticles were prepared by coprecipitation and treated with different concentrations of Fe(NO3)3 solution. Untreated and treated particles were studied using a vibrating sample magnetometer, transmission electron microscope, by X-ray diffraction, X-ray energy dispersive spectroscopy and X photoelectron spectroscopy. The results showed that, after treatment, the ZnFe2O4/γ-Fe2O3 forms disphase nanoparticles, with enlarged size, enhanced magnetic properties and with a surface parceled with Fe(NO3)3. The size of the particles and their magnetic properties are related to the concentration of the treatment solution. The particle size and magnetic properties could be controlled by controlling the concentration of treating solution, therefore nanoparticles can be more widely used.

Abstract: In this paper we present new results on magnetic and magnetoelastic uniformity measurements on Fe78Si7B15 amorphous ribbons and wires. The measurements are performed using an automatic instrumentation device based on the magnetostrictive delay line technique, with the ability to determine the B(H) and (H) functions along the length of a ribbon with parametric control of field and frequency. According to these results, it has been determined that magnetic and magnetoelastic uniformity functions are subject to the history of the under test samples.

Abstract: The rigid seals currently being used for the ash unloading device with the impeller under the hopper of the electrostatic precipitator are easy targets of wear and tear. In addition, the airproof capability of these seals is not perfect. In this light, an advanced powder magnetic seal design which installs permanent magnets at the top of the vane and utilizes the magnetism of Fe3O4 in fly ash to seal the space between two vanes is discussed in this paper. In the self-designed device, three categories of permanent magnet parameters and four kinds of powders with respective with respective magnetic powder mass fractions of 7%, 9%, 12%, and 15% were chosen. The airproof capability was also measured. The results show that this device has excellent airproof capability, can withstand wear and tear, and has a low replacement frequency.

Abstract: Passive magnetic bearing with Halbach array is presented in this paper. The array uses permanent magnets with radial and axial magnetization to augment the magnetic field on one side of the array and cancel it on the other side. The design of the bearing consists of ring-shaped magnets of 60x70 mm and 75x85 mm with different orientation of magnetization. The designed passive magnetic bearing has air gap of 2.5 mm, stiffness 129297 N/m and maximal value of load 200 N. The bearing ensures magnetic levitation and stabilization of rotor in a work point. The paper presents the design of the passive magnetic bearing as well as the experimental setup together with investigation results.

Abstract: BiFeO3-based single-phase multiferroics have been widely studied in both ceramics and films. However, the macroscopic magnetic properties of BiFeO3 ceramics were now most very weak. In this work, MnO2 and Co2O3 were used as B-site substitutes in BiFeO3 ceramics in order to the enhancement of magnetic properties. The change of magnetization was analyzed based on the phase composition and the microstructure of ceramics.

Abstract: Micro-composite sol-gel coating was introduced into bio-limited forming technology for the first time, and the feasibility of the micro-composite sol-gel coating on microorganism was verified. The composite coated microorganism was observed by using optical microscopy. The results showed that the micro-particles of carbonyl iron could remain being fixed on the surface of cells of spirulina platensis by sol-gel process after repeated washings and collections and by using second sol-gel process the micro structures of microorganism would be kept well after drying. The co-deposition mechanism of the composite coating was also discussed.

Abstract: This work investigates the influence of initial compound synthesis prehistory on the phase sequence during formation of single-phase Sr2FeMoO6 (SFMO). Analytical-grade SrCO3, Fe2O3 and MoO3 (sample No.1) and partially reduced precursors of SrFeO3-x (SFO) and SrMoO4-y (SMO) (sample No.2) were used as initial reagents. In the latter case, kinetic limitations of SFMO phase formation are resolved by increasing the diffusivity of both of Fe3+ and Mo5+ and decreasing diffusion lengths to the reaction zone. This enhances the double-perovskite growth rate, lowers synthesis temperature and increases the intensity of X-ray reflections of (011) and (013) planes suggesting a superstructural ordering of Fe3+ and Mo5+ cations. Samples No.1 and No.2 have both a Тс ~ 420K while the magnetization value at 77 K in the sample No.2 is higher by a factor 2.3 compared to that of sample No.1. A decrease of the oxygen vacancy concentration by annealing Sr2FeMoO5.82 lowered magnetization of the samples and promoted the formation of a second magnetic phase with Тс = 700 К. We suppose that an increase of oxygen partial pressure during annealing causes formation of clusters with antiferromagnetic coupling in Fe3+-О2--Fe3+ chains. In order to increase the magnetoresistive effect at temperatures relevant for technical application, weak intergrain bonds should be formed.

Abstract: Thermodynamics of Heisenberg ferromagnets is described by means of a fluctuating exchange field operating on the atomic magnetic moments. A self-consistent method for calculating field characteristics is developed at arbitrary temperatures. It is shown that transitions in a paramagnetic state may pass both continuously and stepwise on temperature subject to magnitude of single-site susceptibility.