Modelling of Spin-Dependent Mechanical Friction at Atomic Level

In this work a simple 2D model of pseudostatic friction at atomic level has been prepared, in the frame of which both Lennard-Jones potential and spin-dependent term of exchange interaction has been included. As an example, it has been demonstrated, that for iron both average lateral and normal forces between atoms of "base" and "slider" in the tribological node are altered through the change of relative direction of spins, by over a dozen of percent, when the interatomic distance is comparable to the lattice constant. Spin-dependent correction of atomic-level friction coefficient has been estimated

Thermal Compensation Model of Magnetic Circuits with Modern Magnetic Materials

In this work a quantitative analysis of thermal compensation has been performed for a magnetic circuit producing magnetic field in the air gap. The considered system consists of Sm₃Co₁₇ type permanent magnet (as a source of magnetic field), nanocrystalline FINEMET alloy (as ultra-soft magnetic medium) and Fe-Ni low Curie temperature compensative material (as a magnetic shunt). Distribution of magnetic field induction in the circuit has been calculated numerically within standard one-dimensional approximation, considering nonlinearities of compensative material as well as demagnetization susceptibility of permanent magnet. It has been theoretically predicted, that an appropriate choice of the compensative element thickness improves significantly thermal stability of magnetic field in the air gap

Model of Anisotropic Electrical Resistivity in Rough Thin Films

In this work a new model of electrical resistivity is proposed in order to study the relationship between surface roughness geometry and thin films resistivity. The model is based on the numerical dynamic averaging of electron mean free path over whole simulated structure of rough film. For current-in-plane configuration the resistivity increases with decreasing film thickness faster than for current-perpendicular-to-plane one. Our simulations showed that big roughness depth and fine in-plane spatial period of roughness are crucial factors increasing the resistivity of ultrathin metallic layers

Thermal Compensation Model of Magnetic Circuits with Modern Magnetic Materials

In this work a quantitative analysis of thermal compensation has been performed for a magnetic circuit producing magnetic field in the air gap. The considered system consists of Sm₃Co₁₇ type permanent magnet (as a source of magnetic field), nanocrystalline FINEMET alloy (as ultra-soft magnetic medium) and Fe-Ni low Curie temperature compensative material (as a magnetic shunt). Distribution of magnetic field induction in the circuit has been calculated numerically within standard one-dimensional approximation, considering nonlinearities of compensative material as well as demagnetization susceptibility of permanent magnet. It has been theoretically predicted, that an appropriate choice of the compensative element thickness improves significantly thermal stability of magnetic field in the air gap

Surface Magnetostriction Model for MagNEMS

In this work the influence of surface roughness on magnetostrictive nano-actuator parameters has been analyzed theoretically. A mechanical and magnetoelastic behavior of investigated cantilever bimorphic system has been described in the frame of the simple analytical model. Realistic material parameters have been incorporated into the model for high-magnetostrictive galfenol (Fe-Ga) thin films on silicon substrate. It has been shown that for 5 nm thick galfenol film a flat surface magnetostrictive effects modify the cantilever deflection and force only by 3%, whereas in the case of rough surface this influence increases to about 15%, when dimensions of roughness steps are comparable to the distances between them

Modelling of thermomagnetic curves obtained with Mössbauer spectrometry for two-phase nanocrystalline alloys

Thermomagnetic curves obtained with Mössbauer spectrometry for two-phase nanocrystalline alloys have been analyzed theoretically. The main goal was to understand a slope jump in the temperature dependence of the hyperfine field for crystalline phase of higher Curie temperature at the Curie point of the amorphous phase. We propose a simple model introducing an effective exchange integral for one phase depending on mean spin value in the other phase. We also consider a strong spin polarization of the amorphous phase by penetrating field originating from nanocrystallites. Results of numerical calculations within the mean field approximation (MFA) reproduce qualitatively the experimental curves for nanocrystalline FINEMET and Fe-Nb-B alloys

Modeling of Magnetic Hyperfine Field Distribution for Spherical Nanoparticles of bcc Structure

We propose a simple model for temperature evolution of magnetic hyperfine field distribution of spherical bcc Fe nanoparticles. We performed mean field approximation calculations of mean spin value in each spherical shell of nanoparticle. Considering magnetic hyperfine field values reported for iron thin films we predicted possible values of hyperfine fields in the internal and surface region of the particles as a function of temperature

The Magnetic Specific Heat of the BEG Model

The magnetic contribution to the specific heat of the Blume-Emery-Griffiths model with spin-one is studied by the cluster variational method in pair approximation. The nearest neighbour correlation functions are taken into account. The temperature dependencies of the specific heat are calculated and discussed in the context of the phase diagrams obtained recently for the thin film with bilayer geometry

LASER SCATTEROMETRY FOR DETECTION OF SQUAT DEFECTS IN RAILWAY RAILS

The paper concerns a defectoscopy of squats occurring on the surface of the rail head. Disadvantages of traditional methods being used in detection of such defects were also presented. Authors proposed a new method based on simplified laser scatterometry to detect these defects. Physical model of the laser beam scattering by edges of such defects and simulation results were given. An experimental set-up for practical testing of this method was designed and constructed. This system enabled measurements of squat defects occurring in the section of the rail extracted from the track. The analysis of obtained results was performed. Authors also indicated directions of further research and development

Iron-containing phases in metallurgical and coke dusts as well as in bog iron ore

Several samples of dusts from steel and coke plants (collected mostly with electro filters) were subjected to the investigation of content of mineral phases in their particles. Additionally, sample of bog iron ore and metallurgical slurry was studied. Next, the magnetic susceptibility of all the samples was determined, and investigations of iron-containing phases were performed using transmission Mössbauer spectrometry. The values of mass-specific magnetic susceptibility varied in a wide range: from 59 to above 7000 × 10−8 m3kg−1. The low values are determined for bog iron ore, metallurgical slurry, and coke dusts. The extremely high was obtained for metallurgical dusts. The Mössbauer spectra and X-ray diffraction patterns point to the presence of the following phases containing iron: hematite and oxidized magnetite (in coke and metallurgical dusts as well as metallurgical slurry), traces of magnetite fi ne grains fraction (in metallurgical dusts), amorphous glassy silicates with paramagnetic Fe3+ and Fe2+ ions, traces of pyrrhotite (in coke dusts), α-Fe and nonstoichiometric wüstite (in metallurgical slurry), as well as ferrihydrite nanoparticles (in bog iron ore). For individual samples of metallurgical dusts, the relative contributions of Fe2+/3+ ions in octahedral B sites and Fe2+ ions in tetrahedral A sites in magnetite spinel structure differs considerably