Magnetic Eld Research Articles

Imaging of Magnetic Domains and Domain Walls in Spherical Fe-Si Powder Using Magnetic Force Microscopy

The commercial Fe-Si powder, produced by Hoganes Corporation, represents promising soft magnetic material for technological applications. The powder consists of spherical particles with diameter up to 150 μm. Internal microstructure of the powder is formed by grains of diameter of about 30 μm. Each separate grain has a random orientation of the easy magnetization axis and is su ciently large to split into several magnetic domains. A comparative study of the atomic force microscopy (AFM) topography and the corresponding magnetic force microscopy (MFM) images was employed in order to examine the correlation between the grain size, boundaries of grains and characterization of the magnetic domains, which gives us an important knowledge about possible behavior of particles under the in uence of the external magnetic eld and further utilization of the spherical Fe-Si particles in electrotechnical industry. The grain size and the crystallographic orientation of grains were analyzed by the electron backscattering di raction (EBSD) technique.

Stress-Induced Changes in Closure Domain Structure Dynamics in Bistable Ferromagnetic Microwire

A new experimental method for the study of closure domain structure dynamics in bistable ferromagnetic microwires is proposed. The simple experimental set-up enables detection of the presence of a free domain wall in the wire after application of a well-de ned rectangular magnetic eld pulse. The changes in closure domain structure dynamics, caused by applied tensile stress, are demonstrated by measurements on Fe77.5B15Si7.5 glasscoated microwire. Minimum critical eld for the release of a domain wall from the closure domain structure increases with increasing stress, while on the other hand, the minimum time needed for this process rapidly decreases with increasing stress.

Magnetovision Scanning System for Detection of Dangerous Objects

This paper presents an application of magnetovision based measurements to develop a method for passive detection of dangerous ferromagnetic objects. Scanning system was designed and built to study the magnetic eld vector distributions. The measurements of the Earth's eld disturbances caused by ferromagnetic objects were carried out. The ability for passive detection of selected dangerous objects was demonstrated. Further data processing allowed for determining the (x,y) coordinates of the object relative to the plane of measurement, and even the possibility of calculating the distance from the object. The results obtained indicate that it is possible to detect and determine the location of dangerous ferromagnetic objects. This opens the new way to use magnetovision in public security systems, in particular for the detection of dangerous objects by police and sapper robots.

High Resolution Tips for Switching Magnetization MFM

Switching magnetization magnetic force microscopy (SM-MFM) is based on two-pass magnetic force microscopy with opposite orientation of tip magnetization between two scans. The sum of the scanned data with reversed tip magnetization depicts local van der Waals forces, and their di erence maps the local magnetic forces. Tip magnetization can be easily reversed in external magnetic eld during the scanning. The separation of the forces mapped enables scanning in close proximity of the sample (∼ 5 nm). Therefore, extremely high spatial resolution (10 nm) is achievable by the SM-MFM. Image phase resolution of the MFM method depends on various geometric parameters of the tip, such as tip length, its apex radius and taper angle. The parameters are determined by the evaporation process, within which the standard atomic force microscopy tips are coated with magnetic layer. In this work we show that the thickness of the coated layer is important for the SM-MFM spatial resolution.

Formation of Accelerated Particle Beam in Isochronous Cyclotron

In the literature there is usually considered a dependence of the one of main beam parameters the value of energy spread, ∆E/E, on cyclotron characteristics for magnetic eld by form closed to isochronous one [1]. Since the output of ion beams from considered installation is realized in decreasing eld, there was carried out an estimation of energetic spread of the beam with nite phase width ∆φ in case of one-revolution output for real magnetic eld that has a decreasing area.

Production of Mo+Beams Using an Arc Discharge Ion Source

A new method of Mo ion beam production is presented in the paper. The method bases on the chemical sputtering/etching of the molybdenum parts (e.g. anode) of the arc discharge ion source by the chloride containing plasma. A mixture of CCl4 (or CHCl3) vapor and air was used as the feeding substance. The separated Mo beam current of approximately 18 μA was achieved. The measurements of the ion current dependences on the discharge and lament currents as well as on the magnetic eld ux density from the electromagnet surrounding the discharge chamber were performed in order to nd the optimal working parameters of the ion source.

Preparation and Characterization of Aligned Iron Oxide Carbon Nanotube Thin Film. Acta Physica Polonica A 125, 77 (2014), ERRATUM

Thin lms of acid-functionalized multiwall carbon nanotubes (O-MWCNT) with di erent concentrations and coated O-MWCNT with Fe3O4 nanoparticles (MWCNT/Fe3O4) were prepared on glass substrate at 300 ◦C by spray pyrolysis technique. In order to study the e ect of nanotubes alignment on the physical properties of carbon nanotube lms, thin lm of iron oxide nanoparticles coated carbon nanotubes was deposited under magnetic eld of 0.4 T. All samples were characterized using UV Vis spectroscopy, X-ray di raction, scanning electron microscopy, and the Hall e ect experiment. Results show that the electrical conductivity and optical transmittance of carbon nanotubes thin lms depend on the concentration of carbon nanotubes and their arrangement at the lms. Aligning carbon nanotubes in thin lms leads to an obvious improvement in electrical and optical properties of thin lms.

Analysis of the Effect of Magnetostimulation on Viscoelastic Properties of Blood in Patients with Lasting Pain

The aim of the current work was to analyze the in uence of alternating magnetic eld on the viscoelastic properties of blood in vivo in patients with lasting pain problems. Oscillatory techniques, also called the dynamic mechanical analysis, have been used in the current work to study the viscoelastic properties of blood. The blood samples were collected from patients of a neurological ward complaining about spinal cord and lower limbs pain. Altogether 25 patients took part in the study. A blood sample was collected from each patient twice: before the magnetostimulation and after ve treatments. For each blood sample, the hematocrit value was measured using the standard method. Plasma viscosity and the complex whole blood viscosity were measured by means of a rotary-oscillating rheometer Contraves LS40. Magnetic eld was generated by the instrument Viofor JPS and the magnetostimulation treatments were performed using di erent programs. The analysis of the results included estimation of the hematocrit value, plasma viscosity, complex whole blood viscosity and its components: viscous and elastic viscosity at four chosen amplitudes of the shear rate as a function of the applied treatment program. The results obtained in the study suggest that rheological properties of blood change depending on the applied magnetostimulation program.

Characterization of Radiation Defect Centers in Neutron Irradiated Si Using Inverse Laplace Transformation to Analysis of Photocurrent Relaxation Waveforms

High-resolution photoinduced transient spectroscopy has been applied to investigating the e ect of the 1 MeV neutron uence on the electronic properties of radiation defects in Czochralski grown silicon in magnetic eld. A new approach to the analysis of the photocurrent relaxation waveforms as a function of time and temperature has been presented. It is based on using a two-dimensional numerical procedure with implementation of the inverse Laplace transformation for creating images of the sharp spectral fringes depicting the temperature dependences of the thermal emission rate for detected defect centers. In the material irradiated with the uence of 3× 10 cm−2, the dominant traps with activation energies of 75 meV and 545 meV are tentatively identi ed with an aggregate of three Si interstitials and the trivacancy, respectively. In the material irradiated with the uence by the order of magnitude higher, the activation energies of the main traps are found to be 115, 350, 505, 545, and 590 meV. These traps are tentatively attributed to an aggregate of four Si interstitials, as well as to vacancy related centers such as V3 (2-/-), V2O (-/0), V3 (-/0) and V4 (-/0), respectively.

Myofascial Trigger Points and the Body Posture~-~Deactivating them Applying Magnetic Fields (preliminary reports)

Myofascial pain syndrome is sensory, motor, autonomic disorder caused by the occurrence of trigger points (TrP). In literature the possibilities of deactivating TrPs through exposure to magnetic eld (MF) can be noticed. The aim of current research is an attempt at answering the question whether MF changes TrP activity. Tests were carried out on 22 volunteers, who were divided into three groups. First was exposed to static MF using MagneticUnit discs, second was exposed to slow changing MF using Viofor-JPS. The third was exposed to magnetoledotherapy, also using Viofor-JPS.

Electron-Positron Annihilation in Ultra-Strong Magnetic Fields. Comparison of One- and Two-Photon Annihilation at Middly Relativistic Regime

We consider the oneand two-photon e+e− annihilation processes in an ultra-strong magnetic eld, at middly relativistic regime. Such conditions are reached in neutron stars and especially in magnetars, where electrons and positrons ow within the magnetar corona with average momenta of the order of p ∼ m0c, where m0 electron mass, c light speed. We pay special attention to the ratio of the total annihilation rates of both processes. The well-known result is that in the limit p → 0 and for magnetic induction above the critical Schwinger value B0 = 4.41×10 T, one-photon annihilation dominates over the two-photon process. Results presented in this article verify the current knowledge about this ratio in magnetars; the calculations indicate that for particles moving with middly relativistic momenta both processes can be equally important.

The Influence of a Magnetic Field on the Formation of Corrosion Defects in Selected Metals and Steels, Analysed Using Positron Annihilation Method

The method of positron lifetime measurement was used to analyse the in uence of a magnetic eld on the kinetics of corrosion defect formation in near-surface layers of iron, titanium as well as S20 and S0H18N9 steel grades. The listed metals, which belong to ferroand paramagnetic materials, have di erent sensitivity to corrosion. It was found that not only the presence of a magnetic eld, but also its direction in uence the dimensions and the concentration of defects formed during corrosion.

Field Induced Unusual Magnetic Behavior at Low Temperature in Pr0.67Ca0.33MnO3

In this study, magnetic properties of Pr0.67Ca0.33MnO3 compound were investigated in detail. The magnetization versus temperature (M T ) curve showed that this material undergoes a charge order transition at 200 K. A more pronounced FM phase appeared below 56 K. At T = 5 K, a eld induced sharp step like magnetisation transition associated with phase separation was observed. However, after application of 7 T magnetic eld at 5 K, the magnetic behaviour of sample was changed completely and full FM behaviour was observed. The more interesting is that the sample remains in the FM state and does not retrieve the initial magnetic state until warmed up to charge order transition temperature. Large negative magnetic entropy change (−26.18 J/(kg K) at 38 K and 5 T) was attributed to step like magnetisation transition.

Magnetoresistance of Electrochemically Produced NiFe and CoNiFe Nanowires

CoNiFe and NiFe nanowires were electrochemically produced by dc electrodeposition on highly ordered porous anodic alumina oxide templates. Scanning electron microscope images of nanowires after removing the alumina membrane showed that these nanowires are uniform with the diameters of about 220 300 nm and about 25 30 μm length. The energy dispersive X-ray analysis showed that the composition of the nanowires is Ni88Fe12, Co7Ni82Fe11. Magnetic eld was applied by an electromagnet and resistance was measured by four point technique.

EPR Study of Gamma Irradiated Cholestanone Single Crystal

Cholestanone (C27H46O) single crystals were irradiated with Co-γ rays at room temperature. The spectra were recorded for di erent orientations of the crystal in the magnetic eld at 120 K using the EPR technique. Radiation damage center was attributed to ĊHCH2CH2 radical. The principal values of the hyper ne coupling tensor of the unpaired electron with the protons and the principal values of the g tensor were determined. The results were found to be in good agreement with the existing literature.

Crack Detection Using Fluxgate Magnetic Field Sensor

In this study, the variation of the magnetic ux distribution in a magnetised ferromagnetic material which has in homogeneity as a crack is studied. An orthogonal uxgate magnetic eld sensor was used in the inspection of cracks. In the uxgate sensor, the sensing element (Co0.94Fe0.06)72.5Si12.5B15 amorphous ferromagnetic wire was placed inside a pickup coil winding with 50 μm copper wire and connected to a signal generator and the output from pick-up coil was detected using a lock-in ampli er. The surface pro le of magnetic materials with a crack was obtained using a specially designed 3-dimensional moving system. A large decrease in the output voltage of the sensor was observed when the sensor was moved on the top of the crack, after the further movement of the sensor the output voltage came back to the previous value.

Preparation and Characterization of Aligned Iron Oxide Carbon Nanotube Thin Film

Thin lms of acid-functionalized multiwall carbon nanotubes (O-MWCNT) with di erent concentrations and coated O-MWCNT with Fe3O4 nanoparticles (MWCNT/Fe3O4) were prepared on glass substrate at 300 ◦C by spray pyrolysis technique. In order to study the e ect of nanotubes alignment on the physical properties of carbon nanotube lms, thin lm of iron oxide nanoparticles coated carbon nanotubes was deposited under magnetic eld of 0.4 T. All samples were characterized using UV Vis spectroscopy, X-ray di raction, scanning electron microscopy, and the Hall e ect experiment. Results show that the electrical conductivity and optical transmittance of carbon nanotubes thin lms depend on the concentration of carbon nanotubes and their arrangement at the lms. Aligning carbon nanotubes in thin lms leads to an obvious improvement in electrical and optical properties of thin lms.

Coating Effect on Magnetic Properties of Fe36Co36B19.2Si4.8Mo3W1Amorphous Ribbons

In this research, the electrodeposition technique was employed to prepare ne-grained nickel, iron and iron-cobalt coatings with 1 μm thicknesses on the substrate of the Fe36Co36B19.2Si4.8Mo3W1 amorphous ribbons. The coating e ect on magnetic properties was examined at room temperature using an ADE Magnetics EV9 vibrating sample magnetometer with maximum magnetic eld strength of 1750 kA/m. It is found that Ni, Fe, and Fe Co coated amorphous ribbons show 0.60, 0.71, and 1.01 T saturation magnetization, respectively, while uncoated ribbon has 1.55 T.

Magnetized Kantowski--Sachs bulk viscous string cosmological models with decaying vacuum energy density $\Lambda (t)$

In this paper, we deal with bulk viscous magnetized Kantowski{Sachs string cosmological models in the presence of time variable cosmological term . To obtain a deterministic model, we assume the conditions 1 and = constant, where is the shear, the expansion in the model, and the coecient of bulk viscosity. The value of cosmological constant for the models is found to be small and positive, which is supported by the results from recent observations (SN 1a). The behavior of the model in the presence and absence of magnetic elds together with physical

On a Class of Sobolev-Type Equations

The article surveys the works of T.G. Sukacheva and her students studying the models of incompressible viscoelastic Kelvin Voigt uids in the framework of the theory of semilinear Sobolev-type equations. We focus on the unstable case because of greater generality. The idea is illustrated by an example: the non-stationary thermoconvection problem for the order 0 Oskolkov model. Firstly, we study the abstract Cauchy problem for a semilinear nonautonomous Sobolev-type equation. Then, we treat the corresponding initialboundary value problem as its concrete realization. We prove the existence and uniqueness of a solution to the stated problem. The solution itself is a quasi-stationary semi-trajectory. We describe the extended phase space of the problem. Other problems of hydrodynamics can also be investigated in this way: for instance, the linearized Oskolkov model, Taylor's problem, as well as some models describing the motion of an incompressible viscoelastic Kelvin Voigt uid in the magnetic eld of the Earth.