bluuebunny/crossref_metadata_2025 huggingface dataset:
Transmission and Reflection Coefficients for Damage Identification in 1D Elements
Authors: Krawczuk Marek , Palacz Magdalena , Zak Arkadiusz , Ostachowicz Wiesław M.
Published: September 2009

According to the latest research results presented in the literature changes in propagating waves are one of the most promising parameters for damage identification algorithms. Numerous publications describe methods of damage identification based on the analysis of signals reflected from damage. They also include complicated signal processing techniques. Such methods work well for damage localisation, but it is rather difficult to use them in order to estimate the size of damage. It is natural that propagating wave reflects from any structural discontinuity. The bigger the disturbance the bigger part of a propagating wave reflects from it. The amount of energy reflected and transmitted through any discontinuity can expressed as reflection and transmission coefficients. In the literature different application for these coefficients may be found – the most often cited application is connected with localising changes in the geometry of structures. Changes in the coefficients due to cross section variations in rods and beams or due to existence of stiffeners in plates are well documented. However there are no application of using the reflection and transmission coefficients for damage size identification. For this reason the analysis presented in this paper has been carried out.
The article presents a method of damage identification in 1D elements based on the wave propagation phenomenon and changes in reflection and transmission coefficients. The changes in transmission and reflection coefficients for waves propagating in isotropic rods with different types of damage have been analysed. The rods have been modelled with the elementary, two and three mode theories or rods. For numerical modelling the Spectral Finite Element Method has been used. Several examples are given in the paper.
Silsesquioxane-Based Hybrid Nanocomposites of Polymethacrylate Type with Self-Assembling Properties
Authors: Simionescu Bogdana , Olaru Mihaela , Aflori Magda , Buruiana Emil C. , Cotofana Corneliu
Published: September 2009

The aim of the study was to synthesize and characterize silsesquioxane-based hybrid nanocomposites with self-assembling properties to be used in monumental stone conservation. Through radical polymerization of 3-(trimethoxysilyl)propyl methacrylate, a monomer that contains both methacrylate and silica phases, in the presence of a primary amine surfactant, at different silica precursor:ethanol molar ratios, new types of hybrid nanocomposites, in which silica was dispersed as domains with typical sizes in the nanometer range, were obtained. The self-assembling properties of the synthesized composites have been ascribed to the supramolecular assembling abilities of the surfactants, as well as to the combination of linear, ladder, and cagelike fragments of silsesquioxane type. The incorporation of surfactant within the sol-gel derived matrix may also lead to the obtaining of compounds that avoid cracking of the hybrid gel while drying inside the stone.
Manufacturing and Investigation of the MWCNT/Polymer Nanocomposites
Authors: Elksnite Ilze , Bitenieks Juris , Zicans Janis , Bledzki Andrzej K.
Published: September 2009

Multiwall carbon nanotube (MWCNT) reinforced polyvinylacetate nanocomposites (PVAc) have been investigated. Optimal technological parameters for manufacturing of the PVAc/MWCNT nanocomposites by solution casting are defined. Some physical, calorimetric, thermo gravimetric and electrical properties of the investigated PVAc/MWCNT nanocomposites are revealed. Electrical properties of the PVAc/MWCNT nanocomposites are significantly improved already at negligible MWCNT volumetric content. Obtained level of conductivity is sufficient for both antistatic purposes and electrostatic charge mitigation.
Enhanced Dispersion of MWCNTs and Synergistic Properties in Multiphase Epoxy Nanocomposites by Incorporation of Inorganic Nanoparticles
Authors: Sumfleth Jan , de A. Prado L. A. S. , Richau S. , Sriyai M. , Schulte K.
Published: September 2009

In the present work we report that the addition of inorganic nanoparticles to MWCNT epoxy composites leads to the formation of a hybrid structures which cause different states of dispersion for the multiphase nanocomposites containing either MWCNTs and titania or MWCNTs and silica. The microstructure is characterised by titania nanoparticles attached to the surface of MWCNTs leading to an enhanced dispersion of MWCNTs. The hydrophilic surface of fumed silica nanoparticles causes the formation of independent networks of silica and MWCNTs. Therefore, the change of the state of dispersion is less pronounced compared to the MWCNT/titania structures.
Changes in the state of dispersion lead to a decrease in electrical conductivity for the MWCNT/titania systems. Conversely, an almost independent behaviour was found for the MWCNT/silica nanocomposites due to their interpenetrating networks. Besides the altered state of dispersion, the hybrid structure leads synergistic effects in terms of the glass transition of the nanocomposites. Although a decrease of the glass transition temperature (Tg) is observed for the nanocomposites containing only one kind of filler, the combination of nanoparticles can reduce the decrease of Tg.
Evaluation of Health Risks of Nanoparticles – A Contribution to a Sustainable Development of Nanotechnology
Authors: Potthoff Annegret , Meissner Tobias , Richter Volkmar , Busch Wibke , Kühnel Dana , Bastian Susanne , Iwe Maria , Springer Armin
Published: September 2009

The increasing use of nanoparticles makes it necessary to check up possible toxicological risks of this new materials class. In this paper we describe on two nanopowders (tungsten carbide, titanium nitride) which methods and parameters of a chemical-physical characterization are needed in forefront of toxicological experiments. This includes investigation on the powder itself as well as on particles suspended in water and physiological media, respectively. The most important result is that nanoparticles agglomerate in serum-free medium within minutes, whereas in the present of serum an agglomeration is inhibited. Hence, we have physiological suspensions with well-distributed stabilized particles which allow performing toxicological testing under reproducible conditions. Furthermore we could prove that tungsten carbide particles were taken up into cells, but no acute toxicity was found determined by means of in vitro viability tests with different cells.
Ti/C and Ti/B Nanocomposites: Comparison of Sorption-Desorption Properties
Authors: Morozova Olga S. , Khomenko Tatiana I. , Leonov Alexandr V. , Borchers Christine , Kurmaev Ernst , Moewes Alexandr
Published: September 2009

Hydrogen sorption-desorption properties of Ti/B and Ti/C nanocomposites prepared under ball-milling of the corresponding powders in H2 flow were studied using kinetic, microscopic and spectroscopic techniques. Amorphous boron was found to be more effective in spurring Ti – H2 interaction than carbon because of the following properties: (1) significant fragmentation of Ti powder by preventing agglomeration of the particles; (2) unhindered hydrogen access to the surface of Ti nanoparticles through the boron matrix; (3) appearance of new occupation sites available for H atoms, which are characterized by low H2 desorption temperature. The dynamics of the formation of these sites and the H2 distribution between different occupation sites in dependence on phase composition and morphology were studied for the Ti/B system.
Mechanical and Corrosion Properties of Ni-Free Austenitic Stainless Steel/Hydroxyapatite Nanocomposites
Authors: Tulinski Maciej , Jurczyk Mieczyslaw
Published: September 2009

In the present work, a nanocrystalline nickel-free stainless steels as well as nickel-free stainless steel/hydroxyapatite nanocomposites have been synthesized by the combination of mechanical alloying (MA), heat treatment and nitriding. The microhardness of the final bulk material was studied using Vickers method. Corrosion potentiodynamic tests were performed in Ringer’s solution. The results show that nickel-free stainless steel/hydroxyapatite nanocomposites could be promising bionanomaterials for use as a hard tissue replacement implants.
Mechanical and Corrosion Properties of Titanium–Hydroxyapatite Nanocomposites
Authors: Niespodziana Katarzyna , Jurczyk Karolina , Jurczyk Mieczyslaw
Published: September 2009

In the present work Ti-HA (3, 10, 20, 50 vol%) nanocomposites were produced by the combination of mechanical alloying and powder metallurgical process. The experimental results show, that Ti-HA nanocomposites have better mechanical and corrosion properties in comparison with microcrystalline titanium. For example: Vickers microhardness of Ti-10 vol% HA nanocomposite is 1500 HV0.2 (pure Ti metal – 250 HV0.2) and corrosion resistance in Ringer solution is Ic = 1.19 • 10-7 A/cm2, Ec = -0.41 V for Ti-10 vol% HA and Ic = 1.31 • 10-5 A/cm2, Ec = -0.36 V for Ti. In conclusion, titanium – ceramics nanocomposite are suitable for hard tissue replacement from the point of view of both mechanical and corrosion properties.
Cu-Si Nanocomposites Based on Porous Silicon Matrix
Authors: Bandarenka Hanna , Shapel Aliaksandr , Balucani Marco
Published: September 2009

Cu-Si nanocomposites formed by an immersion displacement deposition of Cu into porous silicon (PS) matrix have been experimentally studied. SEM and AES were used to investigate the structure and elemental composition of Cu-Si samples. The top part of the Cu-PS samples is shown to demonstrate the following structure: large faceted Cu grains at the top, a porous fine-grained copper film underneath the large grains, and the copper pointed rods extended from the surface into the PS layer. The top part of the silicon skeleton of the PS layer is converted into the copper by the etching followed by Cu displacement deposition. The porosity of the porous layer and displacement deposition times are found to form Cu-Si nanocomposites of various structures and various Cu-Si contents because of various extent of the silicon skeleton transformation into copper.
Synthesis of Cobalt Ferrite Nanowires Using FeOOH as a Template
Authors: Camacho Meza Jose G. , Martínez Carlos A. , Monreal Romero Humberto , García Perla E.
Published: September 2009

In this work, cobalt ferrite nanowires were chemically synthesized using FeOOH array a template. The FeOOH nanoarray was obtained by the hydrolysis and precipitation of Fe+3, from FeCl3.4 H2O. The cobalt ion (Co+2) was added in order to make it interact with FeOOH nanorods of 20 nm of diameter and 150 nm of length. These nanorods are grouped into packages having different orientations due to the interaction with the cobalt ions. The arrays were calcinated at 700 and 800 °C to obtain cobalt ferrite nanowires with 70 nm of diameter and some micrometers of length. The morphology and the average size of the nanorods and nanowires were determined using Field Emission Scanning Electron Microscopy (FESEM). The Fourier Transform Infrared Spectroscopy (FTIR) was used to study the interaction between the nanorods and the cobalt ions. The phases of the material were identified using X-ray Diffraction.
Optical and Magneto-Optical Studies of Composite Materials Containing Semimagnetic Semiconductor Nanoparticles
Authors: Savchuk Andriy I. , Fediv Volodymyr I. , Savchuk Tetyana A. , Stolyarchuk Ihor D. , Kandyba Yevheniy O. , Ostafiychuk Dmytro I. , Ivanchak Svitlana A. , Makoviy Vitaliy V.
Published: September 2009

Сomposite films containing II-VI based semiconductor nanoparticles have been prepared by different physical and chemical techniques. Non-magnetic CdS1-xSex nanoparticles were grown by melting of the semiconductor doped fine powder borosilicate glass. The composite semimagnetic semiconductor Cd1-xMnxTe based films were fabricated by embedding in SiO2 matrix with using of pulsed laser deposition technique. New chemical approach to synthesis of Cd1-xMnxS nanoparticles in polymer matrix has been proposed. The optical absorption edge for CdS1-xSex , Cd1-xMnxTe nanoparticles and exciton structure in the spectrum of Cd1-xMnxS nanoparticles shifted to the higher-energy side compared to those for bulk crystals due to the quantum confinement effect. Magneto-optical Faraday effect for non-magnetic semiconductor nanoparticles in glass demonstrates only small changes as compared with that of bulk semiconductors. The revealed peculiarities in spectral and magnetic field dependences of the Faraday rotation for the studied semimagnetic semiconductor composite films can be attributed to the influence of dimensionality on spin exchange parameters for such kind of nanostructures.
Polymer Nanocomposite Development for Electronic Industry Needs
Authors: Koskinen Jari , Karttunen Mikko , Paajanen Mika , Sarlin Juha
Published: September 2009

The properties of polymeric materials have been enhanced by developing nanocomposites in several projects at the Technical Research Centre of Finland VTT. The improvement of conductivity, dielectric, mechanical properties and the thermal stability of polymer materials opens new application potential in electronic industry. In this paper the results of several projects are presented. By applying nano-POSS particles in polypropylene and epoxy the break down voltage was increased by 10 - 20%. The use of carbon nanotubes in polyaniline enhanced the conductivity by two decades compared to the commercially available polymers.
Mechanical Properties of Highly Filled Latex-Based Polystyrene/Laponite Nanocomposites
Authors: Ruggerone Riccardo , Plummer Christopher J. G. , Herrera Norma Negrete , Bourgeat-Lami Elodie , Månson Jan Anders E.
Published: September 2009

Nanocomposite films containing up to 50 wt. % laponite have been prepared from emulsion polymerized polystyrene (PS)/laponite latexes with the laponite attached to the PS particle surfaces. Below Tg, the observed stiffness increases are accounted for by classical models for mechanical reinforcement, but these severely underestimate the stiffness above Tg. An alternative model has therefore been proposed, in which the laponite and PS with reduced mobility form a cellular network, consistent with TEM observations. This cellular network is also argued to play an important role in the decrease in fracture resistance at high laponite contents, through decreases in matrix ductility and breakdown of the laponite stacks.
Melt Spinning of Carbon Nanotube Modified Polypropylene for Electrically Conducting Nanocomposite Fibres
Authors: Skrifvars Mikael , Soroudi Azadeh
Published: September 2009

Blends of polypropylene with multi-walled carbon nanotubes (CNT) have been prepared and melt spun to fibre filaments. The resulted filaments have been characterised regarding conductivity, thermal properties, and morphology. DSC suggests that carbon nanotubes act as nucleating sites in polypropylene and the TGA shows a high increase in thermal stability. Conductivity around 0.001 S/cm are achieved for both as-spun fibre and drawn fibre. A higher load of CNT up to 15 wt % increases the conductivity to 2.8 S/cm in as-spun fibre, but due to a high fibre diameter variation during spinning resulting in fibre breakage, melt spinning is very difficult. This is due to a non-uniform stress distribution during the drawing steps which can be a result of a non-homogeneous PP-CNT blend and the spinning machine process limitations. Differences in conductivities for extruded rods, as-spun fibre and drawn fibre which are made from the same blends, suggests that the crystallinity can affect the conductivity of the PP/CNT fibre.
Electrical Properties of Electrospun Nanofibers of PEO/Carbon Black Composite
Authors: Li Wai Kit , Wong Y.W.
Published: September 2009

Electrospinning is an efficient technique for the fabrication of polymer nanofibers. The charges inside the polymer jet tend to repel each other so as to stretch and reduce the diameter of the polymer fibers. By rotating the collector at a fast angular speed, nanofibers with specific orientation can be obtained. In this study, nanofibers of Polyethylene oxide (PEO) with carbon black were prepared by electrospinning. PEO was dissolved in a mixture of water and ethanol. PEO is known as an electrolytic polymer. With the blending of carbon black powders, its electrical properties along the fiber direction were investigated. The fiber morphology and characteristics were studied by SEM and polarized FTIR.
Synthesis and Magnetic Properties of Pr0.7Ca0.3MnO3 Manganite Films
Authors: Patrin G.S. , Polyakova K.P. , Patrusheva T.N. , Velikanov D.A. , Volkov Nikita V. , Balaev D.A. , Patrin K. G. , Klabukov A.A.
Published: September 2009

Data on the magnetic properties of polycrystalline Pr0.7Ca0.3MnO3 manganite films obtained for the first time by extraction pyrolysis are presented. The effect of synthesis temperature on the magnetic properties of the manganite films is shown.
Penetration of RF Electromagnetic Field through Thin Films of La0.67Sr0.33MnO3 Manganite
Authors: Nosov A. , Rinkevich A. , Gribov I. , Moskvina N. , Vassiliev V. , Vladimirova E. , Szymczak H. , Lewandowski S.J. , Gierlowski P. , Abaloshev A. , Ranno L.
Published: September 2009

Peculiarities of penetration of electromagnetic waves through the bulk and thin film samples of the La0.67Sr0.33MnO3 manganite were investigated for the frequency range from 50 kHz to 20 MHz. Strong variations of penetration coefficient in the applied dc magnetic field were observed both for ferromagnetic and paramagnetic states. Local dynamic magnetic ordering in the paramagnetic temperature range was observed. The experimental data reveal weak dependence of electromagnetic properties on microstructure of the films. The upper frequency limit of the dynamic polaron correlations in the paramagnetic phase was estimated.
Correlation between Ionic Radius of Substituting Element and Magnetic Properties of Bi1-xAxFeO3-x/2 (A= Ca, Sr, Pb, Ba) Multiferroics
Authors: Khomchenko V.A. , Kopcewicz Michael , Lopes Armandina M. Lima , Pogorelov Yuri G. , Araujo J.P. , Vieira Joaquim M. , Kholkin Andréi L.
Published: September 2009

Investigation of crystal structure and magnetic properties of the diamagnetically- substituted Bi1-xAxFeO3-x/2 (A= Ca, Sr, Pb, Ba; x= 0.2, 0.3) polycrystalline samples has been carried out. It has been shown that the heterovalent A2+ substitution result in the formation of oxygen vacancies in the host lattice. The solid solutions have been found to possess a rhombohedrally distorted perovskite structure described by the space group R3c. Magnetization measurements have shown that the magnetic state of these compounds is determined by the ionic radius of the substituting elements. A-site substitution with the biggest ionic radius ions has been found to suppress the spiral spin structure of BiFeO3 giving rise to the appearance of weak ferromagnetism.
Magnetic Properties of the La0.50Ba0.50MnO3 Nanomanganites
Authors: Trukhanov S.V. , Trukhanov A.V. , Botez Christian E. , Szymczak H.
Published: September 2009

Nanocrystalline La0.50Ba0.50MnO3 manganite was synthesized by an optimized sol-gel method. The initial sample was subjected to step-by-step heat treatment under air atmosphere. The ion stoichiometry, the morphology of crystallites of ceramics, and the magnetic properties were studied. It is established that the average crystallite size increases with increasing annealing temperature. All of the samples studied are characterized by a perovskite-like cubic structure, with the unit cell parameter a increasing continuously with the average crystallite size. The most significant lattice compression occurs in the sample with an average crystallite size of ~ 30 nm. The increase in the average crystallite size causes a nonmonotonic increase in the Curie temperature and in the spontaneous magnetic moment. The anomalous behavior of the magnetic properties of the La0.50Ba0.50MnO3 manganites obtained is explained by the competition between two size effects, namely, the frustration of the indirect exchange interactions Mn3+ – O – Mn4+ on the nanocrystallite surface and the crystal lattice compression due to the crystallite surface tension.
Influence of Oxigen Deficiency on Magnetic, Magnetoresistive and Magnetoelastic Properties of La1-xSrxMnO3-y Manganites
Authors: Zashchirinskii D.M. , Koroleva L.A. , Khapaeva T.M. , Gurskii L.I. , Kalanda N.A. , Trukhan B.M.
Published: September 2009

The influence of oxygen deficiency on magnetization, paramagnetic susceptibility, electrical resistivity, magnetoresistance and magnetostriction of La1-xSrxMnO3-y (x = 0, 0.2, 0.4; y = 0, 0.13, 0.2) is studied. These properties demonstrate that the ferro – antiferromagnetic magnetic two-phase state are in the oxygen deficiency samples. In samples with y  0 in lattice sites, in which the oxygen ions are absent, electrons in twos are disposed from maintenance of a crystal electroneutrality. They partially (in x = 0.4, y = 0.13) or fully (in x = 0.4, y = 0.2; x = 0.2, y = 0.13, 0.2) compensate single-charge acceptors (Sr2+ ions). In non-compensated donors two electron spins are antiparallel and do not form of the ferromagnetic nanoregions from the s-d exchange gain (ferrons). In sites of lattice with the oxygen vacancies the broken Mn-O-Mn connections present which break the ferromagnetic exchange interactions in them decreasing the middle magnetization in samples with x = 0.2, 0.4 and y = 0.13 and provoking a transition to superparamagnetic behavior in samples with x = 0.2, 0.4 and y = 0.2.
Determining Crystal Field Distortions of YVO3 through X-Ray Scattering
Authors: Beale Thomas A.W. , Johnson Roger D. , Bland Stewart R. , Hatton Peter D. , Bouchenoir Laurence , Boothroyd Andrew T. , Prabhakaran D.
Published: September 2009

We present resonant x-ray scattering experimental data from YVO3. By scattering at the vanadium K edge we are able to observe diffraction from the anisotropic tensor of susceptibility at the Bragg forbidden (010). The resonant energy spectra from these reflections are unusually complex, giving an indication of the crystal field distortions around the vanadium site.
Mechanical and Magnetic Properties of Polydisperse Magnetoelastics
Authors: Nikitin L.V. , Talipov R.A. , Kazakov A.P. , Stepanov G.V.
Published: September 2009

In this work are considered new magneto-controlled materials – magnetoelastics, their elastic and magnetic properties. Much attention is devoted to influence of distribution of magnetic particles by their size on these properties. It was found that the application of a magnetic field on magnetoelastics with larger particles leads to a considerable rise of the shear modulus. It was shown that damping of torsional vibrations strongly depends on both value of magnetic field and concentration of large particles. A comparison between shear modulus, obtained from classic method and from torsional vibrations was made and a good coincidence of results was found. It was found out that hysteresis loops for considered polymer materials have unusual character.
Determination of Magnetic Moments of Magnetite Nanoparticles Aggregates by Optical Methods
Authors: Yerin Constantine V.
Published: September 2009

Magnetic birefringence in kerosene based magnetic fluid in variable and pulsing field is investigated. It is shown, that the size of aggregates of defining effect is about 70 nanometers. The absence of spontaneous magnetisation at such aggregates is installed. The value of the parameter connecting the permanent and induced magnetic moments of the aggregate of nanoparticles is experimentally defined.
Non-Equilibrium Magnetization of a Dilute Suspension of Magnetic Particles
Authors: Tyatyushkin Alexander
Published: September 2009

A suspension of magnetic particles in a viscous liquid magnetized in an alternating uniform magnetic field is theoretically studied. The suspension is regarded as so dilute that interaction of a single particle with the applied magnetic field can be considered without taking into account the influence of other particles. The complex magnetic susceptibility of the suspension is found as a function of the frequency of the applied magnetic field. The heat generation power density averaged over the period of the oscillations is calculated.
Peculiarities of Magnetic Fluid Microdrops Instability in Thin Layer in Magnetic Field
Authors: Dikansky Yury , Zakinyan Arthur , Nechaeva Oksana
Published: September 2009

The behavior of a magnetic fluid drops in a thin film under the action of a perpendicular magnetic field is investigated. Instability of the form of a drop and formation of star-like patterns in the spot of contact of the deformed drop with layer boundaries is detected. The disintegration of a drop attended fractal pattern formation is investigated. Dependence of character of these processes on a size of drops, concentration and rate of a magnetic field rise is determined.
Magnetodynamics and Self-Organization in Strongly Non-Equilibrium Ferrosuspensions
Authors: Kashevsky Bronislav , Kashevsky Sergei , Prokhorov Igor
Published: September 2009

This paper presents computational and experimental studies of two phenomena occurring in magnetic suspensions under strongly non-equilibrium conditions created by high-frequency (in comparison with the inverse characteristic time of the particle mechanical motion) magnetic fields. First is the dynamic magnetic hysteresis in a dilute suspension of highly-coercive particles subjected to linearly polarized fields. Energy absorption by particles is of great interest for cancer treatment, chemical technology, biology and smart materials science. Second is related to polymer composite technologies and represents dissipative self-organization of a system of magnetically soft particles in a drying thin layer of polymer solution set under a rotating magnetic field
Structural Aspects of Stabilization of Magnetic Fluids by Mono-Carboxylic Acids
Authors: Avdeev M.V. , Bica Doina , Vekas L. , Aksenov V. L. , Feoktystov A.V. , Rosta L. , Garamus V.M. , Willumeit R.
Published: September 2009

The structure of magnetic fluids (magnetite in decahydronaphtalene) stabilized with saturated mono-carboxylic acids of different chain lengths (lauric, myristic, palmitic and stearic acids) is studied by means of magnetization analysis and small-angle neutron scattering. It is shown that magnetite nanoparticles are dispersed in the carrier approximately with the same size distribution whose mean value and width are significantly less as compared to the classical stabilization with non-saturated oleic acid. The found thickness of the surfactant shell around magnetite is analyzed with respect to stabilizing properties of mono-carboxylic acids.
Contrast Variation in Small-Angle Neutron Scattering from Magnetic Fluids Stabilized by Different Mono-Carboxylic Acids
Authors: Feoktystov A.V. , Avdeev M.V. , Aksenov V. L. , Petrenko V.I. , Bulavin L.A. , Bica Doina , Vekas L. , Garamus V.M. , Willumeit R.
Published: September 2009

Contrast variation method in small-angle neutron scattering (non-polarized neutrons) is applied to magnetic fluids (MFs) with magnetite dispersed in benzene and coated with myristic or oleic acid in zero external magnetic field. The basic functions approach for polydisperse superparamagnetic systems is used to get structure parameters of particles in MFs.
Synthesis and Effect of Some Parameters through Reverse Micelles Route of Iron Oxide Nanoparticles
Authors: Arabi H. , Nateghi S. , Sadeghi S.
Published: September 2009

Iron oxide nanoparticles were synthesis by reverse micelle method. X-ray diffraction technique and vibration sample magnetometer were applied to characterize the produced samples at different conditions and parameters for synthesis route. There is no significant difference between samples prepared at 5°C and room temperature except a better crystalline at room temperature. The molar ratio of water to surfactant (w parameter) and concentration of the salt solution on size and magnetic properties of nanoparticles have been investigated. Increasing w leads to producing particles with larger size i.e. for w=16.83, 11.22, and 5.6, particles size are 15.22, 11.66 and 10.5 nm, respectively. The size of nanoparticles are in the range of 9 to 20 nanometers
Magnetic Structure of Fe/V Superlattices with Variable Thickness of Iron Layers
Authors: Kudasov Yu. B. , Maslov Dmitry Andreevich
Published: September 2009

The model of magnetic structure of Fe/V superlattices is discussed. An individual iron layer of 2 or 3 ML in thickness is assumed to be a XY system. An interlayer interaction through vanadium spacers leads to the appearing of effective field for each iron layer. The infinite and finite superlattices are investigated. Calculations of magnetic structure of Fe2/V12/Fe3/V12 superlattice show that divergence in estimations of the critical temperature obtained by neutron scattering and MOKE is due to inhomogeneity of magnetic moment distribution in the finite superlattice.
SQUID-Based Relaxometric Diagnostics of Magnetic Nanoparticles
Authors: Volkov Ivan , Snigirev Oleg , Maresov Alexander , Volkov Alexander , Torii Yasukuni , Tanaka Saburo
Published: September 2009

The method of SQUID-based relaxometric diagnostics has been applied to the ensembles of non-interacting near-spherical Fe3O4 and Co nanoparticles in order to reveal the behavior of the anisotropy constant upon varying the molecular surrounding of nanoparticles by using different polymer matrices. The transmission electron microscopy (TEM) and X-ray diffraction techniques have been employed to obtain the structural information about objects of study. The relaxation curves measured with the SQUID-relaxometer in the time range from about 50 s to several tens of seconds after application of a pulse of low dc magnetizing field have been approximated by theoretical dependences calculated within the framework of activation Néel–Arrhenius law with account for the size distribution functions retrieved from TEM data. From results of approximations, the values of anisotropy constant have been determined.
Magnetic, Thermal and Transport Properties of High-Pressure Synthesized Nanocrystalline EuC6
Authors: Tsvyashchenko A.V. , Sidorov V.A. , Fomicheva L.N. , Thompson J.D. , Ronning F. , Ponomarev A.N.
Published: September 2009

Bulk nanocrystalline EuC6 was prepared by the route of high pressure and high temperature synthesis. The material exhibits ferromagnetic behavior at low temperature. Its magnetic moment saturates at 2 K and 6 T to a value s ~0.64 B/f.u. The magnetic susceptbility obeys the Curie-Weiss law above ~60 K and the value of paramagnetic moment and Curie-Weiss temperature were found to be eff = 2.48 B and p = +12.5 K, respectively. Magnetic measurements show that europium atoms in the pressure synthesized EuC6 are not in a purely Eu+2 state but rather in a mixed-valence state.
Magnetic Force Microscopy on Co/Pt Multilayers
Authors: Karoutsos V. , Poulopoulos Panagiotis , Angelakeris M. , Papaioannou E.T. , Fumagalli Paul , Flevaris N.K.
Published: September 2009

Co/Pt multilayers reside among the best candidates for perpendicular magneto-optic recording. In this work, Co/Pt multilayers were prepared by electron-beam evaporation under ultrahigh vacuum conditions on polyimide. X-ray diffraction measurements revealed the high quality of multilayer stacking. Magneto-optic polar Kerr effect experiments were used in order to obtain magnetization hysteresis loops of the films. We have studied the magnetic-domain morphology on the surface of the films via Magnetic Force Microscopy. The field applied during these measurements was 2.3 kOe oriented perpendicular to the film plane; this field seems to stabilize and enhance out-of-plain stripe domains against in plain domains that may be expected from magnetization curves. Finally, we observed that when the applied field approaches the magnetic saturation field, then the domain morphology turns to be dominated by bubble domains.
The Neel Temperature and Sublattice Magnetization for the Stacked Triangular-Lattice Antiferromagnet with a Weak Interlayer Coupling
Authors: Ignatenko A.N. , Irkhin Valentin Yu. , Katanin A.A.
Published: September 2009

The quantum Heisenberg antiferromagnet on the stacked triangular lattice with the intralayer nearest-neighbor exchange interaction J and interlayer exchange J' is considered within the non-linear -model with the use of the renormalization group (RG) approach. For J'  J the asymptotic formula for the Neel temperature TNeel and sublattice magnetization are obtained. RG turns out to be insufficient to describe experimental data since it does not take into account the 2-vortices. Therefore TNeel is estimated using the Monte-Carlo result for the 2D correlation length [10] which has a Kosterlitz-type behavior near the temperature TKT where the vortices are activated.
Magnetic Properties of Hexagonally Ordered Arrays of Fe Antidots by Vacuum Thermal Evaporation on Nanoporous Alumina Templates
Authors: López Antón Ricardo , Vega Victor , Prida V.M. , Fernández A. , Pirota K.R. , Vázquez Manuel
Published: September 2009

Highly ordered arrays of Fe antidot films were fabricated by thermal vapor deposition technique using nanoporous alumina templates. The film thickness varies from 20 up to 100 nm, and the antidots array has about 50 nm in diameter and 105 nm of periodic interspacing. Scanning electron microscopy and atomic force microscopy measurements confirmed that the Fe antidots film retains the well-ordered hexagonal structure of the nanoporous alumina template. Meanwhile, the micromagnetic structure was studied by magnetic force microscopy and SQUID measurements. A stripe magnetic domain pattern featuring a large out-of-plane magnetization component is found in the films. Noteworthily, the magnetic domains are not pinned by the nanopores but, on the contrary, several antidots are included in each magnetic domain. According to the magnetic measurements, the easy magnetization axis of the Fe antidot array remains in the film plane, while the hard one lies perpendicular to the plane, which can be explained on the basis of the different contributions of the nanoholes to the total magnetic anisotropy of the antidots film.
Band Structure Calculations and Magnetic Relaxation in Correlated Semiconductors FeSb2 and RuSb2
Authors: Gippius A.A. , Okhotnikov K.S. , Baenitz M. , Shevelkov A.V.
Published: September 2009

A comparative study of electronic properties of the two isostructural narrow-band semiconductors FeSb2 and RuSb2 by means of experimental NQR spectroscopy as well as theoretical ab-initio band structure calculations is presented. The temperature dependence of 1/T1 consists of two distinct intervals: above 40 K (HT) with activated behavior for FeSb2 with D/kB @ 450 K and below 40 K (LT) with smooth maximum at 10 K. Here the relaxation is governed by in-gap states. We propose the model of inherent Sb-deficiency (as prepared non-stoichiometry) of both FeSb2 and RuSb2 as a possible reason of the in-gap states. This results in creation of a small portion of Fe (Ru) ions possessing formal oxidation number +3 with d5 configuration and forming narrow energy level of localized S = ½ spins near the bottom of the conduction band. Due to much higher gap value in RuSb2, the activation mechanism for RuSb2 in the HT range is inefficient and the 1/T1 dependence in the HT range is more close to T2 behavior characteristic for phonon relaxation mechanism by two-phonon (Raman) scattering.
Antiferromagnetic Ordering of the 3d Ions in Compounds with Ca3Ga2Ge4O14 Structure
Authors: Ivanov V.Y. , Mukhin A.A. , Prokhorov A.S. , Mill B.V.
Published: September 2009

Compounds with the Ca3Ga2Ge4O14 structure containing Co2+, Mn2+ and Fe3+ ions in 3f position were synthesized and their magnetic properties were studied at low temperatures. Long range antiferromagnetic ordering in triangular net lattice has been observed with TN = 7–40 K.
Minimizing the Effect of Noise in High-Speed Reversal of a Magnetic Dipole
Authors: Pankratov A.L. , Vdovichev S.N. , Nefedov I.M. , Adamchik D.A.
Published: September 2009

The effect of noise on the reversal of a magnetic dipole is investigated on the basis of computer simulation of the Landau-Lifshits equation. It is demonstrated that at the reversal by the pulse with sinusoidal shape, there exists the optimal duration, which minimizes the mean reversal time (MRT) and the standard deviation (SD, jitter). Both the MRT and the jitter significantly depend on the angle  between the reversal magnetic field and the anisotropy axis. At the optimal angle the MRT can be decreased by a factor of 7 for damping =1 and up to 2 orders of magnitude for =0.01, and the jitter can be decreased from 1 to 3 orders of magnitude in comparison with the uniaxial symmetry case. It has been demonstrated that fluctuations can not only decrease the reversal time, as it has been known before for the magnetic systems and is correct for small angles only, but it can also significantly, up to the factor of two, increase the reversal time.
Structural and Magnetic Phase Transitions in ErFe2Hx Hydrides
Authors: Shreder L.A. , Gaviko V.S. , Mushnikov N.V. , Terent’ev P.B.
Published: September 2009

Temperature dependences of the lattice parameters, magnetization and magnetic susceptibility have been measured for the ErFe2Hx hydrides with different hydrogen content x and for the ErFe2D3.1 deuteride. For the samples with a hydrogen content of about 3.1, structural transition from the cubic to the rhombohedral phase has been observed in the temperature range 280 – 310 K. Small variation of hydrogen content does not shift the transition temperature, but influences the amount of the low-temperature rhombohedral phase. The temperature dependence of magnetization shows up an anomaly in the range of the phase transition, which is due to the difference in the magnitudes of magnetic moments and exchange interactions in two phases. Structural and magnetic studies point to a diffusion nature of the phase transition. Upon heating the samples in vacuum there takes place decomposition of the hydride. The hydride with x = 1.6 which forms at the intermediate stage of decomposition possesses an ordering temperature higher than that for the parent ErFe2 compound.
Circular Magnetization Processes in CoFeNi Electroplated Wires
Authors: García-Miquel H. , García-Chocano V.M. , Kurlyandskaya G.V.
Published: September 2009

Circular magnetization processes in electroplated wires is an important topic having straight connection with sensor applications of these soft magnetic materials. In present work the longitudinal and circular hysteresis loops were measured and corresponding magnetization processes were studied in Cu98Be2/Co16Fe20Ni64 wires. The longitudinal hysteresis loops, Mz-Hz, were measured by inductive technique in a frequency range of 10 to 70 Hz. The circular magnetization curves (Mφ- Hφ) were measured for frequencies of 50 and 100 kHz in the Hφ field up to 1500A/m for different values of the axial external field of 0 to 500 A/m. The longitudinal and circular magnetization curves are comparatively analyzed.
Domain Wall Dynamics in a Double-Layer Magnetic Film with Different Uniaxial Anisotropy the Layers
Authors: Randoshkin V.V. , Sysoev N.N. , Mastin A.A.
Published: September 2009

Motion of an isolated domain wall in a double-layered magnetic film, whose layers differ in their uniaxial anisotropy only, is investigated through solving the Slonczewski equations by a numerical method. Dependences of the threshold field and the limiting velocity of disruption of the steady state motion of the film on the anisotropy and thicknesses of layers are obtained. Also, we showed that in domain wall unsteady motion regime, a dependence of domain wall velocity from magnetic field contains a series velocity peaks that relies on steady motion of Bloch lines across film and domain wall velocity in such cases can’t be simply increased by increasing magnetic field and restricted by some volume.
Confined-Chalcogenide Phase Change Memory with Thin Metal Interlayer for Low Reset Current by Finite Element Modeling
Authors: Harnsoongnoen S. , Sa-Ngiamsak Chiranut , Siritaratiwat Apirat
Published: September 2009

This paper reports on the confined-chalcogenide phase change memory with thin metal interlayer (CCTMI) with the operating reset current of 0.6mA-30ns. This cell offers low reset current with simple architecture and fabrication. Thermal and heat flux distribution of both the normal-bottom-contact (NBC) and a proposed CCTMI PCM cells were carefully analyzed and simulated by two-dimensional finite element modeling. It is intriguingly found that the reset operation current of the CCTMI cell is 44% lower than that of the NBC. CCTMI has capability to solve an over-programming fail issue due to confined heat dissipation in active area.
Comparative Investigations of Structure and Absorptive Capacity of Nano- and Microsized Magnetic-Operated Particles for their Application in Medicine and Biology
Authors: Yanovsky Yu.G. , Komissarova L.Kh. , Danilin A.N. , Zaraysky E.I.
Published: September 2009

For the first time, the comparative investigations of structure and sorption efficiency of nano- and microsized magnetic-operated particles in respect to both the antigen and virus hepatitis B and also to the substance-markers (low-, middle- and highmolecular substances) were carried out. The sorption efficiency of magnetic particles: magnetite (Fe3O4), cobalt-ferrite (CoFe2O4), composite ferro-carbon (FeC) to the substances of different molecular weight was evaluated in vitro experiments. The high absorptive capacity to low- and highmolecular substance-markers has been observed for microsized composites of FeC. Absorptive capacity of the nanosized Fe3O4 and CoFe2O4 particles to the substance-markers was low. But the nanosized Fe3O4 and CoFe2O4 particles had a good absorptive capacity to virus of hepatitis B and its antigen (HBsAg). The sorption efficiency results of nano- and microsized magnetic particles correlate with the structure of their surface.
Coupled Electromagnetic-Thermal Field Investigation in Induction Heating Device
Authors: Iatcheva Ilona Ilieva , Stancheva Rumena , Tahrilov Hristofor , Lilianova Ilonka
Published: September 2009

The aim of the work is precise coupled –electromagnetic and temperature field analysis of an induction heating system by finite element method. Presented example is referred to real induction heating system. The problem was solved as nonlinear, transient and axisymmetrical. The numerical model of the coupled fields is based on the finite element method and electromagnetic and temperature distributions have been obtained using COMSOL 3.3 software package.
Role of Electronic Band Structure and Lattice Parameters in Magnetism of the R2(Fe,M)17, М = Si, Al Compounds
Authors: Kuchin Anatoly G. , Knyazev Yu.V. , Kuz’min Y.I. , Lukoyanov A.V. , Nekrasov I.A. , Anisimov V.I. , Kourov N.I. , Medvedeva I.V. , Voronin V.I.
Published: September 2009

Magnetic, electronic, structural and magnetovolume properties of the R2Fe17-xMx (R = Y, Lu, Ce; M = Si or Al) compounds were studied. We pioneered to apply electronic band parameters determination to account for the anomalous volume dependence of ferromagnetism in these compounds.
Domain Structure Reversible Reconstruction of Amorphous Ferromagnetic by Water Molecules Weak Adsorption
Authors: Zubov V.E. , Kudakov A.D. , Levshin N.L. , Mezenkov N.A.
Published: September 2009

Influence of water molecules reversible adsorption on domain structure and domain
wall structure in amorphous Fe-rich ferromagnet samples is investigated by magnetooptical method. Before investigation the samples were kept in the air. Domain structure of the samples significantly changes in wacuum: instead one 180-degree domain wall several domain walls appear which are oriented with angle 45o to the long side of the sample. This effect is completely reversible. Another new effect is found: domain wall width on the sample surface in vacuum is 35% bigger (13.5 µm) than in atmosphere of water vapor (10 µm).
ESD Affected GMR Head Detection by Using Machine Model: Wavelet Transform Technique Approach
Authors: Suwannata N. , Sompongse D. , Rakpongsiri P. , Siritaratiwat Apirat
Published: September 2009

This report proposes the wavelet transform technique using the 4th Daubechies order to detect glitches on a magnetic recording head signal in the time-domain. It is found that the glitch occurs when the electrostatic discharged (ESD) level of the machine model (MM) on giant magnetoresistive (GMR) heads is in the range of 6-9 V. The electrical test parameter and scanning electron microscope (SEM) photograph of recording heads shows no change in reader sensor. However, the parameter and SEM results clearly show the visible GMR damage when the MM-ESD voltage (VESD) is 10 V. The glitch in magnetic response signal of the GMR head occurs when the VESD is increased. Therefore, the wavelet transform technique can be a novel instrument to forecast the GMR degradation due to the MM-ESD effect.
An EMI Immunity Study of TMR Heads in Quasi-Static Tester due to the Direction of Sweeping Frequency
Authors: Siritaratiwat Apirat , Kruesubthaworn A. , Ungvichian V.
Published: September 2009

This report aims to investigate a comparative effect of Electromagnetic Interference (EMI) on recording heads due to sweeping directions of low-to-high and high-to-low frequencies. Four selected Quasi-Static Tester (QST) parameters; MR resistance, MR amplitude asymmetry, Barkhausen noise and Hysteresis, are used for monitoring the effect of EMI on Head Gimbal Assembly (HGA). It is undoubtedly found that the Asymmetry and Hysteresis parameters provide insufficient indication of EMI effect for both sweeping frequency directions. On the other hand, it is discovered that the sweeping direction of the low-to-high frequency is more effective to two test parameters; MR resistance and Barkhausen noise, than the other direction. The dramatic energy accumulation is possibly explained this phenomenon but this energy level is not high enough to cause the Hysteresis change.
Magnetic Phase Diagram and Charge Transport in TmB12
Authors: Bogach A.V. , Demishev S.V. , Flachbart K. , Gabani S. , Glushkov V.V. , Levchenko A.V. , Shitsevalova N.Y. , Sluchanko D.N. , Sluchanko N.E.
Published: September 2009

High precision measurements of magnetoresistance =f(T,H) and magnetization M(T,H) have been carried out on single crystals of rare earth dodecaboride TmB12 at temperatures 1.8–30 K in magnetic fields up to 80 kOe. The high accuracy measurements and precise temperature stabilization allowed us to perform numerical differentiation and analyze quantitatively a behavior of derivative d()/dH=f(T,H) and magnetic susceptibility (T,H)=dM/dH in paramagnetic and magnetically ordered phases of thulium dodecaboride. It was shown that negative magnetoresistance anomalies observed in present study in paramagnetic state of TmB12 can be consistently interpreted in frameworks of a simple relation between resistivity and magnetization - /M2 proposed by K. Yosida (Phys. Rev., 107, 396 (1957)). A local magnetic susceptibility loc(T,H)=(1/H(d(/)/dH))1/2 was deduced directly from the magnetoresistance measurements and compared with bulk susceptibility (T,H)=dM/dH results of the present study. Moreover, the susceptibility dependences loc(T,H) and (T,H) have been applied to analyze in detail the H-T magnetic phase diagram of TmB12.
Inhomogeneous Current Distribution in a Bimetal Ferromagnet/Superconductor Film in a Longitudinal Magnetic Field
Authors: Avdeev Maxim , Khusainov Mansur G. , Proshin Yurii N. , Tsarevskii Sergey
Published: September 2009

The proximity effect of the ferromagnetic metal/superconductor (FM/S) bilayers in а external longitudinal magnetic field is considered in the dirty limit. The critical temperature and the superconducting current distribution versus applied magnetic field’s magnitude, film’s thicknesses and a transparency of the contact is calculated, with taking into account аn umklapp processes possibility on the interface of the FM/S contact. It is shown that superconducting current is strictly inhomogeneous and asymmetrical. It is shown also that the current inhomogeneity depends heavily from the FM/S interface transparency.