bluuebunny/crossref_metadata_2025 huggingface dataset:
Flexible AC Transmission System Controllers: An Evaluation
Authors: Georgilakis Pavlos S. , Vernados Peter G.
Published: December 2010

Electricity market activities and a growing demand for electricity have led to heavily stressed power systems. This requires operation of the networks closer to their stability limits. Cost effective solutions are preferred over network extensions. The flexible alternating current transmission system (FACTS), a new technology based on power electronics, offers an opportunity to enhance controllability, stability, and power transfer capability of ac transmission systems. This paper provides a comprehensive review and evaluation of FACTS controllers.
Generation Expansion Planning of Crete Power System for High Penetration of Renewable Energy Sources
Authors: Karapidakis Emmanuel S. , Katsigiannis Yiannis A. , Georgilakis Pavlos S. , Thalassinakis Emmanuel
Published: December 2010

In this paper the Crete’s Island power system, which is the largest isolated power system in Greece, is analyzed in two long term scenarios in order to estimate the corresponding costs and benefits associated with a significant high electricity production from renewable energy sources (RES) technologies in the period 2009-2020. In the first scenario, a 20% RES energy penetration in year 2020 is assumed, while in the second scenario the final RES energy penetration is increased to 50%, and it is achieved with the installation of hydro pumped storage systems. Long-range Energy Alternatives Planning (LEAP) software is used to develop the electricity demand model, as well as to estimate the gross electricity generation in Crete and the annual CO2 equivalent emissions for the considered scenarios. This study demonstrates that substantial RES production till 2020 is technically feasible, and provides benefits in the forms of carbon emission reductions, energy adequacy and dependency.
Hybrid Commutation Converter in HVDC Systems
Authors: Balan Horia , Buzdugan Maria , Vadan I. , Simion E. , Karaissas P.
Published: December 2010

This paper deals with DC – AC static converter systems, of very high voltages and currents, used for electricity power transmission. It has been analyzed three types of converters: with forced commutation, with commutation from load and the solution proposed by the authors. There are shown the advantages in hybrid switching converters, which in essence connect, constructive and as principle of operation, the advantages of the two known conversion systems. The analysis of the benefits of the proposed solution is done by comparing the circulating power of assets and also by analyzing the power factor. Not in the last, must be mentioned the paper contribution to the development of the theoretical base design for switching converters with hybrid commutation.
Design and Optimization of UAQ4 Experimental Maglev Module
Authors: D'Ovidio Gino , Crisi Francesco , Lanzara Giovanni
Published: December 2010

This paper presents the design of a novel superconducting levitated module for UAQ4 train whose feasibility has been successfully tested and confirmed in laboratory. The work concept of self-balancing “V” shaped levitation module is described and the results of levitation tests performed using a measurement set up are discussed. Lastly the levitation module performances are also carried out using numerical finite element analyses by varying the sideslip angle of the module and work system configuration.
Proposal of Flux Concentrated Radial and Axial Magnetic Bearings
Authors: Okada Yohji , Miyazawa Hidetoshi , Kondo Ryou , Enokizono Masato
Published: December 2010

New flux concentrated hybrid (HB) type radial and axial magnetic bearings are proposed in this paper. It is intended to use ferrite permanent magnet (PM) for producing high bias flux. The capability of proposed magnetic bearings is confirmed using commercial FEM code “ANSYS”. The results show high possibility with less expensive PMs.
Evaluation of the Iron Loss of the Actual Stator Core to Achieve High Efficiency of the Rotating Machine
Authors: Oka Mohachiro , Kanada Tugunori , Kai Takayuki , Enokizono Masato
Published: December 2010

In this paper, the iron loss of an actual stator core of the complex configuration was evaluated by using the proposed effective magnetic path length and the excitation inner core, which were developed in this research. The iron loss of an actual stator core in the manufacturing process was described. Iron losses of actual stator cores before and after the varnish processing were measured using the excitation inner core of several kinds of shapes. As a result, iron losses of actual stator cores evaluated using the proposed effective magnetic path length were within appropriate values.
Development of Lorentz Force Type Magnetic Bearing
Authors: Kurita Nobuyuki , Ishikawa Takeo , Okada Yohji
Published: December 2010

Lead batteries are used mainly for energy storage. However they are using chemicals and heavy materials, which will affect to environment badly. Therefore, clean energy storage systems are under development using magnetic bearing. However, the eddy current causes serious rotational loss for energy storage flywheel. Therefore, Lorentz force type magnetic bearing is proposed. The rotating loss is expected to be negligible due to the constant flux in the airgap. To confirm the operation of proposed magnetic bearing, an experimental setup is fabricated and basic characteristics are tested. The rotor flywheel could run-up to 3000 min-1 with 0.65 mm maximum amplitude.
Electromagnetic Analysis and Comparison of Conventional-Wound Cores and Octagonal-Wound Cores of Distribution Transformers
Authors: Hernández I. , Cañedo J.M. , Olivares-Galván J.C. , Georgilakis Pavlos S.
Published: December 2010

This paper presents comparative results of an electromagnetic study performed in two different wound core transformer configurations in order to know the best configuration that reduce excitation current and core losses. The results show that octagonal wound-core (OWC) reduces the excitation current and eddy-current losses with respect conventional-wound core (CWC). The results were obtained applying 2D and 3D FEM simulations, taking into account the non-linear properties of the core. In the last part of this paper, several grades of grain oriented electrical steels and the combination of them are analyzed to find the best mixing percentage to reduce eddy-current losses and excitation current.
Piezoelectric Devices for Power Harvesting on Mechanical Displacements
Authors: Niţu Constantin , Niţu S. , Grămescu B. , Mihalache C.
Published: December 2010

The paper presents the ability of the piezoelectric devices to capture the environmental vibrations, in order to generate electric power for supplying electronic small portable devices. Theoretical and experimental investigations were performed, both for stack and cantilever beam configuration of the piezoelectric devices, with good agreement between results. An improved mechanical architecture is proposed.
Analysis of the Gap Bandwidth of some High Impedance Surfaces in the Microwave Range
Authors: Matekovits Ladislau , de Sabata Aldo
Published: December 2010

This work numerically explores the relations between the positions and the widths of the frequency bandgaps that occur in some shielded high impedance surfaces and the geometrical dimensions of the structures. The reported parameterized results are useful for design issues and for circuit models conception and validation.
Comparative Analysis of Mitochondrial DNA by Using Nucleotide Genomic Signals
Authors: Cristea Paul Dan , Tuduce Rodica
Published: December 2010

The nucleotide imbalance, the nucleotide pair imbalance and the nucleotide path of mitochondrial Nucleotide Genomic Signals (mtNuGSs) for several taxa have been analyzed comparatively. Evolutionary changes of conservative segments, as well as individual mutations of hyper-variable segments have been identified. An innovative technique, based on reference-offset representation of sets of related signals has been used throughout the study.
Comparison of Iron Losses in Multiple Grain Size Iron Laminations under Sinusoidal and SPWM Excitation
Authors: Rovolis P. , Kladas Antonios G. , Tegopoulos J.
Published: December 2010

The paper presents a methodology for determination of harmonic iron losses in laminated iron cores under both sinusoidal and sinusoidal pulse width modulated voltage excitations (SPWM) excitation for various frequencies. The method is based on measurements performed by using a convenient Epstein device supplied by a sinusoidal and a SPWM source, which are stored and processed in a PC by using an appropriate data acquisition card. It is shown that the switching frequency does not considerably affect iron losses under SPWM supply and vary non-linearly with flux density with respect to the ones measured under sinusoidal excitation for the same fundamental frequency.
Effect of Stress on the Magnetic Characteristics of SmFe Thin Films
Authors: Wakiwaka Hiroyuki , Ohtake Kazuyuki , Itoh Naoki , Takeuchi Toshiyuki , Tashiro Kunihisa , Kiyomiya Teruo , Makimura Mika
Published: December 2010

SmFe is a kind of giant magnetostrictive material. Though Terfenol-D has a positive magnetostriction constant, SmFe has a negative magnetostriction constant. Furthermore, the permeability of SmFe is bigger than the permeability of a Tb system material. Since the permeability is big, it is expected that the merit is big, when a sensor device is constructed using SmFe. This paper describes an SmFe thin film and a method for introducing stress into the SmFe thin film. Next, the results of measuring the magnetic characteristic using VSM, while the stress is applied, are shown. Finally, it is shown that a highly sensitive force sensor can be constructed using an SmFe thin film, because the differential permeability greatly changes on the SmFe thin film, when tensile stress was applied, from the measured magnetic characteristic.
Stochastic Dynamics of Magnetic Nanoparticles at Finite Temperatures
Authors: Zverev V.V. , Usachev G.A.
Published: December 2010

We consider unstable motion in small magnetic particles, driven by an external magnetic field and influenced by thermal fluctuations. Our studies demonstrate both temporal and spatial complexity of the dynamics in this system. The results are obtained using numerical simulations of the Landau-Lifshitz-Gilbert equations.
FMR in Ferromagnet with Electron Spin-Orbital Clusters
Authors: Yurasov N.I.
Published: December 2010

The spin-orbital subsystem model with electron clusters was used for studying the frequency spectra ferromagnetic resonance (FMR). A new type of ferromagnetic order and new region of FMR were found. The new region may be in the microwave region or in the infrared region (IR). The volume of spin-orbital electron cluster is equal to 1-50 cubic nanometer approximately.
Simulating Processes of Magnetic Phase Nucleation in Defect-Containing Magnets of Finite Thickness
Authors: Gareyeva Ye.R. , Yumaguzin A.R. , Vakhitov R.M.
Published: December 2010

Nucleation processes in phase transitions of a spin-reorientation type in real magnets are examined in the paper. The basic simulation of new-phase nuclei condensing on defects is chosen to be the magnetization distribution corresponding to a 0-degree domain wall. The numeric implementation of the corresponding variation problem for a sample of a finite thickness gives stable states of the considered magnetic heterogeneities and demonstrates that the structure and properties depend mainly on the defect parameters and the sample-quality factor. The obtained dependencies allow describing the behavior of the new-phase nuclei in the vicinity of the spin-reorientation phase transition quite consistently with the experimental data.
Spin-Reorientation Transition in Rare-Earth Intermetallics
Authors: Pirogov A.N. , Bogdanov S.G. , Choi Young Hyun , Rozenfeld E.V. , Choi Yong , Skryabin Yu.N.
Published: December 2010

The Tm2Fe17 compound has been studied by means of powder neutron diffraction. The compound undergoes a spin-reorientation transition (SRT) of the “easy axis – easy plane” type with increasing temperature from 75 K to 100 K. The SRT is accompanied by a distinct anomaly in the temperature dependencies of the Tm- and Fe-ion magnetizations, significative of large magnetization anisotropy. Using three sublattices model, the parameter of the Tm-Fe interaction and constants of magnetic anisotropy are determined.
Spin Polarized Current in Magnetic Nanojunctions
Authors: Chigarev S.G. , Epshtein E.M. , Gulyaev Y.V. , Zilberman P.E.
Published: December 2010

Two channels of the s-d exchange interaction are considered in magnetic junctions. The first channel describes the interaction of transversal spins with the lattice magnetization. The second channel describes the interaction of longitudinal spins with the magnetization. We show that the longitudinal channel leads to a number of significant effects: 1) drastic lowering of the current-instability threshold down to three (or even more) orders of magnitude; 2) creation of sufficiently large distortion of equilibrium due to the current- driven spin injection leading to inversion of populations of the energy spin subbands and laser-like instability in the THz frequency range at room temperature. External magnetic field is likely to tend to additionally lower the instability threshold due to the proximity effect of purely magnetic reorientation phase transition. This effect demonstrates new properties: the giant magnetoresistance (GMR) becomes strongly current-dependent and the exchange switching becomes of very low threshold. We derived some matching condition that should be satisfied to achieve high spin injection level. Some characteristic quantities appeared in the condition, namely, the so called "spin resistances" , where the a number of a layer in the junction. For a three-layer junction ( ), the matching condition is , where the number corresponds to the main functional layer. We investigated also the junctions having variable lateral dimensions of the layers, for example, a ferromagnetic rod contacting with a very thin ferromagnetic film. A large enhancement of the current density can appear near the contact region, leading to the spin injection luminescence.
Relationship between the Spontaneous Magnetization, Spontaneous Magnetostriction and Heat Capacity in the Compound Mn5Ge3
Authors: Podgonykh S.M. , Bolotin K.E.
Published: December 2010

Spontaneous magnetization Ms of the ferromagnetic compound Mn5Ge3 with the Curie temperature TC=305 K has been studied in the temperature range from 2 to 400 K. The relationships between the magnetic part of the heat capacity (CMAG), the magnetic part of the volume thermal expansion coefficient (TEC) MAG, and the Ms for the compound Mn5Ge3 have been considered. It has been found that the magnetic part of the heat capacity can be well approximated by the dependence CMAG(T)=a×|dMs2/dT|–b×|dMs4/dT| with a>0 and b>0, and the magnetic part of the TEC, by the dependence  MAG=C1×dMs2/dT+C2×dMs4/dT with C1<0 and C2>0 in the whole temperature. It is assumed that the main sources in the formation of the observed CMAG(T) and MAG(T) dependences are the changes in the elastic, magnetoelastic, magnetovolume, and magnetostatic energies of the sample that appear as a result of the spontaneous magnetostrictive deformation with temperature changing.
Magnetic Structure and Properties of the Intercalated Compound Fe0.5TiSe2
Authors: Baranov N.V. , Selezneva N.V. , Pleshchev Valery G. , Mushnikov N.V. , Maksimov V.I.
Published: December 2010

The intercalated compound Fe0.5TiSe2 has been studied by means of X-ray, neutron diffraction, electrical resistivity and magnetization measurements. This compound with Fe atoms located between Se-Ti-Se sandwiches has a monoclinic crystal structure and exhibits a long-range antiferromagnetic (AF) ordering below TN = 135 K. At T < TN, the Fe magnetic moments with a value ~ 3.0 µB are directed at an angle of (74.4±0.5)º to the layers and form a tilted antiferromagnetic structure with the propagation vector (½, 0, ½). It has been shown that application of magnetic field above 300 kOe may lead to transformations of the AF structure.
Determination of Texture Degree of NdFeB-Magnets by Means of Neutron Diffraction
Authors: Teplykh A.E. , Bogdanov S.G. , Choi Yong , Kudrevatykh Nikolai V. , Pirogov A.N. , Popov A.G. , Skryabin Yu.N. , Vyatkin V.P.
Published: December 2010

Six samples of Nd-Fe-B-permanent magnets, distinguished in the texture degree, have been measured by neutron diffraction in the reflection and transmission regimes. The texture in the samples was formed by application of impulses of external magnetic field 0H = 4 T. Analysis of the obtained neutron diagrams by means of the Fullprof program allowed quantitative determination of the texture degree and conclusion to be made that the texture degree grows with an increase in numbers of magnetic field impulses.
The Magnetocaloric Effect in Ni-Mn-X (X=Ga, in) Heusler Alloys and Manganites with Magnetic Transition close to Room Temperature
Authors: Buchelnikov Vasiliy D. , Drobosyuk Mikhail , Smyshlyaev E.A. , Pavlukhina O.O. , Andreevskikh A.V. , Sokolovskiy V.V. , Taskaev Sergey , Koledov V.V. , Shavrov V.G. , Khovaylo V.V. , Fediy A.A.
Published: December 2010

The magnetocaloric effect (MCE) in theNi2+xMn1-xGa (x = 0.33, 0.36, 0.39), Ni50Mn25In25, Ni54Mn21Ga18In7, Ni53.5Mn21.5Ga16In9, Ni45Co5Mn36.5In13.5 Heusler alloys and in the La0.7BayCa0.3-yMnO3 (y = 0.12, 0.24, 0.3) manganites at the Curie points have been measured by the direct method. For the magnetic field change H = 2 T, the maximal adiabatic temperature change Tad in the Ni2+xMn1-xGa alloys is larger than 0.6 K. For the Ni50Mn25In25 alloy the maximal value of Tad = 1.51 K (for the same magnetic field change H = 2 T) is observed at the magnetic phase transition temperature.
Effect of Cold Rolling on the Magnetic Behavior of Ni3Al-Based Superalloy
Authors: Stepanova N.N. , Mitropolskaya S.Yu. , Davidov D.I. , Kazantseva N.V.
Published: December 2010

Paramagnetic VKNA superalloy on the base of Ni3Al intermetallic phase (L12 superlattice) under cold rolling deformation demonstrates superparamagnetic behavior associated with the formation of nanosized ferromagnetic clusters within the paramagnetic matrix. It may be assumed that these clusters correspond to the long-period phase with DO22 superlattice.
Solid-State Synthesis of Co-Sm(110) Epitaxial Films with Large Magnetocrystalline Anisotropy
Authors: Zhigalov V.S. , Myagkov V.G. , Frolov G.I. , Bykova L.E. , Komogortsev S.V. , Bondarenko G.N. , Nizhankovskii V.I.
Published: December 2010

Solid-state synthesis of a Sm2Co7 (110) hard magnetic phase prepared by successive deposition of Co and Sm layers onto a MgO(001) surface at a temperature of 400 С has been experimentally studied. Upon annealing at 500 С, the structure of the material changes, which leads to the formation of an epitaxial Sm2Co17 (110) phase. The first and second magnetocrystalline anisotropy constants of the Co-Sm have been determined.
Magnetoresistance of Ni50Mn37(Sn1-XInx)13 Alloys
Authors: Gerasimov E.G. , Podgonykh S.M. , Mushnikov N.V. , Dyakina V.P. , Kanomata T.
Published: December 2010

Magnetic properties, electrical resistivity and magnetoresistance of the Ni50Mn37(Sn1 xInx)13 (x=0.2, 0.5) Heusler alloys were studied in magnetic fields up to 360 kOe in the temperature range 4-400 K. It was found that the alloys exhibit a martensite phase transformation at a critical temperature TM240 K for x=0.2 and TM350 K for x=0.5. The TM temperature is lower than the Curie temperature of the austenite phase TCA in the alloy with x=0.2 and is higher than TCA in the alloy with x=0.5. The spontaneous martensite transformation in both alloys is accompanied by a large change (~48%) of the electrical resistivity. A large negative magnetoresistance (~45%) is observed for the alloy with x=0.2 upon the field-induced martensite transformation. The analysis of the obtained results allows us to conclude that the large magnetoresistance in the alloys is mainly due to the changes in the crystal structure and only slightly depends on the changes in the magnetic ordering.
Nonlinear Nonstationary Dynamics of Nèel-Type Domain Walls in Magnetic Films with in-Plane Anisotropy
Authors: Dubovik M.N. , Filippov B.N. , Kassan-Ogly Felix A.
Published: December 2010

Within the framework of two-dimensional model of magnetization distribution and exact allowance for main interactions nonlinear dynamic behavior of Nèel-type domain walls in thin magnetically uniaxial films with in-plane anisotropy has been studied. Two possible wall internal structure dynamic rearrangement scenarios have been revealed.
Domain Structure and Properties of Soft Magnetic Iron- Based Alloys with Different Magnetic Treatment
Authors: Dragoshanskii Yu.N. , Shulika V.V. , Potapov A.P. , Tiunov V.F.
Published: December 2010

The paper deals with the domain structure and electromagnetic characteristics of soft magnetic iron-based alloys, which are formed by the impact of thermomagnetic treatment (TMT) - cooling of the material in the presence of a magnetic field. The effect of reducing the specific magnetic loss in materials, using a constant or alternating (different frequency) magnetic field is determined. It is shown that the minimum magnetic losses in the materials are obtained after TMT in an alternating magnetic field at high (~ 80 kHz) frequencies. This shows up the perspectives of TMT of soft magnets.
Formation of Structure and Properties during Thermomagnetic and Ion-Beam Treatments of Soft Magnetic Materials
Authors: Gubernatorov V.V. , Dragoshanskii Yu.N. , Sycheva T.S. , Kositsyna Irina I. , Ivchenko V.A.
Published: December 2010

A new way of considerable improvement of properties of soft magnetic alloys is offered. This way actually consists in the use of an ion beam treatment in the manufacturing technology for these alloys. Depending on the properties, which need improvement (magnetic softness or magnetostriction), the ion beam treatment is performed before or after a thermomagnetic treatment.
Quasibloch 0-Degree Domain Walls in Ferromagnet Films
Authors: Magadeev E.B. , Vakhitov R.M.
Published: December 2010

Structure of magnetic heterogeneities of the 0-degree-domain-wall type in a thin film of a cubic ferromagnet with a uniaxial anisotropy induced along [011] is examined. Strict calculations of demagnetizing fields are shown to lead to quasibloch solutions with values of material parameters lying in certain ranges. Besides, the magnetization vector’s leaving the domain wall plane means the rotation of plane orientation by the angle π/4. The transition boundary between the described structures is found.
Non–Uniform Magnetoelectric Effect in Bilayered Ferromagnetic Structure with Antiferromagnetic Coupling at Interface
Authors: Gareeva Z.V. , Doroshenko R.A.
Published: December 2010

Theoretical analysis of peculiarities of electric polarization arising on magnetic non – homogeneity in bilayered structure with interlayer antiferromagnetic coupling has been performed. It has been shown that the total electric polarization can be of the positive and of the negative sign or equal to zero depending on the relation between layers parameters. Electric polarization can be governed by applied magnetic field through magnetization processes occurring in a system; in its turn the electric field affects the distribution of magnetic moments.
Ferromagnetic Semiconductors and Half-Metal Compounds Obtained by Laser Deposition
Authors: Danilov Y.A. , Kudrin Alexei V. , Vikhrova O.V. , Zvonkov B.N.
Published: December 2010

Laser deposition method was used for growing ferromagnetic semiconductor and half-metal compound layers. GaMnAs and InMnAs layers were grown by alternating laser ablation of solid targets (semiconductor and Mn) in hydrogen and arsine flow. The layers exhibited ferromagnetic properties (detected by Hall effect measurements) from 10 K to room temperature (for InMnAs). Half-metal compound layers were deposited by the techniques of reactive laser deposition (MnAs, MnP) and alternating laser deposition (MnSb). The half-metal layers exhibit ferromagnetism at temperatures up to 300 K.
The Remagnetization Process Feature of Trilayer Nanodisks
Authors: Ognev A.V. , Stebliy M.E. , Samardak A.S. , Nogaret A. , Chebotkevich L.A.
Published: December 2010

The remagnetization process and the distribution of magnetic moments in arrays of trilayer nanodisks Co(10 nm)/Pd(0.8 nm)/Co(10 nm) with diameters D = 200 and 400 nm were studied by the magnetooptical Kerr effect (MOKE) and magnetic force microscopy (MFM). It is shown that in the nanodisks with D = 200 nm the magnetisation reversal process can be carried out by the vortex states or one-domain configurations with the antiparallel orientation of moments in the adjacent ferromagnetic layers. In arrays of nanodisks with D = 400 nm the vortex states are formed only.
Magnetization Reversal and Domain Structure оf Magnetic Tunnel Junctions
Authors: Samardak A.S. , Sukovatitsina E.V. , Ognev A.V. , Anisimova M. , Wahlström Erik , Chebotkevich L.A.
Published: December 2010

This paper is devoted to the investigation of crystalline structure, surface morphology, magnetic anisotropy, coercive force and domain structure of spin-valves with a single and double MgO barrier layers. It is shown that domain structure and magnetization reversal are the same for both systems, but otherwise the behavior of tunnel magnetoresistance is different. The approach to control magnetic anisotropy in soft magnetic layer using temperature annealing is demonstrated. It makes these structures possible for new applications in nanoelectronics.
Peculiarities of Magnetic Properties of Ni-Ge Layered Films
Authors: Chernichenko A.V. , Edelman I.S. , Velikanov D.A. , Marushchenko D.A. , Greben’kova Y.E. , Turpanov I.A. , Patrin G.S.
Published: December 2010

The surface morphology and magnetic properties of layered Ni-Ge films were investigated. The films surface has been shown to consist of the grains of 2 - 4 nm in height with the average radius of about 40-80 nm. Magnetization temperature dependences are different for FC and ZFC processes; in the latter case, the magnetization maximum is observed near the temperature Tm~50K. The exchange bias effect is observed at low temperatures. The results are explained by the formation of the antiferromagnetic phase in the interface between Ni and Ge layers due to the Ge and Ni mutual diffusion.
Exchange Interaction in the Co-SiO2 Nanocomposite Films
Authors: Denisova Elena  A. , Iskhakov Rauf S. , Stolyar S.V. , Komogortsev S.V. , Chekanova L.A. , Maltsev V.K. , Kalinin Y. , Sitnikov A.V.
Published: December 2010

The properties of Co-SiO2 nanogranular composite films, containing a Co volume fraction ranging from 0.3 to 0.8, have been characterized by means of magnetic measurements, NMR study, and ferromagnetic resonance. Thermal decrease of CoX(SiO2)100-X magnetization follows the T3/2 law and allows to estimate the exchange interaction constant A. With growing nominal Co content the transitions from granular to continuous structural state at 36% Co are registered by FMR measurements. The spectrum of standing spin-wave has been detected in the perpendicular experiment configuration for films with the Co content above 52 vol. %. It is found that the type of the dispersion relation of spin waves in Co-SiO2 composite films is affected by the exchange coupling fluctuations.
Magnetic Structure of Nanowires and Magnetostatic Interaction
Authors: Ivanov A.A. , Orlov V.A. , Podolsky N.N.
Published: December 2010

The ground state magnetization of nanowires built of ferromagnetic crystallites is considered taking into account the magnetostatic interaction. The criterion of formation of domains is found. The thickness of a domain wall is calculated analytically and the results are compared with the numerical simulations. We show that when the exchange coupling between crystallites is absent its role is played by magnetostatics that ensures the existence of stable domain structure. The direction of the induced anisotropy axis is shown to be determined by the shape of crystallites.
CEMS Analysis of Phase Formation in Nanostructured Films (Fe/Si)3
Authors: Varnakov S.N. , Ovchinnikov S.G. , Bartolomé Juan , Rubín Javier , Badía L. , Bondarenko G.V.
Published: December 2010

Determination of stable phases formed at the Fe/Si interface in (Fe/Si)n structure, grown by thermal evaporation in an ultrahigh vacuum system was performed using conversion electron Mössbauer spectroscopy (CEMS).
Structure and Magnetic Properties of Gd/Ti Nanoscale Multilayers
Authors: Svalov Andrey V. , Vas’kovskiy V.O. , Barandiarán José M. , Balymov K.G. , Sorokin A.N. , Orue Iñaki , Larrañaga A. , Schegoleva N.N. , Kurlyandskaya G.V.
Published: December 2010

Structure and magnetic properties of nanoscale [Gd/Ti]n multilayers prepared by rf-sputtering are studied. It is found that the decrease in the Gd layer thickness LGd leads to beginning of the structure transformation in Gd layers from the fine-crystalline to amorphous state when LGd becomes less than 2 nm. The Curie temperature TC decreases as a function of the Gd layer thickness in the same way as in early studied epitaxially grown Gd films, i.e. in case for which the finite-size effect plays most important role. A deviation of the TC(LGd) behaviour at very low LGd from the fit according to the finite-size law is probably caused by the island-like structure of the Gd layers.
Temperature Dependence of Magnetoimpedance in FeNi/Cu/FeNi Film Structures with Different Geometries
Authors: Volchkov Stanislav O. , Bukreev D.A. , Lepalovskij V.N. , Semirov A.V. , Kurlyandskaya G.V.
Published: December 2010

The magnetoimpedance (MI) in thin films and magnetic multilayers has been extensively studied in recent years. One of the important problems which is still under discussion is the temperature dependence of MI of the multilayered nanostructures for temperatures up to 200 oC. In this work magnetic properties and temperature dependence of the magnetoimpedance of Fe19Ni81/Cu/Fe19Ni81 multilayers with opened and closed magnetic pathes were studied and comparatively analyzed for the functional temperature interval of + 23 oC to + 160 oC.
Ideas by S.V. Vonsovsky and Modern Model Treatment of Magnetism
Authors: Irkhin Valentin Yu.
Published: December 2010

A review of fundamental works by Shubin and Vonsovsky on the formulation of the polar and s–d(f) exchange models is given. Their ideas are compared with subsequent developments in the theory of magnetism in d- and f-metals and their compounds. Modern approaches including various slave-boson and slave-fermion representations, formation of exotic quasiparticles etc. are discussed. Internal connections between different many-electron models (the Heisenberg, Hubbard, t–J, Anderson Hamiltonians) are presented. Description of anomalous rare-earth and actinide compounds (Kondo lattices, systems with heavy fermions and non-Fermi-liquid behavior) within the framework of the s–d(f) exchange model and related models is considered.
Two-Threshold Stability Loss in Magnetic System with Nonmagnetic Interlayer
Authors: Zakharov Yu.V. , Vlasov A.Yu. , Avakumov R.
Published: December 2010

In present paper the magnetization of magnetic film consisting of two soft magnetic layers separated by a nonmagnetic interlayer is considered. The film is applied to stiff magnetic substrate. To obtain boundary conditions at the boundary between soft magnetic layers we introduce effective constant of interlayer interaction.
Magnetic States of Nanodot Arrays. Physical and Numerical Experiments
Authors: Nefedev K. , Ivanov Y. , Peretyatko A. , Belokon V.
Published: December 2010

The research method for the investigation of magnetic states of single nanoparticles, 1D arrays, 2D, and quasi-2D arrays is used. The possibility of the nanodots magnetic states reconstruction by the space distribution of gradient dipole-dipole interaction force is theoretically justified. The comparison is made between the results of nanoarchitecture numerical simulation in an external magnetic field and experimental data.
Magnetoresistance Peculiarities in Ferromagnetic-Polymer Structure
Authors: Vorob’eva Natalya V. , Lachinov Aleksei N. , Lachinov Alexey A. , Garifullina F.F.
Published: December 2010

Two types of magnetoresistive effects can be observed in the multilayer structure of the ferromagnet/polydiphenylenephthalide/non-magnetic metal. One can see the effect of resistance switching in an external magnetic field and also the angular magnetoresistive dependence. The similarities and differences of these effects and other known magnetoresistive effects are considered. The conclusion is drawn that the peculiarities of the magnetoresistance in the ferromagnetic-polymer system are formed in the ferromagnet-polymer interface and the special features of charge injection into the conductive nanoscale channels of the polymer film have the determinative importance.
Structural and Magnetic Properties of Nickel Oxide Nanopowders
Authors: Mironova-Ulmane Nina , Kuzmin A. , Grabis J. , Sildos I. , Voronin V.I. , Berger I.F. , Kazantsev V.A.
Published: December 2010

Structure and magnetic properties of nickel oxide (NiO) nanopowders have been studied by X-ray/neutron diffraction, SQUID magnetometer, and micro-Raman spectroscopy. Our diffraction data indicate that at room temperature all NiO powders are antiferromagnetically ordered and have a rhombohedral (R-3m) phase. The SQUID magnetometry and Raman spectroscopy measurements support the presence of the antiferromagnetic ordering.
Phase Transitions in 3D Site-Diluted Potts Model with Spin States q=4
Authors: Murtazaev Akai K. , Babaev A.B. , Aznaurova G.Ya.
Published: December 2010

We study the phase transitions and critical phenomena in 3D site-diluted (with nonmagnetic impurities) Potts model with spin states q=4 by Monte-Carlo method. The systems with linear sizes L=20-32 and spin concentrations p=1.00, 0.90, 0.65 are examined. Using the Binder cumulants method the forth order it is shown that the second-order phase transition is observed in strongly diluted model at spin concentration p=0.65; the pure model (p=1.00) and weakly diluted one (p=0.90) reveals the first-order phase transition. On the basis of finite-size scaling theory the static critical parameters of heat capacity, susceptibility, magnetization, and correlation length exponent are calculated.
Random Magnetic Anisotropy and Ferromagnetic Resonance in Nanosrystalline Alloy Fe73.5CuNb3Si13.5B9
Authors: Komogortsev S.V. , Iskhakov Rauf S. , Kuznetsov P. , Belyaeva A. , Bondarenko G. , Chekanova L.A. , Balaev A. , Eremin E.V.
Published: December 2010

In the paper, we will present experimental results on the Fe73.5CuNb3Si13.5B9 ferromagnetic resonance (FMR) line width as a function of annealing conditions, as well as the annealing-temperature dependence of the crystallite size, coercive force, and the magnetic anisotropy field. We shall show the interrelationship of these quantities, demonstrate that these parameters are all traceable to the nanoparticle crystallization, and indicate how they can be examined by extending the random anisotropy theory. To obtain quantitative parameters of random magnetic anisotropy we investigate the magnetization curves approaching saturation. This technique allows one to quantitatively determine the local magnetic anisotropy field (Ha) and magnetic anisotropy correlation radius (Rc), as well as to estimate the averaged magnetic anisotropy field (L) and ferromagnetic correlation radius (RL).
Experimental and Numerical Investigations of the Magnetization Curves in the Nanocomposites Consisted of Several Ferromagnetic Phases
Authors: Komogortsev S.V. , Smirnov S. , Iskhakov Rauf S. , Momot N. , Balaev A. , Chekanova L.A. , Denisova Elena  A. , Eremin E.V.
Published: December 2010

The magnetization correlation function for two-phase one-dimentional chain of the ferromagnetic exchange-coupled nanoparticles with a random anisotropy was calculated. The dependence of the magnetic correlation radius and the average magnetic anisotropy constant on the intrinsic size of the phase inhomogeneity was founded. The data allows estimating the applicability limits of the analytical equations for the magnetization curves approaching saturation of two-phase ferromagnetic nanomaterials.
Effect of Alloying Elements on the Structure Peculiarities and Mechanical Properties of High-Strength Magnetic Fe-Cr-Co Based Alloys
Authors: Serikov V.V. , Kleinerman N.M. , Vershinin A.V. , Beloserov E.V. , Mushnikov N.V. , Ivanova G.V. , Shchegoleva N.N. , Uimin Mikhail A.
Published: December 2010

Structure and mechanical properties of high-strength alloys on the basis of the Fe-Cr-Co system with W, Ga, Cu and Al additives have been investigated by the Mossbauer technique. It is shown that the magnitude of yield strength is independent of the dopants, whereas the relative elongation is controlled by the process of phase separation in the alloys which is dependent on additions.
Variation of Electroresistive Properties of Nanocrystalline Nd0.7Sr0.3MnO3 by Thermobaric Treatment under a Pressure of 9 GPa
Authors: Medvedeva I.V. , Dyachkova T. , Tyutyunnik A. , Zaynulin Y. , Marchenkov V. , Marchenkova E. , Yang C.P. , Chen S.S. , Bärner K.
Published: December 2010

Polycrystalline Nd1-xSrxMnO3 was subjected to a thermobaric treatment, that is, a quenching under a high quasihydrostatic pressure of 9 GPa , starting from the temperature 1000 °C. This results in a strong change of the electroresistive and magnetoresistive properties. The changes in the electrical transport might result from the increase of oxygen deficient regions in the boundaries between the nanosized grains.
The Spin-Reorientation Transition in a Nanocrystalline Nd-Ho-Fe-Co-B Alloy and its Influence on the Hysteresis Loops
Authors: Volegov A.S. , Kudrevatykh Nikolai V. , Tereshina Irina S. , Neznakhin D.S. , Sabiryanova Y.A.
Published: December 2010

The temperature dependence of coercivity (Hc) of a nanocrystalline (Nd0.55Ho0.45)2.7(Fe0.8Co0.2)14B1.2 alloy in a wide temperature range, including the spin reorientation (SR) transition interval, has been investigated. A considerable decrease in the Hc for the SR in the range 150–4.2 K was detected and interpreted as being an effect caused by the anisotropy change of the 2-14-1 phase nanograins, i.e., from the uniaxial to the easy-cone type.
Dynamic Magnetoelastic Effects in the Fe80Si10B10 Amorphous Ribbons Associated with Surface Crystallization
Authors: Il’yasov R.S. , Fedorova N.V.
Published: December 2010

The dynamic magnetoelastic properties of the Fe80Si10B10 amorphous alloy at different stages of the thermal crystallization process were studied by the method of double electromagnetic acoustic transformation. An anomalous increase in the dynamical magnetostriction and ultrasound damping and a decrease of sound velocity were found. According to the Mössbauer spectroscopy data, they are related to the formation of a component of magnetic moments that is perpendicular to the ribbon surface.
New Look at Substructure Formation during Recrystallization of Soft Magnetic Materials
Authors: Gubernatorov V.V. , Ol’kov S.A. , Sycheva T.S.
Published: December 2010

Changes in the orientation and substructure of crystallites in metals were studied during the migration of grain boundaries in the recrystallization process. It is determined that the changes are caused by a significant moving force of recrystallization and the presence of inhomogeneities in the structure of metals. These inhomogeneities, having the structure and properties different from the basic metal, form a substantial contribution to the moving force of recrystallization.
Microstructure and Magnetic Hysteresis in Nanocrystalline Nd-Fe-Co-B Alloys on the Base of Nd2Fe14B Phase
Authors: Kudrevatykh Nikolai V. , Volegov A.S. , Glebov A.V. , Andreev S.V. , Pushin Vladimir , Markin P.E. , Neznakhin D.S.
Published: December 2010

Using the electron microscopy (SEM and TEM), X-ray structure analysis and precise magnetometry methods (VSM, SQUID-magnetometer), the microstructure and magnetic hysteresis properties of industrial manufactured hard magnetic rare-earth based alloys of Nd-Fe-Co-B compositions (BZMP and MQP-B brands) that are widely applied as fillers for bonded magnets (magnetoplasts and magnetoelasts) have been studied. The obtained results allow selecting the proper temperature range for bonded magnets applications on the base of BZMP and MQP-B fillers.
Frustrations and Phase Transitions in Low-Dimensional Magnetic Systems
Authors: Kassan-Ogly Felix A. , Filippov B.N.
Published: December 2010

The phenomena of frustrations appearance and suppression of phase transition or, on the contrary, the phase transition appearance and suppression of frustrations are studied on the base of exact solutions for 1D 3-state [1], 4-state standard [2] Potts models and the Ising model [3] with allowance for the interactions between nearest J and next-nearest neighbors J'. We also studied these phenomena in the Ising model on 2D triangular, honeycomb, and kagome lattices, using the exact analytical solutions for maximum eigenvalue of Kramers-Wannier transfer matrix [4] и [5]. In 1D case we mainly used the analytical expressions for spin-spin correlation functions and formulas for entropy and binding energy, while in 2D case, specific heat, entropy, and binding energy expressed through the maximum eigenvalue of Kramers-Wannier transfer matrix were used.
Quantum Amplifier with Spin-Polarized Electrons Injection
Authors: Viglin N.A. , Ustinov V.V. , Pavlov T.N. , Tsvelihovskaya V.M.
Published: December 2010

A promising idea to use the transport of spin-polarized conduction electrons in a magnetic hetero-structure in order to invert population of the charge-carrier spin level in one of its layers, aiming at creation of an active environment for the electromagnetic radiation amplification, has been realized in a number of FMС/SC structures in which FMС is a ferromagnetic conductor and SC is a semiconductor. The n-InSb single crystals, featured by a high mobility of charge carriers, narrow ESR line, and anomalously high absolute value of the negative g-factor (g = −52), were used as SC. The following materials were used as FMC playing a role of spin polarizer: (i) ferromagnetic semiconductors EuO0.98Gd0.02O and HgCr2Se4, (ii) Geisler alloys Co2MnSn, Ni2MnSn and Co2MnSb. We have demonstrated that the spin-polarized electrons injection into the n-InSb semiconductor from the above-mentioned ferromagnetic materials results in a generation of the laser-type electromagnetic radiation.
The Effect of Hydrostatic Pressure on Crystal and Orbital Structures of LaMnO3 and LaMn0.5Ga0.5O3
Authors: Gonchar Liudmila E. , Nikiforov Anatoliy E. , Leskova Julia V. , Firsin Anton A. , Kozlenko D.P.
Published: December 2010

The crystal structure of manganite under pressure is investigated. The influence of external hydrostatical pressure is studied. The theoretical study of magnetic interactions and NMR spectra under pressure is carried out. The influence of Ga-doping is discussed.
Microscopic Mechanisms of Magnetoelectric Coupling in 3d Oxides
Authors: Moskvin A.S.
Published: December 2010

We present a short overview of different microscopic models for nonrelativistic and relativistic magnetoelectric coupling in 3d oxides including so-called "spin current scenario" and ab-initio calculations.
Application of 3s X-Ray Photoelectron Spectra for Determination of Charge States and Magnetic Moments of 3d Ions in Oxides
Authors: Galakhov Vadim R.
Published: December 2010

There are presented core-level 3s X-ray photoelectron spectra of some 3d oxides. The possibility to extract additional information on intra- and interatomic exchange effects from 3s X-ray photoelectron spectra is demonstrated. The results pointed to the possibility of using X-ray photoelectron 3s spectra for estimation of local spin magnetic moments localized on 3d elements in manganese and iron oxides. We have found that for doped manganites, the Mn formal valency from 3+ to 3.3+ is not accompanied by any decrease in the Mn 3s splitting. This fact can be explained by the holes in the O 2p states (d4L ground-state configuration). For Cu, Ni, and Co oxides, the charge-transfer effect dominates the multiplet effect in the 3s spectra which allows to estimate the occupancy of 3d states.
Spin Injection as a Source of the Metamagnetic Phase Transition
Authors: Zyuzin A.A. , Zyuzin A.Y.
Published: December 2010

We consider a metamagnetic phase transition of itinerant electrons in the metamagnetic- ferromagnetic metal junction. The current flow between a ferromagnetic metal and a metamagnetic metal produces the non-equilibrium spin imbalance acting as an effective magnetic field and initiating the first-order type transition from low- to high-magnetization states of the metamagnet in the vicinity of the ferromagnet. We show that the current dependence of the length of high-magnetization state region diverges at some threshold value, due to nonequilibrium shift, generated in a contact between the high and low magnetization states of the metamagnetic metal.
Spin Relaxation in GaAs Doped with Magnetic (Mn) Atoms
Authors: Akimov Ilya A. , Astakhov G.V. , Dzhioev R.I. , Kavokin K.V. , Korenev V.I. , Kusrayev Y.G. , Yakovlev D.R. , Bayer M. , Molenkamp L.W.
Published: December 2010

The GaAs doped with donors manifests long times of spin relaxation, while in the case of acceptors (or magnetic impurities) spin relaxation rate increases markedly, in accordance with theoretical predictions. From the practical point of view, this situation is unfavorable, since the devices based on spin degrees of freedom require long times of the spin memory. Therefore semiconductors such as p-GaAs were not considered as promising materials for spintronics. In the present work this conclusion is refuted by means of investigation of the spin dynamics of electrons in epitaxial layers of gallium arsenide doped with Mn impurities. In spite of the expectations, we have discovered the suppression of the spin relaxation of electrons in GaAs:Mn by two orders of magnitude. This effect is a consequence of compensation of the hole and manganese effective magnetic fields due to the antiferromagnetic interaction. The analogous results obtained for the case of GaAs quantum well doped with Mn [R. C. Myers, et al., Nature Materials 7, 203 (2008)] were interpreted as the result of the spin precession of magnetic acceptors rather than electrons. Through separate measurements of g-factor by means of time resolved spectroscopy it has been proved that long times of spin relaxation in p-GaAs:Mn relate to electrons and not to magnetic acceptors. The oscillation frequency of the angle of Kerr rotation depends linearly on the magnetic field and complies with g=0.46±0.02, i.e. the electronic g-factor.
Spin Polarons at High Temperatures in Undoped Lanthanum Manganites
Authors: Arbuzova T.I. , Naumov Sergey V. , Kostromitina Natalia V.
Published: December 2010

Magnetic properties of undoped samples of lanthanum manganites in the temperature range 77-650K are reported. The ferromagnetic Curie temperature increases when the unit-cell volume decreases and the number of cation defects increases. Uncorrelated polarons and noninteracting moments of Mn ions are present in the region TC < T < 440K. Above 2TC < 440 K < T, the nonstoihiometric LaMnO3 compound passes into the homogeneous paramagnetic state.
Structural, Magnetic and Electrical Properties of the Slightly Doped Lanthanum Manganites
Authors: Bulatov A.R. , Bogdanova K.G. , Golenischev-Kutuzov V.A. , Elokhina L.V. , Neifel’d E.A. , Korolev A.V.
Published: December 2010

The temperature dependences of the transverse and longitudinal hypersound velocities at the frequencies (0.5-0.7) GHz were measured in the La1-xSrx MnO3 (x = 0.125; 0.15; 0.175) compositions. Structural phase transitions the position of which is confirmed by the electric resistance and magnetic measurements data for the same samples are observed. These results were analyzed within the model of the competing Jahn-Teller distortions and magnetic ordering. Anomalies in the behavior of the longitudinal hypersound velocities were related to the local Jahn-Teller distortions the suppression of which upon magnetic ordering is considered as a possible origin of a colossal magnetoresistance.