The percolation effect and optimization of soft magnetic properties of FeSiAl magnetic powder cores

Energy Technology Data Exchange (ETDEWEB)

Bai, Ruru [College of Material Science and Engineering, Nanchang University, Nanchang 330031, Jiangxi (China); Zhu, Zhenghou, E-mail: z00708@sina.com [College of Material Science and Engineering, Nanchang University, Nanchang 330031, Jiangxi (China); Zhao, Hui, E-mail: candyzhaohui@126.com [College of Material Science and Engineering, Nanchang University, Nanchang 330031, Jiangxi (China); Institute of Space Science and Technology, Nanchang University, Nanchang 330031, Jiangxi (China); Mao, Shenghua [Jiangxi Aite magnetic materials Co. Ltd., Yichun 336000, Jiangxi (China); Zhong, Qi [College of Material Science and Engineering, Nanchang University, Nanchang 330031, Jiangxi (China)

2017-07-01

Highlights: • A new magnetic percolation phenomenon of ρ-μe in MPCs was discovered. • The soft magnetic properties of FeSiAl MPCs were studied. • The comprehensive magnetic properties of MPCs were optimized. • The formation mechanism of magnetic conductive path was explained. - Abstract: In this paper, a new magnetic percolation phenomenon between the green compact density ρ and effective permeability μe in FeSi{sub 9.6}Al{sub 6.5} magnetic powder cores, was discovered. The Magnetic Percolation Area of ρ is the range of 5.6 g/cm{sup 3} ∼ 5.78 g/cm{sup 3}, and the percolation threshold is 5.78 g/cm{sup 3}. As a result of the guidance of the percolation theory, the best comprehensive magnetic properties have been optimized through adjusting the distribution of powders. The special distribution of the magnetic powder cores with the best comprehensive magnetic properties was as follows: the content 60% with the particle size distribution of 100–200 mesh, the content 20% with the particle size distribution of 200–325 mesh and the content 20% with the particle size distribution of ≥400 mesh. When the green compact density ρ of cores was 5.79 g/cm{sup 3}, and the frequency was in the range of 1 kHz ∼ 100 kHz, the best comprehensive magnetic properties were as follows: μe = 91, ∆μ = 0.61%, μe(H80 Oe) = 43, μe(H100 Oe) = 33, μe(H120 Oe) = 26, Pc(50 mT/20 kHz) = 30.58 kW/m{sup 3}, Pc(50 mT/50 kHz) = 76.85 kW/m{sup 3}, Pc(50 mT/100 kHz) = 178 kW/m{sup 3}. Not only have those cores the excellent constant magnetic properties with frequency, the excellent DC superposition characteristic and the lower loss at high frequency, but also the effective permeability outstandingly goes up, which has important significance for the miniaturization of inductance components.

Magnetic properties and high frequency characteristics of FeCoN thin films

Directory of Open Access Journals (Sweden)

Tae-Jong Hwang

2016-05-01

Full Text Available (Fe65Co35N soft magnetic thin films were prepared by reactive RF magnetron sputtering with the sputtering power of 100 W on thermally oxidized Si substrate in various nitrogen partial pressures (PN2. A strong uniaxial in-plane magnetic anisotropy with the easy-axis coercive field as low as 1∼2 Oe was observed in films grown at PN2 in the range from 3.3% to 5.5%. The saturation magnetizations for those films were about 20 KG. Outside this range, almost isotropic magnetization curves were observed. Vector network analyzer and grounded coplanar waveguide were used to measure the ferromagnetic resonance (FMR signals up to 25 GHz. The FMR signals were detected only in anisotropic films and their FMR frequencies were well fit to the Kittel formula. The obtained g-values and damping parameters at magnetic fields >20 kOe for films grown at PN2 of 3.3%, 4.8% and 5.5% were 1.96, 1.86, 1.92 and 0.0055, 0.0047, 0.0046, respectively. This low damping factor qualifies FeCoN thin films for high-frequency applications.

Magnetic moment investigation by frequency mixing techniques.

Science.gov (United States)

Teliban, I; Thede, C; Chemnitz, S; Bechtold, C; Quadakkers, W J; Schütze, M; Quandt, E

2009-11-01

Gas turbines and other large industrial equipment are subjected to high-temperature oxidation and corrosion. Research and development of efficient protective coatings is the main task in the field. Also, knowledge about the depletion state of the coating during the operation time is important. To date, practical nondestructive methods for the measurement of the depletion state do not exist. By integrating magnetic phases into the coating, the condition of the coating can be determined by measuring its magnetic properties. In this paper, a new technique using frequency mixing is proposed to investigate the thickness of the coatings based on their magnetic properties. A sensor system is designed and tested on specific magnetic coatings. New approaches are proposed to overcome the dependency of the measurement on the distance between coil and sample that all noncontact techniques face. The novelty is a low cost sensor with high sensibility and selectivity which can provide very high signal-to-noise ratios. Prospects and limitations are discussed for future use of the sensor in industrial applications.

Annealing effects on magnetic properties of silicone-coated iron-based soft magnetic composites

International Nuclear Information System (INIS)

Wu Shen; Sun Aizhi; Zhai Fuqiang; Wang Jin; Zhang Qian; Xu Wenhuan; Logan, Philip; Volinsky, Alex A.

2012-01-01

This paper focuses on novel iron-based soft magnetic composites synthesis utilizing high thermal stability silicone resin to coat iron powder. The effect of an annealing treatment on the magnetic properties of synthesized magnets was investigated. The coated silicone insulating layer was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. Silicone uniformly coated the powder surface, resulting in a reduction of the imaginary part of the permeability, thereby increasing the electrical resistivity and the operating frequency of the synthesized magnets. The annealing treatment increased the initial permeability, the maximum permeability, and the magnetic induction, and decreased the coercivity. Annealing at 580 °C increased the maximum permeability by 72.5%. The result of annealing at 580 °C shows that the ferromagnetic resonance frequency increased from 2 kHz for conventional epoxy resin coated samples to 80 kHz for the silicone resin insulated composites. - Highlights: ► Silicone uniformly coated the powder, increased the operating frequency of SMCs. ► The annealing treatment increased the DC properties of SMCs. ► Annealing at 580 °C increased the maximum permeability by 72.5%. ► Compared with epoxy coated, the SMCs had higher resistivity annealing at 580 °C.

High-frequency parameters of magnetic films showing magnetization dispersion

International Nuclear Information System (INIS)

Sidorenkov, V.V.; Zimin, A.B.; Kornev, Yu.V.

1988-01-01

Magnetization dispersion leads to skewed resonance curves shifted towards higher magnetizing fields, together with considerable reduction in the resonant absorption, while the FMR line width is considerably increased. These effects increase considerably with frequency, in contrast to films showing magnetic-anisotropy dispersion, where they decrease. It is concluded that there may be anomalies in the frequency dependence of the resonance parameters for polycrystalline magnetic films

Low frequency acoustic properties of bilayer membrane acoustic metamaterial with magnetic oscillator

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Nansha Gao

2017-07-01

Full Text Available A bilayer membrane acoustic metamaterial was proposed to overcome the influence of the mass law on traditional acoustic materials and obtain a lightweight thin-layer structure that can effectively isolate low frequency noise. The finite element analysis (FEA results agree well with the experimental results. It is proved that the sound transmission losses (STLs of the proposed structures are higher than those of same surface density acoustic materials. The introduction of the magnetic mass block is different from the traditional design method, in which only a passive mass block is fixed on the membrane. The magnetic force will cause tension in the membrane, increase membrane prestress, and improve overall structural stiffness. The effects of the geometry size on the STLs are discussed in detail. The kind of method presented in this paper can provide a new means for engineering noise control. Keywords: Bilayer membrane acoustic metamaterial, Low frequency sound insulation, Sound transmission loss, Magnet oscillator

Improved high-frequency soft magnetic properties of FeCo films on organic ferroelectric PVDF substrate

Energy Technology Data Exchange (ETDEWEB)

Li, Dong; Wang, Zhen; Han, Xuemeng; Li, Yue; Guo, Xiaobin; Zuo, Yalu; Xi, Li, E-mail: xili@lzu.edu.cn

2015-02-01

FeCo films with various thicknesses were fabricated by direct-current magnetron sputtering on corning glass and organic ferroelectric PVDF substrates at the same time with 5 nm Ru seed layer and 5 nm Ta protective layer. The in-plane uniaxial anisotropy field of FeCo on glass substrate increases from 24 to 36 Oe with the increase of FeCo film thickness from 5 to 100 nm. However, a large in-plane anisotropy field of FeCo on PVDF substrate increases with FeCo thickness from 5 to 20 nm and gradually decreases with the FeCo thickness further increasing. Atomic force microscope images of FeCo on glass show quite smooth surface with root-mean-square roughness around 0.5 nm and have none visible granules on the surface for all samples. While, AFM images of FeCo on PVDF show quite rough surface with RMS roughness around 25 nm and have visible granules with the smallest granules appearing at the FeCo thickness of 20 nm. The permeability spectra show the typical ferromagnetic resonance phenomenon and can be well fitted by the LLG equation with the obtained experimental parameters. The ferromagnetic resonance frequency can reach 7.0 GHz for the 20 nm FeCo film on PVDF. Moreover, the quality factor of this sample can respectively reach 26, 12 and 7 at 1.0, 2.0, and 3.0 GHz, indicating the potential real 3G application for high-frequency devices. - Highlights: 1.Magnetic and morphological properties of FeCo films on PVDF substrates are studied. 2.The large anisotropy field of FeCo films on PVDF is obtained. 3.Improved high frequency properties of FeCo films on flexible substrates are obtained. 4.The origin of improved high frequency properties of FeCo films on PVDF is studied.

Static Magnetic Properties of AL800 Garnet Material

Energy Technology Data Exchange (ETDEWEB)

Kuharik, J. [Fermilab; Madrak, R. [Fermilab; Makarov, A. [Fermilab; Pellico, W. [Fermilab; Sun, S. [Fermilab; Tan, C. Y. [Fermilab; Terechkine, I. [Fermilab

2017-05-17

A second harmonic tunable RF cavity is being devel-oped for the Fermilab Booster. This device, which prom-ises reduction of the particle beam loss at the injection, transition, and extraction stages, employs perpendicularly biased garnet material for frequency tuning. The required range of the tuning is significantly wider than in previously built and tested tunable RF devices. As a result, the mag-netic field in the garnet comes fairly close to the gyromag-netic resonance line at the lower end of the frequency range. The chosen design concept of a tuner for the cavity cannot ensure uniform magnetic field in the garnet mate-rial; thus, it is important to know the static magnetic prop-erties of the material to avoid significant increase in the lo-cal RF loss power density. This report summarizes studies performed at Fermilab to understand variations in the mag-netic properties of the AL800 garnet material used to build the tuner of the cavity.

Effect of Low-Frequency AC Magnetic Susceptibility and Magnetic Properties of CoFeB/MgO/CoFeB Magnetic Tunnel Junctions

Directory of Open Access Journals (Sweden)

Yuan-Tsung Chen

2014-01-01

Full Text Available In this investigation, the low-frequency alternate-current (AC magnetic susceptibility (χac and hysteresis loop of various MgO thickness in CoFeB/MgO/CoFeB magnetic tunneling junction (MTJ determined coercivity (Hc and magnetization (Ms and correlated that with χac maxima. The multilayer films were sputtered onto glass substrates and the thickness of intermediate barrier MgO layer was varied from 6 to 15 Å. An experiment was also performed to examine the variation of the highest χac and maximum phase angle (θmax at the optimal resonance frequency (fres, at which the spin sensitivity is maximal. The results reveal that χac falls as the frequency increases due to the relationship between magnetization and thickness of the barrier layer. The maximum χac is at 10 Hz that is related to the maximal spin sensitivity and that this corresponds to a MgO layer of 11 Å. This result also suggests that the spin sensitivity is related to both highest χac and maximum phase angle. The corresponding maximum of χac is related to high exchange coupling. High coercivity and saturation magnetization contribute to high exchange-coupling χac strength.

Very-low-frequency magnetic plasma

International Nuclear Information System (INIS)

Pendry, J.B.; O'Brien, S.

2002-01-01

We show that a set of current-carrying wires can exhibit an effective magnetic permeability at very low frequencies of a few hertz. The resonant permeability, which is negative above the resonance frequency, arises from the oscillations of the wires driven by the applied magnetic field. We show that a large, frequency-specific and tunable effective permeability can be realized for a wide range of strengths of the applied field. (author)

Comparison of Microinstability Properties for Stellarator Magnetic Geometries

International Nuclear Information System (INIS)

Rewoldt, G.; Ku, L.-P.; Tang, W.M.

2005-01-01

The microinstability properties of seven distinct magnetic geometries corresponding to different operating and planned stellarators with differing symmetry properties are compared. Specifically, the kinetic stability properties (linear growth rates and real frequencies) of toroidal microinstabilities (driven by ion temperature gradients and trapped-electron dynamics) are compared, as parameters are varied. The familiar ballooning representation is used to enable efficient treatment of the spatial variations along the equilibrium magnetic field lines. These studies provide useful insights for understanding the differences in the relative strengths of the instabilities caused by the differing localizations of good and bad magnetic curvature and of the presence of trapped particles. The associated differences in growth rates due to magnetic geometry are large for small values of the temperature gradient parameter n identical to d ln T/d ln n, whereas for large values of n, the mode is strongly unstable for all of the different magnetic geometries

Tailoring the soft magnetic properties of sputtered multilayers by microstructure engineering for high frequency applications

Directory of Open Access Journals (Sweden)

Claudiu V. Falub

2017-05-01

Full Text Available Soft magnetic Ni78.5Fe21.5, Co91.5Ta4.5Zr4 and Fe52Co28B20 thin films laminated with SiO2, Al2O3, AlN, and Ta2O5 dielectric interlayers were deposited on 8” Si wafers using DC, pulsed DC and RF cathodes in the industrial, high-throughput Evatec LLS-EVO-II magnetron sputtering system. A typical multilayer consists of a bilayer stack up to 50 periods, with alternating (50-100 nm thick magnetic layers and (2-20 nm thick dielectric interlayers. We introduced the in-plane magnetic anisotropy in these films during sputtering by a combination of a linear magnetic field, seed layer texturing by means of linear collimators, and the oblique incidence inherent to the geometry of the sputter system. Depending on the magnetic material, the anisotropy field for these films was tuned in the range of ∼(7-120 Oe by choosing the appropriate interlayer thickness, the aspect ratios of the linear collimators in front of the targets, and the sputter process parameters (e.g. pressure, power, DC pulse frequency, while the coercivity was kept low, ∼(0.05-0.9 Oe. The alignment of the easy axis (EA on the 8” wafers was typically between ±1.5° and ±4°. We discuss the interdependence of structure and magnetic properties in these films, as revealed by atomic force microscopy (AFM, X-ray reflectivity (XRR with reciprocal space mapping (RSM and magneto-optical Kerr effect (MOKE measurements.

Manipulating Electromagnetic Waves in Magnetized Plasmas: Compression, Frequency Shifting, and Release

International Nuclear Information System (INIS)

Avitzour, Yoav; Shvets, Gennady

2008-01-01

A new approach to manipulating the duration and frequency of microwave pulses using magnetized plasmas is demonstrated. The plasma accomplishes two functions: (i) slowing down and spatially compressing the incident wave, and (ii) modifying the propagation properties (group velocity and frequency) of the wave in the plasma during a uniform in space adiabatic in time variation of the magnitude and/or direction of the magnetic field. The increase in the group velocity results in the shortening of the temporal pulse duration. Depending on the plasma parameters, the frequency of the outgoing compressed pulse can either change or remain unchanged. Such dynamic manipulation of radiation in plasma opens new avenues for manipulating high power microwave pulses

Two-frequency radiospectrometer for studying paramagnetics under a strong magnetic field

International Nuclear Information System (INIS)

Vertii, A.A.; Gudym, I.Y.; Ivanchenko, I.V.

1994-01-01

A two-frequency radiospectrometer for studying electron paramagnetic resonance in the 120-150-GHz band and nuclear magnetic resonance in the 180-200-MHz band is described. The spectrometer is used to measure the properties of paramagnetics by a double-resonance technique in a magnetic field of up to 5 T at a temperature ranging from 1.7 to 20 degrees K

Electro-magnetic properties of composites with aligned Fe-Co hollow fibers

Directory of Open Access Journals (Sweden)

Seungchan Cho

2016-05-01

Full Text Available A novel Fe-Co binary hollow fiber was synthesized by electroless plating using hydrolyzed polyester fiber and its anisotropy characteristic was investigated for electromagnetic wave absorbing materials. The hollow fibers in parallel with magnetic field show higher saturated magnetization of 202 emu/g at the applied magnetic field of 10 kOe and lower coercivity (27.658 Oe, compared with the random and vertical oriented hollow fibers. From complex permittivity measurement, the Fe-Co hollow fiber composites clearly display a single dielectric resonance, located at ∼14 GHz. The Fe-Co hollow fibers not only provide excellent EM properties in GHz frequency ranges, resulting mainly from the strong resonance, but also adjust the soft magnetic properties through fiber alignments. The cavitary structure of the Fe-Co hollow fibers, not only giving rise to a dielectric loss resonance and also adjusting its peak frequency, may be a pathway to useful EM wave absorptive devices in GHz frequency ranges.

Effect of Mg{sup 2+} and Ti{sup 4+} dopants on the structural, magnetic and high-frequency ferromagnetic properties of barium hexaferrite

Energy Technology Data Exchange (ETDEWEB)

Shams, Mohammad H. [Department of Physics, University of Isfahan, Hezar Jarib Street, Isfahan 81746-73441 (Iran, Islamic Republic of); Rozatian, Amir S.H., E-mail: a.s.h.rozatian@phys.ui.ac.ir [Department of Physics, University of Isfahan, Hezar Jarib Street, Isfahan 81746-73441 (Iran, Islamic Republic of); Yousefi, Mohammad H. [Department of Physics, University of Isfahan, Hezar Jarib Street, Isfahan 81746-73441 (Iran, Islamic Republic of); Valíček, Jan [Institute of Physics, Faculty of Mining and Geology, VŠB – Technical University of Ostrava, 17. Listopadu 15, 70833 Ostrava-Poruba (Czech Republic); Šepelák, Vladimir [Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen (Germany); Slovak Academy of Sciences, Watsonova 45, 04001 Košice (Slovakia)

2016-02-01

The doped barium hexaferrite, BaFe{sub 12−x}(Mg{sub 0.5}Ti{sub 0.5}){sub x}O{sub 19} with 1≤x≤5, is synthesized by a solid state ceramic method. Its crystalline structure, morphology, as well as static and dynamic magnetic properties are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometry, and vector network analysis, respectively. The cation distribution of Mg{sup 2+} and Ti{sup 4+} in the hexagonal structure of BaFe{sub 12−x}(Mg{sub 0.5}Ti{sub 0.5}){sub x}O{sub 19} is investigated by {sup 57}Fe Mössbauer spectroscopy. The effect of Mg{sup 2+} and Ti{sup 4+} dopants on static and high-frequency magnetic properties of the ferrite is studied. - Highlights: • The BaFe{sub 12−x}(MgTi){sub 0.5x}O{sub 19} (x =1– 5) are synthesized by a solid state reaction method. • The Mg{sup 2+} and Ti{sup 4+} dopants take positions 12k for x=1 and 4f{sub 1} and 4f{sub 2} for x=5. • The coercivity and magnetization are decreased with an increase in Mg–Ti content. • The ferromagnetic resonance frequency is decreased with increase of x. • The FMR is shifted to lower frequencies due to the reduction of the anisotropy field.

Annealing effects on magnetic properties of silicone-coated iron-based soft magnetic composites

Science.gov (United States)

Wu, Shen; Sun, Aizhi; Zhai, Fuqiang; Wang, Jin; Zhang, Qian; Xu, Wenhuan; Logan, Philip; Volinsky, Alex A.

2012-03-01

This paper focuses on novel iron-based soft magnetic composites synthesis utilizing high thermal stability silicone resin to coat iron powder. The effect of an annealing treatment on the magnetic properties of synthesized magnets was investigated. The coated silicone insulating layer was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. Silicone uniformly coated the powder surface, resulting in a reduction of the imaginary part of the permeability, thereby increasing the electrical resistivity and the operating frequency of the synthesized magnets. The annealing treatment increased the initial permeability, the maximum permeability, and the magnetic induction, and decreased the coercivity. Annealing at 580 °C increased the maximum permeability by 72.5%. The result of annealing at 580 °C shows that the ferromagnetic resonance frequency increased from 2 kHz for conventional epoxy resin coated samples to 80 kHz for the silicone resin insulated composites.

Exponential Frequency Spectrum in Magnetized Plasmas

International Nuclear Information System (INIS)

Pace, D. C.; Shi, M.; Maggs, J. E.; Morales, G. J.; Carter, T. A.

2008-01-01

Measurements of a magnetized plasma with a controlled electron temperature gradient show the development of a broadband spectrum of density and temperature fluctuations having an exponential frequency dependence at frequencies below the ion cyclotron frequency. The origin of the exponential frequency behavior is traced to temporal pulses of Lorentzian shape. Similar exponential frequency spectra are also found in limiter-edge plasma turbulence associated with blob transport. This finding suggests a universal feature of magnetized plasma turbulence leading to nondiffusive, cross-field transport, namely, the presence of Lorentzian shaped pulses

Effect of metallurgical factors on the bulk magnetic properties of non-oriented electrical steels

Energy Technology Data Exchange (ETDEWEB)

Ghosh, Pampa, E-mail: pampaghosh@gmail.com [Department of Mining and Materials Engineering, McGill University, 3610 University Street, Montreal, Que., Canada H3A 0C5 (Canada); Chromik, Richard R., E-mail: richard.chromik@mcgill.ca [Department of Mining and Materials Engineering, McGill University, 3610 University Street, Montreal, Que., Canada H3A 0C5 (Canada); Knight, Andrew M. [Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alta., Canada T6G 2V4 (Canada); Wakade, Shekhar G. [GM Powertrain, General Motors Company, 823 Joslyn Avenue, Building B, 4AJ35, Pontiac, MI 48340-2920 (United States)

2014-04-01

Non-oriented electrical steel (NOES) is one of the most common material used in electrical motors. Core loss and permeability are the most important properties that the motor manufacturers look for. Both these properties are structure sensitive and depend on several metallurgical factors; such as chemistry, grain size, crystallographic texture, cleanliness and stress states in non-oriented electrical steels. It has been observed in this course of the study that the grain size and Si content of NOES are the primary controlling factors to core loss, especially at higher frequencies. On the contrary, crystallographic texture plays an important role at lower frequencies. At higher frequency, core loss increases with increasing grain size and decreasing Si content of the steels. Small difference in grain size (∼50 μm) at lower frequency range has little influence on the magnetic properties but has significant adverse effect as frequency reaches high enough. - Highlights: • Magnetic properties of a set of electrical steels were measured. • Crystallographic texture, chemistry and grain size were studied for their effects on core loss and permeability. • Structure–magnetic property relationships were identified for the electrical steels.

Impact of the interaction of material production and mechanical processing on the magnetic properties of non-oriented electrical steel

Science.gov (United States)

Leuning, Nora; Steentjes, Simon; Stöcker, Anett; Kawalla, Rudolf; Wei, Xuefei; Dierdorf, Jens; Hirt, Gerhard; Roggenbuck, Stefan; Korte-Kerzel, Sandra; Weiss, Hannes A.; Volk, Wolfram; Hameyer, Kay

2018-04-01

Thin laminations of non-grain oriented (NO) electrical steels form the magnetic core of rotating electrical machines. The magnetic properties of these laminations are therefore key elements for the efficiency of electric drives and need to be fully utilized. Ideally, high magnetization and low losses are realized over the entire polarization and frequency spectrum at reasonable production and processing costs. However, such an ideal material does not exist and thus, achievable magnetic properties need to be deduced from the respective application requirements. Parameters of the electrical steel such as lamination thickness, microstructure and texture affect the magnetic properties as well as their polarization and frequency dependence. These structural features represent possibilities to actively alter the magnetic properties, e.g., magnetization curve, magnetic loss or frequency dependence. This paper studies the influence of production and processing on the resulting magnetic properties of a 2.4 wt% Si electrical steel. Aim is to close the gap between production influence on the material properties and its resulting effect on the magnetization curves and losses at different frequencies with a strong focus on occurring interdependencies between production and mechanical processing. The material production is realized on an experimental processing route that comprises the steps of hot rolling, cold rolling, annealing and punching.

Impact of the interaction of material production and mechanical processing on the magnetic properties of non-oriented electrical steel

Directory of Open Access Journals (Sweden)

Nora Leuning

2018-04-01

Full Text Available Thin laminations of non-grain oriented (NO electrical steels form the magnetic core of rotating electrical machines. The magnetic properties of these laminations are therefore key elements for the efficiency of electric drives and need to be fully utilized. Ideally, high magnetization and low losses are realized over the entire polarization and frequency spectrum at reasonable production and processing costs. However, such an ideal material does not exist and thus, achievable magnetic properties need to be deduced from the respective application requirements. Parameters of the electrical steel such as lamination thickness, microstructure and texture affect the magnetic properties as well as their polarization and frequency dependence. These structural features represent possibilities to actively alter the magnetic properties, e.g., magnetization curve, magnetic loss or frequency dependence. This paper studies the influence of production and processing on the resulting magnetic properties of a 2.4 wt% Si electrical steel. Aim is to close the gap between production influence on the material properties and its resulting effect on the magnetization curves and losses at different frequencies with a strong focus on occurring interdependencies between production and mechanical processing. The material production is realized on an experimental processing route that comprises the steps of hot rolling, cold rolling, annealing and punching.

MAGNETIC WOVEN FABRICS - PHYSICAL AND MAGNETIC PROPERTIES

Directory of Open Access Journals (Sweden)

GROSU Marian C

2015-05-01

Full Text Available A coated material is a composite structure that consists of at least two components: base material and coating layer. The purpose of coating is to provide special properties to base material, with potential to be applied in EMI shielding and diverse smart technical fields. This paper reports the results of a study about some physical and magnetic properties of coated woven fabrics made from cotton yarns with fineness of 17 metric count. For this aim, a plain woven fabric was coated with a solution hard magnetic polymer based. As hard magnetic powder, barium hexaferrite (BaFe12O19 was selected. The plain woven fabric used as base has been coated with five solutions having different amounts of hard magnetic powder (15% - 45% in order to obtain five different magnetic woven fabrics. A comparison of physical properties regarding weight (g/m2, thickness (mm, degree of charging (% and magnetic properties of magnetic woven samples were presented. Saturation magnetizing (emu/g, residual magnetizing (emu/g and coercive force (kA/m of pure hard magnetic powder and woven fabrics have been studied as hysteresis characteristics. The magnetic properties of the woven fabrics depend on the mass percentage of magnetic powder from coating solution. Also, the residual magnetism and coercive field of woven fabrics represents only a part of bulk barium hexafferite residual magnetism and coercive field.

Ultra-low-frequency dust-electromagnetic modes in self-gravitating magnetized dusty plasmas

International Nuclear Information System (INIS)

Banerjee, A.K.; Alam, M.N.; Mamun, A.A.

2001-01-01

Obliquely propagating ultra-low-frequency dust-electromagnetic waves in a self-gravitating, warm, magnetized, two fluid dusty plasma system have been investigated. Two special cases, namely, dust-Alfven mode propagating parallel to the external magnetic field and dust- magnetosonic mode propagating perpendicular to the external magnetic field have also been considered. It has been shown that effects of self-gravitational field, dust fluid temperature, and obliqueness significantly modify the dispersion properties of these ultra-low-frequency dust-electromagnetic modes. It is also found that in parallel propagating dust-Alfven mode these effects play no role, but in obliquely propagating dust-Alfven mode or perpendicular propagating dust-magnetosonic mode the effect of self-gravitational field plays destabilizing role whereas the effect of dust/ion fluid temperature plays stabilizing role. (author)

Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples.

Science.gov (United States)

Hong, Hyobong; Lim, Eul-Gyoon; Jeong, Jae-Chan; Chang, Jiho; Shin, Sung-Woong; Krause, Hans-Joachim

2016-06-09

The setup of a planar Frequency Mixing Magnetic Detection (p-FMMD) scanner for performing Magnetic Particles Imaging (MPI) of flat samples is presented. It consists of two magnetic measurement heads on both sides of the sample mounted on the legs of a u-shaped support. The sample is locally exposed to a magnetic excitation field consisting of two distinct frequencies, a stronger component at about 77 kHz and a weaker field at 61 Hz. The nonlinear magnetization characteristics of superparamagnetic particles give rise to the generation of intermodulation products. A selected sum-frequency component of the high and low frequency magnetic field incident on the magnetically nonlinear particles is recorded by a demodulation electronics. In contrast to a conventional MPI scanner, p-FMMD does not require the application of a strong magnetic field to the whole sample because mixing of the two frequencies occurs locally. Thus, the lateral dimensions of the sample are just limited by the scanning range and the supports. However, the sample height determines the spatial resolution. In the current setup it is limited to 2 mm. As examples, we present two 20 mm × 25 mm p-FMMD images acquired from samples with 1 µm diameter maghemite particles in silanol matrix and with 50 nm magnetite particles in aminosilane matrix. The results show that the novel MPI scanner can be applied for analysis of thin biological samples and for medical diagnostic purposes.

Microwave processed NiMg ferrite: Studies on structural and magnetic properties

International Nuclear Information System (INIS)

Chandra Babu Naidu, K.; Madhuri, W.

2016-01-01

Ferrites are magnetic semiconductors realizing an important role in electrical and electronic circuits where electrical and magnetic property coupling is required. Though ferrite materials are known for a long time, there is a large scope in the improvement of their properties (vice sintering and frequency dependence of electrical and magnetic properties) with the current technological trends. Forth coming technology is aimed at miniaturization and smart gadgets, electrical components like inductors and transformers cannot be included in integrated circuits. These components are incorporated into the circuit as surface mount devices whose fabrication involves low temperature co-firing of ceramics and microwave monolithic integrated circuits technologies. These technologies demand low temperature sinter-ability of ferrites. This article presents low temperature microwave sintered Ni–Mg ferrites of general chemical formula Ni_1_−_xMg_xFe_2O_4 (x=0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) for potential applications as transformer core materials. The series of ferrites are characterized using X-ray diffractometer, scanning electron microscopy, Fourier transform infrared and vibrating sample magnetometer for investigating structural, morphological and magnetic properties respectively. The initial permeability is studied with magnesium content, temperature and frequency in the temperature range of 308 K–873 K and 42 Hz–5 MHz. - Highlights: • First article on microwave processed NiMgFe_2O_4 giving. • The article gives systematic magnetic studies. • Cation distribution is discussed based on magnetic moments from VSM. • Promising candidates for transformer core and soft magnet manufacturing.

Microwave processed NiMg ferrite: Studies on structural and magnetic properties

Energy Technology Data Exchange (ETDEWEB)

Chandra Babu Naidu, K.; Madhuri, W., E-mail: madhuriw12@gmail.com

2016-12-15

Ferrites are magnetic semiconductors realizing an important role in electrical and electronic circuits where electrical and magnetic property coupling is required. Though ferrite materials are known for a long time, there is a large scope in the improvement of their properties (vice sintering and frequency dependence of electrical and magnetic properties) with the current technological trends. Forth coming technology is aimed at miniaturization and smart gadgets, electrical components like inductors and transformers cannot be included in integrated circuits. These components are incorporated into the circuit as surface mount devices whose fabrication involves low temperature co-firing of ceramics and microwave monolithic integrated circuits technologies. These technologies demand low temperature sinter-ability of ferrites. This article presents low temperature microwave sintered Ni–Mg ferrites of general chemical formula Ni{sub 1−x}Mg{sub x}Fe{sub 2}O{sub 4} (x=0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) for potential applications as transformer core materials. The series of ferrites are characterized using X-ray diffractometer, scanning electron microscopy, Fourier transform infrared and vibrating sample magnetometer for investigating structural, morphological and magnetic properties respectively. The initial permeability is studied with magnesium content, temperature and frequency in the temperature range of 308 K–873 K and 42 Hz–5 MHz. - Highlights: • First article on microwave processed NiMgFe{sub 2}O{sub 4} giving. • The article gives systematic magnetic studies. • Cation distribution is discussed based on magnetic moments from VSM. • Promising candidates for transformer core and soft magnet manufacturing.

Soft magnetic properties of FeRuGaSi alloy films: SOFMAX

International Nuclear Information System (INIS)

Hayashi, K.; Hayakawa, M.; Ishikawa, W.; Ochiai, Y.; Iwasaki, Y.; Aso, K.

1988-01-01

To advance new soft magnetic materials of an FeGaSi alloy into the commercial world, improvements on various properties were designed by introducing additive elements without sacrificing its high saturation magnetic induction. The detailed studies on the diversified properties, such as saturation magnetic induction, film internal stress, wear resistivity, and so on, were performed. High-frequency permeability of the laminated structure film was also investigated. As a result, the Ru-added FeRuGaSi alloy films, whose typical compositions are Fe 72 Ru 4 Ga 7 Si 17 and Fe 68 Ru 8 Ga 7 Si 17 (at. %), prove to be excellent soft magnetic materials especially appropriate for the magnetic recording/playback head core use

Analysis of the magnetic properties in hard-magnetic nanofibers composite

Science.gov (United States)

Murillo-Ortíz, R.; Mirabal-García, M.; Martínez-Huerta, J. M.; Cabal Velarde, J. G.; Castaneda-Robles, I. E.; Lobo-Guerrero, A.

2018-03-01

The magnetic properties of the strontium hexaferrite nanoparticles were studied as they were embedded at different concentrations in poly(vinyl alcohol) (PVA) nanofibers. These nanoparticles were prepared using the Pechini method and a low frequency sonication process obtaining a 3.4 nm average diameter. The composite consisting of hard magnetic nanoparticles homogeneously dispersed in a polymeric matrix was fabricated using a homemade electrospinning with 25 kV DC power supply. The obtained nanofibers had an average diameter of 110 nm, and nanoparticles were arranged and distributed within the nanofibers under the influence of a strong electric field. The configuration of the magnetic nanoparticles in the PVA nanofibers was such that the interparticle exchange interaction became negligible, while the magnetostatic interaction turned out predominant. The results reveal a considerable improvement in the energy product (BHmax) and in the squareness ratio (Mr/Ms) for nanoparticle concentrations between 15 and 30% per gram of PVA. The nanoparticles arrangement occurred at densities below the percolation concentration enhanced the hard-magnetic properties of the nanofibers, which indicates that the organization of the particles along the fibers induces anisotropy from the magnetostatic interaction among the magnetic nanoparticles. Finally, we close the discussion analyzing the observed effect below the percolation threshold, where the induced anisotropy caused the reduction of the full-width at half-maximum of the switching field distribution curves.

Ultra-low-frequency dust-electromagnetic modes in self-gravitating magnetized dusty plasmas

International Nuclear Information System (INIS)

Mamun, A.A.

1999-07-01

Obliquely propagating ultra-low-frequency dust-electromagnetic waves in a self-gravitating, warm, magnetized two fluid dusty plasma system have been investigated. Two special cases, namely, dust-Alfven mode propagating parallel to the external magnetic field and dust-magnetosonic mode propagating perpendicular to the external magnetic field have also been considered. It has been shown that effects of self-gravitational field, dust fluid temperature, and obliqueness significantly modify the dispersion properties of these ultra-low-frequency dust-electromagnetic modes. It is also found that these effects of self-gravitational field and dust/ion fluid temperature play no role in parallel propagating dust-Alfven mode, but in obliquely propagating dust-Alfven mode or perpendicular propagating dust-magnetosonic mode the effect of self-gravitational field plays a destabilizing role whereas the effect of dust/ion fluid temperature plays a stabilizing role. (author)

High-frequency spin-dependent tunnelling in magnetic nanocomposites: Magnetorefractive effect and magnetoimpedance

Energy Technology Data Exchange (ETDEWEB)

Granovsky, Alexander [Faculty of Physics, Lomonosov Moscow State University, Moscow 119992 (Russian Federation)]. E-mail: granov@magn.ru; Kozlov, Andrey [Faculty of Physics, Lomonosov Moscow State University, Moscow 119992 (Russian Federation); Nedukh, Sergey [Institute of Radiophysics and Electronics NAS of Ukraine, Kharkov 61085 (Ukraine); Tarapov, Sergey [Institute of Radiophysics and Electronics NAS of Ukraine, Kharkov 61085 (Ukraine)

2005-07-15

Since the dielectric permittivity is linear with frequency-dependent conductivity, high-frequency properties for any kind of magnetic materials with the high magnetoresistance depend on magnetization. It manifests as magnetorefractive effect (MRE) in the infrared region of spectrum and as magnetoimpedance (MI) in the frequency range between radio and microwaves. The main mechanism of both MRE and MI in nanocomposites with tunnel-type magnetoresistance is high-frequency spin-dependent tunnelling. We report on recent results of theoretical and experimental investigations of MRE and MI in nanocomposites Co{sub 51.5}Al{sub 19.5}O{sub 29}, Co{sub 50.2}Ti{sub 9.1}O{sub 40.7}, Co{sub 52.3}Si{sub 12.2}O{sub 35.5} and (Co{sub 0,4}Fe{sub 0,6}){sub 48}(MgF){sub 52}. Most of the obtained experimental data for MRE and MI are consistent with the theory based on considering the tunnel junction between adjacent granules in percolation cluster as a capacitor.

High frequency oscillations evoked by peripheral magnetic stimulation.

Science.gov (United States)

Biller, S; Simon, L; Fiedler, P; Strohmeier, D; Haueisen, J

2011-01-01

The analysis of somatosensory evoked potentials (SEP) and / or fields (SEF) is a well-established and important tool for investigating the functioning of the peripheral and central human nervous system. A standard technique to evoke SEPs / SEFs is the stimulation of the median nerve by using a bipolar electrical stimulus. We aim at an alternative stimulation technique enabling stimulation of deep nerve structures while reducing patient stress and error susceptibility. In the current study, we apply a commercial transcranial magnetic stimulation system for peripheral magnetic stimulation of the median nerve. We compare the results of simultaneously recorded EEG signals to prove applicability of our technique to evoke SEPs including low frequency components (LFC) as well as high frequency oscillations (HFO). Therefore, we compare amplitude, latency and time-frequency characteristics of the SEP of 14 healthy volunteers after electric and magnetic stimulation. Both low frequency components and high frequency oscillations were detected. The HFOs were superimposed onto the primary cortical response N20. Statistical analysis revealed significantly lower amplitudes and increased latencies for LFC and HFO components after magnetic stimulation. The differences indicate the inability of magnetic stimulation to elicit supramaximal responses. A psycho-perceptual evaluation showed that magnetic stimulation was less unpleasant for 12 out of the 14 volunteers. In conclusion, we showed that LFC and HFO components related to median nerve stimulation can be evoked by peripheral magnetic stimulation.

Magnetic Frequency Response of HL-LHC Beam Screens

Energy Technology Data Exchange (ETDEWEB)

Morrone, M. [CERN; Martino, M. [CERN; De Maria, R. [CERN; Fitterer, M. [Fermilab; Garion, C. [CERN

2017-10-12

Magnetic fields used to control particle beams in accelerators are usually controlled by regulating the electrical current of the power converters. In order to minimize lifetime degradation and ultimately luminosity loss in circular colliders, current-noise is a highly critical figure of merit of power converters, in particular for magnets located in areas with high beta-function, like the High Luminosity Large Hadron Collider (HL-LHC) insertions. However, what is directly acting upon the beam is the magnetic field and not the current of the power converter, which undergoes several frequency-dependent transformations until the desired magnetic field, seen by the beam, is obtained. Beam screens are very rarely considered when assessing or specifying the noise figure of merit, but their magnetic frequency response is such that they realize relatively effective low pass filtering of the magnetic field produced by the system magnet-power converter. This work aims at filling this gap by quantifying the expected impact of different beam screen layouts for the most relevant HL-LHC insertion magnets. A welldefined post-processing technique is used to derive the frequency response of the different multipoles from multi-physics Finite Element Method (FEM) simulation results. In addition, a well approximated analytical formula for the low-frequency range of multi-layered beam screens is presented.

Iron Oxide Nanoparticle-Based Magnetic Ink Development for Fully Printed Tunable Radio-Frequency Devices

KAUST Repository

Vaseem, Mohammad; Ghaffar, Farhan A.; Farooqui, Muhammad Fahad; Shamim, Atif

2018-01-01

. Functionalized iron oxide nanoparticles are successfully embedded in the SU8 matrix to make a magnetic substrate. The as-fabricated substrate is characterized for its magnetostatic and microwave properties. A frequency tunable printed patch antenna

GEMAS: Unmixing magnetic properties of European agricultural soil

Science.gov (United States)

Fabian, Karl; Reimann, Clemens; Kuzina, Dilyara; Kosareva, Lina; Fattakhova, Leysan; Nurgaliev, Danis

2016-04-01

High resolution magnetic measurements provide new methods for world-wide characterization and monitoring of agricultural soil which is essential for quantifying geologic and human impact on the critical zone environment and consequences of climatic change, for planning economic and ecological land use, and for forensic applications. Hysteresis measurements of all Ap samples from the GEMAS survey yield a comprehensive overview of mineral magnetic properties in European agricultural soil on a continental scale. Low (460 Hz), and high frequency (4600 Hz) magnetic susceptibility k were measured using a Bartington MS2B sensor. Hysteresis properties were determined by a J-coercivity spectrometer, built at the paleomagnetic laboratory of Kazan University, providing for each sample a modified hysteresis loop, backfield curve, acquisition curve of isothermal remanent magnetization, and a viscous IRM decay spectrum. Each measurement set is obtained in a single run from zero field up to 1.5 T and back to -1.5 T. The resulting data are used to create the first continental-scale maps of magnetic soil parameters. Because the GEMAS geochemical atlas contains a comprehensive set of geochemical data for the same soil samples, the new data can be used to map magnetic parameters in relation to chemical and geological parameters. The data set also provides a unique opportunity to analyze the magnetic mineral fraction of the soil samples by unmixing their IRM acquisition curves. The endmember coefficients are interpreted by linear inversion for other magnetic, physical and chemical properties which results in an unprecedented and detailed view of the mineral magnetic composition of European agricultural soils.

Frequency and Magnetic Field Dependence of the Skin Depth in Co-rich Soft Magnetic Microwires

Directory of Open Access Journals (Sweden)

A. Zhukov

2016-11-01

Full Text Available We studied giant magnetoimpedance (GMI effect in magnetically soft amorphous Co-rich microwires in the extended frequency range. From obtained experimentally dependences of GMI ratio on magnetic field and different frequencies we estimated the penetration depth and its dependence on applied magnetic field and frequency

Measurement of dielectric and magnetic properties of soil

International Nuclear Information System (INIS)

Patitz, W.E.; Brock, B.C.; Powell, E.G.

1995-11-01

The possibility of subsurface imaging using SAR technology has generated a considerable amount of interest in recent years. One requirement for the successful development of a subsurface imagin system is an understanding of how the soil affects the signal. In response to a need for an electromagnetic characterization of the soil properties, the Radar/Antenna department has developed a measurement system which determines the soils complex electric permittivity and magnetic permeability at UHF frequencies. The one way loss in dB is also calculated using the measured values. There are many reports of measurements of the electric properties of soil in the literature. However, most of these are primarily concerned with measuring only a real dielectric constant. Because some soils have ferromagnetic constituents it is desirable to measure both the electric and magnetic properties of the soil

Analysis of photonic band gap in dispersive properties of tunable three-dimensional photonic crystals doped by magnetized plasma

International Nuclear Information System (INIS)

Zhang HaiFeng; Liu Shaobin; Yang Huan; Kong Xiangkun

2013-01-01

In this paper, the magnetooptical effects in dispersive properties for two types of three-dimensional magnetized plasma photonic crystals (MPPCs) containing homogeneous dielectric and magnetized plasma with diamond lattices are theoretically investigated for electromagnetic (EM) wave based on plane wave expansion (PWE) method, as incidence EM wave vector is parallel to the external magnetic field. The equations for two types of MPPCs with diamond lattices (dielectric spheres immersed in magnetized plasma background or vice versa) are theoretically deduced. The influences of dielectric constant, plasma collision frequency, filling factor, the external magnetic field, and plasma frequency on the dispersive properties for both types of structures are studied in detail, respectively, and some corresponding physical explanations are also given. From the numerical results, it has been shown that the photonic band gaps (PBGs) for both types of MPPCs can be manipulated by plasma frequency, filling factor, the external magnetic field, and the relative dielectric constant of dielectric, respectively. Especially, the external magnetic field can enlarge the PBG for type-2 structure (plasma spheres immersed in dielectric background). However, the plasma collision frequency has no effect on the dispersive properties of two types of three-dimensional MPPCs. The locations of flatbands regions for both types of structures cannot be tuned by any parameters except for plasma frequency and the external magnetic field. The analytical results may be informative and of technical use to design the MPPCs devices.

On the determination of the dynamic properties of a transformer oil based ferrofluid in the frequency range 0.1–20 GHz

International Nuclear Information System (INIS)

Fannin, P.C.; Vekas, L.; Marin, C.N.; Malaescu, I.

2017-01-01

Complex susceptibility measurements provide a unique and efficient means for the investigation and determination of the dynamic properties of magnetic fluids. In particular, measurement of the frequency, f(Hz), and field, H(kA/m), dependent, complex susceptibility, χ(ω, Η)= χ′(ω, Η)−iχ″(ω, Η), of magnetic fluids has proven to be a valuable and reliable technique for investigating such properties. The experimental data presented here was obtained from measurements of a transformer oil based ferrofluid, with measurements being performed over the frequency range 0.1–20 GHz and polarising fields 0–168 kA/m. In the case of transformer oil magnetic fluids, the normal measurement emphasis has been on the investigation of their dielectric properties, including the effects which lightning may have on these properties. Little has been reported on the measurement of the corresponding magnetic susceptibility, χ(ω), of such fluids and in this paper we address this fact. Thus we consider it worthwhile, in the case of a transformer with magnetic fluid transformer oil, being affected as a result of a lightening occurrence, to have knowledge of the fluids dynamic properties, at the microwave frequencies. In the process of determining the sample susceptibility profiles, it was found that the peak value of the χ″(ω) component, was approximately constant over the frequency range 2.4–6.3 GHz. From this it was determined that the fluid was effectively operating as a wideband absorber over a bandwidth of 3.9 GHz. - Highlights: • Complex magnetic susceptibility measurements in the frequency range 0.1–20 GHz. • Determination of the dynamic properties of a transformer oil based ferrofluid. • Wideband attenuator ( Absorber) in the frequency range 2.4–6.3 GHz.

Fabrication of CoZn alloy nanowire arrays: Significant improvement in magnetic properties by annealing process

International Nuclear Information System (INIS)

Koohbor, M.; Soltanian, S.; Najafi, M.; Servati, P.

2012-01-01

Highlights: ► Increasing the Zn concentration changes the structure of NWs from hcp to amorphous. ► Increasing the Zn concentration significantly reduces the Hc value of NWs. ► Magnetic properties of CoZn NWs can be significantly enhanced by appropriate annealing. ► The pH of electrolyte has no significant effect on the properties of the NW arrays. ► Deposition frequency has considerable effects on the magnetic properties of NWs. - Abstract: Highly ordered arrays of Co 1−x Zn x (0 ≤ x ≤ 0.74) nanowires (NWs) with diameters of ∼35 nm and high length-to-diameter ratios (up to 150) were fabricated by co-electrodeposition of Co and Zn into pores of anodized aluminum oxide (AAO) templates. The Co and Zn contents of the NWs were adjusted by varying the ratio of Zn and Co ion concentrations in the electrolyte. The effect of the Zn content, electrodeposition conditions (frequency and pH) and annealing on the structural and magnetic properties (e.g., coercivity (Hc) and squareness (Sq)) of NW arrays were investigated using X-ray diffraction (XRD), scanning electron microscopy, electron diffraction, and alternating gradient force magnetometer (AGFM). XRD patterns reveal that an increase in the concentration of Zn ions of the electrolyte forces the hcp crystal structure of Co NWs to change into an amorphous phase, resulting in a significant reduction in Hc. It was found that the magnetic properties of NWs can be significantly improved by appropriate annealing process. The highest values for Hc (2050 Oe) and Sq (0.98) were obtained for NWs electrodeposited using 0.95/0.05 Co:Zn concentrations at 200 Hz and annealed at 575 °C. While the pH of electrolyte is found to have no significant effect on the structural and magnetic properties of the NW arrays, the electrodeposition frequency has considerable effects on the magnetic properties of the NW arrays. The changes in magnetic property of NWs are rooted in a competition between shape anisotropy and

Detection of the pedogenic magnetic fraction in volcanic soils developed on basalts using frequency-dependent magnetic susceptibility: comparison of two instruments

Science.gov (United States)

Grison, Hana; Petrovsky, Eduard; Kapicka, Ales; Hanzlikova, Hana

2017-05-01

In studies of the magnetic properties of soils, the frequency-dependent magnetic susceptibility percentage (χFD%) is often used for the identification of ultrafine magnetically superparamagnetic/stable single-domain (SP/SSD) particles. This parameter is commonly used as an indicator for increased pedogenesis. In strongly magnetic soils, the SP/SSD magnetic signal (mostly bio-pedogenic) may be masked by lithological signals; making pedogenesis hard to detect. In this study, we compare results for the detection of ultrafine SP/SSD magnetic particles in andic soils using two instruments: a Bartington MS2B dual-frequency meter and an AGICO Kappabridge MFK1-FA. In particular, the study focuses on the effect of pedogenesis by investigating the relationship between specific soil magnetic and chemical properties (soil organic carbon and pHH2O). The values of χFD% obtained with the MS2B varied from 2.4 to 5.9 per cent, and mass-specific magnetic susceptibility (χLF) from 283 to 1688 × 10-8 m3 kg-1, while values of χFD% and χLF obtained with the MFK1-FA varied from 2.7 to 8.2 per cent and from 299 to 1859 × 10-8 m3 kg-1, respectively. Our results suggest that the detection of the SP/SSD magnetic fraction can be accomplished by comparing relative trends of χFD% along the soil profile. Moreover, the discrimination between bio-pedogenic and lithogenic magnetic contributions in the SP/SSD fraction is possible by comparing the χFD% and χLF data determined in the fine earth (<2 mm) and the coarse fraction (4-10 mm) samples down the soil profile.

Magnetic properties in an ash flow tuff with continuous grain size variation: a natural reference for magnetic particle granulometry

Science.gov (United States)

Till, J.L.; Jackson, M.J.; Rosenbaum, J.G.; Solheid, P.

2011-01-01

The Tiva Canyon Tuff contains dispersed nanoscale Fe-Ti-oxide grains with a narrow magnetic grain size distribution, making it an ideal material in which to identify and study grain-size-sensitive magnetic behavior in rocks. A detailed magnetic characterization was performed on samples from the basal 5 m of the tuff. The magnetic materials in this basal section consist primarily of (low-impurity) magnetite in the form of elongated submicron grains exsolved from volcanic glass. Magnetic properties studied include bulk magnetic susceptibility, frequency-dependent and temperature-dependent magnetic susceptibility, anhysteretic remanence acquisition, and hysteresis properties. The combined data constitute a distinct magnetic signature at each stratigraphic level in the section corresponding to different grain size distributions. The inferred magnetic domain state changes progressively upward from superparamagnetic grains near the base to particles with pseudo-single-domain or metastable single-domain characteristics near the top of the sampled section. Direct observations of magnetic grain size confirm that distinct transitions in room temperature magnetic susceptibility and remanence probably denote the limits of stable single-domain behavior in the section. These results provide a unique example of grain-size-dependent magnetic properties in noninteracting particle assemblages over three decades of grain size, including close approximations of ideal Stoner-Wohlfarth assemblages, and may be considered a useful reference for future rock magnetic studies involving grain-size-sensitive properties.

Controlled drug release under a low frequency magnetic field: effect of the citrate coating on magnetoliposomes stability

KAUST Repository

Nappini, Silvia; Bonini, Massimo; Bombelli, Francesca Baldelli; Pineider, Francesco; Sangregorio, Claudio; Baglioni, Piero; Nordè n, Bengt

2011-01-01

The paper describes the effect of a low-frequency alternating magnetic field (LF-AMF) on the permeability and release properties of large (LUVs) and giant (GUVs) unilamellar vesicles loaded with citrate coated cobalt ferrite nanoparticles (NPs). The citrate shell allows a high loading of NPs in lipid vesicles without modifying their magnetic properties. The increase of magnetic LUVs permeability upon exposure to LF-AMF has been evaluated as the fluorescence self-quenching of carboxyfluorescein (CF) entrapped inside the liposome aqueous pool. Liposome leakage has been monitored as a function of field frequency, time exposure and concentration of the citrate coated NPs. Confocal Laser Scanning Microscopy (CLSM) experiments performed on magnetic GUVs labeled with the fluorescent probe DiIC18 and loaded with Alexa 488-C5-maleimide fluorescent dye provided insights on the release mechanism induced by LF-AMF. The results show that LF-AMF strongly affects vesicles permeability, suggesting the formation of pores in the lipid bilayer due to both hyperthermic effects and nanoparticle oscillations in the vesicles pool at the applied frequency. The behaviour of these magnetic vesicles in the presence of LF-AMF makes this system a good candidate for controlled drug delivery. © 2011 The Royal Society of Chemistry.

Exfoliated BN shell-based high-frequency magnetic core-shell materials.

Science.gov (United States)

Zhang, Wei; Patel, Ketan; Ren, Shenqiang

2017-09-14

The miniaturization of electric machines demands high frequency magnetic materials with large magnetic-flux density and low energy loss to achieve a decreased dimension of high rotational speed motors. Herein, we report a solution-processed high frequency magnetic composite (containing a nanometal FeCo core and a boron nitride (BN) shell) that simultaneously exhibits high electrical resistivity and magnetic permeability. The frequency dependent complex initial permeability and the mechanical robustness of nanocomposites are intensely dependent on the content of BN insulating phase. The results shown here suggest that insulating magnetic nanocomposites have potential for application in next-generation high-frequency electric machines with large electrical resistivity and permeability.

Properties of magnetized Coulomb crystals of ions with polarizable electron background

Science.gov (United States)

Kozhberov, A. A.

2018-06-01

We have studied phonon and thermodynamic properties of a body-centered cubic (bcc) Coulomb crystal of ions with weakly polarized electron background in a uniform magnetic field B. At B = 0, the difference between phonon moments calculated using the Thomas-Fermi (TF) and random phase approximations is always less than 1% and for description of phonon properties of a crystal, TF formalism was used. This formalism was successfully applied to investigate thermodynamic properties of magnetized Coulomb crystals. It was shown that the influence of the polarization of the electron background is significant only at κ TF a > 0.1 and T ≪ T p ( 1 + h2 ) - 1 / 2 , where κTF is the Thomas-Fermi wavenumber, a is the ion sphere radius, T p ≡ ℏ ω p is the ion plasma temperature, h ≡ ω B / ω p , ωB is the ion cyclotron frequency, and ωp is the ion plasma frequency.

Low frequency electric and magnetic fields

Science.gov (United States)

Spaniol, Craig

1989-01-01

Following preliminary investigations of the low frequency electric and magnetic fields that may exists in the Earth-ionospheric cavity, measurements were taken with state-of-the art spectrum analyzers. As a follow up to this activity, an investigation was initiated to determine sources and values for possible low frequency signal that would appear in the cavity. The lowest cavity resonance is estimated at about 8 Hz, but lower frequencies may be an important component of our electromagnetic environment. The potential field frequencies produced by the electron were investigated by a classical model that included possible cross coupling of the electric and gravitation fields. During this work, an interesting relationship was found that related the high frequency charge field with the extremely low frequency of the gravitation field. The results of numerical calculations were surprisingly accurate and this area of investigation is continuing. The work toward continued development of a standardized monitoring facility is continuing with the potential of installing the prototype at West Virginia State College early in 1990. This installation would be capable of real time monitoring of ELF signals in the Earth-ionoshpere cavity and would provide some directional information. A high gain, low noise, 1/f frequency corrected preamplifier was designed and tested for the ferrite core magnetic sensor. The potential application of a super conducting sensor for the ELF magnetic field detection is under investigation. It is hoped that a fully operational monitoring network could pinpoint the location of ELF signal sources and provide new information on where these signals originate and what causes them, assuming that they are natural in origin.

Impact of Ion Bombardment on the Structure and Magnetic Properties of Fe78Si13B9 Amorphous Alloy

Science.gov (United States)

Wu, Yingwei; Peng, Kun

2018-06-01

Amorphous Fe78Si13B9 alloy ribbons were bombarded by ion beams with different incident angles ( θ ). The evolution of the microstructure and magnetic properties of ribbons caused by ion beam bombardment was investigated by x-ray diffraction, transmission electron microscope and vibrating sample magnetometer analysis. Low-incident-angle bombardment led to atomic migration in the short range, and high-incident-angle bombardment resulted in the crystallization of amorphous alloys. Ion bombardment induces magnetic anisotropy and affects magnetic properties. The effective magnetic anisotropy was determined by applying the law of approach to saturation, and it increased with the increase of the ion bombardment angle. The introduction of effective magnetic anisotropy will reduce the permeability and increase the relaxation frequency. Excellent high-frequency magnetic properties can be obtained by selecting suitable ion bombardment parameters.

Relationships between some soil physical and chemical properties with magnetic properties in different soil moisture regimes in Golestan province

Directory of Open Access Journals (Sweden)

M. Valaee

2016-09-01

mm and 846 mm in Touskstan uplands (Udic regime, respectively. this study was conducted in four soil moisture regimes (Aridic, Xeric, Udic and Aquic, for exploring the relationships between soil properties and magnetic measures. In each regimes, 25 soil profiles were drug, described and soil samples were collected from each of soil horizons. Soil samples were air-dried and sieved using a 2 mm sieve. The dithionite-citrate bicarbonate (DCB method was used to measure Fed and acid ammonium oxalate for Feo. In this study, a set of environmental magnetic parameters including magnetic susceptibility at low frequency (χlf, saturation isothermal remnant magnetization (SIRM, isothermal remnant magnetization (IRM100 mT were measured. Magnetic susceptibility (χ was measured at low frequency (0.47 kHz; χlf and high frequency (4.7 kHz; χhf using a Bartington MS2 dual frequency sensor using approximately 20 g of soil held in a four-dram clear plastic vial (2.3 cm diameter. Frequency dependent susceptibility (χfd was determined by the difference between the high and low frequency measurements as a percentage of χ at low frequency. IRM was measured at the field of 100 mT generated in a Molspin pulse magnetizer (IRM100mT and at the back field of 100mT (IRM−100mT. The IRM acquired in the maximum field of 1000 mT was measured and defined as the saturation isothermal remnant magnetization (SIRM of the soil sample. Results and Discussion: The results showed that moisture regime induced significant differences for soil physical and chemical properties. Diversities in genetic soil horizons and soil development degree have been increased from Aridic to Udic soil moisture regime. The results also indicated that selected properties including magnetic measures and physical and chemical properties were significantly different in four soil moisture regimes. With increasing rainfall and reducing temperature from aridic to udic soil moisture regime, soil organic matter was increased

Magnetic properties of fishes from rivers near Semarang, Central Java

Science.gov (United States)

Khumaedi; Nurbaiti, U.; Setyaningsi, N. E.

2018-03-01

Magnetic properties, in the form of magnetic susceptibility (χ) and frequency-dependent susceptibility (χ fd) were measured on scores of samples made of fishes from river nearby Semarang, Central Java. Semarang is one of the major cities in Indonesia, where the river systems are very likely to be contaminated by anthropogenic activities. The objective of this study is to identify the presence of heavy metals in the fishes that will determine the suitability of these fishes for healthy food. The results show that magnetic susceptibility varies from -0.3 to 13.8 × 10-8 m3/kg, while the frequency-dependent susceptibility is less than 3% indicating the predominance of ferromagnetic minerals. Quantitative chemical analyses on four samples show consistently high concentration of Ca, while Fe, Hg, Cu, Pb, Cd, and Ni present a few in some of the samples. This finding shows that the fishes are suitable for the ongoing research on environmental magnetism.

Low-frequency waves in magnetized dusty plasmas revisited

International Nuclear Information System (INIS)

Salimullah, M.; Khan, M.I.; Amin, R.; Nitta, H.; Shukla, P.K.

2005-10-01

The general dispersion relation of any wave is examined for low-frequency waves in a homogeneous dusty plasma in the presence of an external magnetic field. The low-frequency parallel electromagnetic wave propagates as a dust cyclotron wave or a whistler in the frequency range below the ion cyclotron frequency. In the same frequency regime, the transverse electromagnetic magnetosonic wave is modified with a cutoff frequency at the dust-ion lower-hybrid frequency, which reduces to the usual magnetosonic wave in absence of the dust. Electrostatic dust-lower- hybrid mode is also recovered propagating nearly perpendicular to the magnetic field with finite ion temperature and cold dust particles which for strong ion-Larmor radius effect reduces to the usual dust-acoustic wave driven by the ion pressure. (author)

Soft magnetism, magnetostriction, and microwave properties of FeGaB thin films

International Nuclear Information System (INIS)

Lou, J.; Insignares, R. E.; Cai, Z.; Ziemer, K. S.; Liu, M.; Sun, N. X.

2007-01-01

A series of (Fe 100-y Ga y ) 1-x B x (x=0-21 and y=9-17) films were deposited; their microstructure, soft magnetism, magnetostrictive behavior, and microwave properties were investigated. The addition of B changes the FeGaB films from polycrystalline to amorphous phase and leads to excellent magnetic softness with coercivity s , self-biased ferromagnetic resonance (FMR) frequency of 1.85 GHz, narrow FMR linewidth (X band) of 16-20 Oe, and a high saturation magnetostriction constant of 70 ppm. The combination of these properties makes the FeGaB films potential candidates for tunable magnetoelectric microwave devices and other rf/microwave magnetic device applications

Fabrication of CoZn alloy nanowire arrays: Significant improvement in magnetic properties by annealing process

Energy Technology Data Exchange (ETDEWEB)

Koohbor, M. [Department of Physics, University of Kurdistan, Sanandaj (Iran, Islamic Republic of); Soltanian, S., E-mail: s.soltanian@gmail.com [Department of Physics, University of Kurdistan, Sanandaj (Iran, Islamic Republic of); Department of Electrical and Computer Engineering, University of British Columbia, Vancouver (Canada); Najafi, M. [Department of Physics, University of Kurdistan, Sanandaj (Iran, Islamic Republic of); Department of Physics, Hamadan University of Technology, Hamadan (Iran, Islamic Republic of); Servati, P. [Department of Electrical and Computer Engineering, University of British Columbia, Vancouver (Canada)

2012-01-05

Highlights: Black-Right-Pointing-Pointer Increasing the Zn concentration changes the structure of NWs from hcp to amorphous. Black-Right-Pointing-Pointer Increasing the Zn concentration significantly reduces the Hc value of NWs. Black-Right-Pointing-Pointer Magnetic properties of CoZn NWs can be significantly enhanced by appropriate annealing. Black-Right-Pointing-Pointer The pH of electrolyte has no significant effect on the properties of the NW arrays. Black-Right-Pointing-Pointer Deposition frequency has considerable effects on the magnetic properties of NWs. - Abstract: Highly ordered arrays of Co{sub 1-x}Zn{sub x} (0 {<=} x {<=} 0.74) nanowires (NWs) with diameters of {approx}35 nm and high length-to-diameter ratios (up to 150) were fabricated by co-electrodeposition of Co and Zn into pores of anodized aluminum oxide (AAO) templates. The Co and Zn contents of the NWs were adjusted by varying the ratio of Zn and Co ion concentrations in the electrolyte. The effect of the Zn content, electrodeposition conditions (frequency and pH) and annealing on the structural and magnetic properties (e.g., coercivity (Hc) and squareness (Sq)) of NW arrays were investigated using X-ray diffraction (XRD), scanning electron microscopy, electron diffraction, and alternating gradient force magnetometer (AGFM). XRD patterns reveal that an increase in the concentration of Zn ions of the electrolyte forces the hcp crystal structure of Co NWs to change into an amorphous phase, resulting in a significant reduction in Hc. It was found that the magnetic properties of NWs can be significantly improved by appropriate annealing process. The highest values for Hc (2050 Oe) and Sq (0.98) were obtained for NWs electrodeposited using 0.95/0.05 Co:Zn concentrations at 200 Hz and annealed at 575 Degree-Sign C. While the pH of electrolyte is found to have no significant effect on the structural and magnetic properties of the NW arrays, the electrodeposition frequency has considerable effects on

Development of Ferrite-Coated Soft Magnetic Composites: Correlation of Microstructure to Magnetic Properties

Science.gov (United States)

Sunday, Katie Jo

Soft magnetic composites (SMCs) comprised of ferrite-coated ferrous powder permit isotropic magnetic flux capabilities, lower core losses, and complex designs through the use of traditional powder metallurgy techniques. Current coating materials and methods are vastly limited by the nonmagnetic properties of organic and some inorganic coatings and their inability to withstand high heat treatments for proper stress relief of core powder after compaction. Ferrite-based coatings are ferrimagnetic, highly resistive, and boast high melting temperatures, thus providing adequate electrical barriers between metallic particles. These insulating layers are necessary for reducing eddy current losses by increasing resistivity in order to improve the overall magnetic efficiency and subsequent frequency range. The goals of this work are to correlate ferrite-coated Fe powder composites microstructure for the coating and core powder to magnetic properties such as permeability, coercivity, and core loss. We first explore the relevant concepts of SMC materials from their composition to processing steps to pertinent properties. This thesis employs a suite of characterization techniques for powder and composite properties. We use X-ray diffraction, scanning electron microscopy, and transmission electron microscopy to provide a complete understanding of the effect of processing conditions on ferrite-coated Fe-based SMCs. Magnetic, mechanical, and electrical properties are then analyzed to correlate microstructural features and determine their effect on such properties. In the second part of this thesis, we present a proof of concept study on Al2O3- and Al2O3- Fe3O4-coated Fe powder composites, illustrating magnetization is highly dependent on ferromagnetic volume. We then expand on previous work to compare an ideal, crystalline state using Fe3O 4-Fe thin film heterostructures to a highly strained state using bulk powder studies. Fe3O4-coated Fe composites are produced via mechanical

Magnetic and microwave absorption properties of La-Nd-Fe alloys

Energy Technology Data Exchange (ETDEWEB)

Qiao, Ziqiang [School of Material Science and Engineering & Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Technology, Guilin 541004 (China); Pan, Shunkang, E-mail: skpan88@163.com [School of Material Science and Engineering & Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Technology, Guilin 541004 (China); Xiong, Jilei [Chinalco Guangxi Non Ferrous Jinyuan Rare Earth CO., LTD, Hezhou 542603 (China); Cheng, Lichun; Yao, Qingrong [School of Material Science and Engineering & Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Technology, Guilin 541004 (China); School of Materials and Engineering, Central South University, Changsha 410083 (China); Lin, Peihao [School of Material Science and Engineering & Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Technology, Guilin 541004 (China)

2017-02-01

Through arc smelting and high energy ball milling method to synthesized the powders of La{sub x}Nd{sub 2-x}Fe{sub 17} (x=0.0, 0.2, 0.4, 0.6). By x-ray diffraction (XRD), scanning electron microscopy (SEM) and laser particle analyzer (LPS) to study the structural, morphology, particle size distribution of the powders, respectively. The electromagnetic parameters and saturation magnetization of the powers were measured by a vector network analyzer (VNA) and vibrating sample magnetometer (VSM), respectively. The saturation magnetization decreases with the La increasing. The minimum absorption peak frequency shifts towards a lower frequency region with an increase of La concentration. The microwave absorbing properties of the composite with different ratios of La{sub 0.2}Nd{sub 1.8}Fe{sub 17}/Ni were studied. The microwave absorbing peaks of the composite shift to higher frequencies, and the microwave absorbing properties improved with the Ni content increase to 20%. The minimum reflection loss is −32.5 dB at 9.8 GHz and the bandwidth less than −10 dB (Microwave absorption rate 90%) reaches 3 GHz with a thickness of 1.8 mm.

On the determination of the dynamic properties of a transformer oil based ferrofluid in the frequency range 0.1-20 GHz

Science.gov (United States)

Fannin, P. C.; Vekas, L.; Marin, C. N.; Malaescu, I.

2017-02-01

Complex susceptibility measurements provide a unique and efficient means for the investigation and determination of the dynamic properties of magnetic fluids. In particular, measurement of the frequency, f(Hz), and field, H(kA/m), dependent, complex susceptibility, χ(ω, Η)= χ‧(ω, Η)-iχ″(ω, Η), of magnetic fluids has proven to be a valuable and reliable technique for investigating such properties. The experimental data presented here was obtained from measurements of a transformer oil based ferrofluid, with measurements being performed over the frequency range 0.1-20 GHz and polarising fields 0-168 kA/m. In the case of transformer oil magnetic fluids, the normal measurement emphasis has been on the investigation of their dielectric properties, including the effects which lightning may have on these properties. Little has been reported on the measurement of the corresponding magnetic susceptibility, χ(ω), of such fluids and in this paper we address this fact. Thus we consider it worthwhile, in the case of a transformer with magnetic fluid transformer oil, being affected as a result of a lightening occurrence, to have knowledge of the fluids dynamic properties, at the microwave frequencies. In the process of determining the sample susceptibility profiles, it was found that the peak value of the χ″(ω) component, was approximately constant over the frequency range 2.4-6.3 GHz. From this it was determined that the fluid was effectively operating as a wideband absorber over a bandwidth of 3.9 GHz.

MESSENGER Magnetic Field Observations of Upstream Ultra-Low Frequency Waves at Mercury

Science.gov (United States)

Le, G.; Chi, P. J.; Boardsen, S.; Blanco-Cano, X.; Anderosn, B. J.; Korth, H.

2012-01-01

The region upstream from a planetary bow shock is a natural plasma laboratory containing a variety of wave particle phenomena. The study of foreshocks other than the Earth's is important for extending our understanding of collisionless shocks and foreshock physics since the bow shock strength varies with heliocentric distance from the Sun, and the sizes of the bow shocks are different at different planets. The Mercury's bow shock is unique in our solar system as it is produced by low Mach number solar wind blowing over a small magnetized body with a predominately radial interplanetary magnetic field. Previous observations of Mercury upstream ultra-low frequency (ULF) waves came exclusively from two Mercury flybys of Mariner 10. The MESSENGER orbiter data enable us to study of upstream waves in the Mercury's foreshock in depth. This paper reports an overview of upstream ULF waves in the Mercury's foreshock using high-time resolution magnetic field data, 20 samples per second, from the MESSENGER spacecraft. The most common foreshock waves have frequencies near 2 Hz, with properties similar to the I-Hz waves in the Earth's foreshock. They are present in both the flyby data and in every orbit of the orbital data we have surveyed. The most common wave phenomenon in the Earth's foreshock is the large-amplitude 30-s waves, but similar waves at Mercury have frequencies at near 0.1 Hz and occur only sporadically with short durations (a few wave cycles). Superposed on the "30-s" waves, there are spectral peaks at near 0.6 Hz, not reported previously in Mariner 10 data. We will discuss wave properties and their occurrence characteristics in this paper.

Effect of the carbonyl iron particles on acoustic absorption properties of magnetic polyurethane foam

Science.gov (United States)

Geng, Jialu; Wang, Caiping; Zhu, Honglang; Wang, Xiaojie

2018-03-01

Elastomeric matrix embedded with magnetic micro-sized particles has magnetically controllable properties, which has been investigated extensively in the last decades. In this study we develop a new magnetically controllable elastomeric material for acoustic applications at lower frequencies. The soft polyurethane foam is used as matrix material due to its extraordinary elastic and acoustic absorption properties. One-step method is used to synthesize polyurethane foam, in which all components including polyether polyols 330N, MDI, deionized water, silicone oil, carbonyl iron particle (CIP) and catalyst are put into one container for curing. Changing any component can induce the change of polyurethane foam's properties, such as physical and acoustic properties. The effect of the content of MDI on acoustic absorption is studied. The CIPs are aligned under extra magnetic field during the foaming process. And the property of polyurethane foam with aligned CIPs is also investigated. Scanning electron microscope (SEM) is used to observe the structure of pore and particle-chain. The two-microphone impedance tube and the transfer function method are used to test acoustic absorption property of the magnetic foams.

High-frequency domain wall excitations in magnetic garnet films with in-plane magnetization

International Nuclear Information System (INIS)

Synogach, V.T.; Doetsch, H.

1996-01-01

Magnetic garnet films of compositions (YBi) 3 Fe 5 O 12 and (LuBi) 3 Fe 5 O 12 are grown by liquid-phase epitaxy on [110]- and [100]-oriented substrates of gadolinium gallium garnet, respectively. All films have in-plane magnetization. 180 degree and 90 degree domain walls in these films are studied by microwave technique. In addition to the known low-frequency mode of wall translation new multiple resonant modes of both 90 degree and 180 degree domain walls with very small linewidth (4.2 MHz) are observed at frequencies near 1 GHz. Resonances are effectively excited by an rf magnetic field which is parallel or perpendicular to the wall plane. Resonance frequencies are shown to have nonlinear dispersion dependence on the mode number: they decrease with increasing in-plane magnetic field normal to the wall plane. copyright 1996 The American Physical Society

Magnetic Frequency Response of HL-LHC Beam Screens

CERN Document Server

Morrone, M; De Maria, R; Fitterer, M; Garion, C

2017-01-01

Magnetic fields used to control particle beams in accelerators are usually controlled by regulating the electrical current of the power converters. In order to minimize lifetime degradation and ultimately luminosity loss in circular colliders, current-noise is a highly critical figure of merit of power converters, in particular for magnets located in areas with high beta-function, like the High Luminosity Large Hadron Collider (HL-LHC) insertions. However, what is directly acting upon the beam is the magnetic field and not the current of the power converter, which undergoes several frequency-dependent transformations until the desired magnetic field, seen by the beam, is obtained. Beam screens are very rarely considered when assessing or specifying the noise figure of merit, but their magnetic frequency response is such that they realize relatively effective low pass filtering of the magnetic field produced by the system magnet-power converter. This work aims at filling this gap by quantifying the expected im...

Robust Magnetic Properties of a Sublimable Single-Molecule Magnet.

Science.gov (United States)

Kiefl, Evan; Mannini, Matteo; Bernot, Kevin; Yi, Xiaohui; Amato, Alex; Leviant, Tom; Magnani, Agnese; Prokscha, Thomas; Suter, Andreas; Sessoli, Roberta; Salman, Zaher

2016-06-28

The organization of single-molecule magnets (SMMs) on surfaces via thermal sublimation is a prerequisite for the development of future devices for spintronics exploiting the richness of properties offered by these magnetic molecules. However, a change in the SMM properties due to the interaction with specific surfaces is usually observed. Here we present a rare example of an SMM system that can be thermally sublimated on gold surfaces while maintaining its intact chemical structure and magnetic properties. Muon spin relaxation and ac susceptibility measurements are used to demonstrate that, unlike other SMMs, the magnetic properties of this system in thin films are very similar to those in the bulk, throughout the full volume of the film, including regions near the metal and vacuum interfaces. These results exhibit the robustness of chemical and magnetic properties of this complex and provide important clues for the development of nanostructures based on SMMs.

Tuning stress-induced magnetic anisotropy and high frequency properties of FeCo films deposited on different curvature substrates

International Nuclear Information System (INIS)

Wang, Z.K.; Feng, E.X.; Liu, Q.F.; Wang, J.B.; Xue, D.S.

2012-01-01

It is important to control magnetic anisotropy of ferromagnetic materials. In this work, FeCo thin films are deposited on the curving substrates by electrochemical deposition to adjust the stress-induced magnetic anisotropy. The compressive stress is produced in the as-deposited films after the substrates are flattened. A simplified theoretical model of ferromagnetic resonance is utilized to measure the intrinsic magnetic anisotropy field and saturation magnetization. The results show that the stress-induced magnetic anisotropy and the resonance frequency increase with the increase of substrate curvature. The induced easy axis is perpendicular to the compressive stress direction.

Comprehensive high frequency electron paramagnetic resonance studies of single molecule magnets

Science.gov (United States)

Lawrence, Jonathan D.

This dissertation presents research on a number of single molecule magnet (SMM) compounds conducted using high frequency, low temperature magnetic resonance spectroscopy of single crystals. By developing a new technique that incorporated other devices such as a piezoelectric transducer or Hall magnetometer with our high frequency microwaves, we were able to collect unique measurements on SMMs. This class of materials, which possess a negative, axial anisotropy barrier, exhibit unique magnetic properties such as quantum tunneling of a large magnetic moment vector. There are a number of spin Hamiltonians used to model these systems, the most common one being the giant spin approximation. Work done on two nickel systems with identical symmetry and microenvironments indicates that this model can contain terms that lack any physical significance. In this case, one must turn to a coupled single ion approach to model the system. This provides information on the nature of the exchange interactions between the constituent ions of the molecule. Additional studies on two similar cobalt systems show that, for these compounds, one must use a coupled single ion approach since the assumptions of the giant spin model are no longer valid. Finally, we conducted a collection of studies on the most famous SMM, Mn12Ac. Three different techniques were used to study magnetization dynamics in this system: stand-alone HFEPR in two different magnetization relaxation regimes, HFEPR combined with magnetometry, and HFEPR combined with surface acoustic waves. All of this research gives insight into the relaxation mechanisms in Mn12Ac.

Frequency-domain analysis of resonant-type ring magnet power supplies

International Nuclear Information System (INIS)

Kim, J.M.S.; Reiniger, K.W.

1993-01-01

For fast-cycling synchrotrons, resonant-type ring magnet power supplies are commonly used to provide a dc-biased ac excitation for the ring magnets. Up to the present, this power supply system has been analyzed using simplified analytical approximation, namely assuming the resonant frequency of the ring magnet network is fixed and equal to the accelerator frequency. This paper presents a frequency-domain analysis technique for a more accurate analysis of resonant-type ring magnet power supplies. This approach identifies that, with the variation of the resonant frequency, the operating conditions of the power supply changes quite dramatically because of the high Q value of the resonant network. The analytical results are verified, using both experimental results and simulation results

Influence of cold isostatic pressing on the magnetic properties of Ni-Zn-Cu ferrite

Science.gov (United States)

Le, Trong Trung; Valdez-Nava, Zarel; Lebey, Thierry; Mazaleyrat, Frédéric

2018-04-01

In power electronics, there is the need to develop solutions to increase the power density of converters. Interleaved multicellular transformers allow interleaving many switching cells and, as a result, a possible increase in the power density. This converter is often composed of a magnetic core having the function of an intercell transformer (ICT) and, depending on the complexity of the designed architecture, its shape could be extremely complex. The switching frequencies (1-10 MHz) for the new wide band gap semiconductors (SiC, GaN) allow to interleave switching cell at higher frequencies than silicon-based semiconductors (materials, but their limit in frequency drive raises the need of higher frequency magnetic materials, such Ni-Zn ferrites. These materials can operate in medium and high power converters up to 10 MHz. We propose to use Ni0,30Zn0,57Cu0,15Fe2O4 ferrite and to compress it by cold isostatic pressing (CIP) into a a green ceramic block and to machine it to obtain the desired ICT of complex shape prior sintering. We compare the magnetic permeability spectra and hysteresis loops the CIP and uniaxially pressed ferrites. The effect of temperature and sintering time as well as high-pressure on properties will be presented in detail. The magnetic properties of the sintered cores are strongly dependent on the microstructure obtained.

Iron Oxide Nanoparticle-Based Magnetic Ink Development for Fully Printed Tunable Radio-Frequency Devices

KAUST Repository

Vaseem, Mohammad

2018-01-30

The field of printed electronics is still in its infancy and most of the reported work is based on commercially available nanoparticle-based metallic inks. Although fully printed devices that employ dielectric/semiconductor inks have recently been reported, there is a dearth of functional inks that can demonstrate controllable devices. The lack of availability of functional inks is a barrier to the widespread use of fully printed devices. For radio-frequency electronics, magnetic materials have many uses in reconfigurable components but rely on expensive and rigid ferrite materials. A suitable magnetic ink can facilitate the realization of fully printed, magnetically controlled, tunable devices. This report presents the development of an iron oxide nanoparticle-based magnetic ink. First, a tunable inductor is fully printed using iron oxide nanoparticle-based magnetic ink. Furthermore, iron oxide nanoparticles are functionalized with oleic acid to make them compatible with a UV-curable SU8 solution. Functionalized iron oxide nanoparticles are successfully embedded in the SU8 matrix to make a magnetic substrate. The as-fabricated substrate is characterized for its magnetostatic and microwave properties. A frequency tunable printed patch antenna is demonstrated using the magnetic and in-house silver-organo-complex inks. This is a step toward low-cost, fully printed, controllable electronic components.

Dielectric and magnetic properties of (Zn, Co) co-doped SnO2 nanoparticles

International Nuclear Information System (INIS)

Rajwali, Khan; Fang Ming-Hu

2015-01-01

Polycrystalline samples of (Zn, Co) co-doped SnO 2 nanoparticles were prepared using a co-precipitation method. The influence of (Zn, Co) co-doping on electrical, dielectric, and magnetic properties was studied. All of the (Zn, Co) co-doped SnO 2 powder samples have the same tetragonal structure of SnO 2 . A decrease in the dielectric constant was observed with the increase of Co doping concentration. It was found that the dielectric constant and dielectric loss values decrease, while AC electrical conductivity increases with doping concentration and frequency. Magnetization measurements revealed that the Co doping SnO 2 samples exhibits room temperature ferromagnetism. Our results illustrate that (Zn, Co) co-doped SnO 2 nanoparticles have an excellent dielectric, magnetic properties, and high electrical conductivity than those reported previously, indicating that these (Zn, Co) co-doped SnO 2 materials can be used in the field of the ultrahigh dielectric material, high frequency device, and spintronics. (paper)

Crystal structure, magnetic properties and advances in hexaferrites: A brief review

Science.gov (United States)

Jotania, Rajshree

2014-10-01

Hexaferrites are hard magnetic materials and specifically ferri-magnetic oxides with hexagonal magnetoplumbite type crystallographic structure. Hexagonal ferrites are used as permanent magnets, high-density perpendicular and magneto-optical recording media, and microwave devices like resonance isolators, filters, circulators, phase shifters because of their high magnetic permeability, high electrical resistivity and moderable permittivity. In addition to these; hexagonal ferrites have excellent chemical stability, mechanical hardness and low eddy current loss at high frequencies. The preparation of hexaferrites is a complicated process. Various experimental techniques like standard ceramic techniques, solvent free synthesis route, co precipitation, salt-melt, ion exchange, sol-gel, citrate synthesis, hydrothermal synthesis, spray drying, water-in-oil microemulsion, reverse micelle etc are used to prepare hexaferrite materials. Structural, dielectric and magnetic properties, crystallite size of hexaferrites depend upon nature of substituted ions, method of preparation, sintering temperature and time. The recent interest is nanotechnology, the development of hexaferrite fibres and composites with carbon nano tubes (CNT). Magnetic properties of some doped and un-doped hexaferrites are discussed here. Recent advances in hexaferrites also highlighted in present paper.

Magnetic materials fundamentals, products, properties, applications

CERN Document Server

Hilzinger, Rainer

2013-01-01

At a practical level, this compendium reviews the basics of soft and hard magnetic materials, discusses the advantages of the different processing routes for the exploitation of the magnetic properties and hence assists in proper, fail-safe and economic application of magnetic materials. Essential guidelines and formulas for the calculation of the magnetic and electrical properties, temperature and long-term stability of permanent magnets, of inductive components and magnetic shielding are compiled. Selected fields of application and case studies illustrate the large diversity of technical applications. Application engineers will appreciate the comprehensive compilation of the properties and detailed characteristic curves of modern soft and hard magnetic materials. Materials scientists will enjoy the presentation of the different processing routes and their impact on the magnetic properties and students will profit from the survey from the basics of magnetism down to the applications in inductive components, ...

Excitation and propagation of electromagnetic fluctuations with ion-cyclotron range of frequency in magnetic reconnection laboratory experiment

International Nuclear Information System (INIS)

Inomoto, Michiaki; Tanabe, Hiroshi; Ono, Yasushi; Kuwahata, Akihiro

2013-01-01

Large-amplitude electromagnetic fluctuations of ion-cyclotron-frequency range are detected in a laboratory experiment inside the diffusion region of a magnetic reconnection with a guide field. The fluctuations have properties similar to kinetic Alfvén waves propagating obliquely to the guide field. Temporary enhancement of the reconnection rate is observed during the occurrence of the fluctuations, suggesting a relationship between the modification in the local magnetic structure given by these fluctuations and the intermittent fast magnetic reconnection

Global low-frequency modes in weakly ionized magnetized plasmas: effects of equilibrium plasma rotation

International Nuclear Information System (INIS)

Sosenko, P.; Pierre, Th.; Zagorodny, A.

2004-01-01

The linear and non-linear properties of global low-frequency oscillations in cylindrical weakly ionized magnetized plasmas are investigated analytically for the conditions of equilibrium plasma rotation. The theoretical results are compared with the experimental observations of rotating plasmas in laboratory devices, such as Mistral and Mirabelle in France, and KIWI in Germany. (authors)

Influence of cold isostatic pressing on the magnetic properties of Ni-Zn-Cu ferrite

Directory of Open Access Journals (Sweden)

Trong Trung Le

2018-04-01

Full Text Available In power electronics, there is the need to develop solutions to increase the power density of converters. Interleaved multicellular transformers allow interleaving many switching cells and, as a result, a possible increase in the power density. This converter is often composed of a magnetic core having the function of an intercell transformer (ICT and, depending on the complexity of the designed architecture, its shape could be extremely complex. The switching frequencies (1-10 MHz for the new wide band gap semiconductors (SiC, GaN allow to interleave switching cell at higher frequencies than silicon-based semiconductors (<1 MHz. Intercell transformers must follow this increase in frequency times-fold the number of switching cells. Current applications for ICT transformers use Mn-Zn based materials, but their limit in frequency drive raises the need of higher frequency magnetic materials, such Ni-Zn ferrites. These materials can operate in medium and high power converters up to 10 MHz. We propose to use Ni0,30Zn0,57Cu0,15Fe2O4 ferrite and to compress it by cold isostatic pressing (CIP into a a green ceramic block and to machine it to obtain the desired ICT of complex shape prior sintering. We compare the magnetic permeability spectra and hysteresis loops the CIP and uniaxially pressed ferrites. The effect of temperature and sintering time as well as high-pressure on properties will be presented in detail. The magnetic properties of the sintered cores are strongly dependent on the microstructure obtained.

Magnetism and Microwave Absorption Properties of Fe3O4 Microflake-Paraffin Composites Without and With Magnetic Orientation

Science.gov (United States)

Wang, Peng; Zhang, Junming; Chen, Yuanwei; Wang, Guowu; Wang, Dian; Wang, Tao; Li, Fashen

2018-01-01

We have synthesized thin Fe3O4 microflakes by a simple hydrothermal method and prepared Fe3O4 microflake-paraffin composites without and with magnetic orientation using the method of simple ultrasonic mixing and rotating samples in a magnetic field. X-ray diffractometer, Mössbauer spectrum, scanning electron microscope and vibrating sample magnetometer were used to characterize the samples. The complex permittivity and permeability of Fe3O4 microflake-paraffin composites without and with magnetic orientation were measured in the frequency range of 0.1-18 GHz by a vector network analyzer using a coaxial method. The reflection loss (RL) was calculated by the measured electromagnetic parameters using transmission line theory. The measurement of electromagnetic parameters shows that magnetic orientation makes the complex permittivity and permeability increase. The calculated RL shows that the Fe3O4 microflake-paraffin composite with magnetic orientation has enhanced microwave absorption properties in the frequency range of 1-3 GHz and the thickness range of 2.9-3.5 mm, indicating that the Fe3O4 microflake-paraffin composite with magnetic orientation is a promising thin microwave absorption material in the L-S band.

Enhancing the magnetic properties of magnetic nanoparticles

DEFF Research Database (Denmark)

Ahlburg, Jakob; Saura-Múzquiz, Matilde; Stingaciu, Marian

with a similar magnetic performance. There are several different ways of enhancing magnetic properties of 3d magnetic compounds. This includes, size control, core-shell particles or mixing hard and soft magnetic materials together to achieve an exchange coupling between the compounds and enhancing the magnetic...... energy product. In order to control the particle size, a hydrothermal synthesis is preferred. This followed by reduction or the oxides into either core shell particles, or a mixture of magnetic oxides and a metallic phase....

Low-frequency dielectric dispersion and magnetic properties of La, Gd modified Pb(Fe1/2Ta1/2)O3 multiferroics

International Nuclear Information System (INIS)

Choudhury, R.N.P.; Rodriguez, C.; Bhattacharya, P.; Katiyar, R.S.; Rinaldi, C.

2007-01-01

Pb(Fe 1/2 Ta 1/2 )O 3 (PFT) modified by rare-earth (La and Gd) ions has been synthesized in a single phase using a double-stage synthesis (i.e., Columbite) technique. Scanning electron micrographs (SEM) of the pellet samples have shown a significant change in their grain size and uniform distribution of Gd/La at the Fe-sites. The room temperature X-ray structural analysis shows that the reported cubic (or tetragonal) structure of PFT has been distorted to a monoclinic system on substitution of La/Gd at the Fe-site. Detailed studies of dielectric properties of the above compound on La/Gd substitution have shown strong dielectric dispersion at low frequency (i.e. relaxor behavior) with drastic change in transition temperature. Magnetic characterization shows that though the PFT sample displays an antiferromagnetic transition at ∼150 K, the rare-earth ions-substituted samples do not. Furthermore, temperature dependence of magnetization measurements shows that spin glass transition observed in PFT at low temperatures (5-20 K) does not exist in the La and Gd substituted PFT. Doping of Gd in PFT increases the sample magnetization, especially at low temperature

Low-frequency electrostatic dust-modes in a nonuniform magnetized dusty plasma

International Nuclear Information System (INIS)

Paul, S.K.; Duha, S.S.; Mamun, A.A.

2004-07-01

A self-consistent and general description of obliquely propagating low frequency electrostatic dust-modes in a inhomogeneous, magnetized dusty plasma system has been presented. A number of different situations, which correspond to different low-frequency electrostatic dust-modes, namely, dust-acoustic mode, dust-drift mode, dust-cyclotron mode, dust-lower-hybrid mode, and other associated modes (such as, accelerated and retarded dust-acoustic modes, accelerated and retarded dust-lower-hybrid modes, etc.), have also been investigated. It has been shown that the effects of obliqueness and inhomogeneities in plasma particle number densities introduce new electrostatic dust modes as well as significantly modify the dispersion properties of the other low-frequency electrostatic dust-modes. The implications of these results to some space and astrophysical dusty plasma systems, especially to planetary ring-systems and cometary tails, are briefly mentioned. (author)

Preparation and investigation of structural, magnetic and microwave absorption properties of cerium doped barium hexaferrite

Directory of Open Access Journals (Sweden)

P Kameli

2015-01-01

Full Text Available In this study the structure, magnetic and microwave absorption properties of cerium (Ce doped barium hexaferrite with general formulae BaCexFe12-xO19 (x=0.0, 0.05, 0.1, 0.15, 0.2 have been investigated. These samples have been prepared by sol- gel method. Influence of replacing Fe+3 ion by rare- earth Ce+3 ion on the structural, magnetic and microwave absorption properties have been investigated by X- ray diffraction (XRD, Fourier transform infrared (FT-IR, Vibrating sample magnetometer (VSM and vector network analyzer (VNA. X-ray diffraction analysis indicated that the samples are of single phase with space group p63/mmc. The magnetic properties of samples indicated that with the Ce doping the saturation magnetization show no regular behavior. Moreover, coercivity (Hc first decreased and reached to the minimum value for x=0.1 sample and then increased with Ce content increasing. Also, measurement of electromagnetic wave absorption in X and Ku frequency bands indicated that the maximum of reflection loss obtained for x=0.15 sample. Moreover, result indicated that absorption peak shifted toward a lower frequency when thickness was increased.

Simulation of stress-modulated magnetization precession frequency in Heusler-based spin torque oscillator

International Nuclear Information System (INIS)

Huang, Houbing; Zhao, Congpeng; Ma, Xingqiao

2017-01-01

We investigated stress-modulated magnetization precession frequency in Heusler-based spin transfer torque oscillator by combining micromagnetic simulations with phase field microelasticity theory, by encapsulating the magnetic tunnel junction into multilayers structures. We proposed a novel method of using an external stress to control the magnetization precession in spin torque oscillator instead of an external magnetic field. The stress-modulated magnetization precession frequency can be linearly modulated by externally applied uniaxial in-plane stress, with a tunable range 4.4–7.0 GHz under the stress of 10 MPa. By comparison, the out-of-plane stress imposes negligible influence on the precession frequency due to the large out-of-plane demagnetization field. The results offer new inspiration to the design of spin torque oscillator devices that simultaneously process high frequency, narrow output band, and tunable over a wide range of frequencies via external stress. - Highlights: • We proposed stress-modulated magnetization precession in spin torque oscillator. • The magnetization precession frequency can be linearly modulated by in-plane stress. • The stress also can widen the magnetization frequency range 4.4–7.0 GHz. • The stress-modulated oscillation frequency can simplify STO devices.

Simulation of stress-modulated magnetization precession frequency in Heusler-based spin torque oscillator

Energy Technology Data Exchange (ETDEWEB)

Huang, Houbing, E-mail: hbhuang@ustb.edu.cn; Zhao, Congpeng; Ma, Xingqiao, E-mail: xqma@sas.ustb.edu.cn

2017-03-15

We investigated stress-modulated magnetization precession frequency in Heusler-based spin transfer torque oscillator by combining micromagnetic simulations with phase field microelasticity theory, by encapsulating the magnetic tunnel junction into multilayers structures. We proposed a novel method of using an external stress to control the magnetization precession in spin torque oscillator instead of an external magnetic field. The stress-modulated magnetization precession frequency can be linearly modulated by externally applied uniaxial in-plane stress, with a tunable range 4.4–7.0 GHz under the stress of 10 MPa. By comparison, the out-of-plane stress imposes negligible influence on the precession frequency due to the large out-of-plane demagnetization field. The results offer new inspiration to the design of spin torque oscillator devices that simultaneously process high frequency, narrow output band, and tunable over a wide range of frequencies via external stress. - Highlights: • We proposed stress-modulated magnetization precession in spin torque oscillator. • The magnetization precession frequency can be linearly modulated by in-plane stress. • The stress also can widen the magnetization frequency range 4.4–7.0 GHz. • The stress-modulated oscillation frequency can simplify STO devices.

Low frequency electric and magnetic fields - the topic of cancer

International Nuclear Information System (INIS)

Thommesen, G.

1988-01-01

A review is made of the literature about the biological effects of low frequency electric and magnetic fields. It is still an unsettled question whether extremely low frequency magnetic fields may increase the incidence of cancer. Experimental data arise mainly from exposure to field strengths or frequencies seldom or never encountered by people. The results give no clear explanation to the increase in cancer incidence reported in epidemiological works. The spectre of possible mechanisms imply that no simple dose/effect relationship should be expected, as conflicting mechanisms may dominate at different exposure levels. There is therefore no basis at present for giving numerical value to cancer risk from exposure to low frequency electric or magnetic fields

Preparation and influence of pH on the dynamic magnetic property of magnetic FeCoC films

Energy Technology Data Exchange (ETDEWEB)

Feng, Hongmei; Wei, Jinwu; Zhu, Zengtai; Cao, Derang; Liu, Qingfang [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Wang, Jianbo, E-mail: wangjb@lzu.edu.cn [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Key Laboratory for Special Function Materials and Structural Design of the Ministry of the Education, Lanzhou University, Lanzhou 730000 (China)

2016-07-01

FeCoC films were successfully prepared by electrochemical deposition method in different citric acid concentrations and pH values. The morphology, structure and magnetic properties were investigated. FeCoC films deposited at different citric acid concentrations have good soft magnetic performance. As the pH value increases from 2.49 to 6.02, the atomic ratio of Fe:Co range from 0.72 to 0.95. The coercivities of the films deposited at different pH values first increase and then decrease with increasing pH. The resonance frequency of the films can be tuned by controlling the pH value, and in an appropriate pH value a wide absorption peak can be obtained. - Highlights: • We have successfully prepared FeCoC soft magnetic films by electrochemical deposition method. • The resonance frequency can be controlled by changing pH value. • A widely absorption peak will be obtained when the pH value is appropriate.

Low-frequency transient electric and magnetic fields coupling to child body

International Nuclear Information System (INIS)

Ozen, S.

2008-01-01

Much of the research related to residential electric and magnetic field exposure focuses on cancer risk for children. But until now only little knowledge about coupling of external transient electric and magnetic fields with the child's body at low frequency transients existed. In this study, current densities, in the frequency range from 50 Hz up to 100 kHz, induced by external electric and magnetic fields to child and adult human body, were investigated, as in residential areas, electric and magnetic fields become denser in this frequency band. For the calculations of induced fields and current density, the ellipsoidal body models are used. Current density induced by the external magnetic field (1 μT) and external electric field (1 V/m) is estimated. The results of this study show that the transient electric and magnetic fields would induce higher current density in the child body than power frequency fields with similar field strength. (authors)

The Properties of the Space-Charge and Net Current Density in Magnetized Plasmas

International Nuclear Information System (INIS)

Hatami, M. M.

2013-01-01

A hydrodynamic model is used to investigate the properties of positive space-charge and net current density in the sheath region of magnetized, collisional plasmas with warm positive ions. It is shown that an increase in the ion-neutral collision frequency, as well as the magnitude of the external magnetic field, leads to an increase in the net current density across the sheath region. The results also show that the accumulation of positive ions in the sheath region increases by increasing the ion-neutral collision frequency and the magnitude of the magnetic field. In addition, it is seen that an increase in the positive ion temperatures causes a decrease in the accumulation of positive ions and the net current density in the sheath region. (basic plasma phenomena)

Static and low frequency electric and magnetic fields

International Nuclear Information System (INIS)

Thommesen, G.; Tynes, T.

1994-01-01

The biological effects of exposure to low frequency electric and magnetic fields are reviewed with the objective of summarizing effects directly relevant to considerations of the health and safety of exposed people. Static and low frequency electric and magnetic fields may elicit biological reactions. Whether exposure to such fields may affect human health at field strengths present in everyday or occupational life is still unsettled. There is unsufficient knowledge to establish any dose concept relevant to health risk. 196 refs., 6 tabs

Magnetic structure and resonance properties of hexagonal antidot lattice

International Nuclear Information System (INIS)

Marchenko, A.I.; Krivoruchko, V.N.

2012-01-01

Static and resonance properties of ferromagnetic films with an antidot lattice (pores in the film) are studied. The description of the system is based on micromagnetic modeling and analytical solution of the Landau-Lifshitz equation. The dependences of ferromagnetic resonance spectra on the in-plane direction of applied magnetic field and on the lattice parameters are investigated. The dependences of a dynamic system response on frequency at fixed magnetic field and on field at fixed frequency, when the field changes cause the static magnetic order to change are explored. It is found that the specific peculiarities of the system dynamics leave unchange for both of these experimental conditions. Namely, for low damping the resonance spectra contain three quasi-homogeneous modes which are due to the resonance of different regions (domains) of the antidot lattice cell. It is shown the angular field dependences of each mode are characterized by a twofold symmetry and the related easy axes are mutually rotated by 60 degrees. As the result, a hexagonal symmetry of the system static and dynamic magnetic characteristics is realized. The existence in the resonance spectrum of several quasi-homogeneous modes related to different regions of the unit cell could be fundamental for working elements of magnonic devices.

Synthesis, nanostructure and magnetic properties of FeCo-reduced graphene oxide composite films by one-step electrodeposition

International Nuclear Information System (INIS)

Cao, Derang; Li, Hao; Wang, Zhenkun; Wei, Jinwu; Wang, Jianbo; Liu, Qingfang

2015-01-01

FeCo-reduced graphene oxide (FeCo-RGO) composite film was fabricated on indium tin oxide substrate using one-step electrodeposition method. Raman spectroscopy and field emission scanning electron microscope results show that the reduced graphene oxide is coprecipitated with the FeCo film. The energy-dispersive spectrometer results demonstrate that the atomic ratio of Fe/Co in FeCo-RGO composite film is larger than that of the FeCo film under the same fabrication condition. As a result, the FeCo-RGO composite film exhibits good soft magnetic properties and high-frequency properties as well as the FeCo film. The magnetic anisotropy field and saturation magnetization of FeCo-RGO composite film are increased when compared with FeCo film. Furthermore, the ferromagnetic resonance frequency is improved from 2.15 GHz for the FeCo film to 3.9 GHz for the FeCo-RGO composite film. - Highlights: • FeCo-reduced graphene oxide composite film was fabricated on indium tin oxide substrate. • One step electrodeposition method was used. • Good soft magnetic properties were exhibited by the composite films. • Increase of resonance frequency from 2.15 GHz for FeCo film to 3.9 GHz for composite film

Connection between microstructure and magnetic properties of soft magnetic materials

International Nuclear Information System (INIS)

Bertotti, G.

2008-01-01

The magnetic behavior of soft magnetic materials is discussed with some emphasis on the connection between macroscopic properties and underlying micromagnetic energy aspects. It is shown that important conceptual gaps still exist in the interpretation of macroscopic magnetic properties in terms of the micromagnetic formulation. Different aspects of hysteresis modeling, power loss prediction and magnetic non-destructive evaluation are discussed in this perspective

Synthesis of FeCo magnetic nanoalloys and investigation of heating properties for magnetic fluid hyperthermia

Science.gov (United States)

Çelik, Özer; Fırat, Tezer

2018-06-01

In this study, size controlled FeCo colloidal magnetic nanoalloys in the range of 11.5-37.2 nm were synthesized by surfactant assistant ball milling method. Magnetic separation technique was performed subsequent to synthesis process so as to obtain magnetic nanoalloy fluid with narrow size distribution. Particle distribution was determined by transmission electron microscope (TEM) while X-ray diffraction (XRD) measurements verified FeCo alloy formation as BCC structure. Vibrating sample magnetometer (VSM) method was used to investigate magnetic properties of nanoalloys. Maximum saturation magnetization and maximum coercivity were obtained as 172 Am2/kg for nanoparticles with the mean size of 37.2 nm and 19.4 mT for nanoparticles with the mean size of 13.3 nm, respectively. The heating ability of FeCo magnetic nanoalloys was determined through calorimetrical measurements for magnetic fluid hyperthermia (MFH) applications. Heat generation mechanisms were investigated by using linear response theory and Stoner-Wohlfarth (S-W) model. Specific absorption rate (SAR) values were obtained in the range of 2-15 W/g for magnetic field frequency of 171 kHz and magnetic field strength in between 6 and 14 mT.

Dual-frequency magnetic particle imaging of the Brownian particle contribution

Energy Technology Data Exchange (ETDEWEB)

Viereck, Thilo, E-mail: t.viereck@tu-bs.de; Kuhlmann, Christian; Draack, Sebastian; Schilling, Meinhard; Ludwig, Frank

2017-04-01

Magnetic particle imaging (MPI) is an emerging medical imaging modality based on the non-linear response of magnetic nanoparticles to an exciting magnetic field. MPI has been recognized as a fast imaging technique with high spatial resolution in the mm range. For some applications of MPI, especially in the field of functional imaging, the determination of the particle mobility (Brownian rotation) is of great interest, as it enables binding detection in MPI. It also enables quantitative imaging in the presence of Brownian-dominated particles, which is otherwise implausible. Discrimination of different particle responses in MPI is possible via the joint reconstruction approach. In this contribution, we propose a dual-frequency acquisition scheme to enhance sensitivity and contrast in the detection of different particle mobilities compared to a standard single-frequency MPI protocol. The method takes advantage of the fact, that the magnetization response of the tracer is strongly frequency-dependent, i.e. for low excitation frequencies a stronger Brownian contribution is observed.

Magnetic properties of iron nanoparticle

International Nuclear Information System (INIS)

Carvell, J.; Ayieta, E.; Gavrin, A.; Cheng, Ruihua; Shah, V. R.; Sokol, P.

2010-01-01

Magnetic properties of Fe nanoparticles with different sizes synthesized by a physical deposition technique have been investigated experimentally. We have used a high pressure sputtering technique to deposit iron nanoparticles on a silicon substrate. The nanoparticles are then analyzed using atomic force microscopy (AFM), transmission electron microscopy (TEM), and superconducting quantum interference device techniques. TEM and AFM data show that the particle size could be tuned by adjusting the deposition conditions. The magnetic properties have been investigated from temperature dependent magnetization M(T) and field dependent magnetization M(H) measurements. The results show that two phases including both ferromagnetic and superparamagnetic particles are present in our system. From these data we extracted the superparamagnetic critical size to be 9 nm for our samples. Ferromagnetic particles are single magnetic domain particles and the magnetic properties can be explained by the Stoner and Wohlfarth model. For the superparamagnetic phase, the effective anisotropy constant, K eff , decreases as the particle size increases.

Analysis of the Extremely Low Frequency Magnetic Field Emission from Laptop Computers

Directory of Open Access Journals (Sweden)

Brodić Darko

2016-03-01

Full Text Available This study addresses the problem of magnetic field emission produced by the laptop computers. Although, the magnetic field is spread over the entire frequency spectrum, the most dangerous part of it to the laptop users is the frequency range from 50 to 500 Hz, commonly called the extremely low frequency magnetic field. In this frequency region the magnetic field is characterized by high peak values. To examine the influence of laptop’s magnetic field emission in the office, a specific experiment is proposed. It includes the measurement of the magnetic field at six laptop’s positions, which are in close contact to its user. The results obtained from ten different laptop computers show the extremely high emission at some positions, which are dependent on the power dissipation or bad ergonomics. Eventually, the experiment extracts these dangerous positions of magnetic field emission and suggests possible solutions.

Effect of processing parameters on the magnetic properties and microstructures of molybdenum permalloy compacts made by powder metallurgy

Energy Technology Data Exchange (ETDEWEB)

Zhang, Zhangming; Xu, Wei; Guo, Ting; Jiang, Yinzhu; Yan, Mi, E-mail: mse_yanmi@zju.edu.cn

2014-05-01

Highlights: • Effect of processing parameters on the properties of MP powder cores was studied. • Effective magnetic permeability was enhanced from 45 to 160 after annealing. • A core loss of 780 mw/cm{sup 3} (100 kHz, 100 mT) was obtained. - Abstract: Effects of compaction and annealing process on the magnetic properties and microstructures of molybdenum permalloy (MP) powder cores have been investigated. MP compacts, with density as high as 92% of the theoretical value, were obtained under 1800 MPa compaction pressure. The MP powder cores show an enhanced effective magnetic permeability of 160 after post-annealing at 690 °C, which is attributed to the relief of internal stress rather than the phase transformation evidenced by the XRD analysis. However, higher annealing temperature destroys the insulating layer, resulting in the drop of the electrical resistivity, the effective magnetic permeability as well as the frequency stability. The results show that the samples compacted at 1800 MPa and annealed at 690 °C exhibit excellent magnetic properties, with core loss of 780 mw/cm{sup 3} (100 kHz, 100 mT) and effective magnetic permeability of 160 whose frequency stability is up to 1 MHz.

The study of magnetic properties and relaxation processes in Co/Au bimetallic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Hrubovčák, Pavol [Department of Condensed Matter Physics, P.J. Šafárik University, Park Angelinum 9, Košice (Slovakia); Zeleňáková, Adriana, E-mail: adriana.zelenakova@upjs.sk [Department of Condensed Matter Physics, P.J. Šafárik University, Park Angelinum 9, Košice (Slovakia); Zeleňák, Vladimir [Department of Inorganic Chemistry, P.J. Šafárik University, Moyzesova 11, Košice (Slovakia); Kováč, Jozef [Institute of Experimental Physics, SAS, Watsonova 41, Košice (Slovakia)

2015-11-15

Co/Au bimetallic fine nanoparticles were prepared employing the method of microemulsion using reverse micelle as nanoreactor, controlling the particles size. Magnetic and structural properties of two different samples Co/Au1 and Co/Au2 with almost comparable size of Co core and different size of Au layer were studied. The investigation of magnetic relaxation processes present in the particles was carried out by means of ac and dc magnetization data obtained at different temperatures and magnitudes of magnetic field. We observed the existence of superspin glass state characterized by the strong inter-particle interactions in the nanoparticle systems. In this paper, we discuss the attributes of novel superspin glass magnetic state reflected on various features (saturated FC magnetization at low temperatures, shift of the Cole–Cole arc downwards) and calculated parameters (relaxation time, critical exponent zv ∼ 10 and frequency dependent criterion p < 0.05). Comparison of the magnetic properties of two studied samples show that the thickness of diamagnetic Au shell significantly influences the magnetic interactions and change the relaxation dynamics. - Highlights: • Co/Au fine nanoparticles prepared by reverse micelle as nanoreactor, controlling the size. • Existence of superspin glass state confirmed from ac magnetic susceptibility study. • Individual particles exhibit the collective behavior below glass temperature T{sub SSG}. • Influence of diamagnetic shell on the magnetic properties of core–shell nanoparticles.

Magnetic hybride layers. Magnetic properties of locally exchange-coupled NiFe/IrMn layers; Magnetische Hybridschichten. Magnetische Eigenschaften lokal austauschgekoppelter NiFe/IrMn-Schichten

Energy Technology Data Exchange (ETDEWEB)

Hamann, Christine

2010-10-06

By the lateral modification of the magnetic properties of exchange-coupled NiFe/IrMn layers soft-magnetic layers were produced, which show both new static and dynamic properties. As lateral structuration methods hereby the localoxidation as well as ion implantation were applied. By means of thes procedures it has been succeeded to mould specific magnetic domain configurations with strp structure into the layers. In dependence of the structure orientation as well as strip period the remagnetization behavior as well as the magnetic-resonance frequency and damping of the layers could directly be modified. The new dynamical properties are hereby discussed in the framework of the coupling via dynamical charges and the direct affection of the effective field of the artificially inserted domain state. The presented results prove by this the large potential of the lateral magneto-structuration for the tuning of specifical static as well as dynamic properties of magnetically thin layers.

Passive inference of collision frequency in magnetized capacitive argon discharge

Science.gov (United States)

Binwal, S.; Joshi, J. K.; Karkari, S. K.; Kaw, P. K.; Nair, L.

2018-03-01

A non-invasive method of determining the collision frequency νm by measuring the net plasma impendence in a magnetized, capacitive-coupled, radio-frequency (rf) discharge circuit is developed. The collision frequency has been analytically expressed in terms of bulk plasma reactance, wherein standard sheath models have been used to estimate the reactance offered due to the capacitive rf sheaths at the discharge plates. The experimental observations suggest that in the un-magnetized case, νm remains constant over a range of rf current but steadily increases as the background pressure reduces. In the magnetized case, the collision frequency has been observed to decay with the increase in rf current while it remains unaffected by the background pressure. A qualitative discussion has been presented to explain these characteristics.

Dynamic rheological properties of viscoelastic magnetic fluids in uniform magnetic fields

International Nuclear Information System (INIS)

Yamaguchi, Hiroshi; Niu Xiaodong; Ye Xiaojiang; Li Mingjun; Iwamoto, Yuhiro

2012-01-01

The dynamic rheological properties of viscoelastic magnetic fluids in externally applied uniform magnetic fields are investigated by a laboratory-made cone-plate rheometer in this study. In particular, the effects of the magnetic field on the viscoelastic properties (the complex dynamic modulus) of the viscoelastic magnetic fluids are studied. In the investigation, three viscoelastic magnetic fluids are made by mixing a magnetic fluid and a viscoelastic fluid with different mass ratios. As a supplementation to the experimental investigation, a theoretical analysis is also presented. The present study shows that the viscosity and elasticity of the viscoelastic magnetic fluids are significantly influenced by the magnetic field and the concentrations of the magnetic particles in the test fluids. Theoretical analysis qualitatively explains the present findings. - Highlights: ► The dynamic rheological properties of the viscoelastic magnetic fluids in uniform magnetic fields are investigated. ► Both the magnetic field strength and the concentration of the magnetic particles in the fluids have significant effects on the viscosity and elasticity of the viscoelastic magnetic fluids. ► Theoretical prediction and analysis qualitatively explains the present findings.

Magnetic properties of melt-spun FeMnAlB alloys

International Nuclear Information System (INIS)

Betancourt, I.; Nava, F.

2007-01-01

Magnetic properties of melt spun Fe 89-x Mn 11 Al x (x=2,4,8,15) and Fe 87-y Mn 11 Al 2 By(y=6,8,10) alloy series were studied by vibrating sample magnetometry and complex permeability measurements. The saturation magnetization exhibited an initial high value of 210emu/g followed by a decreasing tendency with increasing Al and B additions (up to 139emu/g). On the other hand, the initial permeability showed variations within the range 1000-2000, whereas the relaxation frequency displayed a maximum of 2MHz for the 4at% Al alloy

Radio frequency sheaths in an oblique magnetic field

International Nuclear Information System (INIS)

Myra, J. R.; D'Ippolito, D. A.

2015-01-01

The physics of radio-frequency (rf) sheaths near a conducting surface is studied for plasmas immersed in a magnetic field that makes an oblique angle θ with the surface. A set of one-dimensional equations is developed that describes the dynamics of the time-dependent magnetic presheath and non-neutral Debye sheath. The model employs Maxwell-Boltzmann electrons, and the magnetization and mobility of the ions is determined by the magnetic field strength, and wave frequency, respectively. The angle θ, assumed to be large enough to insure an electron-poor sheath, is otherwise arbitrary. Concentrating on the ion-cyclotron range of frequencies, the equations are solved numerically to obtain the rectified (dc) voltage, the rf voltage across the sheath, and the rf current flowing through the sheath. As an application of this model, the sheath voltage-current relation is used to obtain the rf sheath impedance, which in turn gives an rf sheath boundary condition for the electric field at the sheath-plasma interface that can be used in rf wave codes. In general, the impedance has both resistive and capacitive contributions, and generalizes previous sheath boundary condition models. The resistive part contributes to parasitic power dissipation at the wall

Novel Fe-based nanocrystalline powder cores with excellent magnetic properties produced using gas-atomized powder

Science.gov (United States)

Chang, Liang; Xie, Lei; Liu, Min; Li, Qiang; Dong, Yaqiang; Chang, Chuntao; Wang, Xin-Min; Inoue, Akihisa

2018-04-01

FeSiBPNbCu nanocrystalline powder cores (NPCs) with excellent magnetic properties were fabricated by cold-compaction of the gas-atomized amorphous powder. Upon annealing at the optimum temperature, the NPCs showed excellent magnetic properties, including high initial permeability of 88, high frequency stability up to 1 MHz with a constant value of 85, low core loss of 265 mW/cm3 at 100 kHz for Bm = 0.05 T, and superior DC-bias permeability of 60% at a bias field of 100 Oe. The excellent magnetic properties of the present NPCs could be attributed to the ultrafine α-Fe(Si) phase precipitated in the amorphous matrix and the use of gas-atomized powder coated with a uniform insulation layer.

Minimization of nanosatellite low frequency magnetic fields

Energy Technology Data Exchange (ETDEWEB)

Belyayev, S. M., E-mail: belyayev@isr.lviv.ua [Lviv Centre of Institute for Space Research, Lviv 79060 (Ukraine); Royal Institute of Technology, Stockholm 11428 (Sweden); Dudkin, F. L. [Lviv Centre of Institute for Space Research, Lviv 79060 (Ukraine)

2016-03-15

Small weight and dimensions of the micro- and nanosatellites constrain researchers to place electromagnetic sensors on short booms or on the satellite body. Therefore the electromagnetic cleanliness of such satellites becomes a central question. This paper describes the theoretical base and practical techniques for determining the parameters of DC and very low frequency magnetic interference sources. One of such sources is satellite magnetization, the reduction of which improves the accuracy and stability of the attitude control system. We present design solutions for magnetically clean spacecraft, testing equipment, and technology for magnetic moment measurements, which are more convenient, efficient, and accurate than the conventional ones.

Study of AC Magnetic Properties and Core Losses of Fe/Fe3O4-epoxy Resin Soft Magnetic Composite

Science.gov (United States)

Laxminarayana, T. A.; Manna, Subhendu Kumar; Fernandes, B. G.; Venkataramani, N.

Soft Magnetic Composites (SMC) were prepared by coating of nanocrystalline Fe3O4 particles, synthesized by co-precipitation method, on atomized iron powder of particle size less than 53 μm in size using epoxy resin as a binder between iron and Fe3O4. Fe3O4 was chosen, for its high electric resistivity and suitable magnetic properties, to keep the coating layer magnetic and seek improvement to the magnetic properties of SMC. SEM images and XRD patterns were recorded in order to investigate the coatings on the surface of iron powder. A toroid was prepared by cold compaction of coated iron powder at 1050 MPa and subsequently cured at 150˚C for 1 hr in argon atmosphere. For comparison of properties, a toroid of uncoated iron powder was also compacted at 1050 MPa and annealed at 600˚C for 2 hr in argon atmosphere. The coated iron powder composite has a resistivity of greater than 200 μΩm, measured by four probe method. A comparison of Magnetic Hysteresis loops and core losses using B-H Loop tracer in the frequency range 0 to 1500 Hz on the coated and uncoated iron powder is reported.

Effects of low frequency electromagnetic field on the as-cast microstructures and mechanical properties of superhigh strength aluminum alloy

International Nuclear Information System (INIS)

Zuo Yubo; Cui Jianzhong; Dong Jie; Yu Fuxiao

2005-01-01

A new superhigh strength Al-Zn-Mg-Cu alloy was made by low frequency electromagnetic casting (LFEC) and conventional direct chill (DC) casting, respectively. The effects of low frequency electromagnetic field on the as-cast microstructures and mechanical properties were investigated. The results show that under the low frequency electromagnetic field (25 Hz, 32 mT), the microstructures of LFEC ingot from the border to the center on the cross section are all fine equiaxed or nearly equiaxed grains. The grains are much finer and more uniform than that of DC ingot. It was found that magnetic flux density plays an important role on the microstructure formation of LFEC ingots. With increasing the magnetic flux density, grains become finer and more uniform. In the range of experimental parameters, the optimum magnetic flux density for LFEC process is found to be 32 mT. The mechanical tests show that for this new superhigh strength Al-Zn-Mg-Cu alloy, the as-cast mechanical properties of LFEC ingot are much higher than that of DC ingot

Synthesis, magnetic and microstructural properties of Alnico magnets with additives

Energy Technology Data Exchange (ETDEWEB)

Ahmad, Zubair, E-mail: dza.isit@yahoo.com [School of Materials Science and Engineering, South China, University of Technology, Guangzhou 510640 (China); Liu, Zhongwu [School of Materials Science and Engineering, South China, University of Technology, Guangzhou 510640 (China); Ul Haq, A. [Riphah International University, I-14, Islamabad (Pakistan)

2017-04-15

The phase formation, crystal structure, crystallographic texture, microstructure and magnetic properties of Alnico-8 alloys with varying Co and Nb content have been investigated and presented. Alnico-8 alloys were fabricated by induction melting and casting techniques. Magnetic properties in the alloys were induced by optimized thermomagnetic treatment and subsequent aging. The 37.9Fe-32Co-14Ni-7.5Al-3.1Cu-5.5Ti alloy exhibits coercivity of 110 kA/m, remanence of 0.66 T and energy product of 31.2 kJ/m{sup 3}. The addition of 35 wt% Co in conjunction with 1.5 wt% Nb to 37.9Fe-14Ni-7.5Al-3.1Cu-5.5Ti alloys led to increase the magnetic properties, especially coercivity. The enhancement of the coercivity is attributed to ideal shape anisotropy and optimum mass fraction of ferromagnetic Fe-Co rich particles, which are 25–30 nm in diameter and 300–350 nm in length. The 33.4Fe-35Co-14Ni-7.5Al-5.5Ti-3.1Cu-1.5 Nb alloy yields the optimum magnetic properties of coercivity of 141.4 kA/m, remanence of 0.83 T and energy product of 42.4 kJ/m{sup 3}. The good magnetic properties in the studied alloys are attributed to the nanostructured microstructure comprising textured Fe-Co-Nb rich α{sub 1} phase and Al-Ni-Cu rich α{sub 2} phase. - Highlights: • Synthesize of Alnico-8 magnets by casting and thermomagnetic treatment. • High coercivity up to 148.3 kA/m can be obtained with Alnico magnets. • Properties are affected by intrinsic properties of spinodal phases and thermal cycle. • Magnet exhibits properties as: H{sub c}=141.4 kA/m, B{sub r}=0.83 T and (BH){sub max}=42.4 kJ/m{sup 3}.

Structure and magnetic properties of iron-based soft magnetic composite with Ni-Cu-Zn ferrite-silicone insulation coating

Science.gov (United States)

Li, Wangchang; Wang, Wei; Lv, Junjun; Ying, Yao; Yu, Jing; Zheng, Jingwu; Qiao, Liang; Che, Shenglei

2018-06-01

This paper investigates the structure and magnetic properties of Ni-Cu-Zn ferrite-silicone coated iron-based soft magnetic composites (SMCs). Scanning electron microscopy coupled with a energy-dispersive spectroscopy (EDS) analysis revealed that the Ni-Cu-Zn ferrite and silicone resin were uniformly coated on the surface of iron powders. By controlling the composition of the coating layer, low total core loss of 97.7 mW/cm3 (eddy current loss of 48 mW/cm3, hysteresis loss of 49.7 mW/cm3, measured at 100 kHz and 0.02 T) and relatively high effective permeability of 72.5 (measured at 100 kHz) were achieved. In addition, the as-prepared SMCs displayed higher electrical resistivity, good magnetic characteristics over a wide range of frequencies (20-200 kHz) and ideal the D-C bias properties (more than 75% at H = 50 Oe). Furthermore, higher elastic modulus and hardness of SMCs, which means that the coating layer has good mechanical properties and is not easily damaged during the pressing process, were obtained in this paper. The results of this work indicate that the Ni-Cu-Zn ferrite-silicone coated SMCs have desirable properties which would make them suitable for application in the fields of the electric-magnetic switching devices, such as inductance coils, transformer cores, synchronous electric motors and resonant inductors.

Enhancing the magnetic properties of magnetic nanoparticles

DEFF Research Database (Denmark)

Ahlburg, Jakob; Saura-Múzquiz, Matilde; Stingaciu, Marian

with a similar magnetic performance. There are several different ways of enhancing magnetic properties of 3d magnetic compounds. This includes, size control, core-shell particles or mixing hard and soft magnetic materials together to achieve an exchange coupling between the compounds and enhancing the magnetic...... energy product. In order to control the particle size, a hydrothermal synthesis is preferred. This followed by reduction or the oxides into either core shell particles, or a mixture of magnetic oxides and a metallic phase.......Strong magnets with a high energy product are vital when optimizing the efficiency in the electric industry. But since the rare earth metals, normally used for making strong permanent magnets, are both expensive and difficult to mine, a great demand has come to cheaper types of magnets...

Estimation of the frequency and magnetic field dependence of the skin depth in Co-rich magnetic microwires from GMI experiments

Directory of Open Access Journals (Sweden)

Arcady Zhukov

2016-09-01

Full Text Available We studied giant magnetoimpedance (GMI effect in magnetically soft amorphous Co-rich microwires in the extended frequency range. From obtained experimentally dependences of the GMI ratio on magnetic field at different frequencies we estimated the penetration depth and its dependence on applied magnetic field and frequency.

Nanolaminated FeCoB/FeCo and FeCoB/NiFe soft magnetic thin films with tailored magnetic properties deposited by magnetron sputtering

Science.gov (United States)

Hida, Rachid; Falub, Claudiu V.; Perraudeau, Sandrine; Morin, Christine; Favier, Sylvie; Mazel, Yann; Saghi, Zineb; Michel, Jean-Philippe

2018-05-01

Thin films based on layers of Fe52Co28B20 (at%), Fe65Co35 (at%), and Ni80Fe20 (at%) were deposited by sputtering on 8″ bare Si and Si/200 nm-thermal-SiO2 wafers by simultaneous use of two or more cathodes. Due to the continuous rotation of the substrate cage, such that the substrates faced different targets alternately, the multilayers consisted of stacks of alternating, nanometer-thick regular layers. The composition of the films was determined by Rutherford Backscattering Spectrometry (RBS) and Nuclear Reactive Analysis (NRA), whereas Plasma Profiling Time of Flight Mass Spectrometry (PP-TOFMS) analysis gave depth profile information about the chemical elements. The structural and magnetic properties of the films were investigated by X-ray Diffraction and by TEM analysis, B-H loop tracer and high frequency single coil technique permeametry, respectively. The linear dependence of the coercivity of these thin films versus the grain size can be explained by the random anisotropy model. These novel, composite soft magnetic multilayers, with tunable in-plane anisotropy, allow operation at tunable frequencies, as shown by broadband (between 100 MHz and 10 GHz) RF measurements that exhibit a classical Landau-Lifschitz-Gilbert (LLG) behavior and, combine the magnetic properties of the individual materials in an advantageous way. This article presents a method to produce nanostructured soft magnetic multilayers, the properties of which can easily be tuned by choosing the ratio of the individual nanolayers. In this way it's possible to combine soft magnetic materials with complementary properties, e.g. high saturation magnetization, low coercivity, high specific resistivity and low magnetostriction

Effect of process on the magnetic properties of bonded NdFeB magnet

International Nuclear Information System (INIS)

Li, J.; Liu, Y.; Gao, S.J.; Li, M.; Wang, Y.Q.; Tu, M.J.

2006-01-01

The effects of magnetic separation, coupling treatment, lubricating treatment, preform and biaxial molding on the density and magnetic properties of bonded NdFeB magnet were investigated. The results demonstrate that magnetic separation separates the powders with low coercive force; coupling treatment improves the interfaces between the powders and the binders; decrease in volume fraction of the binder increases magnetic properties of the magnet; granular arrangement improves both the magnetic and mechanical properties when powders are arranged in certain size; lubricating treatment improves the formability of the magnet and preform and biaxial molding improves both density and magnetic properties greatly. Combining these methods, the density of the bonded NdFeB magnet can reach 6.52 g/cm 3 and the maximum energy product can reach 114 kJ/m 3

Effect of process on the magnetic properties of bonded NdFeB magnet

Energy Technology Data Exchange (ETDEWEB)

Li, J. [School of Materials Science and Engineering, Sichuan University, Chengdu, 610065 (China); Liu, Y. [School of Materials Science and Engineering, Sichuan University, Chengdu, 610065 (China)]. E-mail: liuying5536@163.com; Gao, S.J. [School of Materials Science and Engineering, Sichuan University, Chengdu, 610065 (China); Li, M. [School of Materials Science and Engineering, Sichuan University, Chengdu, 610065 (China); Wang, Y.Q. [South-West Magnetic Science and Technology Developing Company, Mianyang, 621600 (China); Tu, M.J. [School of Materials Science and Engineering, Sichuan University, Chengdu, 610065 (China)

2006-04-15

The effects of magnetic separation, coupling treatment, lubricating treatment, preform and biaxial molding on the density and magnetic properties of bonded NdFeB magnet were investigated. The results demonstrate that magnetic separation separates the powders with low coercive force; coupling treatment improves the interfaces between the powders and the binders; decrease in volume fraction of the binder increases magnetic properties of the magnet; granular arrangement improves both the magnetic and mechanical properties when powders are arranged in certain size; lubricating treatment improves the formability of the magnet and preform and biaxial molding improves both density and magnetic properties greatly. Combining these methods, the density of the bonded NdFeB magnet can reach 6.52 g/cm{sup 3} and the maximum energy product can reach 114 kJ/m{sup 3}.

Structural and magnetic properties of Ni-Zn doped BaM nanocomposite via citrate precursor

International Nuclear Information System (INIS)

Rana, Kush; Thakur, Preeti; Thakur, Atul; Tomar, Monika; Gupta, Vinay

2016-01-01

Ni-Zn substituted M-type barium ferrite nanocomposite has been prepared via citrate precursor method. Nanocomposite having composition BaNi_0_._5Zn_0_._5Fe_1_1O_1_9 was sintered at 900°C for 3hrs and characterized by using different characterization techniques. X-ray diffraction (XRD) confirmed the formation of double phase with most prominent peak at (114). Average crystallite size for pure BaM and BNZFO were found to be 36 nm & 45 nm. Field emission scanning electron microscopy (FESEM) confirmed the formation of hexagonal platelets with a layered structure. Magnetic properties of these samples were investigated by using vibrating sample magnetometer (VSM). Magnetic parameters like saturation magnetization (M_s), coericivity (H_c) and squareness ratio (SQR) of nanocomposite were found to be 60 emu/g, 3663 Oe and 0.6163 respectively. These values were noticed to be higher as compared to pure BaM. Enhanced magnetic properties of nanocomposite were strongly dependent on exchange coupling. Therefore these properties make this nanocomposite a suitable candidate for magnetic recording and high frequency applications.

IDENTIFYING ANTHROPOGENIC METALLIC POLLUTANTS USING FREQUENCY DEPENDENT MAGNETIC SUSCEPTIBILITY MEASUREMENTS IN ABUJA METROPOLIS

Directory of Open Access Journals (Sweden)

Jatto S. Solomon

2017-07-01

Full Text Available Soil formed from lithological and weathering processes of parent rocks generally exhibit paramagnetic properties due to some minerals contained in the rocks and thus have significant value of magnetic susceptibility. This susceptibility arising from the influence of the parent rocks tend to mask anthropogenic grains pollutants released into the environment by human activities. Hence, it becomes difficult to identify the effect of the lithological and anthropogenic magnetic susceptibility in complex soil found in urban areas. The superparamagnetic effect of lithological soil, a single state domain and multi-domain state of anthropogenic grains can easily be investigated by frequency dependent measurements where readings between 0-2.0% indicates the absence of lithological influence, 2.0-8.0% indicates multi-domain grains or mixture of both single stage and multi-domian grains and 8.0-12% indicates the superparamagntic (SP grain from lithological origin. In this work frequency dependent measurements were carried out along 5 selected road networks within the 5 districts of Abuja phase 1. Measurements were also carried out in 379 random points at the surface and depth of 40.0cm to investigate the distribution of anthropogenic grains in Abuja metropolis using the Bartington susceptibility meter. Frequency dependent measurements along the selected road networks indicate0-3.0% immediately after the roads pavement to a distance of about 3.0m from the road, indicating that the magnetic susceptibility arise mostly form anthropogenic influence rather than lithological processes. At the distance of 3.0-8.0m, frequency dependent values of about 3.0-8.0% were recorded, indicating mixture of both superparamagnetic and multi-domain grains. Beyond the distance of 8.0m, the frequency dependent values are mostly above 8.0.0%, indicating virtually all SP grains. The spatial distribution frequency dependent surface map shows the presence of anthropogenic grains in

The magnetic properties of the hollow cylindrical ideal remanence magnet

DEFF Research Database (Denmark)

Bjørk, Rasmus

2016-01-01

We consider the magnetic properties of the hollow cylindrical ideal remanence magnet. This magnet is the cylindrical permanent magnet that generates a uniform field in the cylinder bore, using the least amount of magnetic energy to do so. The remanence distribution of this magnet is derived...

Synthesis, electrical and magnetic properties of sodium borosilicate glasses containing Co-ferrites nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Othman, H.A. [Department of Physics, Faculty of Science, Menoufia University, Shibin El-Kom 32511, Menoufia (Egypt); Eltabey, M.M. [Department of Basic Engineering Science, Faculty of Engineering, Menoufia University, Shibin El-Kom, Menoufia (Egypt); Department of Physics, Faculty of Science, Jazan University (Saudi Arabia); Ibrahim, Samia E.; El-Deen, L.M. Sharaf; Elkholy, M.M. [Department of Physics, Faculty of Science, Menoufia University, Shibin El-Kom 32511, Menoufia (Egypt)

2017-02-01

Co-ferrites nanoparticles that have been prepared by the co-precipitation method were added to sodium borosilicate (Na{sub 2}O–B{sub 2}O{sub 3}–SiO{sub 2}) glass matrix by the solid solution method and they were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and magnetization measurements. (XRD) revealed the formation of the Co-ferrite magnetic crystalline phase embedded in an amorphous matrix in all the samples. The investigated samples by (TEM) showed the formation of the cobalt ferrite nanoparticles with a spherical shape and highly monodispersed with an average size about 13 nm. IR data revealed that the BO{sub 3} and BO{sub 4} are the main structural units of these samples network. IR spectra of the investigated samples showed the characteristic vibration bands of Co-ferrite. Composition and frequency dependent dielectric properties of the prepared samples were measured at room temperature in the frequency range 100–100 kHz. The conductivity was found to increase with increasing cobalt ferrite content. The variations of conductivity and dielectric properties with frequency and composition were discussed. Magnetic hysteresis loops were traced at room temperature using VSM and values of saturation magnetization M{sub S} and coercive field H{sub C} were determined. The obtained results revealed that a ferrimagnetic behavior were observed and as Co-ferrite concentration increases the values of M{sub S} and H{sub C} increase from 2.84 to 8.79 (emu/g) and from 88.4 to 736.3 Oe, respectively.

Magnetic and Electrical Properties of Leachate

Directory of Open Access Journals (Sweden)

Kartika Kirana

2011-11-01

Full Text Available Heavy metals content as well as magnetic and electrical properties of leachate from Sarimukti, West Java were studied in an attempt to seek correlation between heavy metals content and magnetic/electrical properties. Such correlation is expected to open the way for the use of magnetic/electrical properties as proxy indicators for the concentration of heavy metals in the leachate. The number of leachate samples studied is 21; 15 were taken spatially at depth of 1 m while the remaining 6 samples were taken vertically at a particular point. Measurement results showed that the heavy metals content in the leachate has a smaller concentration, except for Fe. The correlation between magnetic susceptibility and heavy metals content was found to be not so significant. The best correlation coefficient between magnetic susceptibility with heavy metals in leachate was found in Zn. Correlation between electrical conductivity and heavy metal is also not so significant, except for Zn and Cd. The use of magnetic properties as proxy indicator for heavy metals content in leachate is plausible provided that the magnetic susceptibility exceeds certain threshold value. Correlation between magnetic susceptibility, electrical conductivity and heavy metal content would be good if each quantity has a large value.

On-chip measurement of the Brownian relaxation frequency of magnetic beads using magnetic tunneling junctions

DEFF Research Database (Denmark)

Donolato, M.; Sogne, E.; Dalslet, Bjarke Thomas

2011-01-01

We demonstrate the detection of the Brownian relaxation frequency of 250 nm diameter magnetic beads using a lab-on-chip platform based on current lines for exciting the beads with alternating magnetic fields and highly sensitive magnetic tunnel junction (MTJ) sensors with a superparamagnetic free...

Overview of Planar Magnetic Technology — Fundamental Properties

DEFF Research Database (Denmark)

Ouyang, Ziwei; Andersen, Michael A. E.

2014-01-01

The momentum towards high efficiency, high frequency, and high power density in power supplies limits wide use of conventional wire-wound magnetic components. This article gives an overview of planar magnetic technologies with respect to the development of modern power electronics. The major...... advantages and disadvantages in the use of planar magnetics for high frequency power converters are covered, and publications on planar magnetics are reviewed. A detailed survey of winding conduction loss, leakage inductance and winding capacitance for planar magnetics is presented so power electronics...

Modern permanent magnetic materials - preparation and properties

International Nuclear Information System (INIS)

Rodewald, W.

1989-01-01

First of all, the basic properties of the classical (steel, AlNiCo) permanent magnetic materials and the modern rare-earth (RE) permanent magnetic materials are compared. Since the properties of RE permanent magnets depend on the particular production process, the fundamentals of the main industrial processes (powder metallurgy, rapid-solidification technique) are described and the typical properties are explained. Furthermore the production processes in development such as mechanical alloying, melt spinning technique and extrusion upsetting are briefly outlined. For applying the permanent magnets, they have to be completely magnetized. The magnetization behaviour of the various RE permanent magnets is discussed by means of the internal demagnetization curve. Finally the various influences on the temperature stability of RE permanent magnets are compiled. (orig./MM) [de

Resolution improvement of low frequency AC magnetic field detection for modulated MR sensors.

Science.gov (United States)

Hu, Jinghua; Pan, Mengchun; Hu, Jiafei; Li, Sizhong; Chen, Dixiang; Tian, Wugang; Sun, Kun; Du, Qingfa; Wang, Yuan; Pan, Long; Zhou, Weihong; Zhang, Qi; Li, Peisen; Peng, Junping; Qiu, Weicheng; Zhou, Jikun

2017-09-01

Magnetic modulation methods especially Micro-Electro-Mechanical System (MEMS) modulation can improve the sensitivity of magnetoresistive (MR) sensors dramatically, and pT level detection of Direct Current (DC) magnetic field can be realized. While in a Low Frequency Alternate Current (LFAC) magnetic field measurement situation, frequency measurement is limited by a serious spectrum aliasing problem caused by the remanence in sensors and geomagnetic field, leading to target information loss because frequency indicates the magnetic target characteristics. In this paper, a compensation field produced with integrated coils is applied to the MR sensor to remove DC magnetic field distortion, and a LFAC magnetic field frequency estimation algorithm is proposed based on a search of the database, which is derived from the numerical model revealing the relationship of the LFAC frequency and determination factor [defined by the ratio of Discrete Fourier Transform (DFT) coefficients]. In this algorithm, an inverse modulation of sensor signals is performed to detect jumping-off point of LFAC in the time domain; this step is exploited to determine sampling points to be processed. A determination factor is calculated and taken into database to figure out frequency with a binary search algorithm. Experimental results demonstrate that the frequency measurement resolution of the LFAC magnetic field is improved from 12.2 Hz to 0.8 Hz by the presented method, which, within the signal band of a magnetic anomaly (0.04-2 Hz), indicates that the proposed method may expand the applications of magnetoresistive (MR) sensors to human healthcare and magnetic anomaly detection (MAD).

Quantitative interpretation of magnetic properties as a way to characterize biogeophysical signatures of biodegraded contaminated sites

Science.gov (United States)

Ustra, A.; Kessouri, P.; Leite, A.; Mendonça, C. A.; Bandeira, N.

2017-12-01

Magnetic minerals in soils and rocks are one way to study biogechemical and paleoenvironmental processes. The ultrafine fraction of these minerals (superparmagnetic (SP) and stable single domain (SSD)) are usually investigated in environmental magnetism studies, since changes in mineralogy, concentration, size and morphology of the magnetic grains can be related to biogeochemical processes. In this study, we use low-field frequency dependent susceptibility (FDS) and isothermal remanent magnetization (IRM) to characterize the magnetic properties of materials in environmental magnetism. Magnetic susceptibility (MS) measurements are frequently used as a proxy of magnetic minerals present in soils and rocks. MS is a complex function of magnetic mineralogy and grain size, as well as magnitude and frequency of the applied field. This work presents a method for inverting low-field FDS data. The inverted parameters can be interpreted in terms of grain size variations of magnetic particles on the SP-SSD transition. This work also presents a method for inverting IRM demagnetization curves, to obtain the saturation magnetization, the individual magnetic moment for an assemblage of ultrafine SP minerals and estimate the concentration of magnetic carriers. IRM magnetization curves can be interpreted as resulting from distinct contributions of different mineral phases, which can be described by Cummulative Log-Gaussian (CLG) distributions. Each acquisition curve provides fundamental parameters that are characteristic of the respective mineral phase. The CLG decomposition is widely used in an interpretation procedure named mineral unmixing. In this work we present an inversion method for mineral unmixing, implementing the genetic algorithm to find the parameters of distinct components. These methodologies have been tested by synthetic models and applied to data from environmental magnetism studies. In this work we apply the proposed methodologies to characterize the magnetic

study of irradiation effects on physical properties of some magnetic semiconductor materials

International Nuclear Information System (INIS)

Ahmed, I.A.A.

2011-01-01

The effect of gamma irradiation on the structure , magnetic and electrical properties of ferrite samples with chemical formula Mg x Cu 0.5-x Zn 0.5 Fe 2 O 4 (where x=0.0 , 0.2 and 0.4) were studied. The samples were prepared by conventional ceramic method.X-ray diffraction parameters, magnetization, initial permeability, electrical resistivity and dielectric constant were measured for the investigated samples before and after irradiation. Both magnetization and initial permeability were measured on toroidal samples used as transformer cores.The initial permeability (μ-i) was measured as a function of temperature at constant frequency of 10 khz and then curie temperatures (T c ) were determined. The Dc resistivity (ρ DC ) and the dielectric constant are measured on tablet form samples using the two probes technique.The real and imaginary parts of dielectric constant ε ' and ε '' were measured as a function of frequency within the range 45 Hz - 5 MHz before and after irradiation.

Magnetic dynamic properties of electron-doped La(0.23)Ca(0.77)MnO3 nanoparticles.

Science.gov (United States)

Dolgin, B; Puzniak, R; Mogilyansky, D; Wisniewski, A; Markovich, V; Jung, G

2013-02-20

Magnetic properties of basically antiferromagnetic La(0.23)Ca(0.77)MnO(3) particles with average sizes of 12 and 60 nm have been investigated in a wide range of magnetic fields and temperature. Particular attention has been paid to magnetization dynamics through measurements of the temperature dependence of ac-susceptibility at various frequencies, the temperature and field dependence of thermoremanent and isothermoremanent magnetization originating from nanoparticles shells, and the time decay of the remanent magnetization. Experimental results and their analysis reveal the major role in magnetic behaviour of investigated antiferromagnetic nanoparticles played by the glassy component, associated mainly with the formation of the collective state formed by ferromagnetic clusters in frustrated coordination at the surfaces of interacting antiferromagnetic nanoparticles. Magnetic behaviour of nanoparticles has been ascribed to a core-shell scenario. Magnetic transitions have been found to play an important role in determining the dynamic properties of the phase separated state of coexisting different magnetic phases.

Magnetic dynamic properties of electron-doped La0.23Ca0.77MnO3 nanoparticles

International Nuclear Information System (INIS)

Dolgin, B; Markovich, V; Jung, G; Puzniak, R; Wisniewski, A; Mogilyansky, D

2013-01-01

Magnetic properties of basically antiferromagnetic La 0.23 Ca 0.77 MnO 3 particles with average sizes of 12 and 60 nm have been investigated in a wide range of magnetic fields and temperature. Particular attention has been paid to magnetization dynamics through measurements of the temperature dependence of ac-susceptibility at various frequencies, the temperature and field dependence of thermoremanent and isothermoremanent magnetization originating from nanoparticles shells, and the time decay of the remanent magnetization. Experimental results and their analysis reveal the major role in magnetic behaviour of investigated antiferromagnetic nanoparticles played by the glassy component, associated mainly with the formation of the collective state formed by ferromagnetic clusters in frustrated coordination at the surfaces of interacting antiferromagnetic nanoparticles. Magnetic behaviour of nanoparticles has been ascribed to a core–shell scenario. Magnetic transitions have been found to play an important role in determining the dynamic properties of the phase separated state of coexisting different magnetic phases. (paper)

AC magnetic properties of the soft magnetic composites based on Supermalloy nanocrystalline powder prepared by mechanical alloying

Energy Technology Data Exchange (ETDEWEB)

Neamtu, B.V., E-mail: bogdan.neamtu@stm.utcluj.ro [Materials Science and Engineering Department, Technical University of Cluj-Napoca, 400614 Cluj-Napoca (Romania); Institut Neel, CNRS/Universite J. Fourier, BP166, 38042 Grenoble, Cedex 9 (France); Geoffroy, O. [Institut Neel, CNRS/Universite J. Fourier, BP166, 38042 Grenoble, Cedex 9 (France); Grenoble Electrical Engineering, University J. Fourier, BP 46, F-38402 Saint-Martin d' Heres Cedex (France); Chicinas, I. [Materials Science and Engineering Department, Technical University of Cluj-Napoca, 400614 Cluj-Napoca (Romania); Isnard, O. [Institut Neel, CNRS/Universite J. Fourier, BP166, 38042 Grenoble, Cedex 9 (France)

2012-05-25

Highlights: Black-Right-Pointing-Pointer Nanocrystalline soft magnetic composites were obtained. Black-Right-Pointing-Pointer The cutting frequency of the produced nanocrystalline SMC exceeds 100 kHz. Black-Right-Pointing-Pointer A long annealing at low temperature leads to an improvement of the permeability (12%). - Abstract: The preparation and characterization of the nanocrystalline soft magnetic composite core based on Supermalloy powder obtained via mechanical alloying route are presented. The AC magnetic properties of the compacts were determined in frequency range from 100 Hz to 100 kHz for flux densities of 0.05 and 0.1 T. Composite materials were obtained by covering the Supermalloy particles with a polymer binder, then compacted into toroidal shape and finally polymerized. It is found that an increase of the compacting pressure from 600 MPa to 800 MPa leads to an increase of the compacts permeability by more than 8%. Also, reducing the polymer content from 2 wt.% to 0.5 wt.% leads to an increase of the magnetic losses (at 100 kHz and 0.1 T) by 380%. The removal of the stresses induced during compaction has been accomplished by a heat treatment at 170 Degree-Sign C for 120 h. This leads to a significant increase (12%) of the relative initial permeability of the compacts.

Magneto-thermal-acoustic differential-frequency imaging of magnetic nanoparticle with magnetic spatial localization: a theoretical prediction

Science.gov (United States)

Piao, Daqing

2017-02-01

The magneto-thermo-acoustic effect that we predicted in 2013 refers to the generation of acoustic-pressure wave from magnetic nanoparticle (MNP) when thermally mediated under an alternating magnetic field (AMF) at a pulsed or frequency-chirped application. Several independent experimental studies have since validated magneto-thermoacoustic effect, and a latest report has discovered acoustic-wave generation from MNP at the second-harmonic frequency of the AMF when operating continuously. We propose that applying two AMFs with differing frequencies to MNP will produce acoustic-pressure wave at the summation and difference of the two frequencies, in addition to the two second-harmonic frequencies. Analysis of the specific absorption dynamics of the MNP when exposed to two AMFs of differing frequencies has shown some interesting patterns of acoustic-intensity at the multiple frequency components. The ratio of the acoustic-intensity at the summation-frequency over that of the difference-frequency is determined by the frequency-ratio of the two AMFs, but remains independent of the AMF strengths. The ratio of the acoustic-intensity at the summation- or difference-frequency over that at each of the two second-harmonic frequencies is determined by both the frequency-ratio and the field-strength-ratio of the two AMFs. The results indicate a potential strategy for localization of the source of a continuous-wave magneto-thermalacoustic signal by examining the frequency spectrum of full-field non-differentiating acoustic detection, with the field-strength ratio changed continuously at a fixed frequency-ratio. The practicalities and challenges of this magnetic spatial localization approach for magneto-thermo-acoustic imaging using a simple envisioned set of two AMFs arranged in parallel to each other are discussed.

Weak ferromagnetism and temperature dependent dielectric properties of Zn{sub 0.9}Ni{sub 0.1}O diluted magnetic semiconductor

Energy Technology Data Exchange (ETDEWEB)

Ahmed, Raju [Department of Electrical and Electronic Engineering, Shahjalal University of Science and Technology, Sylhet 3114 (Bangladesh); Department of Applied Physics, Electronics and Communication Engineering, University of Dhaka, Dhaka 1000 (Bangladesh); Moslehuddin, A.S.M.; Mahmood, Zahid Hasan [Department of Applied Physics, Electronics and Communication Engineering, University of Dhaka, Dhaka 1000 (Bangladesh); Hossain, A.K.M. Akther, E-mail: akmhossain@phy.buet.ac.bd [Department of Physics, Bangladesh University of Engineering and Technology, Dhaka 1000 (Bangladesh)

2015-03-15

Highlights: • Single phase wurtzite structure was confirmed from XRD analysis. • Weak ferromagnetic behaviour at room temperature. • Pure semiconducting properties confirmed from temperature dependent conductivity. • Smaller dielectric properties at higher frequency. • Possible potential application in high frequency spintronic devices. - Abstract: In this study the room temperature ferromagnetic behaviour and dielectric properties of ZnO based diluted magnetic semiconductor (DMS) have been investigated using nominal chemical composition Zn{sub 0.9}Ni{sub 0.1}O. The X-ray diffraction analysis confirmed formation of single phase hexagonal wurtzite structure. An increase in grain size with increasing sintering temperature was observed from scanning electron microscopy. Field dependent DC magnetization values indicated dominant paramagnetic ordering along with a slight ferromagnetic behaviour at room temperature. Frequency dependent complex initial permeability showed some positive values around 12 at room temperature. In dielectric measurement, an increasing trend of complex permittivity, loss tangent and ac conductivity with increasing temperature were observed. The temperature dependent dispersion curves of dielectric properties revealed clear relaxation at higher temperature. Frequency dependent ac conductivity was found to increase with frequency whereas complex permittivity and loss tangent showed an opposite trend.

Magnetic Properties of NdAl2

DEFF Research Database (Denmark)

Bak, P.

1974-01-01

The magnetic properties of NdAl2 are calculated using a Hamiltonian including crystal-field and isotropic exchange interaction terms. A two-dimensional mean-field theory is evaluated to calculate single-crystal magnetization curves. It is shown that the magnetic properties can be understood using...... the crystal-field parameters derived from the magnetic exciton spectrum measured by Houmann et al. by means of inelastic neutron scattering. The combined lambda -Schottky anomaly in the heat capacity is explained. No additional parameters are introduced....

Natural Frequencies and Vibrating Modes for a Magnetic Planetary Gear Drive

Directory of Open Access Journals (Sweden)

Lizhong Xu

2012-01-01

Full Text Available In this paper, a dynamic model for a magnetic planetary gear drive is proposed. Based on the model, the dynamic equations for the magnetic planetary gear drive are given. From the magnetic meshing forces and torques between the elements for the drive system, the tangent and radial magnetic meshing stiffness is obtained. Using these equations, the natural frequencies and the modes of the magnetic planetary gear drive are investigated. The sensitivity of the natural frequencies to the system parameters is discussed. Results show that the pole pair number and the air gap have obvious effects on the natural frequencies. For the planetary gear number larger than two, the vibrations of the drive system include the torsion mode of the center elements, the translation mode of the center elements, and the planet modes. For the planetary gear number equal to two, the planet mode does not occur, the crown mode and the sun gear mode occur.

High-frequency, transient magnetic susceptibility of ferroelectrics

Science.gov (United States)

Grimes, Craig A.

1996-10-01

A significant high-frequency magnetic susceptibility was measured both in weakly polarized and nonpolarized samples of barium titanate, lead zirconate titanate, and carnauba wax. Magnetic susceptibility measurements were made from 10 to 500 MHz using a thin film permeameter at room temperature; initial susceptibilities ranged from 0.1 to 2.5. These values are larger than expected for paramagnets and smaller than expected for ferromagnets. It was found that the magnetic susceptibility decreases rapidly with exposure to the exciting field. The origin of the magnetic susceptibility is thought to originate with the applied time varying electric field associated with the susceptibility measurements. An electric field acts to rotate an electric dipole, creating a magnetic quadrupole if the two moments are balanced, and a net magnetic dipole moment if imbalanced. It is thought that local electrostatic fields created at ferroelectric domain discontinuities associated with grain boundaries create an imbalance in the anion rotation that results in a net, measurable, magnetic moment. The origin of the magnetic aftereffect may be due to the local heating of the material through the moving charges associated with the magnetic moment.

Magnetic characterization of the stator core of a high-speed motor made of an ultrathin electrical steel sheet using the magnetic property evaluation system

Directory of Open Access Journals (Sweden)

Mohachiro Oka

2018-04-01

Full Text Available Recently, the application areas for electric motors have been expanding. For instance, electric motors are used in new technologies such as rovers, drones, cars, and robots. The motor used in such machinery should be small, high-powered, highly-efficient, and high-speed. In such motors, loss at high-speed rotation must be especially minimal. Eddy-current loss in the stator core is known to increase greatly during loss at high-speed rotation of the motor. To produce an efficient high-speed motor, we are developing a stator core for a motor using an ultrathin electrical steel sheet with only a small amount of eddy-current loss. Furthermore, the magnetic property evaluation for efficient, high-speed motor stator cores that use conventional commercial frequency is insufficient. Thus, we made a new high-speed magnetic property evaluation system to evaluate the magnetic properties of the efficient high-speed motor stator core. This system was composed of high-speed A/D converters, D/A converters, and a high-speed power amplifier. In experiments, the ultrathin electrical steel sheet dramatically suppressed iron loss and, in particular, eddy-current loss. In addition, a new high-speed magnetic property evaluation system accurately evaluated the magnetic properties of the efficient high-speed motor stator core.

Magnetic characterization of the stator core of a high-speed motor made of an ultrathin electrical steel sheet using the magnetic property evaluation system

Science.gov (United States)

Oka, Mohachiro; Enokizono, Masato; Mori, Yuji; Yamazaki, Kazumasa

2018-04-01

Recently, the application areas for electric motors have been expanding. For instance, electric motors are used in new technologies such as rovers, drones, cars, and robots. The motor used in such machinery should be small, high-powered, highly-efficient, and high-speed. In such motors, loss at high-speed rotation must be especially minimal. Eddy-current loss in the stator core is known to increase greatly during loss at high-speed rotation of the motor. To produce an efficient high-speed motor, we are developing a stator core for a motor using an ultrathin electrical steel sheet with only a small amount of eddy-current loss. Furthermore, the magnetic property evaluation for efficient, high-speed motor stator cores that use conventional commercial frequency is insufficient. Thus, we made a new high-speed magnetic property evaluation system to evaluate the magnetic properties of the efficient high-speed motor stator core. This system was composed of high-speed A/D converters, D/A converters, and a high-speed power amplifier. In experiments, the ultrathin electrical steel sheet dramatically suppressed iron loss and, in particular, eddy-current loss. In addition, a new high-speed magnetic property evaluation system accurately evaluated the magnetic properties of the efficient high-speed motor stator core.

Investigation of magnetic properties of Fe{sub 3}O{sub 4} nanoparticles using temperature dependent magnetic hyperthermia in ferrofluids

Energy Technology Data Exchange (ETDEWEB)

Nemala, H.; Thakur, J. S.; Lawes, G.; Naik, R., E-mail: rnaik@wayne.edu [Department of Physics and Astronomy, Wayne State University, Detroit, Michigan 48202 (United States); Naik, V. M. [Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, Michigan 48128 (United States); Vaishnava, P. P. [Department of Physics, Kettering University, Flint, Michigan 48504 (United States)

2014-07-21

Rate of heat generated by magnetic nanoparticles in a ferrofluid is affected by their magnetic properties, temperature, and viscosity of the carrier liquid. We have investigated temperature dependent magnetic hyperthermia in ferrofluids, consisting of dextran coated superparamagnetic Fe{sub 3}O{sub 4} nanoparticles, subjected to external magnetic fields of various frequencies (188–375 kHz) and amplitudes (140–235 Oe). Transmission electron microscopy measurements show that the nanoparticles are polydispersed with a mean diameter of 13.8 ± 3.1 nm. The fitting of experimental dc magnetization data to a standard Langevin function incorporating particle size distribution yields a mean diameter of 10.6 ± 1.2 nm, and a reduced saturation magnetization (∼65 emu/g) compared to the bulk value of Fe{sub 3}O{sub 4} (∼95 emu/g). This is due to the presence of a finite surface layer (∼1 nm thickness) of non-aligned spins surrounding the ferromagnetically aligned Fe{sub 3}O{sub 4} core. We found the specific absorption rate, measured as power absorbed per gram of iron oxide nanoparticles, decreases monotonically with increasing temperature for all values of magnetic field and frequency. Using the size distribution of magnetic nanoparticles estimated from the magnetization measurements, we have fitted the specific absorption rate versus temperature data using a linear response theory and relaxation dissipation mechanisms to determine the value of magnetic anisotropy constant (28 ± 2 kJ/m{sup 3}) of Fe{sub 3}O{sub 4} nanoparticles.

Influence of the mechanical fatigue progress on the magnetic properties of electrical steel sheets

Directory of Open Access Journals (Sweden)

Karthaus Jan

2017-06-01

Full Text Available The purpose of this paper is to study the variation of the magnetic properties of non-oriented electrical steel sheets with the fatigue state during cyclic mechanical loading. The obtained results are central to the design of variable drives such as traction drives in electric vehicles in which varying mechanical loads, e.g. in the rotor core (centrifugal forces, alter the magnetic properties. Specimens of non-oriented electrical steel are subject to a cyclically varying mechanical tensile stress with different stress amplitudes and number of cycles. The specimens are characterised magnetically at different fatigue states for different magnetic flux densities and magnetising frequencies. The measurements show a variation in magnetic properties depending on the number of cycles and stress magnitude which can be explained by changes in the material structure due to a beginning mechanical fatigue process. The studied effect is critical for the estimation of the impact of mechanical material fatigue on the operational behaviour of electrical machines. Particularly in electrical machines with a higher speed where the rotor is stressed by high centrifugal forces, material fatigue occurs and can lead to deterioration of the rotor’s stack lamination.

Structural and magnetic properties of Ni-Zn doped BaM nanocomposite via citrate precursor

Energy Technology Data Exchange (ETDEWEB)

Rana, Kush; Thakur, Preeti; Thakur, Atul, E-mail: atulphysics@gmail.com [School of Physics and Materials Science, Shoolini University, Solan, India 173212 (India); Tomar, Monika; Gupta, Vinay [Department of Physics and Astrophysics, University of Delhi, Delhi, India 110007 (India)

2016-05-23

Ni-Zn substituted M-type barium ferrite nanocomposite has been prepared via citrate precursor method. Nanocomposite having composition BaNi{sub 0.5}Zn{sub 0.5}Fe{sub 11}O{sub 19} was sintered at 900°C for 3hrs and characterized by using different characterization techniques. X-ray diffraction (XRD) confirmed the formation of double phase with most prominent peak at (114). Average crystallite size for pure BaM and BNZFO were found to be 36 nm & 45 nm. Field emission scanning electron microscopy (FESEM) confirmed the formation of hexagonal platelets with a layered structure. Magnetic properties of these samples were investigated by using vibrating sample magnetometer (VSM). Magnetic parameters like saturation magnetization (M{sub s}), coericivity (H{sub c}) and squareness ratio (SQR) of nanocomposite were found to be 60 emu/g, 3663 Oe and 0.6163 respectively. These values were noticed to be higher as compared to pure BaM. Enhanced magnetic properties of nanocomposite were strongly dependent on exchange coupling. Therefore these properties make this nanocomposite a suitable candidate for magnetic recording and high frequency applications.

Magnetic Properties of (Nia-ZnbX Cu1-X Ferrite Nanoparticle Fabricated by Sol-Gel Process

Directory of Open Access Journals (Sweden)

Yang S.

2017-06-01

Full Text Available In future, more mobile devices with different frequencies will be used at the same time. Therefore, it is expected that the trouble caused by wave interference between devices will be further intensified. In order to prevent this trouble, investigation of selective frequency transmission or absorption material is required. In this paper, magnetic properties of nickel-zinc-copper ferrite nano powder was researched as wave absorber. (Nia-ZnbxCu1-xFe2O4(NZCF nanoparticles were fabricated by the sol-gel method. The influence of copper substitution on lattice parameter change was analyzed by X-ray diffraction (XRD, particle size was analyzed by scanning electron microscopy (SEM, and Magnetic properties analyzed by vibrating sample magnetometer (VSM. The NZCF and Nickel-zinc ferrite (NZF lattice parameter difference was 0.028 Å and particle size was calculated as 30 nm with the XRD peak. The VSM results of (Ni0.3-Zn0.30.6Cu1-0.6Fe2O4 annealed sample at 700°C for 3hous were 58.5 emu/g (Ms, 22.8 Oe (Hc. It was the most suitable magnetic properties for wave absorber in this investigation.

The Characterization of the Magnetic Properties of Soft Magnetic Materials

DEFF Research Database (Denmark)

Larsen, Raino Michael

1996-01-01

The hysteresis curve and magnetic properties such as permeability, saturation induction, residual induction, coercive force and hysteresis losses are presented. The design and construction of equipment making it possible to measure true DC-values as well as AC-properties of toroid rings and cylin......The hysteresis curve and magnetic properties such as permeability, saturation induction, residual induction, coercive force and hysteresis losses are presented. The design and construction of equipment making it possible to measure true DC-values as well as AC-properties of toroid rings...

Extremely low frequency magnetic fields and health risks

Directory of Open Access Journals (Sweden)

M.I. Buzdugan

2009-10-01

Full Text Available In a world abounding in artificially created electromagnetic fields, we consider that a new approach regarding their possible harmful effects on living beings becomes mandatory. The paper reviews briefly the results of some epidemiological studies, the ICNIRP (International Committee on Non-Ionizing Radiation Protection Guidelines and the latest document of the SCENIHR (an organism of the European Commission regarding extremely low frequency (ELF magnetic fields. We are convinced that the best conduct that might be adopted on this matter is the policy of the prudential avoidance. Several examples of possible harmful effects determined by extremely low frequency magnetic fields dedicated to building services engineering in residences are presented, along with several methods of mitigating them.

Electromagnetic wave absorption properties of composites with micro-sized magnetic particles dispersed in amorphous carbon

Energy Technology Data Exchange (ETDEWEB)

Li, Bin Peng [Research Center of Carbon Fiber, Key Laboratory for Liquid–Solid Structural Evolution and Processing of Materials of Ministry of Education, Shandong University, Jinan 250061 (China); Tianjin Binhai New Area Finance Bureau, Tianjin 300450 (China); Wang, Cheng Guo, E-mail: sduwangchg@gmail.com [Research Center of Carbon Fiber, Key Laboratory for Liquid–Solid Structural Evolution and Processing of Materials of Ministry of Education, Shandong University, Jinan 250061 (China); Wang, Wen [Norinco Group China North Material Science and Engineering Technology Group Corporation, Jinan 250031 (China); Yu, Mei Jie; Gao, Rui; Chen, Yang; Xiang Wang, Yan [Research Center of Carbon Fiber, Key Laboratory for Liquid–Solid Structural Evolution and Processing of Materials of Ministry of Education, Shandong University, Jinan 250061 (China)

2014-09-01

Composites with micro-sized magnetic particles dispersed in amorphous carbon were fabricated conveniently and economically by carbonizing polyacrylonitrile (PAN) fibers mixed with micro-sized iron particles under different temperatures. The composites were characterized by X-ray diffraction (XRD) and scanning electric microscope (SEM). The electromagnetic (EM) properties were measured by a vector network analyzer in the frequency range of 2–18 GHz based on which analog computations of EM wave absorption properties were carried out. The influences of temperature on phase composition and EM wave absorption properties were also investigated, indicating that the composites had good electromagnetic absorption properties with both electrical loss and magnetic loss. Effective reflection loss (RL<−10 dB) was observed in a large frequency range of 7.5–18 GHz with the absorber thickness of 2.0–3.0 mm for the paraffin samples with composite powders heated up to 750 °C and the minimum absorption peak around −40 dB appeared at approximately 10 GHz with matching thickness of 2.0 mm for the paraffin sample with composite powders heated up to 800 °C. - Highlights: • High-performance electromagnetic wave absorption materials were fabricated conveniently and economically. • The materials are composites with micro-sized magnetic particles dispersed in porous amorphous carbon. • The influences of temperature on phase composition and electromagnetic wave absorption properties were investigated. • The composites heated up to 750 °C and 800 °C had good electromagnetic wave absorption property.

Soft magnetic properties and damping parameter of (FeCo-Al alloy thin films

Directory of Open Access Journals (Sweden)

Isao Kanada

2017-05-01

Full Text Available For high frequency device applications, a systematic study of the soft magnetic properties and magnetization dynamics of (FeCo-Al alloy thin films has been carried out. A low effective damping parameter αeff of 0.002 and a high saturation magnetization of about 1,800 emu/cc are obtained at y=0.2∼0.3 for (Fe1-yCoy98Al2 alloy thin films deposited onto fused silica and MgO(100 at an ambient temperature during deposition. Those films are of the bcc structure with the orientation normal to the film plane. They possess a columnar structure, grown along the film normal. The column width is found to be about 20 nm for y=0.25. It is concluded that the (FeCo-Al thin films with a damping parameter as low as 0.002 and high saturation magnetization of about 1,800 emu/cc have been successfully fabricated, and that they are potential for future high frequency device applications.

Assessment of extremely low frequency magnetic field exposure from GSM mobile phones

NARCIS (Netherlands)

Calderón, Carolina; Addison, Darren; Mee, Terry; Findlay, Richard; Maslanyj, Myron; Conil, Emmanuelle; Kromhout, Hans; Lee, Ae Kyoung; Sim, Malcolm R.; Taki, Masao; Varsier, Nadège; Wiart, Joe; Cardis, Elisabeth

2014-01-01

Although radio frequency (RF) electromagnetic fields emitted by mobile phones have received much attention, relatively little is known about the extremely low frequency (ELF) magnetic fields emitted by phones. This paper summarises ELF magnetic flux density measurements on global system for mobile

Magnetic hyperthermia properties of iron oxide nanoparticles: The effect of concentration

Science.gov (United States)

Ebrahimisadr, Saeid; Aslibeiki, Bagher; Asadi, Reza

2018-06-01

We investigated the effect of concentration on magnetic hyperthermia properties of Fe3O4 nanoparticles (NPs). The NPs were synthesized by co-precipitation method at 80 °C. Scanning electron microscope image showed that the mean diameter of NPs is about 18 nm. The XRD pattern indicated that the sample is pure Fe3O4 with spinel structure and the FT-IR spectroscopy confirmed formation of metal-oxygen bonds in the octahedral and tetrahedral spinel sub-lattice which further confirmed crystalline structure of the sample. The hyperthermia property of Fe3O4 NPs was investigated via an induction heater generating alternating magnetic field with frequency of 92 kHz. The temperature rise (ΔT) of suspension in the AC magnetic field was studied on different concentrations of NPs and the specific absorption rate (SAR) was obtained from Box-Lucas equation and linear fitting of ΔT-time curve. The results showed that the ΔT sharply increases with increasing the NPs concentration while the SAR remains almost constant.

High-frequency magnetic components

CERN Document Server

Kazimierczuk, Marian K

2013-01-01

A unique text on the theory and design fundaments of inductors and transformers, updated with more coverage on the optimization of magnetic devices and many new design examples The first edition is popular among a very broad audience of readers in different areas of engineering and science. This book covers the theory and design techniques of the major types of high-frequency power inductors and transformers for a variety of applications, including switching-mode power supplies (SMPS) and resonant dc-to-ac power inverters and dc-to-dc power converters. It describes eddy-current phenomena (su

Magnetic properties of HoVOΛ4 in high magnetic fields

International Nuclear Information System (INIS)

Andronenko, S.I.; Bazhan, A.N.; Ioffe, V.A.; Udalov, Yu.P.

1985-01-01

Values magnetization and susceptibility of HoVO 4 , Van Vleck paramagnetic are specified in the 4.2-40 K temperature range and magnetic fields up to 50 kOe. Magnetic properties of HoVO 4 are analyzed using a theoretical model in which the interaction of rare earth ions with the crystal- and magnetic fields is considered. A possibility of rare earth ion interaction with the Bsub(1g), Bsub(2g), Asub(1g) symmetry deformations is also considered. It is stated that magnetic properties of HoVO 4 are completely explained within the frames of the crystal field model; the rare earth ion interactions with deformations are insignificant. Anisotropy of magnetization in the (001) plane is determined by the crystal field B 4 4 , B 6 4 constants; the constants being shown to be positive

Process and magnetic properties of cold pressed Ne Fe B bonded magnets

International Nuclear Information System (INIS)

Rodrigues, DAniel; Concilio, Gilberto Vicente; Landgraf, Fernando Jose Gomes; Zanchetta, Antonio Carlos

1996-01-01

Bonded magnets are polymer composites based on a mixture of a hard magnetic powder and a polymer. This mixture is processed as a traditional powder metallurgy material, cold pressed, or like a thermoplastic material, by injection molding. The polymeric phase to a large extent determines the mechanical properties of the composite, while magnetic powder determines its magnetic properties. They are less expensive and easier to produce, specially in the case of high complexity parts. This paper presents the relationship between process variables and magnetic properties of cold pressed Nd Fe B bonded magnets produced from melt spun flakes mixed with thermosetting resins. The experiments were done using Statistical Design of Experiments. The variables investigates were: uniaxial compaction pressure, binder type; binder content; size of Nd Fe B particles; addition of lubricant; and addition of small quantities of magnetic additives, particles of ferrites, iron, or alnico. (author)

Magnetic properties of metals and alloys

International Nuclear Information System (INIS)

Lyuborskij, F.E.; Livingston, D.D.; Chin, Zh.I.

1987-01-01

The nature of magnetic properties of materials and their dependence on the composition and the material structure are described. Properties and application of such materials as the alloys of the Fe-Ni-Co, Fe-Cr-Co, Co-rare earth, Fe-Si, Ni-Se system are considered. Application outlook for amorphous alloys of the (Fe, Ni, Co) 80 (metalloid) 20 type is shown. Methods for magnetic property measurement are pointed out

Design and development of ITER high-frequency magnetic sensor

NARCIS (Netherlands)

Ma, Y.; Vayakis, G.; Begrambekov, L. B.; Cooper, J.J.; Duran, I.; Hirsch, M.; Laqua, H.P.; Moreau, Ph.; Oosterbeek, J.W.; Spuig, P.; Stange, T.; Walsh, M.

2016-01-01

High-frequency (HF) inductive magnetic sensors are the primary ITER diagnostic set for Toroidal Alfvén Eigenmodes (TAE) detection, while they also supplement low-frequency MHD and plasma equilibrium measurements. These sensors will be installed on the inner surface of ITER vacuum vessel, operated in

Resonant magnetic pumping at very low frequency

International Nuclear Information System (INIS)

Canobbio, Ernesto

1978-01-01

We propose to exploit for plasma heating purposes the very low frequency limit of the Alfven wave resonance condition, which reduces essentially to safety factor q=m/n, a rational number. It is shown that a substantial fraction of the total RF-energy can be absorbed by the plasma. The lowest possible frequency value is determined by the maximum tolerable width of the RF-magnetic islands which develop near the singular surface. The obvious interest of the proposed scheme is the low frequency value (f<=10 KHz) which allows the RF-coils to be protected by stainless steel or even to be put outside the liner

Study on the properties of tunable prohibited band gaps for one-dimensional ternary magnetized plasma photonic crystals

International Nuclear Information System (INIS)

Zhang Haifeng; Zheng Jianping; Zhu Rongjun

2012-01-01

The transfer matrix method was applied to study on the properties of tunable prohibited band gaps for one-dimensional ternary magnetized plasma photonic crystals with TE wave arbitrary incident under ideal conditions. TE wave would be divided into left-handed circularly polarized wave and right-handed circularly polarized wave after propagation through one-dimensional ternary magnetized plasma photonic crystals. The calculated transmission coefficients were used to analyze the effects of parameter of plasma, plasma filling factor, incident angle and relative dielectric constant for dielectric layer on the properties of tunable prohibited band gap. The results illustrate that the width of band gaps can not be broadened by increasing plasma collision frequency, the numbers and width of band gaps can be tuned by changing plasma frequency, plasma filling factor and relative dielectric constant for dielectric layer. The band gaps for right-handed circularly polarized wave can be tuned by the plasma gyro frequency, but band gaps for the left-handed circularly polarized wave can't influenced. Low-frequency region of band gaps will be broadened, while high-frequency region of band gaps will be firstly narrow and then broaden with increasing incident angle. (authors)

Magnetic properties of magnetic glass-like carbon prepared from furan resin alloyed with magnetic fluid

Energy Technology Data Exchange (ETDEWEB)

Nakamura, Kazumasa, E-mail: naka@sss.fukushima-u.ac.jp [Materials Science Area, Graduate School of Symbiotic Systems Science and Technology, Fukushima University, 1 Kanayagawa, Fukushima 960-1296 (Japan); Okuyama, Kyoko [Materials Science Area, Graduate School of Symbiotic Systems Science and Technology, Fukushima University, 1 Kanayagawa, Fukushima 960-1296 (Japan); Takase, Tsugiko [Institute of Environmental Radioactivity (IER), Fukushima University, 1 Kanayagawa, Fukushima 960-1296 (Japan)

2017-03-01

Magnetic glass-like carbons that were heat-treated at different temperatures or were filled with different magnetic nanoparticle contents were prepared from furan resin alloyed with magnetic fluid (MF) or Fe{sub 3}O{sub 4} powder in their liquid-phase states during mixing. Compared to the Fe{sub 3}O{sub 4} powder-alloyed carbon, the MF-alloyed carbon has highly dispersed the nanoparticles, and has the excellent saturation magnetization and coercivity. It is implied that saturation magnetizations are related to changes in the types of phases for the nanoparticles and the relative intensities of X-ray diffraction peaks for iron and iron-containing compounds in the carbons. Additionally, the coercivities are possibly affected by the size and crystallinity of the nanoparticles, the relative amounts of iron, and the existence of amorphous compounds on the carbon surfaces. - Highlights: • Magnetic glass-like carbons were prepared from furan resin alloyed with magnetic fluid. • The nanoparticles of MF-alloyed GLCs were highly dispersed. • MF-alloyed GLCs had excellent magnetic properties compared to powder-alloyed ones. • The magnetic properties changed with treatment temperature and nanoparticle content. • The changes in magnetic properties were investigated with XRD and FE-SEM.

Magnetic activity at infrared frequencies in structured metallic photonic crystals

International Nuclear Information System (INIS)

O'Brien, S.; Pendry, J.P.

2002-01-01

We derive the effective permeability and permittivity of a nanostructured metallic photonic crystal by analysing the complex reflection and transmission coefficients for slabs of various thicknesses. These quantities were calculated using the transfer matrix method. Our results indicate that these structures could be used to realize a negative effective permeability, at least up to infrared frequencies. The origin of the negative permeability is a resonance due to the internal inductance and capacitance of the structure. We also present an analytic model for the effective permeability of the crystal. The model reveals the importance of the inertial inductance due to the finite mass of the electrons in the metal. We find that this contribution to the inductance has implications for the design of metallic magnetic structures in the optical region of the spectrum. We show that the magnetic activity in the structure is accompanied by the concentration of the incident field energy into very small volumes within the structure. This property will allow us to considerably enhance non-linear effects with minute quantities of material. (author)

Structural, magnetic and electrical transport properties in cold-drawn thin Fe-rich wires

International Nuclear Information System (INIS)

Garcia, C.; Chizhik, A.; Val, J.J. del; Zhukov, A.; Blanco, J.M.; Gonzalez, J.

2005-01-01

Microstructural (X-ray diffraction), magnetic properties (hysteresis loop), electrical resistivity, magneto-impedance and stress impedance effects have been investigated in cold-drawn Fe 77.5 B 15 Si 7.5 amorphous wire. Initial amorphous wire (obtained by the in-rotating-water technique) with diameter of 125 μm was submitted to cold-drawn process decreasing the diameter to 50 μm. Such cold-drawn wire was treated by current annealing (currents of 190, 210, 220 and 230 mA during times between 1 and 45 min) for tailoring the magnetic and electrical transport properties. A qualitative analysis of the magnetoimpedance and stress impedance effects is given by considering the influence of the magnetoelastic anisotropy and frequency of the AC driving electrical current on the circular permeability

Microstructure and magnetic properties of inert gas atomized rare earth permanent magnetic materials

International Nuclear Information System (INIS)

Sellers, C.H.; Hyde, T.A.; Branagan, D.J.; Lewis, L.H.; Panchanathan, V.

1997-01-01

Several permanent magnet alloys based on the ternary Nd 2 Fe 14 B (2-14-1) composition have been prepared by inert gas atomization (IGA). The microstructure and magnetic properties of these alloys have been studied as a function of particle size, both before and after heat treatment. Different particle sizes have characteristic properties due to the differences in cooling rate experienced during solidification from the melt. These properties are also strongly dependent on the alloy composition due to the cooling rate close-quote s effect on the development of the phase structure; the use of rare earth rich compositions appears necessary to compensate for a generally inadequate cooling rate. After atomization, a brief heat treatment is necessary for the development of the optimal microstructure and magnetic properties, as seen from the hysteresis loop shape and improvements in key magnetic parameters (intrinsic coercivity H ci , remanence B r , and maximum energy product BH max ). By adjusting alloy compositions specifically for this process, magnetically isotropic powders with good magnetic properties can be obtained and opportunities for the achievement of better properties appear to be possible. copyright 1997 American Institute of Physics

Equivalent magnetic vector potential model for low-frequency magnetic exposure assessment

Science.gov (United States)

Diao, Y. L.; Sun, W. N.; He, Y. Q.; Leung, S. W.; Siu, Y. M.

2017-10-01

In this paper, a novel source model based on a magnetic vector potential for the assessment of induced electric field strength in a human body exposed to the low-frequency (LF) magnetic field of an electrical appliance is presented. The construction of the vector potential model requires only a single-component magnetic field to be measured close to the appliance under test, hence relieving considerable practical measurement effort—the radial basis functions (RBFs) are adopted for the interpolation of discrete measurements; the magnetic vector potential model can then be directly constructed by summing a set of simple algebraic functions of RBF parameters. The vector potentials are then incorporated into numerical calculations as the equivalent source for evaluations of the induced electric field in the human body model. The accuracy and effectiveness of the proposed model are demonstrated by comparing the induced electric field in a human model to that of the full-wave simulation. This study presents a simple and effective approach for modelling the LF magnetic source. The result of this study could simplify the compliance test procedure for assessing an electrical appliance regarding LF magnetic exposure.

Structural, magnetic characterization (dependencies of coercivity and loss with the frequency) of magnetic cores based in Finemet

Science.gov (United States)

Osinalde, M.; Infante, P.; Domínguez, L.; Blanco, J. M.; del Val, J. J.; Chizhik, A.; González, J.

2017-12-01

We report changes of coercivity, induced magnetic anisotropy, magneto-optical domain structure and frequency dependencies of coercivity and energy loss (up to 10 MHz) associated with the structural modifications produced by thermal treatments under applied magnetic field (field annealing) in toroidal wound cores of Fe73.5Cu1Nb3Si15.5B7 amorphous alloy. The thermal treatment (535 °C, 1 h) leads to the typical nanocrystalline structure of α-Fe(Si) nanograins (60-65% relative volume, 10-20 nm average grain size embedded in a residual amorphous matrix, while the magnetic field with the possibility to be applied in two directions to the toroidal core axis, that is in transverse (which is equivalent to the transverse direction of the ribbon) or longitudinal (equivalent to the longitudinal direction of the ribbon), develops a macroscopic uniaxial magnetic anisotropy in the transverse (around 245 J/m3) or longitudinal (around 85 J/m3) direction of the ribbon, respectively. It is remarkable the quasi-unhysteretic character of the cores with these two kinds of field annealing as comparing with that of the as-quenched one. Magneto-optical study by Kerr-effect of the ribbons provides useful information on the domain structure of the surface in agreement with the direction and intensity of the induced magnetic anisotropy. This induced uniaxial magnetic anisotropy plays a very important role on the Hc(f) and EL(f) curves, (f: frequency), being drastic the presence and direction of the induced magnetic anisotropy. In addition, these frequency dependencies show a significant change at the frequency around 100 Hz.

Magnetic properties and magnetoimpedance of FeCoNi/CuBe electroplated tubes with different features of field-annealing induced magnetic anisotropy

Energy Technology Data Exchange (ETDEWEB)

El Kammouni, R.; Chlenova, A.A.; Volchkov, S.O. [Ural Federal University, Laboratory of Magnetic Sensors, Lenin Ave. 51, 620000 Ekaterinburg (Russian Federation); Kurlyandskaya, G.V., E-mail: galina@we.lc.ehu.es [Ural Federal University, Laboratory of Magnetic Sensors, Lenin Ave. 51, 620000 Ekaterinburg (Russian Federation); Departamento de Electricidad y Electrónica, Universidad del País Vasco BCMaterials (UPV/EHU), 48940 Leioa (Spain)

2017-02-01

The effect of field annealing (in direct (DC) or alternating current (AC) field) on the structure, magnetic properties and giant magnetoimpedance (GMI) of CuBe/ Fe{sub 19}Co{sub 17}Ni{sub 64} electroplated tubes was studied. The field and frequency dependences of total impedance and its real part were comparatively analyzed together with magnetization processes features. The GMI sensitivity with respect to an applied field was the subject of special attention in view of possible applications of these materials in small magnetic field sensors. The maximum GMI ratio depends strongly on the heat treatments. The DC field annealing leads to the highest total impedance GMI ratio (ΔZ/Z=250%) and real part of the total impedance GMI ratio (ΔR/R=640%), compared to as-cast and AC field annealed samples. The external field response of DC annealed samples presented a single peak GMI response as a consequence of a strong contribution of the longitudinal effective anisotropy. At the same time, the maximum obtained sensitivity of 13.5%/Oe for DC case is much lower compared to the highest sensitivity values obtained for as-prepared (28.6%/Oe) and DC field annealed (22.0%/Oe) tubes for the low frequency of 2.5 MHz. The weak dependence of ΔZ/Z ratio in the case of AC field annealed samples in the high frequency range is an important advantage for particular sensor applications. - Highlights: • CuBe/FeCoNi tubes were fabricated by electroplating. • The effect of field annealing on the structure, magnetic properties and magnetoimpedance was studied. • The maximum magnetoimpedance ( MI) ratio depends strongly on the heat treatments. • The DC field annealing leads to the highest total impedance MI ratio. • Transformation from one- to two-peaks MI curves was observed in the DC field annealed tubes.

Properties of magnetic nano-particles

DEFF Research Database (Denmark)

Lindgård, Per-Anker

1997-01-01

The intrinsic thermodynamic magnetic properties of clusters are discussed using spin wave theory for a Heisenberg model, with a fixed magnitude of the spins S-i = S and site independent nearest neighbor exchange interaction. The consequences of the more realistic Hubbard model is considered...... in which we allow for a magnetization profile at T = 0 and a structural relaxation, which in turn will give rise to a site dependent exchange interaction. Et is concluded that correlation effects among the electrons play a very important role in small clusters, albeit not modifying the thermodynamic...... properties drastically. The finite cluster size gives foremost rise to a discrete excitation spectrum with a large energy gap to the ground state. The relaxation of the magnetization during the reversal of the external magnetic field is discussed. A first step towards a quantitative understanding...

Monitoring kinetic and frequency-domain properties of eyelid responses in mice with magnetic distance measurement technique

NARCIS (Netherlands)

W.L. den Ouden; G. Perry; S.M. Highstein; C.I. de Zeeuw (Chris); S.K.E. Koekkoek (Bas)

2002-01-01

textabstractClassical eye-blink conditioning in mutant mice can be used to study the molecular mechanisms underlying associative learning. To measure the kinetic and frequency domain properties of conditioned (tone - periorbital shock procedure) and unconditioned eyelid responses

The effects of extremely low frequency magnetic fields on mutation induction in mice

Energy Technology Data Exchange (ETDEWEB)

Wilson, James W. [Department of Genetics, University of Leicester, Leicester LE1 7RH (United Kingdom); Haines, Jackie; Sienkiewicz, Zenon [Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Chilton, Didcot, Oxfordshire OX11 0RQ (United Kingdom); Dubrova, Yuri E., E-mail: yed2@le.ac.uk [Department of Genetics, University of Leicester, Leicester LE1 7RH (United Kingdom)

2015-03-15

Highlights: • The effects of 50 Hz magnetic fields on mutation induction in mice were analyzed. • The frequency of ESTR mutation was established in sperm and blood. • Exposure to 10–300 μT for 2 and 15 h did not result in mutation induction. • Mutagenic effects of 50 Hz magnetic fields are likely to be negligible. - Abstract: The growing human exposure to extremely low frequency (ELF) magnetic fields has raised a considerable concern regarding their genotoxic effects. The aim of this study was to evaluate the in vivo effects of ELF magnetic fields irradiation on mutation induction in the germline and somatic tissues of male mice. Seven week old BALB/c × CBA/Ca F{sub 1} hybrid males were exposed to 10, 100 or 300 μT of 50 Hz magnetic fields for 2 or 15 h. Using single-molecule PCR, the frequency of mutation at the mouse Expanded Simple Tandem Repeat (ESTR) locus Ms6-hm was established in sperm and blood samples of exposed and matched sham-treated males. ESTR mutation frequency was also established in sperm and blood samples taken from male mice exposed to 1 Gy of acute X-rays. The frequency of ESTR mutation in DNA samples extracted from blood of mice exposed to magnetic fields did not significantly differ from that in sham-treated controls. However, there was a marginally significant increase in mutation frequency in sperm but this was not dose-dependent. In contrast, acute exposure X-rays led to significant increases in mutation frequency in sperm and blood of exposed males. The results of our study suggest that, within the range of doses analyzed here, the in vivo mutagenic effects of ELF magnetic fields are likely to be minor if not negligible.

The effects of extremely low frequency magnetic fields on mutation induction in mice

International Nuclear Information System (INIS)

Wilson, James W.; Haines, Jackie; Sienkiewicz, Zenon; Dubrova, Yuri E.

2015-01-01

Highlights: • The effects of 50 Hz magnetic fields on mutation induction in mice were analyzed. • The frequency of ESTR mutation was established in sperm and blood. • Exposure to 10–300 μT for 2 and 15 h did not result in mutation induction. • Mutagenic effects of 50 Hz magnetic fields are likely to be negligible. - Abstract: The growing human exposure to extremely low frequency (ELF) magnetic fields has raised a considerable concern regarding their genotoxic effects. The aim of this study was to evaluate the in vivo effects of ELF magnetic fields irradiation on mutation induction in the germline and somatic tissues of male mice. Seven week old BALB/c × CBA/Ca F 1 hybrid males were exposed to 10, 100 or 300 μT of 50 Hz magnetic fields for 2 or 15 h. Using single-molecule PCR, the frequency of mutation at the mouse Expanded Simple Tandem Repeat (ESTR) locus Ms6-hm was established in sperm and blood samples of exposed and matched sham-treated males. ESTR mutation frequency was also established in sperm and blood samples taken from male mice exposed to 1 Gy of acute X-rays. The frequency of ESTR mutation in DNA samples extracted from blood of mice exposed to magnetic fields did not significantly differ from that in sham-treated controls. However, there was a marginally significant increase in mutation frequency in sperm but this was not dose-dependent. In contrast, acute exposure X-rays led to significant increases in mutation frequency in sperm and blood of exposed males. The results of our study suggest that, within the range of doses analyzed here, the in vivo mutagenic effects of ELF magnetic fields are likely to be minor if not negligible

Properties of pseudo magnetism acting between bodies

Directory of Open Access Journals (Sweden)

Anish Deva

Full Text Available A non-contact force has been found to be always acting between two bodies kept close to each other in different media. The properties of the force are different as compared to other non-contact forces such as gravitation and electrostatics, as was shown in our previous work. The aim of this paper is to find how the force behaves when two objects are brought near each other, one being completely immersed in the medium and the other kept just outside. The magnitude of the force in each medium has been calculated through experiments and then compared with each other. The discrepancies obtained between these magnitudes (10−5 N in water and 10−6 N in engine oil and the varied oscillation patterns (amplitude and frequency obtained from graphs have shown that the force behaves differently with different media. In general, the frequency of the force has been found to be of the order 10−2 Hz. The behaviour has also been found to depend on the nature of the material and shape of the object. This correlation has been ascertained by using a Gauss meter to measure the force acting between two objects and also that of an individual object. The polarity of the force i.e. whether attractive or repulsive, has been found to vary across the length of the objects and graphs have been plotted to demonstrate this property. Keywords: Non-contact force, Medium, Magnetism, Gravitation, Frequency

TUNABLE MAGNETIC AND ELECTRICAL PROPERTIES OF Co-DOPED ZnO FILMS BY VARYING OXYGEN PARTIAL PRESSURE

OpenAIRE

L. G. WANG; H. W. ZHANG; X. L. TANG; Y. X. LI; Z. Y. ZHONG

2011-01-01

High quality Co-doped ZnO films with good reproducibility have been prepared under different oxygen partial pressure by radio-frequency magnetron sputtering. These films were characterized using numerous characterization techniques including X-ray diffraction, electrical transport, and magnetization measurements. The effect of oxygen partial pressure on the structural, magnetic, and electrical properties of Co-doped ZnO films has been systematically studied. It was found that the structural, ...

The decay properties of the trapped magnetic field in HTS bulk superconducting actuator by AC controlled magnetic field

International Nuclear Information System (INIS)

Kim, S.B.; Uwani, Y.; Joo, J.H.; Kawamoto, R.; Jo, Y.S.

2011-01-01

The electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties according to their strong flux pinning force, have been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contract transportation device which moves freely in space. It is certain for our proposed 3-D superconducting actuator to be useful as a transporter used in a clean room where silicon wafers, which do not like mechanical contact and dust, are manufactured. The proposed actuator consists of the trapped HTS bulk as a mover and two-dimensionally arranged electromagnets as a stator. Up to now, the electromagnets consisted with iron core and copper coil were used as a stator, and each electromagnet was individually controlled using DC power supplies. In our previous work, the unstable movement characteristics of HTS bulk were observed under the DC operation, and the AC electromagnets driven with AC controlled current was proposed to solve these problems. In general, the trapped magnetic field in HTS bulk was decayed by a time-varying external magnetic field. Thus, it needs to optimize the shapes of AC electromagnets and operating patterns, the decay properties of the trapped magnetic field in the HTS bulk mover by the AC magnetic field should be cleared. In this paper, the influences of the frequency, the overall operating time, the strength of magnetization field and drive current against the decay of trapped magnetic field were experimentally studied using the fabricated AC electromagnets.

Phase composition and magnetic properties in nanocrystalline permanent magnets based on misch-metal

Science.gov (United States)

Ma, Q.; Wang, J.; Zhang, Z. Y.; Zhang, X. F.; Liu, F.; Liu, Y. L.; Jv, X. M.; Li, Y. F.; Wang, G. F.

2017-09-01

The magnetic properties and phase composition of magnets based on misch-metal (MM) with nominal composition of MM13+xFe84-xB6.5 with x = 0.5, 1, 1.5, 2 and 2.5 using melt-spinning method were investigated. For x = 1.5, it could exhibit best magnetic properties (Hcj = 753.02 kA m-1, (BH)max = 70.77 kJ m-3). X-ray diffraction and energy dispersive spectroscopy show that the multi hard magnetic phase of RE2Fe14B (RE = La, Ce, Pr, Nd) existed in the magnets. The domain wall pinning effect and the exchange coupling interaction between grains are dependent on the abnormal RE-rich phase composition. Optimizing the phase constitution is necessary to improve magnetic properties in MM-Fe-B magnets for utilizing the rare earth resource in a balanced manner.

High frequency write head measurement with the phase detection magnetic force microscope

International Nuclear Information System (INIS)

Abe, M.; Tanaka, Y.

2001-01-01

We demonstrated the measurement of the high frequency (HF) magnetic field of a write head with the phase detection magnetic force microscope. An amplitude-modulated current was applied to the head coil to detect the force gradient induced by the HF magnetic field. Spatial resolution of this method was higher than that of the deflection detection method previously proposed. By the phase detection method, dynamic HF magnetic fields at the poles of the write heads were clearly imaged. HF magnetic field leakage was observed along the P2 pole shape on the air-bearing surface. The frequency dependence of the write head dynamics up to 350 MHz was also investigated. [copyright] 2001 American Institute of Physics

Magnetic properties of ultra-small goethite nanoparticles

International Nuclear Information System (INIS)

Brok, E; Frandsen, C; Madsen, D E; Mørup, S; Jacobsen, H; Birk, J O; Lefmann, K; Bendix, J; Pedersen, K S; Boothroyd, C B; Berhe, A A; Simeoni, G G

2014-01-01

Goethite (α-FeOOH) is a common nanocrystalline antiferromagnetic mineral. However, it is typically difficult to study the properties of isolated single-crystalline goethite nanoparticles, because goethite has a strong tendency to form particles of aggregated nanograins often with low-angle grain boundaries. This nanocrystallinity leads to complex magnetic properties that are dominated by magnetic fluctuations in interacting grains. Here we present a study of the magnetic properties of 5.7 nm particles of goethite by use of magnetization measurements, inelastic neutron scattering and Mössbauer spectroscopy. The ‘ultra-small’ size of these particles (i.e. that the particles consist of one or only a few grains) allows for more direct elucidation of the particles' intrinsic magnetic properties. We find from ac and dc magnetization measurements a significant upturn of the magnetization at very low temperatures most likely due to freezing of spins in canted spin structures. From hysteresis curves we estimate the saturation magnetization from uncompensated magnetic moments to be σ s  = 0.044 A m 2  kg −1 at room temperature. Inelastic neutron scattering measurements show a strong signal from excitations of the uniform mode (q = 0 spin waves) at temperatures of 100–250 K and Mössbauer spectroscopy studies show that the magnetic fluctuations are dominated by ‘classical’ superparamagnetic relaxation at temperatures above ∼170 K. From the temperature dependence of the hyperfine fields and the excitation energy of the uniform mode we estimate a magnetic anisotropy constant of around 1.0 × 10 5  J m −3 . (paper)

Physical properties of elongated magnetic particles: magnetization and friction coefficient anisotropies.

Science.gov (United States)

Vereda, Fernando; de Vicente, Juan; Hidalgo-Alvarez, Roque

2009-06-02

Anisotropy counts: A brief review of the main physical properties of elongated magnetic particles (EMPs) is presented. The most important characteristic of an EMP is the additional contribution of shape anisotropy to the total anisotropy energy of the particle, when compared to spherical magnetic particles. The electron micrograph shows Ni-ferrite microrods fabricated by the authors.We present an overview of the main physical properties of elongated magnetic particles (EMPs), including some of their more relevant properties in suspension. When compared to a spherical magnetic particle, the most important characteristic of an EMP is an additional contribution of shape anisotropy to the total anisotropy energy of the particle. Increasing aspect ratios also lead to an increase in both the critical single-domain size of a magnetic particle and its resistance to thermally activated spontaneous reversal of the magnetization. For single-domain EMPs, magnetization reversal occurs primarily by one of two modes, coherent rotation or curling, the latter being facilitated by larger aspect ratios. When EMPs are used to prepare colloidal suspensions, other physical properties come into play, such as their anisotropic friction coefficient and the consequent enhanced torque they experience in a shear flow, their tendency to align in the direction of an external field, to form less dense sediments and to entangle into more intricate aggregates. From a more practical point of view, EMPs are discussed in connection with two interesting types of magnetic colloids: magnetorheological fluids and suspensions for magnetic hyperthermia. Advances reported in the literature regarding the use of EMPs in these two systems are included. In the final section, we present a summary of the most relevant methods documented in the literature for the fabrication of EMPs, together with a list of the most common ferromagnetic materials that have been synthesized in the form of EMPs.

Research of the Electron Cyclotron Emission with Vortex Property excited by high power high frequency Gyrotron

Science.gov (United States)

Goto, Yuki; Kubo, Shin; Tsujimura, Tohru; Takubo, Hidenori

2017-10-01

Recently, it has been shown that the radiation from a single electron in cyclotron motion has vortex property. Although the cyclotron emission exists universally in nature, the vortex property has not been featured because this property is normally cancelled out due to the randomness in gyro-phase of electrons and the development of detection of the vortex property has not been well motivated. In this research, we are developing a method to generate the vortex radiation from electrons in cyclotron motion with controlled gyro-phase. Electron that rotates around the uniform static magnetic field is accelerated by right-hand circular polarized (RHCP) radiation resonantly when the cyclotron frequency coincides with the applied RHCP radiation frequency. A large number of electrons can be coherently accelerated in gyro-phase by a RHCP high power radiation so that these electrons can radiate coherent emission with vortex feature. We will show that vortex radiation created by purely rotating electrons for the first time.

Magnetic properties of rare-earth intermetallics

International Nuclear Information System (INIS)

Kirchmayr, H.

1978-01-01

A review is given of the concepts at present used to explain the magnetic properties of rare-earth intermetallics which have been the subject of numerous investigations in recent years. Rare-earth intermetallics with the formula Rsub(a)Bsub(b) are divided according to the magnetic moment of the B atom(s). If there is no magnetic moment present at the B-site, the exchange is only between the magnetic moments at the R-sites, which can only be of indirect character. One possible model is still the RKKY model, although it usually gives in practice only a qualitative description of the magnetic properties. Typical R-B compounds with the B-moment equal to zero are (for instance) the RA1 2 compounds, and related compounds such as the RZn and RCd compounds as well as compounds of the general formula RB 2 (B = Ni, Os, Ir, Pd, Ru or Rh). Of all intermetallics with nonzero B-moment, the R-3d intermetallics are the most important. These intermetallics can be formed with Mn, Fe, Co and Ni. In these systems there exist in principle three interactions, namely between the R-R, R-3d and 3d-3d atoms. The most important is usually the latter interaction. After a short discussion of the crystal structures which occur with R-3d intermetallics, the basic magnetic properties of R-3d intermetallics are presented. These properties are discussed with respect to the formation of a magnetic moment at the 3d site in the framework of present band theories. Special emphasis is given to a discussion of the localized or itinerant character of 3d electrons. (author)

Frequency dependent magneto-transport in charge transfer Co(II) complex

Energy Technology Data Exchange (ETDEWEB)

Shaw, Bikash Kumar; Saha, Shyamal K., E-mail: cnssks@iacs.res.in

2014-09-01

A charge transfer chelated system containing ferromagnetic metal centers is the ideal system to investigate the magneto-transport and magneto-dielectric effects due to the presence of both electronic as well as magnetic properties and their coupling. Magneto-transport properties in materials are usually studied through dc charge transport under magnetic field. As frequency dependent conductivity is an essential tool to understand the nature of carrier wave, its spatial extension and their mutual interaction, in the present work, we have investigated frequency dependent magneto-transport along with magnetization behavior in [Co{sub 2}(II)-(5-(4-PhMe)-1,3,4-oxadiazole-H{sup +}-2-thiolate){sub 5}](OAc){sub 4} metal complex to elucidate the nature of above quantities and their response under magnetic field in the transport property. We have used the existing model for ac conduction incorporating the field dependence to explain the frequency dependent magneto-transport. It is seen that the frequency dependent magneto-transport could be well explained using the existing model for ac conduction. -Highlights: • Chelated Co(II) complex is synthesized for magneto-transport applications. • Frequency dependent magneto-transport and magnetization behavior are studied. • Nature of carrier wave, its spatial extension is investigated under magnetic field. • Existing model for ac conduction is used with magnetic field dependence.

Rietveld refinement, dielectric and magnetic properties of Nb modified Bi0.80Ba0.20FeO3 ceramic

Science.gov (United States)

Jangra, Sandhaya; Sanghi, Sujata; Agarwal, Ashish; Rangi, Manisha

2018-05-01

Bi0.80Ba0.20Fe0.95Nb0.05O3 ceramic has been prepared via conventional solid state reaction method. Structure analysis was carried out by X-ray diffraction (XRD) technique at room temperature. XRD pattern confirmed the crystalline nature of prepared sample. Rietveld analysis used for further structural investigations and confirmed the existence of rhombohedral symmetry (R3c space group). The dielectric response shows dispersion at lower frequency range and becomes frequency independent at high frequency. The approximation of conduction mechanism is determined by the temperature dependent behavior of frequency exponent `s'. Fitting results suggests the applicability of small polaron conduction mechanism at lower temperatures and CBH model at higher temperature. Room temperature magnetic measurements give the evidence of significant enhancement in magnetic properties with remanent magnetization (Mr = 0.1218 emu/g) and coercive field (Hc = 3.5342 kOe).

[Effect of extremely low frequency magnetic field on glutathione in rat muscles].

Science.gov (United States)

Ciejka, Elzbieta; Jakubowska, Ewa; Zelechowska, Paulina; Huk-Kolega, Halina; Kowalczyk, Agata; Goraca, Anna

2014-01-01

Free radicals (FR) are atoms, molecules or their fragments. Their excess leads to the development of oxidizing stress, the cause of many neoplastic, neurodegenerative and inflammatory diseases, and aging of the organism. Industrial pollution, tobacco smoke, ionizing radiation, ultrasound and magnetic field are the major FR exogenous sources. The low frequency magnetic field is still more commonly applied in the physical therapy. The aim of the presented study was to evaluate the effect of extremely low frequency magnetic field used in the magnetotherapy on the level of total glutathione, oxidized and reduced, and the redox state of the skeletal muscle cells, depending on the duration of exposure to magnetic field. The male rats, weight of 280-300 g, were randomly devided into 3 experimental groups: controls (group I) and treatment groups exposed to extremely low frequency magnetic field (ELF-MF) (group II exposed to 40 Hz, 7 mT for 0.5 h/day for 14 days and group III exposed to 40 Hz, 7 mT for 1 h/day for 14 days). Control rats were kept in a separate room not exposed to extremely low frequency magnetic field. Immediately after the last exposure, part of muscles was taken under pentobarbital anesthesia. Total glutathione, oxidized and reduced, and the redox state in the muscle tissue of animals were determined after exposure to magnetic fields. Exposure to low magnetic field: 40 Hz, 7 mT for 30 min/day and 60 min/day for 2 weeks significantly increased the total glutathione levels in the skeletal muscle compared to the control group (p magnetic therapy plays an important role in the development of adaptive mechanisms responsible for maintaining the oxidation-reduction balance in the body and depends on exposure duration.

Influence of magnetizing and filtering frequencies on Barkhausen noise response

Czech Academy of Sciences Publication Activity Database

Stupakov, Oleksandr; Melikhov, Y.

2014-01-01

Roč. 50, č. 4 (2014), s. 6100104 ISSN 0018-9464 R&D Projects: GA ČR GA13-18993S Institutional support: RVO:68378271 Keywords : Barkhausen effect * filtering * frequency measurement * magnetic field measurement Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.386, year: 2014

Magnetic field dependent atomic tunneling in non-magnetic glasses

International Nuclear Information System (INIS)

Ludwig, S.; Enss, C.; Hunklinger, S.

2003-01-01

The low-temperature properties of insulating glasses are governed by atomic tunneling systems (TSs). Recently, strong magnetic field effects in the dielectric susceptibility have been discovered in glasses at audio frequencies at very low temperatures. Moreover, it has been found that the amplitude of two-pulse polarization echoes generated in non-magnetic multi-component glasses at radio frequencies and at very low temperatures shows a surprising non-monotonic magnetic field dependence. The magnitude of the latter effect indicates that virtually all TSs are affected by the magnetic field, not only a small subset of systems. We have studied the variation of the magnetic field dependence of the echo amplitude as a function of the delay time between the two excitation pulses and at different frequencies. Our results indicate that the evolution of the phase of resonant TSs is changed by the magnetic field

Magnetic field dependent atomic tunneling in non-magnetic glasses

Science.gov (United States)

Ludwig, S.; Enss, C.; Hunklinger, S.

2003-05-01

The low-temperature properties of insulating glasses are governed by atomic tunneling systems (TSs). Recently, strong magnetic field effects in the dielectric susceptibility have been discovered in glasses at audio frequencies at very low temperatures. Moreover, it has been found that the amplitude of two-pulse polarization echoes generated in non-magnetic multi-component glasses at radio frequencies and at very low temperatures shows a surprising non-monotonic magnetic field dependence. The magnitude of the latter effect indicates that virtually all TSs are affected by the magnetic field, not only a small subset of systems. We have studied the variation of the magnetic field dependence of the echo amplitude as a function of the delay time between the two excitation pulses and at different frequencies. Our results indicate that the evolution of the phase of resonant TSs is changed by the magnetic field.

Analytical solution for the electrical properties of a radio-frequency quadrupole (RFQ) with simple vanes

International Nuclear Information System (INIS)

Lancaster, H.

1982-01-01

Although the SUPERFISH program is used for calculating the design parameters of an RFQ structure with complex vanes, an analytical solution for electrical properties of an RFQ with simple vanes provides insight into the parametric behavior of these more complicated resonators. The fields in an inclined plane wave guide with proper boundary conditions match those in one quadrant of an RFQ. The principle of duality is used to exploit the solutions to a radial transmission line in solving the field equations. Calculated are the frequency equation, frequency sensitivity factors, electric field, magnetic field, stored energy (U), power dissipation, and quality factor

Vibrational Properties of High- Superconductors Levitated Above a Bipolar Permanent Magnetic Guideway

Science.gov (United States)

Liu, Lu; Wang, Jiasu

2014-05-01

A bipolar permanent magnetic guideway (PMG) has a unique magnetic field distribution profile which may introduce a better levitation performance and stability to the high- superconducting (HTS) maglev system. The dynamic vibration properties of multiple YBCO bulks arranged into different arrays positioned above a bipolar PMG and free to levitate were investigated. The acceleration and resonance frequencies were experimentally measured, and the stiffness and damping coefficients were evaluated for dynamic stability. Results indicate that the levitation stiffness is closely related to the field-cooling-height and sample positioning. The damping ratio was found to be low and nonlinear for the Halbach bipolar HTS-PMG system.

The magnetic properties of the hollow cylindrical ideal remanence magnet

DEFF Research Database (Denmark)

Bjørk, Rasmus

2016-01-01

We consider the magnetic properties of the hollow cylindrical ideal remanence magnet. This magnet is the cylindrical permanent magnet that generates a uniform field in the cylinder bore, using the least amount of magnetic energy to do so. The remanence distribution of this magnet is derived...... and the generated field is compared to that of a Halbach cylinder of equal dimensions. The ideal remanence magnet is shown in most cases to generate a significantly lower field than the equivalent Halbach cylinder, although the field is generated with higher efficiency. The most efficient Halbach cylinder is shown...... to generate a field exactly twice as large as the equivalent ideal remanence magnet....

Influence of electrical sheet width on dynamic magnetic properties

CERN Document Server

Chevalier, T; Cornut, B

2000-01-01

Effects of the width of electrical steel sheets on dynamic magnetic properties are investigated by solving diffusion equation on the cross-section of the sheet. Linear and non-linear cases are studied, and are compared with measurement on Epstein frame. For the first one an analytical solution is found, while for the second, a 2D finite element simulation is achieved. The influence of width is highlighted for a width thickness ratio lower than 10. It is shown that the behaviour modification in such cases is conditioned by the excitation signal waveform, amplitude and also frequency.

Study of electric, magnetic properties and improvements in ME effects of NMFO + BZT particulate composites

Energy Technology Data Exchange (ETDEWEB)

Chavan, Pradeep [Department of Physics, Karnatak University, Dharwad 580003, Karnataka (India); Naik, L.R., E-mail: naik_40@rediffmail.com [Department of Physics, Karnatak University, Dharwad 580003, Karnataka (India); Kotnala, R.K. [National Physical Laboratory, K. S. Krishnan Marg, Pusa, New Delhi 110012 (India)

2017-07-01

ME composite materials with the general formula (x)Ni{sub 0.9}Mg{sub 0.1}Fe{sub 2}O{sub 4} + (1 − x)BaZr{sub 0.2}Ti{sub 0.8}O{sub 3} (x = 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized by solid state reaction method. X-ray diffraction (XRD) study reveals the coexistence of piezomagnetic and piezoelectric phases without interacting with each other. The cubic spinel structure of Ni{sub 0.9}Mg{sub 0.1}Fe{sub 2}O{sub 4} (NMFO) piezomagnetic phase and tetragonal perovskite structure of BaZr{sub 0.2}Ti{sub 0.8}O{sub 3} (BZT) piezoelectric phase for synthesized composites were confirmed by XRD measurements. The lattice constant of piezomagnetic and piezoelectric phases increases with increase in composition of the substituent. The dielectric constant and dielectric loss tangent of the composites measured as a function of frequency in the range 10 Hz–1 MHz at room temperature are found to decrease rapidly in low frequency regime and remain constant in high frequency regime shows the dielectric dispersion behavior. The magnetic properties of the composites have been studied using M-H hysteresis loops to see the response of the magnetic field on the NMFO phase in the composites. The saturation magnetization increases with increase in the mole% of piezomagnetic phase in the composites. The ME voltage coefficient measured as a function of the applied DC magnetic field; shows maximum value (8.622 mV cm{sup −1} Oe) for (50%)NMFO + (50%)BZT bulk composites. The addition of NMFO and BZT enhances the ME properties of the composites.

Impact of tillage on soil magnetic properties: results over thirty years different cultivation plots

Science.gov (United States)

Thiesson, Julien; Kessouri, Pauline; Buvat, Solène; Tabbagh, Alain

2010-05-01

Cultivation may favour or not different processes such as air and water circulation, organic matter and fertilizers supplies..., consequently it can a priori induce significant changes in local oxido-reduction conditions which determine the magnetic properties of soils: the soil magnetic signal. If laboratory measurements on soil samples can be slow and irreversible, it is also possible to perform in field measurements by using electromagnetic devices that allow quick and easy measuring over the relevant soil thicknesses both in time (TDEM) and frequency (FDEM) domains. The object of this study is to compare the variation of two magnetic properties (magnetic susceptibility, measured by FDEM apparatus and magnetic viscosity measured by TDEM apparatus) and there ratio along depth for three different types of tillage (no tillage, ploughing, and simplified tillage). An experimental plot of 80 m by 50 m total area, on which these three types of tillage have been conducted for more than thirty years, was surveyed. The plot is divided in five strips of 16 m by 50 m area, each of which being cultivated by one type of tillage only. Each strip is divided in two parts, one half with nitrogen-fixing crop during intercultivation winter period and the other half with bare soil during this period. On each part, the variation along depth of both magnetic properties was assessed by surveying with different devices corresponding to three different volumes of investigation. For the magnetic susceptibility measurements the devices used were the MS2 of Bartington Ltd with the MS2D probe and the CS60 a slingram prototype use in VCP and HCP configurations. For the magnetic viscosity, the devices used were the DECCO from Littlemore ltd. And the VC100, a slingram prototype, used at two heights. Eleven values of the two magnetic properties have been recorded using each device and their medians calculated. The data were inverted to define the median magnetic profiles of each half

Structural, magnetic and electrical properties of Zr-substitued NiZnCo ferrite nanopowders

Energy Technology Data Exchange (ETDEWEB)

Li, Le-Zhong, E-mail: lezhongli@cuit.edu.cn; Zhong, Xiao-Xi; Wang, Rui; Tu, Xiao-Qiang

2017-08-01

Highlights: • The static magnetic properties of NiZnCoZr ferrite nanopowders have been investigated. • The dielectric constant increases with the increase of Zr substitution. • The relaxation peak of tan δ ∼ T curves is observed for x ≥ 0.10. • Electrical transport behavior is found to follow the impurity semiconductor. • The dc resistivity increases at transition temperature with Zr substitution. - Abstract: Zr-substituted NiZnCo ferrite nanopowders, Ni{sub 0.4−x}Zn{sub 0.5}Zr{sub x}Co{sub 0.1}Fe{sub 2.0}O{sub 4} (0 ≤ x ≤ 0.20), were synthesized by the sol-gel auto-combustion method. The effects of Zr substitution on the structural, magnetic and electrical properties have been investigated. The DTA and TG results indicate that there are three steps of combustion process. The X-ray diffraction patterns show that the lattice parameter and the average crystallite size increase with the increase of Zr substitution. The saturation magnetization increases with the increase of Zr substitution when x ≤ 0.05, and then decreases when x > 0.05. Meanwhile, the coercivity initially decreases with the increase of Zr substitution when x ≤ 0.05, and then increases when x > 0.05. The polarization behavior for all the samples in the test frequency range from100 Hz to10 MHz obeys the charge polarization mechanism, which happens since the frequency of the hopping of electron exchange between Fe{sup 2+} and Fe{sup 3+} ions are far from the frequency of alternating-current field. And the dielectric constant increases with the increase of Zr substitution. The relaxation peak of the frequency dependence of dielectric loss is observed for x ≥ 0.10, which is due to the frequency of charge hopping between the Fe{sup 2+} and Fe{sup 3+} exactly matches with the frequency of the external applied field. Electrical transport behavior of the ferrite nanopowders is found to follow the impurity semiconductor, and the effect of Zr substitution on the temperature dependence

Water-dispersible sugar-coated iron oxide nanoparticles. An evaluation of their relaxometric and magnetic hyperthermia properties.

Science.gov (United States)

Lartigue, Lenaic; Innocenti, Claudia; Kalaivani, Thangavel; Awwad, Azzam; Sanchez Duque, Maria del Mar; Guari, Yannick; Larionova, Joulia; Guérin, Christian; Montero, Jean-Louis Georges; Barragan-Montero, Véronique; Arosio, Paolo; Lascialfari, Alessandro; Gatteschi, Dante; Sangregorio, Claudio

2011-07-13

Synthesis of functionalized magnetic nanoparticles (NPs) for biomedical applications represents a current challenge. In this paper we present the synthesis and characterization of water-dispersible sugar-coated iron oxide NPs specifically designed as magnetic fluid hyperthermia heat mediators and negative contrast agents for magnetic resonance imaging. In particular, the influence of the inorganic core size was investigated. To this end, iron oxide NPs with average size in the range of 4-35 nm were prepared by thermal decomposition of molecular precursors and then coated with organic ligands bearing a phosphonate group on one side and rhamnose, mannose, or ribose moieties on the other side. In this way a strong anchorage of the organic ligand on the inorganic surface was simply realized by ligand exchange, due to covalent bonding between the Fe(3+) atom and the phosphonate group. These synthesized nanoobjects can be fully dispersed in water forming colloids that are stable over very long periods. Mannose, ribose, and rhamnose were chosen to test the versatility of the method and also because these carbohydrates, in particular rhamnose, which is a substrate of skin lectin, confer targeting properties to the nanosystems. The magnetic, hyperthermal, and relaxometric properties of all the synthesized samples were investigated. Iron oxide NPs of ca. 16-18 nm were found to represent an efficient bifunctional targeting system for theranostic applications, as they have very good transverse relaxivity (three times larger than the best currently available commercial products) and large heat release upon application of radio frequency (RF) electromagnetic radiation with amplitude and frequency close to the human tolerance limit. The results have been rationalized on the basis of the magnetic properties of the investigated samples.

Effects of Zr alloying on the microstructure and magnetic properties of Alnico permanent magnets

Science.gov (United States)

Rehman, Sajjad Ur; Ahmad, Zubair; Haq, A. ul; Akhtar, Saleem

2017-11-01

Alnico-8 permanent magnets were produced through casting and subsequent thermal treatment process. Magnetic alloy of nominal composition 32.5 Fe-7.5 Al-1.0 Nb-35.0 Co-4.0 Cu-14.0 Ni-6.0 Ti were prepared by arc melting and casting technique. The Zr was added to 32.5 Fe-7.5 Al-1.0 Nb-35.0 Co-4.0 Cu-14.0 Ni-6.0 Ti alloy ranging from 0.3 to 0.9 wt%. The magnets were developed by employing two different heat treatment cycles known as conventional treatment and thermo-magnetic annealing treatment. The samples were characterized by X-ray diffraction method, Scanning electron microscope and magnetometer by plotting magnetic hysteresis demagnetization curves. The results indicate that magnetic properties are strongly depended upon alloy chemistry and process. The 0.6 wt% Zr added alloys yielded the best magnetic properties among the studied alloys. The magnetic properties obtained through conventional heat treatment are Hc = 1.35 kOe, Br = 5.2 kG and (BH)max = 2 MGOe. These magnetic properties were enhanced to Hc = 1.64 kOe, Br = 6.3 kG and (BH)max = 3.7 MGOe by thermo-magnetic annealing treatment.

Structural, dielectric and magnetic properties of cobalt ferrite prepared using auto combustion and ceramic route

International Nuclear Information System (INIS)

Murugesan, C.; Perumal, M.; Chandrasekaran, G.

2014-01-01

Cobalt ferrite is synthesized by using low temperature auto combustion and high temperature ceramic methods. The prepared samples have values of lattice constant equal to 8.40 Å and 8.38 Å for auto combustion and ceramic methods respectively. The FTIR spectrum of samples of the auto combustion method shows a high frequency vibrational band at 580 cm −1 assigned to tetrahedral site and a low frequency vibrational band at 409 cm −1 assigned to octahedral site which are shifted to 590 cm −1 and 412 cm −1 for the ceramic method sample. SEM micrographs of samples show a substantial difference in surface morphology and size of the grains between the two methods. The frequency dependent dielectric constant and ac conductivity of the samples measured from 1 Hz to 2 MHz at room temperature are reported. The room temperature magnetic hysteresis parameters of the samples are measured using VSM. The measured values of saturation magnetization, coercivity and remanent magnetization are 42 emu/g, 1553 Oe, 18.5 emu/g for the auto combustion method, 66.7 emu/g, 379.6 Oe, and 17.3 emu/g for the ceramic method, respectively. The difference in preparation methods and size of the grains causes interesting changes in electrical and magnetic properties

Measurements of intermediate-frequency electric and magnetic fields in households

NARCIS (Netherlands)

Aerts, Sam; Calderon, Carolina; Valič, Blaž; Maslanyj, Myron; Addison, Darren; Mee, Terry; Goiceanu, Cristian; Verloock, Leen; Van den Bossche, Matthias; Gajšek, Peter; Vermeulen, Roel; Röösli, Martin; Cardis, Elisabeth; Martens, Luc; Joseph, Wout

Historically, assessment of human exposure to electric and magnetic fields has focused on the extremely-low-frequency (ELF) and radiofrequency (RF) ranges. However, research on the typically emitted fields in the intermediate-frequency (IF) range (300Hz to 1MHz) as well as potential effects of IF

Conventional magnets. Pt. 2

International Nuclear Information System (INIS)

Marks, N.

1994-01-01

This second paper covers the wide range of techniques associated with a.c. and pulsed magnets and associated power supplies. The necessary changes in magnet design to minimise eddy losses in low frequency magnets are first considered and this leads to a broader discussion of the different types of steel used in magnet yokes. Inductance is then considered and the traditional power supply circuit used for a.c. magnets is described. The paper then presents a simple description of the higher-frequency pulsed magnets and supply circuits used for injection and extraction and contrasts a number of different design concepts for both kicker and septum systems. In conclusion, the relevant properties of high-frequency magnetic materials are briefly reviewed. (orig.)

Magnetic properties of the magnetic hybrid membranes based on various polymer matrices and inorganic fillers

International Nuclear Information System (INIS)

Rybak, Aleksandra; Kaszuwara, Waldemar

2015-01-01

Magnetic hybrid membranes based on ethylcellulose (EC), poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and various magnetic praseodymium and neodymium powder microparticles as fillers were obtained. Permeability, diffusion and sorption coefficients of O 2 , N 2 and synthetic air components were estimated for homogeneous and heterogeneous membranes using the Time Lag method based on constant pressure permeation technique. The microstructure studies and the phase analysis of magnetic membranes were also performed using SEM and XRD. The influence of magnetic parameters, like coercivity, remanence and saturation magnetization of created membranes on the gas transport properties was studied. The results showed that their coercivity depended on composition and microstructure of the magnetic powder. On the other hand, remanence and saturation magnetization increased with the increase of the powder addition in the membrane. It was found that the magnetic membrane's gas transport properties were improved with the increase of membrane's remanence, saturation magnetization and magnetic particle filling. The decrease in powder particle size and associated increase of the membrane's coercivity also positively influenced the gas transport and separation properties of investigated membranes. It was observed that the magnetic ethylcellulose and poly(2,6-dimethyl-1,4-phenylene oxide) membranes had higher gas permeability, while their permselectivity and solubility coefficient values were rather maintained or slightly increased. The results also showed that the magnetic powder content enhanced significantly gas diffusivity in EC and PPO membranes. It was also analyzed the dependence of the drift coefficient w on the magnetic parameters of investigated membranes. The correlation between the membrane selectivity, permeability and magnetic properties with their XRD characteristics was stated. - Highlights: • Membrane's production consisting of EC or PPO polymers and

Magnetic properties of the magnetic hybrid membranes based on various polymer matrices and inorganic fillers

Energy Technology Data Exchange (ETDEWEB)

Rybak, Aleksandra, E-mail: Aleksandra.Rybak@polsl.pl [Department of Physical Chemistry and Technology of Polymers, Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland); Kaszuwara, Waldemar [Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warszawa (Poland)

2015-11-05

Magnetic hybrid membranes based on ethylcellulose (EC), poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and various magnetic praseodymium and neodymium powder microparticles as fillers were obtained. Permeability, diffusion and sorption coefficients of O{sub 2}, N{sub 2} and synthetic air components were estimated for homogeneous and heterogeneous membranes using the Time Lag method based on constant pressure permeation technique. The microstructure studies and the phase analysis of magnetic membranes were also performed using SEM and XRD. The influence of magnetic parameters, like coercivity, remanence and saturation magnetization of created membranes on the gas transport properties was studied. The results showed that their coercivity depended on composition and microstructure of the magnetic powder. On the other hand, remanence and saturation magnetization increased with the increase of the powder addition in the membrane. It was found that the magnetic membrane's gas transport properties were improved with the increase of membrane's remanence, saturation magnetization and magnetic particle filling. The decrease in powder particle size and associated increase of the membrane's coercivity also positively influenced the gas transport and separation properties of investigated membranes. It was observed that the magnetic ethylcellulose and poly(2,6-dimethyl-1,4-phenylene oxide) membranes had higher gas permeability, while their permselectivity and solubility coefficient values were rather maintained or slightly increased. The results also showed that the magnetic powder content enhanced significantly gas diffusivity in EC and PPO membranes. It was also analyzed the dependence of the drift coefficient w on the magnetic parameters of investigated membranes. The correlation between the membrane selectivity, permeability and magnetic properties with their XRD characteristics was stated. - Highlights: • Membrane's production consisting of EC or PPO

The microwave absorbing properties of ZnO/Fe3O4/paraffin composites in low frequency band

Science.gov (United States)

Yin, Pengfei; Deng, Yu; Zhang, Limin; Huang, Juan; Li, Huayao; Li, Youhongyu; Qi, Yali; Tao, Yu

2018-02-01

ZnO/Fe3O4/paraffin composites with good microwave absorption performance in low frequency band were prepared by physical blending technology. The morphology, phase structures, frequency-dependent electromagnetic and microwave absorbing properties of the composites were investigated. The results showed that the addition content of ZnO can adjust the microwave absorbing properties i.e. the position, intensity, and absorption bandwidth of composites, and the synergetic consequence of dielectric loss and magnetic loss is the main microwave absorption mechanism of the composites. The bandwidths with RL below -10 dB over different frequency ranges were obtained in the low frequency range of 0.5 ˜ 3 GHz at a thickness of 5 mm, e.g. 0.93 GHz from 1.59 to 2.52 GHz and 0.85 GHz from 1.26 to 2.11 GHz corresponding to the mass ratios of ZnO and Fe3O4 are 1:2 and 1:4, respectively. Thus, such absorbers can be applied as effective microwave absorbers in low frequency range of 0.5 ˜ 3 GHz.

Frequency dependence of p-mode frequency shifts induced by magnetic activity in Kepler solar-like stars

Science.gov (United States)

Salabert, D.; Régulo, C.; Pérez Hernández, F.; García, R. A.

2018-04-01

The variations of the frequencies of the low-degree acoustic oscillations in the Sun induced by magnetic activity show a dependence on radial order. The frequency shifts are observed to increase towards higher-order modes to reach a maximum of about 0.8 μHz over the 11-yr solar cycle. A comparable frequency dependence is also measured in two other main sequence solar-like stars, the F-star HD 49933, and the young 1 Gyr-old solar analog KIC 10644253, although with different amplitudes of the shifts of about 2 μHz and 0.5 μHz, respectively. Our objective here is to extend this analysis to stars with different masses, metallicities, and evolutionary stages. From an initial set of 87 Kepler solar-like oscillating stars with known individual p-mode frequencies, we identify five stars showing frequency shifts that can be considered reliable using selection criteria based on Monte Carlo simulations and on the photospheric magnetic activity proxy Sph. The frequency dependence of the frequency shifts of four of these stars could be measured for the l = 0 and l = 1 modes individually. Given the quality of the data, the results could indicate that a physical source of perturbation different from that in the Sun is dominating in this sample of solar-like stars.

Frequency characterization of thin soft magnetic material layers used in spiral inductors

International Nuclear Information System (INIS)

Kriga, Adoum; Allassem, Désiré; Soultan, Malloum; Chatelon, Jean-Pierre; Siblini, Ali; Allard, Bruno; Rousseau, Jean Jacques

2012-01-01

The paper details the characterization of thin magnetic materials layers, particularly soft materials, with respect to their behaviour in frequency (from 10 MHz to 1 GHz). The proposed method is suitable for any soft but insulating magnetic material; Yttrium Iron Garnet (YIG) is used as an example. The principle is based on a comparison between simulations for different values of the permeability and measurement values versus frequency of planar inductor structures; an experimental validation is proposed as well. Thin magnetic material is first deposited on an alumina substrate using RF sputtering technique; a planar spiral winding of copper is then deposited on the magnetic material by the same technique. The effective permeability versus frequency is obtained by comparing two samples of spiral windings with and without magnetic material. Network analyser measurements on samples of various geometrical dimensions and of different thicknesses are necessary to determine the effective magnetic permeability; we have obtained a relative effective permeability of about 30 for seven turns spiral inductor of a 17 μm YIG film. - Highlights: ► A simple and original method is presented for the characterization of soft magnetic layer. ► This is a non-destructive method based on standard equipment. ► The principle is based on a comparison between simulations and measurement. ► An experimental validation is proposed as well.

Magnetic losses of commercial REBCO coated conductors in the low frequency range

Science.gov (United States)

De Marzi, G.; Iannone, G.; Gambardella, U.

2018-05-01

We have investigated the frequency dependence of the magnetic losses of different 2 G commercial REBCO coated-conductor tapes in the low frequency range ∼1–10 mHz of applied magnetic field at 5 and 77 K. We explored high field range, well above the penetration field, with fields applied perpendicularly to the flat surface. We found that the in-field hysteresis losses increase with increasing frequencies in all the investigated high-temperature superconductor (HTS) tapes, following a power-law dependence. An electromagnetic 2D finite element method model, based on H-formulation, has also been implemented, in which the frequency dependence of the hysteretic loss is computed taking into account the measured power-law E(J) characteristic for the electric field, and the experimental J c(B). Experimental and numerical findings are in very good agreement, so an extrapolation to higher ramp rate values is possible, thus providing a useful basis for the assessment of the hysteresis losses in fusion and accelerator HTS magnets.

Magnetization Switching of a Co /Pt Multilayered Perpendicular Nanomagnet Assisted by a Microwave Field with Time-Varying Frequency

Science.gov (United States)

Suto, Hirofumi; Kanao, Taro; Nagasawa, Tazumi; Mizushima, Koichi; Sato, Rie

2018-05-01

Microwave-assisted magnetization switching (MAS) is attracting attention as a method for reversing nanomagnets with a high magnetic anisotropy by using a small-amplitude magnetic field. We experimentally study MAS of a perpendicularly magnetized nanomagnet by applying a microwave magnetic field with a time-varying frequency. Because the microwave field frequency can follow the nonlinear decrease of the resonance frequency, larger magnetization excitation than that in a constant-frequency microwave field is induced, which enhances the MAS effect. The switching field decreases almost linearly as the start value of the time-varying microwave field frequency increases, and it becomes smaller than the minimum switching field in a constant-frequency microwave field. To obtain this enhancement of the MAS effect, the end value of the time-varying microwave field frequency needs to be almost the same as or lower than the critical frequency for MAS in a constant-frequency microwave field. In addition, the frequency change typically needs to take 1 ns or longer to make the rate of change slow enough for the magnetization to follow the frequency change. This switching behavior is qualitatively explained by the theory based on the macrospin model.

Study of the polymer permanent magnets properties - rare earths

International Nuclear Information System (INIS)

Takiishi, H.; Benini, H.R.; Lima, L.F.C.P.; Faria, R.N.

1996-01-01

An alternative method for permanent magnet production without the sintering step is polymer bonded magnets. In this work magnets were prepared from magnetic Sm Co 5 or Nd 15 Fe 77 B 8 alloys bonded with 10% wt of resin. For the Nd 15 Fe 77 B 8 alloy the hydrogenation - decomposition - desorption - recombination (HDDR) process have been employed in the preparation of the magnets. Results from the magnetic properties showed that no milling is necessary for the production of polymer bonded Nd-Fe-B magnets. The magnets showed good magnetic properties. (author)

Optimization on microwave absorbing properties of carbon nanotubes and magnetic oxide composite materials

Science.gov (United States)

Mingdong, Chen; Huangzhong, Yu; Xiaohua, Jie; Yigang, Lu

2018-03-01

Based on the physical principle of interaction between electromagnetic field and the electromagnetic medium, the relationship between microwave absorbing coefficient (MAC) and the electromagnetic parameters of materials was established. With the composite materials of nickel ferrite (NiFe2O4), carbon nanotubes (CNTs) and paraffin as an example, optimization on absorbing properties of CNTs/magnetic oxide composite materials was studied at the frequency range of 2-18 GHz, and a conclusion is drawn that the MAC is the biggest at the same frequency, when the CNTs is 10 wt% in the composite materials. Through study on the relationship between complex permeability and MAC, another interesting conclusion is drawn that MAC is obviously affected by the real part of complex permeability, and increasing real part of complex permeability is beneficial for improving absorbing properties. The conclusion of this paper can provide a useful reference for the optimization research on the microwave absorbing properties of CNTs/ferrite composite materials.

Tunable dynamic response of magnetic gels: Impact of structural properties and magnetic fields

Science.gov (United States)

Tarama, Mitsusuke; Cremer, Peet; Borin, Dmitry Y.; Odenbach, Stefan; Löwen, Hartmut; Menzel, Andreas M.

2014-10-01

Ferrogels and magnetic elastomers feature mechanical properties that can be reversibly tuned from outside through magnetic fields. Here we concentrate on the question of how their dynamic response can be adjusted. The influence of three factors on the dynamic behavior is demonstrated using appropriate minimal models: first, the orientational memory imprinted into one class of the materials during their synthesis; second, the structural arrangement of the magnetic particles in the materials; and third, the strength of an external magnetic field. To illustrate the latter point, structural data are extracted from a real experimental sample and analyzed. Understanding how internal structural properties and external influences impact the dominant dynamical properties helps to design materials that optimize the requested behavior.

Transparency of Magnetized Plasma at Cyclotron Frequency

International Nuclear Information System (INIS)

G. Shvets; J.S. Wurtele

2002-03-01

Electromagnetic radiation is strongly absorbed by a magnetized plasma if the radiation frequency equals the cyclotron frequency of plasma electrons. It is demonstrated that absorption can be completely canceled in the presence of a magnetostatic field of an undulator or a second radiation beam, resulting in plasma transparency at the cyclotron frequency. This effect is reminiscent of the electromagnetically induced transparency (EIT) of the three-level atomic systems, except that it occurs in a completely classical plasma. Unlike the atomic systems, where all the excited levels required for EIT exist in each atom, this classical EIT requires the excitation of the nonlocal plasma oscillation. The complexity of the plasma system results in an index of refraction at the cyclotron frequency that differs from unity. Lagrangian description was used to elucidate the physics and enable numerical simulation of the plasma transparency and control of group and phase velocity. This control naturally leads to applications for electromagnetic pulse compression in the plasma and electron/ion acceleration

Magnetic properties of cyclically deformed austenite

Energy Technology Data Exchange (ETDEWEB)

Das, Arpan, E-mail: dasarpan1@yahoo.co.in

2014-06-01

In meta-stable austenitic stainless steels, low cycle fatigue deformation is accompanied by a partial stress/strain-induced solid state phase transformation of paramagnetic γ(fcc) austenite phase to ferromagnetic α{sup /}(bcc) martensite. The measured characteristic of magnetic properties, which are the saturation magnetization, susceptibility, coercivity, retentivity, and the area under the magnetic hysteresis loop are sensitive to the total strain amplitude imposed and the corresponding material behaviour. The morphologies and nucleation characteristics of deformation induced martensites (i.e., ϵ(hcp), α{sup /}(bcc)) have been investigated through analytical transmission electron microscope. It has been observed that deformation induced martensites can nucleate at a number of sites (i.e., shear band intersections, isolated shear bands, shear band–grain boundary intersection, grain boundary triple points, etc.) through multiple transformation sequences: γ(fcc)→ϵ(hcp), γ(fcc)→ϵ(hcp)→α{sup /}(bcc), γ(fcc)→ deformation twin →α{sup /}(bcc) and γ(fcc)→α{sup /}(bcc). - Highlights: • LCF tests were done at various strain amplitudes of 304LNSS. • Quantification of martensite was done through ferritecope. • Magnetic properties were characterised through VSM. • Correlation of magnetic properties with the cyclic plastic response was done. • TEM was done to investigate the transformation micro-mechanisms.

A model explaining synchronization of neuron bioelectric frequency under weak alternating low frequency magnetic field

Energy Technology Data Exchange (ETDEWEB)

Moral, A. del, E-mail: delmoral@unizar.es [Laboratorio de Magnetismo, Departamento de Física de Materia Condensada and Instituto de Ciencia de Materiales, Universidad de Zaragoza and Consejo Superior de Investigaciones Científicas, 50009 Zaragoza (Spain); Laboratorio de Magnetobiología, Departamento de Anatomía e Histología, Facultad de Medicina, Universidad de Zaragoza, 50009 Zaragoza (Spain); Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, 28223 Madrid (Spain); Azanza, María J., E-mail: mjazanza@unizar.es [Laboratorio de Magnetobiología, Departamento de Anatomía e Histología, Facultad de Medicina, Universidad de Zaragoza, 50009 Zaragoza (Spain); Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, 28223 Madrid (Spain)

2015-03-01

A biomagnetic-electrical model is presented that explains rather well the experimentally observed synchronization of the bioelectric potential firing rate (“frequency”), f, of single unit neurons of Helix aspersa mollusc under the application of extremely low frequency (ELF) weak alternating (AC) magnetic fields (MF). The proposed model incorporates to our widely experimentally tested model of superdiamagnetism (SD) and Ca{sup 2+} Coulomb explosion (CE) from lipid (LP) bilayer membrane (SD–CE model), the electrical quadrupolar long range interaction between the bilayer LP membranes of synchronized neuron pairs, not considered before. The quadrupolar interaction is capable of explaining well the observed synchronization. Actual extension of our SD–CE-model shows that the neuron firing frequency field, B, dependence becomes not modified, but the bioelectric frequency is decreased and its spontaneous temperature, T, dependence is modified. A comparison of the model with synchronization experimental results of pair of neurons under weak (B{sub 0}≅0.2–15 mT) AC-MF of frequency f{sub M}=50 Hz is reported. From the deduced size of synchronized LP clusters under B, is suggested the formation of small neuron networks via the membrane lipid correlation. - Highlights: • Neuron pair synchronization under low frequency alternating (AC) magnetic field (MF). • Superdiamagnetism and Ca{sup 2+} Coulomb explosion for AC MF effect in synchronized frequency. • Membrane lipid electrical quadrupolar pair interaction as synchronization mechamism. • Good agreement of model with electrophysiological experiments on mollusc Helix neurons.

A model explaining synchronization of neuron bioelectric frequency under weak alternating low frequency magnetic field

International Nuclear Information System (INIS)

Moral, A. del; Azanza, María J.

2015-01-01

A biomagnetic-electrical model is presented that explains rather well the experimentally observed synchronization of the bioelectric potential firing rate (“frequency”), f, of single unit neurons of Helix aspersa mollusc under the application of extremely low frequency (ELF) weak alternating (AC) magnetic fields (MF). The proposed model incorporates to our widely experimentally tested model of superdiamagnetism (SD) and Ca 2+ Coulomb explosion (CE) from lipid (LP) bilayer membrane (SD–CE model), the electrical quadrupolar long range interaction between the bilayer LP membranes of synchronized neuron pairs, not considered before. The quadrupolar interaction is capable of explaining well the observed synchronization. Actual extension of our SD–CE-model shows that the neuron firing frequency field, B, dependence becomes not modified, but the bioelectric frequency is decreased and its spontaneous temperature, T, dependence is modified. A comparison of the model with synchronization experimental results of pair of neurons under weak (B 0 ≅0.2–15 mT) AC-MF of frequency f M =50 Hz is reported. From the deduced size of synchronized LP clusters under B, is suggested the formation of small neuron networks via the membrane lipid correlation. - Highlights: • Neuron pair synchronization under low frequency alternating (AC) magnetic field (MF). • Superdiamagnetism and Ca 2+ Coulomb explosion for AC MF effect in synchronized frequency. • Membrane lipid electrical quadrupolar pair interaction as synchronization mechamism. • Good agreement of model with electrophysiological experiments on mollusc Helix neurons

A Magnetic Resonance Measurement Technique for Rapidly Switched Gradient Magnetic Fields in a Magnetic Resonance Tomograph

Directory of Open Access Journals (Sweden)

K. Bartušek

2003-01-01

Full Text Available This paper describes a method for measuring of the gradient magnetic field in Nuclear Magnetic Resonance (NMR tomography, which is one of the modern medical diagnostic methods. A very important prerequisite for high quality imaging is a gradient magnetic field in the instrument with exactly defined properties. Nuclear magnetic resonance enables us to measure the pulse gradient magnetic field characteristics with high accuracy. These interesting precise methods were designed, realised, and tested at the Institute of Scientific Instruments (ISI of the Academy of Sciences of the Czech Republic. The first of them was the Instantaneous Frequency (IF method, which was developed into the Instantaneous Frequency of Spin Echo (IFSE and the Instantaneous Frequency of Spin Echo Series (IFSES methods. The above named methods are described in this paper and their a comparison is also presented.

Study on frequency characteristics of wireless power transmission system based on magnetic coupling resonance

Science.gov (United States)

Liang, L. H.; Liu, Z. Z.; Hou, Y. J.; Zeng, H.; Yue, Z. K.; Cui, S.

2017-11-01

In order to study the frequency characteristics of the wireless energy transmission system based on the magnetic coupling resonance, a circuit model based on the magnetic coupling resonant wireless energy transmission system is established. The influence of the load on the frequency characteristics of the wireless power transmission system is analysed. The circuit coupling theory is used to derive the minimum load required to suppress frequency splitting. Simulation and experimental results verify that when the load size is lower than a certain value, the system will appear frequency splitting, increasing the load size can effectively suppress the frequency splitting phenomenon. The power regulation scheme of the wireless charging system based on magnetic coupling resonance is given. This study provides a theoretical basis for load selection and power regulation of wireless power transmission systems.

Magnetic and other properties and sputtering behavior of Co-base amorphous alloy films

International Nuclear Information System (INIS)

Hayashi, K.; Hayakawa, M.; Ochiai, Y.; Matsuda, H.; Ishikawa, W.; Iwasaki, Y.; Aso, K.

1987-01-01

Magnetic and other properties of Co-base amorphous alloy films prepared by sputtering are investigated. A detailed magnetic phase diagram with saturation magnetic flux density, crystallization temperature, and zero-magnetostrictive line on Co-Ta-Zr amorphous alloys were obtained, and the technical knowhow to make a film with well-reproducible characteristics by widely changing the sputtering conditions was related with these physical properties. Especially on alloy sputtering, a phenomenological model for elucidating a composition difference between film and target is presented. After these studies, the film characteristics of B/sub s/ = 12 kG, T/sub x/ = 450 0 C, chemical bondλ/sub s/chemical bond -8 , H/sub c/<10 mOe, and permeabilities of μ(1 MHz) = 7000, μ(100 MHz) = 2000 for the single film of 2 μm in thickness and of μ(1 MHz) = 4000, μ(100 MHz) = 800 for the insulator-sandwiched multilayered film of 10 μm are obtained, and these well-balanced values enable us to apply the materials for high-frequency recording head

Effect of magnet/slot combination on triple-frequency magnetic force and vibration of permanent magnet motors

Science.gov (United States)

Huo, Mina; Wang, Shiyu; Xiu, Jie; Cao, Shuqian

2013-10-01

The relationship between magnet/slot combination and magnetic forces including unbalanced magnetic force (UMF) and cogging torque (CT) of permanent magnet (PM) motors is investigated by using superposition principle and mechanical and magnetic symmetries. The results show that magnetic force can be produced by all magnets passing a single slot, by all slots passing a single magnet, or by eccentricity, which respectively correspond to three frequency components. The results further show that net force/torque can be classified into three typical cases: UMF is suppressed and CT is excited, UMF excited and CT suppressed, and UMF and CT both suppressed, and consequently possible vibrations include three unique groups: rotational modes, translational modes, and balanced modes. The conclusion that combinations with the greatest common divisor (GCD) greater than unity can avoid UMF is mathematically verified, and at the same time lower CT harmonics are preliminarily addressed by the typical excitations. The above findings can create simple guidelines for the suppression of certain UMF and/or CT by using suitable combinations, which in turn can present approach to yield a more desirable response in high performance applications. The superposition effect and predicted relationship are verified by the transient magnetic Finite Element method. Since this work is motivated by symmetries, comparisons are made in order to give further insight into the inner force and vibration behaviors of general rotary power-transmission systems.

Effect of magnetic field frequency on coercivity behavior of nanocrystalline Fe79Hf7B12Si2 glass-coated microwires

International Nuclear Information System (INIS)

Garcia, C.; Zhukova, V.; Gonzalez, J.; Blanco, J.M.; Zhukov, A.

2008-01-01

Dependence of coercitivy, H c , on AC magnetic field frequency, f, has been studied in glass coated Fe 79 Hf 7 B 12 Si 2 microwires exhibiting nanocrystalline structure. Annealing of the samples at 450-600 deg. C changes its structure and consequently the magnetic properties (coercivity and magnetostriction constant). The grain size of the nanocrystals increases from about 17 nm up to 35 nm after annealing at 600 deg. C. For the as-prepared microwires the frequency dependence fits well to √(f). In annealed at 550 deg. C samples H c ∼f 2/3 dependence is observed. In terms of the interpretation of the domain wall propagation, both kind of H c (f) dependences can be interpreted considering depinned domain walls, i.e. neglecting elastic coefficient K of the domain wall motion equation. The H c ∼√(f) corresponds better to low frequency limits while H c ∼f 2/3 is attributed to the high frequency behavior

AN INVESTIGATION ON SOFT MAGNETIC AND NON-MAGNETIC MATERIALS UNDER LOW FREQUENCY FOR BIOMEDICAL SENSOR APPLICATION

Directory of Open Access Journals (Sweden)

Sheroz Khan

2012-02-01

Full Text Available In consequence of the recent development of magnetic sensors in biomedical sector, the investigation of magneticmaterials has been a contributing factor in application stage. This paper proposes a novel technique to investigate materials by obtaining unique distinctive impedance peaks with unique impedance values. A magneto-inductive sensoris used to measure the induction of magnetic and non-magnetic impedance peaks related to the change in permeability, thus characterizing the materials under low frequency.

Magnetic resonance imaging. Recent studies on biological effects of static magnetic and high-frequency electromagnetic fields

International Nuclear Information System (INIS)

Pophof, B.; Brix, G.

2017-01-01

During the last few years, new studies on biological effects of strong static magnetic fields and on thermal effects of high-frequency electromagnetic fields used in magnetic resonance imaging (MRI) were published. Many of these studies have not yet been included in the current safety recommendations. Scientific publications since 2010 on biological effects of static and electromagnetic fields in MRI were researched and evaluated. New studies confirm older publications that have already described effects of static magnetic fields on sensory organs and the central nervous system, accompanied by sensory perceptions. A new result is the direct effect of Lorentz forces on ionic currents in the semicircular canals of the vestibular system. Recent studies of thermal effects of high-frequency electromagnetic fields were focused on the development of anatomically realistic body models and a more precise simulation of exposure scenarios. Strong static magnetic fields can cause unpleasant sensations, in particular, vertigo. In addition, they can influence the performance of the medical staff and thus potentially endanger the patient's safety. As a precaution, medical personnel should move slowly within the field gradient. High-frequency electromagnetic fields lead to an increase in the temperature of patients' tissues and organs. This should be considered especially in patients with restricted thermoregulation and in pregnant women and neonates; in these cases exposure should be kept as low as possible. (orig.) [de

Relationship between Magnetic and Mechanical Properties of Cermet Tools

International Nuclear Information System (INIS)

Ahn, Dong Gil; Lee, Jeong Hee

2000-01-01

The commercial cermet cutting tools consist of multi-carbide and a binder metal of iron group, such as cobalt and nickel which are ferromagnetic. In this paper, a new approach to evaluate the mechanical properties of TiCN based cermet by magnetic properties were studied in relation to binder content and sintering conditions. The experimental cermet was prepared using commercial composition with the other binder contents by PM process. It was found that the magnetic properties of the sintered cermets remarkably depended on the microstructure and the total carbon content. The magnetic saturation was proportional to increment of coercive force. At high carbon content in sintered cermet, the magnetic saturation was increased by decreasing the concentration of solutes such as W, Mo, Ti in Co-Ni binder. As the coercive force increases, the hardness usually increases. The strength and toughness of the cermet also increased with increasing the magnetic saturation. The measurement of magnetic properties made it possible to evaluate the mechanical properties in the cermet cutting tools

Magnetic properties of sulfur-doped graphene

Energy Technology Data Exchange (ETDEWEB)

Zhu, J. [Department of Physics and Astronomy, Clemson University, Clemson, SC (United States); Clemson Nanomaterial Center, Clemson University, Clemson, SC (United States); Park, H. [Department of Physics, The Ohio State University, Columbus, OH (United States); Podila, R., E-mail: rpodila@g.clemson.edu [Department of Physics and Astronomy, Clemson University, Clemson, SC (United States); Clemson Nanomaterial Center, Clemson University, Clemson, SC (United States); COMSET, Clemson University, Clemson, SC (United States); Wadehra, A. [Department of Physics, The Ohio State University, Columbus, OH (United States); Ayala, P. [Faculty of Physics, University of Vienna, Vienna (Austria); Oliveira, L.; He, J. [Department of Physics and Astronomy, Clemson University, Clemson, SC (United States); Zakhidov, A.A.; Howard, A. [Alan G. MacDiarmid NanoTech Institute, The University of Texas at Dallas, Richardson, TX (United States); Wilkins, J. [Department of Physics, The Ohio State University, Columbus, OH (United States); Rao, A.M., E-mail: arao@g.clemson.edu [Department of Physics and Astronomy, Clemson University, Clemson, SC (United States); Clemson Nanomaterial Center, Clemson University, Clemson, SC (United States); COMSET, Clemson University, Clemson, SC (United States)

2016-03-01

While studying magnetism of d- and f-electron systems has been consistently an active research area in physics, chemistry, and biology, there is an increasing interest in the novel magnetism of p-electron systems, especially in graphene and graphene-derived nanostructures. Bulk graphite is diamagnetic in nature, however, graphene is known to exhibit either a paramagnetic response or weak ferromagnetic ordering. Although many groups have attributed this magnetism in graphene to defects or unintentional magnetic impurities, there is a lack of compelling evidence to pinpoint its origin. To resolve this issue, we systematically studied the influence of entropically necessary intrinsic defects (e.g., vacancies, edges) and extrinsic dopants (e.g., S-dopants) on the magnetic properties of graphene. We found that the saturation magnetization of graphene decreased upon sulfur doping suggesting that S-dopants demagnetize vacancies and edges. Our density functional theory calculations provide evidence for: (i) intrinsic defect demagnetization by the formation of covalent bonds between S-dopant and edges/vacancies concurring with the experimental results, and (ii) a net magnetization from only zig-zag edges, suggesting that the possible contradictory results on graphene magnetism in the literature could stem from different defect-types. Interestingly, we observed peculiar local maxima in the temperature dependent magnetizations that suggest the coexistence of different magnetic phases within the same graphene samples. - Highlights: • Magnetic properties of pristine and S-doped graphene were investigated. • Pristine graphene with intrinsic defects exhibits a non-zero magnetic moment. • The addition of S-dopants was found to quench the magnetic ordering. • DFT calculations confirmed that magnetization in graphene arises from defects. • DFT calculations show S-dopants quench local magnetic moment of defect structures.

Nanocrystalline permanent magnets with enhanced properties

International Nuclear Information System (INIS)

Leonowicz, M.

2002-01-01

Parameters of permanent magnets result from the combination of intrinsic properties such as saturation magnetization, magnetic exchange, and magnetocrystalline energy, as well as microstructural parameters such as phase structure, grain size, and orientation. Reduction of grain size into nanocrystalline regime (∼ 50 nm) leads to the enhanced remanence which derives from ferromagnetic exchange coupling between highly refined grains. In this study the fundamental phenomena, quantities, and structure parameters, which define nanophase permanent magnets are presented and discussed. The theoretical considerations are confronted with experimental data for nanocrystalline Sm-Fe-N type permanent magnets. (author)

Photothermal investigation of local and depth dependent magnetic properties

International Nuclear Information System (INIS)

Pelzl, J; Meckenstock, R

2010-01-01

To achieve a spatially resolved measurement of magnetic properties two different photothermal approaches are used which rely on heat dissipated by magnetic resonance absorption or thermal modulation of the magnetic properties, respectively. The heat produced by modulated microwave absorption is detected by the classical photothermal methods such as photoacoustic effect and mirage effect. Examples comprise depth resolution of the magnetization of layered tapes and visualisation of magnetic excitations in ferrites. The second photothermal technique relies on the local modulation of magnetic properties by a thermal wave generated with an intensity modulated laser beam incident on the sample. This technique has a higher spatial resolution and sensitivity and has been used to characterize lateral magnetic properties of multilayers and spintronic media. To extend the lateral resolution of the ferromagnetic resonance detection into the nm-range techniques have been developed which are based on the detection of the modulated thermal microwave response by the thermal probe of an atomic force microscope (AFM) or by detection the thermal expansion of the magnetic sample in the course of the resonant microwave absorption with an AFM or tunnelling microscope. These thermal near field based techniques in ferromagnetic resonance have been successfully applied to image magnetic inhomogeneities around nano-structures and to measure the ferromagnetic resonance from magnetic nano-dots.

Effects of crystalline grain size and packing ratio of self-forming core/shell nanoparticles on magnetic properties at up to GHz bands

International Nuclear Information System (INIS)

Suetsuna, Tomohiro; Suenaga, Seiichi; Sakurada, Shinya; Harada, Koichi; Tomimatsu, Maki; Takahashi, Toshihide

2011-01-01

Self-forming core/shell nanoparticles of magnetic metal/oxide with crystalline grain size of less than 40 nm were synthesized. The nanoparticles were highly concentrated in an insulating matrix to fabricate a nanocomposite, whose magnetic properties were investigated. The crystalline grain size of the nanoparticles strongly influenced the magnetic anisotropy field, magnetic coercivity, relative permeability, and loss factor (tan δ=μ''/μ') at high frequency. The packing ratio of the magnetic metallic phase in the nanocomposite also influenced those properties. High permeability with low tan δ of less than 1.5% at up to 1 GHz was obtained in the case of the nanoparticles with crystalline grain size of around 15 nm with large packing ratio of the nanoparticles. - Research highlights: → Self-forming core/shell nanoparticles of magnetic metal/oxide were synthesized. → Crystalline grain size of the nanoparticle and its packing ratio were controlled. → Magnetic properties changed according to the size and packing ratio.

Magnetic materials. Properties and applications

International Nuclear Information System (INIS)

Bar'yakhtar, V.

1998-01-01

Main theoretical and experimental results of physics of magnetic materials have been stated. Special attention was paid to the problem of creation of magnetic materials for information recording and presentation. The results of fundamental researches have been considered for their effect on creation of magnetic materials with the properties required for production as well as the reverse effect of production financing on the development of fundamental investigations. The relations between the development of high technologies and the society requirements, financing volumes and the level of NIKOR. (author)

Magnetic and optical properties of carbon and silicon decorated free standing buckled germanene: A DFT approach

Science.gov (United States)

Dhar, Namrata; Jana, Debnarayan

2018-04-01

Ab initio magnetic and optical properties of group IV elements (carbon (C) and silicon (Si)) decorated free standing (FS) buckled germanene systems have been employed theoretically. Our study elucidates that, decoration of these elements in proper sites with suitable concentrations form dynamically stable configurations. Band structure is modified due to decoration of these atoms in Ge-nanosheet and pristine semi-metallic germanene undergoes to semiconductors with a finite amount of bandgap. Interestingly, this bandgap value meets closely the requirement of gap for field effect transistor (FET) applications. Moreover, significant magnetic moment is induced in non-magnetic germanene for C decorated structure and ground state in anti-ferromagnetic in nature for this structure. Along with magnetic property, optical properties like dielectric functions, optical absorption, electron energy loss spectra (EELS), refractive index and reflectivity of these systems have also been investigated. Maximum number of plasma frequencies appear for Si decorated configuration considering both parallel and perpendicular polarizations. In addition, birefringence characteristics of these configurations have also been studied as it is an important parameter in various applications of optical devices, liquid crystal displays, light modulators etc.

Superconducting property measuring system by magnetization method

International Nuclear Information System (INIS)

Ikisawa, K.; Mori, T.; Takasu, N.

1988-01-01

Superconducting property measuring system (CMS-370B) for high temperature oxide superconductor has been developed. This system adopts magnetization measurement. The superconducting properties are able to be measured automatically and continuously changing the temperature and external magnetic field. The critical current density as a function of temperature and magnetic field of high temperature superconductor YBa 2 Cu 3 O 7-y (YBCO) has been measured. This paper reports how it was confirmed that this system having the high performance and the accuracy gave the significant contribution to the superconducting material development

Experimental results of high power dual frequency resonant magnet excitation at TRIUMF

International Nuclear Information System (INIS)

Reiniger, K.W.; Heritier, G.

1988-06-01

We present some results of duel frequency resonant magnet excitation at full power using the old NINA synchrotron dipoles. These tests will simulate a typical resonant cell as proposed for the accelerating rings of the TRIUMF KAON Factory. These test have two main purposes: to verify circuit parameters and component ratings for the dual frequency resonant power supply system; and to measure directly electrical losses in a transverse magnet field, such as eddy current losses in magnet conductors, vacuum tubes and core losses in laminations. These data will be required for the detailed design of the accelerator system components. (Author) (Ref., 9 figs., tab.)

Six-Coordinate Ln(III Complexes with Various Coordination Geometries Showing Distinct Magnetic Properties

Directory of Open Access Journals (Sweden)

Mei Guo

2018-01-01

Full Text Available The syntheses, structural characterization, and magnetic properties of three lanthanide complexes with formulas [Ln(L13] (Ln = Dy (1Dy; Er (1Er; and [Dy(L22] (2Dy were reported. Complexes 1Dy and 1Er are isostructural with the metal ion in distorted trigonal-prismatic coordination geometry, but exhibit distinct magnetic properties due to the different shapes of electron density for DyIII (oblate and ErIII (prolate ions. Complex 1Dy shows obvious SMM behavior under a zero direct current (dc field with an effective energy barrier of 31.4 K, while complex 1Er only features SMM behavior under a 400 Oe external field with an effective energy barrier of 23.96 K. In stark contrast, complex 2Dy with the octahedral geometry only exhibits the frequency dependence of alternating current (ac susceptibility signals without χ″ peaks under a zero dc field.

Effect of elastic and plastic tensile mechanical loading on the magnetic properties of NGO electrical steel

Energy Technology Data Exchange (ETDEWEB)

Leuning, N., E-mail: nora.leuning@iem.rwth-aachen.de [Institute of Electrical Machines, RWTH Aachen University, D-52062 Aachen (Germany); Steentjes, S. [Institute of Electrical Machines, RWTH Aachen University, D-52062 Aachen (Germany); Schulte, M.; Bleck, W. [Steel Institute, RWTH Aachen University, D-52072 Aachen (Germany); Hameyer, K. [Institute of Electrical Machines, RWTH Aachen University, D-52062 Aachen (Germany)

2016-11-01

The magnetic properties of non-grain-oriented (NGO) electrical steels are highly susceptible to mechanical stresses, i.e., residual, external or thermal ones. For rotating electrical machines, mechanical stresses are inevitable and originate from different sources, e.g., material processing, machine manufacturing and operating conditions. The efficiency and specific losses are largely altered by different mechanical stress states. In this paper the effect of tensile stresses and plastic deformations on the magnetic properties of a 2.9 wt% Si electrical steel are studied. Particular attention is paid to the effect of magnetic anisotropy, i.e., the influence of the direction of applied mechanical stress with respect to the rolling direction. Due to mechanical stress, the induced anisotropy has to be evaluated as it is related to the stress-dependent magnetostriction constant and the grain alignment. - Highlights: • A detailed look at magnetic anisotropy of FeSi NGO electrical steel. • Study of magnetic behavior under elastic as well as plastic tensile stresses. • Correlation of magnetic behavior with microscopic deformation mechanisms. • Discussion of detrimental and beneficial effects of external stresses. • Loss separation at different polarizations and frequencies under increasing stress.

Effect of elastic and plastic tensile mechanical loading on the magnetic properties of NGO electrical steel

International Nuclear Information System (INIS)

Leuning, N.; Steentjes, S.; Schulte, M.; Bleck, W.; Hameyer, K.

2016-01-01

The magnetic properties of non-grain-oriented (NGO) electrical steels are highly susceptible to mechanical stresses, i.e., residual, external or thermal ones. For rotating electrical machines, mechanical stresses are inevitable and originate from different sources, e.g., material processing, machine manufacturing and operating conditions. The efficiency and specific losses are largely altered by different mechanical stress states. In this paper the effect of tensile stresses and plastic deformations on the magnetic properties of a 2.9 wt% Si electrical steel are studied. Particular attention is paid to the effect of magnetic anisotropy, i.e., the influence of the direction of applied mechanical stress with respect to the rolling direction. Due to mechanical stress, the induced anisotropy has to be evaluated as it is related to the stress-dependent magnetostriction constant and the grain alignment. - Highlights: • A detailed look at magnetic anisotropy of FeSi NGO electrical steel. • Study of magnetic behavior under elastic as well as plastic tensile stresses. • Correlation of magnetic behavior with microscopic deformation mechanisms. • Discussion of detrimental and beneficial effects of external stresses. • Loss separation at different polarizations and frequencies under increasing stress.

LOW-FREQUENCY MAGNETIC FIELD SHIELDING BY A CIRCULAR PASSIVE LOOP AND CLOSED SHELLS

Directory of Open Access Journals (Sweden)

V.S. Grinchenko

2016-05-01

Full Text Available Purpose. To analyze the shielding factors for a circular passive loop and conductive closed shells placed in a homogeneous low-frequency magnetic field. Methodology. We have obtained simplified expressions for the shielding factors for a circular passive loop and a thin spherical shell. In addition, we have developed the numerical model of a thin cubical shell in a magnetic field, which allows exploring its shielding characteristics. Results. We have obtained dependences of the shielding factors for passive loops and shells on the frequency of the external field. Analytically determined frequency of the external magnetic field, below which field shielding of a passive loop is expedient to use, above which it is advisable to use a shielding shell.

Dynamic properties of micro-magnetic noise in soft ferromagnetic materials

Science.gov (United States)

Stupakov, A.; Perevertov, A.

2018-06-01

Dynamic response of magnetic hysteresis, magnetic Barkhausen noise and magneto-acoustic emission in a soft ribbon and electrical steels was studied comprehensively. The measurements were performed under controllable magnetization conditions: sinusoidal/triangular waveforms of the magnetic induction and a triangular waveform of the magnetic field. Magnetizing frequency was varied in a wide range: fmag = 0.5 - 500 and 0.5-100 Hz for the ribbon and the electrical steels, respectively. Magnetization amplitude was fixed on a near-saturation level Hmax ≃ 100 A/m. Barkhausen noise signal was detected by a sample-wrapping/surface-mounted coil and differently filtered. It was found that intensity of the Barkhausen noise rises approximately as a square root function of the magnetizing frequency. Whereas, level of the magneto-acoustic emission follows the hysteresis loss trend with an additional linear term (classical loss component).

A measurement system for two-dimensional DC-biased properties of magnetic materials

International Nuclear Information System (INIS)

Enokizono, M.; Matsuo, H.

2003-01-01

So far, the DC-biased magnetic properties have been measured in one dimension (scalar). However, these scalar magnetic properties are not enough to clarify the DC-biased magnetic properties because the scalar magnetic properties cannot exactly take into account the phase difference between the magnetic flux density B vector and the magnetic filed strength H vector. Thus, the magnetic field strength H and magnetic flux density B in magnetic materials must be measured as vector quantities (two-dimensional), directly. We showed the measurement system using a single-sheet tester (SST) to clarify the two-dimensional DC-biased magnetic properties. This system excited AC in Y-direction and DC in X-direction. This paper shows the measurement system using an SST and presents the measurement results of two-dimensional DC-biased magnetic properties when changing the DC exciting voltage and the iron loss

Three-dimensional magnetic properties of soft magnetic composite materials

International Nuclear Information System (INIS)

Lin, Z.W.; Zhu, J.G.

2007-01-01

A three-dimensional (3-D) magnetic property measurement system, which can control the three components of the magnetic flux density B vector and measure the magnetic field strength H vector in a cubic sample of soft magnetic material, has been developed and calibrated. This paper studies the relationship between the B and H loci in 3-D space, and the power losses features of a soft magnetic composite when the B loci are controlled to be circles with increasing magnitudes and ellipses evolving from a straight line to circle in three orthogonal planes. It is found that the B and H loci lie in the same magnetization plane, but the H loci and power losses strongly depend on the orientation, position, and process of magnetization. On the other hand, the H vector evolves into a unique locus, and the power loss approaches a unique value, respectively, when the B vector evolves into the round locus with the same magnitude from either a series of circles or ellipses

Hard magnetic property and δM(H) plot for sintered NdFeB magnet

International Nuclear Information System (INIS)

Gao, R.W.; Zhang, D.H.; Li, W.; Li, X.M.; Zhang, J.C.

2000-01-01

The hard magnetic properties and the interactions between the grains for sintered Nd 16 Fe 73 Co 5 B 6 magnets are investigated by using δM(H) plot technique. The results show that the δM(H) plot of NdFeB sintered magnet can explain the effects of the microstructure (size, shape and orientation of the grains) and the intergrain interactions on the hard magnetic properties of the magnet. However, the value of δM(H) is positive when the applied field is not strong enough, which means that the common δM(H) plot theory is not completely consistent with the sintered NdFeB magnet

Ultra-low-frequency electrostatic modes in a magnetized dusty plasma

International Nuclear Information System (INIS)

Salimullah, M.; Amin, M.R.; Roy Chowdhury, A.R.; Salahuddin, M.

1997-11-01

A study on the extremely low-frequency possible electrostatic modes in a finite temperature magnetized dusty plasma taking the charged dust grains as the third component has been carried out using the appropriate Vlasov-kinetic theory for the dynamics of the electrons, ions and the dust particles. It is found that the inequalities of charge and number density of plasma species, and the finite-Larmor-radius thermal kinetic effects of the mobile charged dust grains, introduce the existence of very low-frequency electrostatic eigenmodes in the three-component homogeneous magnetized dusty plasma. The relevance of the present investigation to space and astrophysical situations as well as laboratory experiments for dust Coulomb crystallization has been pointed out. (author)

Magnetic Properties of Electrically Contacted Fe4 Molecular Magnets

Science.gov (United States)

Burgess, Jacob; Malavolti, Luigi; Lanzilotto, Valeria; Mannini, Matteo; Totti, Frederico; Ninova, Silviya; Yan, Shichao; Choi, Deung-Jang; Rolf-Pissarczyk, Steffen; Cornia, Andrea; Sessoli, Roberta; Loth, Sebastian

2015-03-01

Single molecule magnets (SMMs) are often large and fragile molecules. This poses challenges for the construction of SMM based spintronics. Device geometries with two electronic leads contacting a molecule may be explored via scanning tunneling microscopy (STM). The Fe4 molecule stands out as a robust, thermally evaporable SMM, making it ideal for such an experiment. Here we present the first STM investigations of individual Fe4 molecules thermally evaporated onto a monolayer of Cu2N on a Cu (100) crystal. Using inelastic electron tunneling spectroscopy (IETS), spin excitations in single Fe4 molecules can be detected at meV energies. Analysis using a Spin Hamiltonian allows extraction of magnetic properties of individual Fe4 molecules, and investigation of the influence of the electronic leads. The tip and sample induce small changes in the magnetic properties of Fe4 molecules, making Fe4 a promising candidate for the development of spintronics devices based on SMMs.

Frequency Dependence of Measured Massive MIMO Channel Properties

DEFF Research Database (Denmark)

Oliveras Martínez, Àlex; Carvalho, Elisabeth De; Nielsen, Jesper Ødum

2016-01-01

A multi-user massive MIMO measurement campaign is conducted to study the channel propagation characteristics (e.g. user correlation, sum of eigenvalues and condition number), focusing on the stability over frequencies and the impact of the array aperture. We use 3 arrays with 64 antennas (6m linear...... array, 2m linear array and 25cm by 28cm squared 2D array) serving 8 users holding a handset with 2 antennas. The study of the measurements shows that the propagation characteristics of the channel are stable for all the measured frequencies. We also observe that user proximity and user handgrip...... stabilize the studied properties of the channel across the frequencies, and in such case the larger the aperture of the array the more stable the properties. The number of base station antennas improves the propagation characteristics of the channel and stabilizes the properties in the frequency domain....

Remote tracking of a magnetic receiver using low frequency beacons

International Nuclear Information System (INIS)

Sheinker, Arie; Ginzburg, Boris; Salomonski, Nizan; Frumkis, Lev; Kaplan, Ben-Zion

2014-01-01

Low frequency magnetic fields feature high penetration ability, which allows communication, localization, and tracking in environments where radio or acoustic waves are blocked or distorted by multipath interferences. In the present work, we propose a method for tracking a magnetic receiver using beacons of low frequency magnetic field, where the receiver includes a tri-axial search-coil magnetometer. Measuring the beacons’ magnetic fields and calculating the total-field signals enables localization without restrictions on magnetometer orientation, allowing on-the-move tracking. The total-field signals are used by a global search method, e.g., simulated annealing (SA) algorithm, to localize the receiver. The magnetic field produced by each beacon has a dipole structure and is governed by the beacon’s position and magnetic moment. We have investigated two different methods for estimating beacons’ magnetic moments prior to localization. The first method requires directional measurements, whereas for the second method the total-field signal is used. Effectiveness of these methods has been proved in numerous field tests. In the present work, we introduce a method for tracking a moving receiver by successive localizations. Using previous localization as a starting point of the search method for the next localization can reduce execution time and chances for divergence. The proposed method has been tested using numerous computer simulations. Successful system operation has been verified in field conditions. The good tracking capability together with simple implementation makes the proposed method attractive for real-time, low power field applications, such as mobile robots navigation. (paper)

Design and development of ITER high-frequency magnetic sensor

Czech Academy of Sciences Publication Activity Database

Ma, Y.; Vayakis, G.; Begrambekov, L.B.; Cooper, J.-J.; Ďuran, Ivan; Hirsch, M.; Laqua, H.P.; Moreau, P.; Oosterbeek, J.W.; Spuig, P.; Stange, T.; Walsh, M.

2016-01-01

Roč. 112, November (2016), s. 594-612 ISSN 0920-3796 Institutional support: RVO:61389021 Keywords : ITER * High-frequency * Magnetic diagnostics * ECHa Subject RIV: JF - Nuclear Energetics OBOR OECD: Nuclear related engineering Impact factor: 1.319, year: 2016

Thermally tunable magnetic metamaterials at THz frequencies

International Nuclear Information System (INIS)

Bui, Son Tung; Nguyen, Van Dung; Bui, Xuan Khuyen; Vu, Dinh Lam; Nguyen, Thanh Tung; Lievens, Peter; Lee, YoungPak

2013-01-01

We investigate theoretically and numerically the tunability of the magnetic property of metamaterial in the THz region via thermal control. One component of the meta-atom is InSb, playing an important role as an alterable metal. When the temperature of the InSb stack increases from 300 to 350 K, the resonance peak of the transmission spectra shows a shift from 0.6 to 0.85 THz accompanied by a stronger magnetic behavior. The S-parameter retrieval method realizes the tunability of the negative permeability achieved in the above heating range. (paper)

Theranostic multimodal potential of magnetic nanoparticles actuated by non-heating low frequency magnetic field in the new-generation nanomedicine

Science.gov (United States)

Golovin, Yuri I.; Klyachko, Natalia L.; Majouga, Alexander G.; Sokolsky, Marina; Kabanov, Alexander V.

2017-02-01

The scope of this review involves one of the most promising branches of new-generation biomedicine, namely magnetic nanotheranostics using remote control of functionalized magnetic nanoparticles (f-MNPs) by means of alternating magnetic fields (AMFs). The review is mainly focused on new approach which utilizes non-heating low frequency magnetic fields (LFMFs) for nanomechanical actuation of f-MNPs. This approach is compared to such traditional ones as magnetic resonance imaging (MRI) and radio-frequency (RF) magnetic hyperthermia (MH) which utilize high frequency heating AMF. The innovative principles and specific models of non-thermal magnetomechanical actuation of biostructures by MNP rotational oscillations in LFMF are described. The discussed strategy allows biodistribution monitoring in situ, delivering drugs to target tissues and releasing them with controlled rate, controlling biocatalytic reaction kinetics, inducing malignant cell apoptosis, and more. Optimization of both LFMF and f-MNP parameters may lead to dramatic improvement of treatment efficiency, locality, and selectivity on molecular or cellular levels and allow implementing both drug and drugless, i.e., pure nanomechanical therapy, in particular cancer therapy. The optimal parameters within this approach differ significantly from those used in MH or MRI because of the principal difference in the f-MNP actuation modes. It is shown that specifically designed high gradient, steady magnetic field enables diagnostic and therapeutic LFMF impact localization in the deep tissues within the area ranging from a millimeter to a few centimeters and 3D scanning of affected region, if necessary.

Theranostic multimodal potential of magnetic nanoparticles actuated by non-heating low frequency magnetic field in the new-generation nanomedicine

Energy Technology Data Exchange (ETDEWEB)

Golovin, Yuri I., E-mail: nano@tsutmb.ru; Klyachko, Natalia L.; Majouga, Alexander G. [M.V. Lomonosov Moscow State University, Chemistry Faculty (Russian Federation); Sokolsky, Marina [University of North Carolina at Chapel Hill, Center for Nanotechnology in Drug Delivery, UNC Eshelman School of Pharmacy (United States); Kabanov, Alexander V. [M.V. Lomonosov Moscow State University, Chemistry Faculty (Russian Federation)

2017-02-15

The scope of this review involves one of the most promising branches of new-generation biomedicine, namely magnetic nanotheranostics using remote control of functionalized magnetic nanoparticles (f-MNPs) by means of alternating magnetic fields (AMFs). The review is mainly focused on new approach which utilizes non-heating low frequency magnetic fields (LFMFs) for nanomechanical actuation of f-MNPs. This approach is compared to such traditional ones as magnetic resonance imaging (MRI) and radio-frequency (RF) magnetic hyperthermia (MH) which utilize high frequency heating AMF. The innovative principles and specific models of non-thermal magnetomechanical actuation of biostructures by MNP rotational oscillations in LFMF are described. The discussed strategy allows biodistribution monitoring in situ, delivering drugs to target tissues and releasing them with controlled rate, controlling biocatalytic reaction kinetics, inducing malignant cell apoptosis, and more. Optimization of both LFMF and f-MNP parameters may lead to dramatic improvement of treatment efficiency, locality, and selectivity on molecular or cellular levels and allow implementing both drug and drugless, i.e., pure nanomechanical therapy, in particular cancer therapy. The optimal parameters within this approach differ significantly from those used in MH or MRI because of the principal difference in the f-MNP actuation modes. It is shown that specifically designed high gradient, steady magnetic field enables diagnostic and therapeutic LFMF impact localization in the deep tissues within the area ranging from a millimeter to a few centimeters and 3D scanning of affected region, if necessary.

Magnetic properties of alluvial soils polluted with heavy metals

Science.gov (United States)

Dlouha, S.; Petrovsky, E.; Boruvka, L.; Kapicka, A.; Grison, H.

2012-04-01

Magnetic properties of soils, reflecting mineralogy, concentration and grain-size distribution of Fe-oxides, proved to be useful tool in assessing the soil properties in terms of various environmental conditions. Measurement of soil magnetic properties presents a convenient method to investigate the natural environmental changes in soils as well as the anthropogenic pollution of soils with several risk elements. The effect of fluvial pollution with Cd, Cu, Pb and Zn on magnetic soil properties was studied on highly contaminated alluvial soils from the mining/smelting district (Příbram; CZ) using a combination of magnetic and geochemical methods. The basic soil characteristics, the content of heavy metals, oxalate, and dithionite extractable iron were determined in selected soil samples. Soil profiles were sampled using HUMAX soil corer and the magnetic susceptibility was measured in situ, further detailed magnetic analyses of selected distinct layers were carried out. Two types of variations of magnetic properties in soil profiles were observed corresponding to indentified soil types (Fluvisols, and Gleyic Fluvisols). Significantly higher values of topsoil magnetic susceptibility compared to underlying soil are accompanied with high concentration of heavy metals. Sequential extraction analysis proved the binding of Pb, Zn and Cd in Fe and Mn oxides. Concentration and size-dependent parameters (anhysteretic and isothermal magnetization) were measured on bulk samples in terms of assessing the origin of magnetic components. The results enabled to distinguish clearly topsoil layers enhanced with heavy metals from subsoil samples. The dominance of particles with pseudo-single domain behavior in topsoil and paramagnetic/antiferromagnetic contribution in subsoil were observed. These measurements were verified with room temperature hysteresis measurement carried out on bulk samples and magnetic extracts. Thermomagnetic analysis of magnetic susceptibility measured on

The concept of a plasma centrifuge with a high frequency rotating magnetic field and axial circulation

Science.gov (United States)

Borisevich, V. D.; Potanin, E. P.

2017-07-01

The possibility of using a rotating magnetic field (RMF) in a plasma centrifuge (PC), with axial circulation to multiply the radial separation effect in an axial direction, is considered. For the first time, a traveling magnetic field (TMF) is proposed to drive an axial circulation flow in a PC. The longitudinal separation effect is calculated for a notional model, using specified operational parameters and the properties of a plasma, comprising an isotopic mixture of 20Ne-22Ne and generated by a high frequency discharge. The optimal intensity of a circulation flow, in which the longitudinal separation effect reaches its maximum value, is studied. The optimal parameters of the RMF and TMF for effective separation, as well as the centrifuge performance, are calculated.

Tunnel-diode resonator and nuclear magnetic resonance studies of low-dimensional magnetic and superconducting systems

Energy Technology Data Exchange (ETDEWEB)

Yeninas, Steven Lee [Iowa State Univ., Ames, IA (United States)

2013-01-01

This thesis emphasizes two frequency-domain techniques which uniquely employ radio frequency (RF) excitations to investigate the static and dynamic properties of novel magnetic and superconducting materials.

Magnetic and structural properties of manganese doped (Al,Ga)N studied with emission Mössbauer spectroscopy

CERN Multimedia

Gallium nitride (GaN) and related compounds form a unique class of semiconductors with extraordinary qualities in terms of their crystal structure, optical properties, and electrical properties. These novel properties have made them useful in a wide range of applications in optoelectronic and high-frequency devices such as light emitting diodes, laser diodes and high power field effect transistors. When doped with a few percents of Mn and in the presence of free holes, GaN has been predicted to be a magnetic semiconductor with Curie temperature above room temperature. Mixed semiconductors of Al$_{x}$Ga$_{1-x}$N (AlGaN) composition, give rise to unexpected and critical magnetic and photonic functionalities when doped with magnetic ion species. Here we propose an experiment on very thoroughly characterised AlGaN doped with Mn utilising extremely dilute $^{57}$Mn (T$_{1/2}$=1.5 min), $^{57}$Co (T$_{1/2}$ = 272 d) and $^{119}$In (T$_{1/2}$=2.1 min) implantations, in order to perform $^{57}$Fe and $^{119}$Sn emiss...

Magnetic properties of permalloy-coated organic tubules

Science.gov (United States)

Krebs, J. J.; Rubinstein, M.; Lubitz, P.; Harford, M. Z.; Baral, S.; Shashidar, R.; Ho, Y. S.; Chow, G. M.; Qadri, S.

1991-11-01

An initial investigation is presented of the ferromagnetic properties of a novel type of magnetic composite, viz., permalloy-coated submicron diameter hollow cylinders or tubules. The tubules form spontaneously from an organic material, a diacetylenic phosopholipid, and were used as templates on which the ferromagnetic material was deposited by electroless deposition. The permalloy-coated tubules were dispersed in an epoxy matrix to measure the magnetization and ferromagnetic resonance (FMR) properties of individual tubules. The nature of the magnetic anisotropy and the FMR spectra observed confirmed that the tubules are well aligned by a magnetic field during the epoxy curing. The FMR spectra are interpreted in terms of a powder pattern distribution of thin-film spectra consistent with the large diameter-to-thickness ratio.

Magnetic and magnetocaloric properties of martensitic Ni2Mn1.4Sn0.6 Heusler alloy

International Nuclear Information System (INIS)

Chernenko, Volodymyr A.; Barandiarán, Jose M.; Rodriguez Fernández, Jesus; Rojas, Daniel P.; Gutiérrez, Jon; Lázpita, Patricia; Orue, Iñaki

2012-01-01

The evolutions of magnetic properties at low temperatures and the influence of magnetic field on the temperature dependence of specific heat in martensitic Ni 2 Mn 1.4 Sn 0.6 Heusler alloy are studied. The frequency-dependent blocking temperature and considerable exchange bias below it are measured in the martensitic phase. From the analysis of the specific heat curves under magnetic field, a large inverse magnetocaloric effect manifested as the magnetic field induced rise of isothermal magnetic entropy and/or magnetic field induced adiabatic temperature decrease in the vicinity of the reverse magnetostructural transformation and a significant value of the conventional magnetocaloric effect at the Curie temperature are obtained. The Debye temperature and electronic coefficient equal to Θ D =310±2 K and γ= 16.6±0.3 mJ/K 2 mol, respectively, do not depend on the magnetic field.

Magnetic properties of confined electron gas

International Nuclear Information System (INIS)

Felicio, J.R.D. de.

1977-04-01

The effects of confinement by a two or three-dimensional harmonic potential on the magnetic properties of a free electron gas are investigated using the grand-canonical ensemble framework. At high temperatures an extension of Darwin's, Felderhof and Raval's works is made taking into account spin effects at low temperature. A comprehensive description of the magnetic properties of a free electron gas is given. The system is regarded as finite, but the boundary condition psi=0 is not introduced. The limits of weak and strong confinement are also analysed [pt

Structural, magnetic and electrical properties of nickel doped Mn-Zn spinel ferrite synthesized by sol-gel method

Energy Technology Data Exchange (ETDEWEB)

Jalaiah, K., E-mail: kjalu4u@gmail.com [Department of Physics, Andhra University, Visakhapatnam 530003 (India); Vijaya Babu, K. [Advanced Analytical Laboratory, Andhra University, Visakhapatnam 530003 (India)

2017-02-01

Manganese ferrites (MnFe{sub 2}O{sub 4}) have been of great interest for their remarkable and soft-magnetic properties (low coercivity, moderate saturation magnetization) accompanied by good chemical stability and mechanical hardness. X-ray diffraction analysis confirmed the presence of single phase cubic spinel ferrite with space group Fm3m for all prepared samples. Structural parameters such as lattice constant, crystallite size were calculated from the studies of X-ray diffraction. The morphological analysis of all the compounds is studied using scanning electron microscope. The magnetic properties were measured using electron spin resonance (ESR) and vibrating sample magnetometer (VSM). The results obtained showed the formation of manganese ferrites with an average particle size are in good agreement with previous results and displayed good magnetic properties. The dielectric and impedance properties are studied over a frequency range 20 Hz–1 MHz at room temperature. - Highlights: • We prepared Mn{sub 0.85}Zn{sub 0.15}Ni{sub x}Fe{sub 2}O{sub 4} (x=0.03, 0.06, 0.09, 0.12 and 0.15) nano-ferrite materials by using sol-gel method. • All the compounds characterized by XRD, SEM, VSM, ESR and dielectric studies. • We get lower coercivity values. • We get good results from ESR spectra.

Magnetic properties and thermal stability of MnBi/NdFeB hybrid bonded magnets

International Nuclear Information System (INIS)

Cao, S.; Yue, M.; Yang, Y. X.; Zhang, D. T.; Liu, W. Q.; Zhang, J. X.; Guo, Z. H.; Li, W.

2011-01-01

Magnetic properties and thermal stability were investigated for the MnBi/NdFeB (MnBi = 0, 20, 40, 60, 80, and 100 wt.%) bonded hybrid magnets prepared by spark plasma sintering (SPS) technique. Effect of MnBi content on the magnetic properties of the hybrid magnets was studied. With increasing MnBi content, the coercivity of the MnBi/NdFeB hybrid magnets increases rapidly, while the remanence and maximum energy product drops simultaneously. Thermal stability measurement on MnBi magnet, NdFeB magnet, and the hybrid magnet with 20 wt.% MnBi indicates that both the NdFeB magnet and the MnBi/NdFeB hybrid magnet have a negative temperature coefficient of coercivity, while the MnBi magnet has a positive one. The (BH) max of the MnBi/NdFeB magnet (MnBi = 20 wt.%) is 5.71 MGOe at 423 K, which is much higher than 3.67 MGOe of the NdFeB magnet, indicating a remarkable improvement of thermal stability.

Modeling drug release from functionalized magnetic nanoparticles actuated by non-heating low frequency magnetic field

Energy Technology Data Exchange (ETDEWEB)

Golovin, Y., E-mail: nano@tsutmb.ru [M.V. Lomonosov Moscow State University, School of Chemistry (Russian Federation); Golovin, D. [G.R. Derzhavin Tambov State University (Russian Federation); Klyachko, N.; Majouga, A.; Kabanov, A. [M.V. Lomonosov Moscow State University, School of Chemistry (Russian Federation)

2017-02-15

Various plausible acceleration mechanisms of drug release from nanocarriers composed of a single-domain magnetic nanoparticle core with attached long macromolecule chains activated by low frequency non-heating alternating magnetic field (AMF) are discussed. The most important system characteristics affecting the AMF exposure impact are determined. Impact of several reasonable mechanisms is estimated analytically or obtained using numerical modeling. Some conditions providing manifold release acceleration as a result from exposure in AMF are found.

Modeling drug release from functionalized magnetic nanoparticles actuated by non-heating low frequency magnetic field

International Nuclear Information System (INIS)

Golovin, Y.; Golovin, D.; Klyachko, N.; Majouga, A.; Kabanov, A.

2017-01-01

Various plausible acceleration mechanisms of drug release from nanocarriers composed of a single-domain magnetic nanoparticle core with attached long macromolecule chains activated by low frequency non-heating alternating magnetic field (AMF) are discussed. The most important system characteristics affecting the AMF exposure impact are determined. Impact of several reasonable mechanisms is estimated analytically or obtained using numerical modeling. Some conditions providing manifold release acceleration as a result from exposure in AMF are found.

Magnetic properties of a classical XY spin dimer in a “planar” magnetic field

Energy Technology Data Exchange (ETDEWEB)

Ciftja, Orion, E-mail: ogciftja@pvamu.edu [Department of Physics, Prairie View A& M University, Prairie View, TX 77446 (United States); Prenga, Dode [Department of Physics, Faculty of Natural Sciences, University of Tirana, Bul. Zog I, Tirana (Albania)

2016-10-15

Single-molecule magnetism originates from the strong intra-molecular magnetic coupling of a small number of interacting spins. Such spins generally interact very weakly with the neighboring spins in the other molecules of the compound, therefore, inter-molecular spin couplings are negligible. In certain cases the number of magnetically coupled spins is as small as a dimer, a system that can be considered the smallest nanomagnet capable of storing non-trivial magnetic information on the molecular level. Additional interesting patterns arise if the spin motion is confined to a two-dimensional space. In such a scenario, clusters consisting of spins with large-spin values are particularly attractive since their magnetic interactions can be described well in terms of classical Heisenberg XY spins. In this work we calculate exactly the magnetic properties of a nanomagnetic dimer of classical XY spins in a “planar” external magnetic field. The problem is solved by employing a mathematical approach whose idea is the introduction of auxiliary spin variables into the starting expression of the partition function. Results for the total internal energy, total magnetic moment, spin–spin correlation function and zero-field magnetic susceptibility can serve as a basis to understand the magnetic properties of large-spin dimer building blocks. - Highlights: • Exact magnetic properties of a dimer system of classical XY spins in magnetic field. • Partition function in nonzero magnetic field obtained in closed-form. • Novel exact analytic results are important for spin models in a magnetic field. • Result provides benchmarks to gauge the accuracy of computational techniques.

Magnetic properties of singlet ground state systems

International Nuclear Information System (INIS)

Diederix, K.M.

1979-01-01

Experiments are described determining the properties of a magnetic system consisting of a singlet ground state. Cu(NO 3 ) 2 .2 1/2H 2 O has been studied which is a system of S = 1/2 alternating antiferromagnetic Heisenberg chains. The static properties, spin lattice relaxation time and field-induced antiferromagnetically ordered state measurements are presented. Susceptibility and magnetic cooling measurements of other compounds are summarised. (Auth.)

Dynamical properties of unconventional magnetic systems

International Nuclear Information System (INIS)

Helgesen, G.

1997-05-01

The Advanced Study Institute addressed the current experimental and theoretical knowledge of the dynamical properties of unconventional magnetic systems including low-dimensional and mesoscopic magnetism, unconventional ground state, quantum magnets and soft matter. The main approach in this Advanced Study Institute was to obtain basic understanding of co-operative phenomena, fluctuations and excitations in the wide range unconventional magnetic systems now being fabricated or envisioned. The report contains abstracts for lectures, invited seminars and posters, together with a list of the 95 participants from 24 countries with e-mail addresses

Magnetic properties measurement of soft magnetic composite material (SOMALOY 700) by using 3-D tester

Science.gov (United States)

Asari, Ashraf; Guo, Youguang; Zhu, Jianguo

2017-08-01

Core losses of rotating electrical machine can be predicted by identifying the magnetic properties of the magnetic material. The magnetic properties should be properly measured since there are some variations of vector flux density in the rotating machine. In this paper, the SOMALOY 700 material has been measured under x, y and z- axes flux density penetration by using the 3-D tester. The calibrated sensing coils are used in detecting the flux densities which have been generated by the Labview software. The measured sensing voltages are used in obtaining the magnetic properties of the sample such as magnetic flux density B, magnetic field strength H, hysteresis loop which can be used to calculate the total core loss of the sample. The results of the measurement are analyzed by using the Mathcad software before being compared to another material.

Magnetic properties of a doped graphene-like bilayer

Energy Technology Data Exchange (ETDEWEB)

Guo, An-Bang [School of Science, Shenyang University of Technology, Shenyang 110870 (China); Jiang, Wei, E-mail: weijiang.sut.edu@gmail.com [School of Science, Shenyang University of Technology, Shenyang 110870 (China); Zhang, Na [Shenyang Normal University, Shenyang 110034 (China)

2017-05-15

A doped graphene-like bilayer is described using a four-sublattice Heisenberg model both ferromagnetic and antiferrimagnetic couplings. The magnetic properties of the bilayer system are studied using the Heisenberg model, retarded Green's function and the linear spin-wave approximation. The spin-wave spectra, energy gap, and the magnetization and quantum fluctuation of the system at the ground state are calculated with various intra- and interlayer couplings. The results indicate that the effect of antiferromagnetic exchange coupling on the magnetic properties of the system is significant. Magnetizations at low temperature show intersection points due to the quantum effects.

Magnetic properties of partially oxidized Fe films

Science.gov (United States)

Garcia, Miguel Angel; Lopez-Dominguez, Victor; Hernando, Antonio

Hybrid magnetic nanostructures exhibit appealing properties due to interface and proximity effects. A simple and interesting system of hybrid magnetic nanomaterials are partially oxidized ferromagnetic films. We have fabricated Fe films by thermal evaporation and performed a partial oxidation to magnetite (Fe3O4) by annealing in air at different times and temperatures. The magnetic properties of the films evolve from those of pure metallic iron to pure magnetite, showing intermediate states where the proximity effects control the magnetic behavior. At some stages, the magnetization curves obtained by SQUID and MOKE magnetometry exhibit important differences due to the dissimilar contribution of both phases to the magneto-optical response of the system This work has been supported by the Ministerio Español de Economia y Competitividad (MINECO) MAT2013-48009-C4-1. V.L.D and M.A.G. acknowledges financial support from BBVA foundation.

Design and development of ITER high-frequency magnetic sensor

Energy Technology Data Exchange (ETDEWEB)

Ma, Y., E-mail: Yunxing.Ma@iter.org [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); Fircroft Engineering, Lingley House, 120 Birchwood Point, Birchwood Boulevard, Warrington, WA3 7QH (United Kingdom); Vayakis, G. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); Begrambekov, L.B. [National Research Nuclear University (MEPhI), 115409, Moscow, Kashirskoe shosse 31 (Russian Federation); Cooper, J.-J. [Culham Centre for Fusion Energy (CCFE), Abingdon, Oxfordshire OX14 3DB (United Kingdom); Duran, I. [IPP Prague, Za Slovankou 1782/3, 182 00 Prague 8 (Czech Republic); Hirsch, M.; Laqua, H.P. [Max-Planck-Institut für Plasmaphysik, Teilinstitut Greifswald, Wendelsteinstraße 1, D-17491 Greifswald (Germany); Moreau, Ph. [CEA Cadarache, 13108 Saint Paul lez Durance Cedex (France); Oosterbeek, J.W. [Eindhoven University of Technology (TU/e), PO Box 513, 5600 MB Eindhoven (Netherlands); Spuig, P. [CEA Cadarache, 13108 Saint Paul lez Durance Cedex (France); Stange, T. [Max-Planck-Institut für Plasmaphysik, Teilinstitut Greifswald, Wendelsteinstraße 1, D-17491 Greifswald (Germany); Walsh, M. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France)

2016-11-15

Highlights: • ITER high-frequency magnetic sensor system has been designed. • Prototypes have been successfully manufactured. • Manufactured prototypes have been tested in various labs. • Test results experimentally validated the design. - Abstract: High-frequency (HF) inductive magnetic sensors are the primary ITER diagnostic set for Toroidal Alfvén Eigenmodes (TAE) detection, while they also supplement low-frequency MHD and plasma equilibrium measurements. These sensors will be installed on the inner surface of ITER vacuum vessel, operated in a harsh environment with considerable neutron/nuclear radiation and high thermal load. Essential components of the HF sensor system, including inductive coil, electron cyclotron heating (ECH) shield, electrical cabling and termination load, have been designed to meet ITER measurement requirements. System performance (e.g. frequency response, thermal conduction) has been assessed. A prototyping campaign was initiated to demonstrate the manufacturability of the designed components. Prototypes have been produced according to the specifications. A series of lab tests have been performed to examine assembly issues and validate electrical and thermo-mechanical aspects of the design. In-situ microwave radiation test has been conducted in the MISTRAL test facility at IPP-Greifswald to experimentally examine the microwave shielding efficiency and structural integrity of the ECH shield. Low-power microwave attenuation measurement and scanning electron microscopic inspection were conducted to probe and examine the quality of the metal coating on the ECH shield.

Fetal exposure to low frequency electric and magnetic fields

Energy Technology Data Exchange (ETDEWEB)

Cech, R; Leitgeb, N; Pediaditis, M [Institute of Clinical Engineering, Graz University of Technology, Inffeldgasse 18, 8010 Graz (Austria)

2007-02-21

To investigate the interaction of low frequency electric and magnetic fields with pregnant women and in particular with the fetus, an anatomical voxel model of an 89 kg woman at week 30 of pregnancy was developed. Intracorporal electric current density distributions due to exposure to homogeneous 50 Hz electric and magnetic fields were calculated and results were compared with basic restrictions recommended by ICNIRP guidelines. It could be shown that the basic restriction is met within the central nervous system (CNS) of the mother at exposure to reference level of either electric or magnetic fields. However, within the fetus the basic restriction is considerably exceeded. Revision of reference levels might be necessary.

Fetal exposure to low frequency electric and magnetic fields

International Nuclear Information System (INIS)

Cech, R; Leitgeb, N; Pediaditis, M

2007-01-01

To investigate the interaction of low frequency electric and magnetic fields with pregnant women and in particular with the fetus, an anatomical voxel model of an 89 kg woman at week 30 of pregnancy was developed. Intracorporal electric current density distributions due to exposure to homogeneous 50 Hz electric and magnetic fields were calculated and results were compared with basic restrictions recommended by ICNIRP guidelines. It could be shown that the basic restriction is met within the central nervous system (CNS) of the mother at exposure to reference level of either electric or magnetic fields. However, within the fetus the basic restriction is considerably exceeded. Revision of reference levels might be necessary

Magnetic properties of hematite nanoparticles

DEFF Research Database (Denmark)

Bødker, Franz; Hansen, Mikkel Fougt; Bender Koch, Christian

2000-01-01

The magnetic properties of hematite (alpha-Fe2O3) particles with sizes of about 16 nm have been studied by use of Mossbauer spectroscopy, magnetization measurements, and neutron diffraction. The nanoparticles are weakly ferromagnetic at temperatures at least down to 5 K with a spontaneous...... magnetization that is only slightly higher than that of weakly ferromagnetic bulk hematite. At T greater than or similar to 100 K the Mossbauer spectra contain a doublet, which is asymmetric due to magnetic relaxation in the presence of an electric field gradient in accordance with the Blume-Tjon model......, Simultaneous fitting of series of Mossbauer spectra obtained at temperatures from 5 K to well above the superparamagnetic blocking temperature allowed the estimation of the pre-exponential factor in Neel's expression for the superparamagnetic relaxation time, tau(0) = (6 +/- 4) X 10(-11) s and the magnetic...

Properties and practical performance of SC magnets in accelerators

International Nuclear Information System (INIS)

Schmueser, P.

1992-01-01

A report is given on the properties and performance of superconducting accelerator magnets in the 5-6 Tesla regime. Most of the information stems from the industrially produced HERA magnets which were thoroughly tested both at industry and at DESY; data from prototype magnets for RHIC and SSC are also included. Persistent current effects were studied in detail. During the commissioning of the proton-electron collider HERA the superconducting magnets worked with high reliability and their properties were exactly as predicted from the magnetic measurements. (author) 11 refs.; 8 figs

Magnetic properties of permalloy films with different thicknesses deposited onto obliquely sputtered Cu underlayers

International Nuclear Information System (INIS)

Li, Xiaoyu; Sun, Xiaojun; Wang, Jianbo; Liu, Qingfang

2015-01-01

In this work, the influence of obliquely sputtered Cu underlayer of 10 nm on the magnetic properties of normally sputtered Permalloy thin films with different thicknesses from 10 nm to 150 nm has been investigated. It has been found that the samples with the Permalloy layer thickness ranging from 10 nm to 70 nm exhibit a good in-plane uniaxial magnetic anisotropy, and the increase of the film thickness leads to a decrease of the anisotropy field and the natural resonance frequency. The critical Permalloy layer thickness for stripe domain initiation of these films is about 80 nm, which is thinner than that of obliquely sputtered Permalloy thin films without an underlayer. The characteristic shapes of hysteresis loops which can be called ''transcritical'' are observed above the critical thickness. The condition and mechanism of appearing stripe domain structure were discussed and it has been found that the frequency response of permeability of the anisotropic films shows the characteristics of multi-peak resonance. - Highlights: • Py films were fabricated on obliquely sputtered Cu underlayers by RF magnetron sputtering. • Effects of Py layer thickness on anisotropy, ferromagnetic resonance frequency have been studied. • Samples with Py layer (<70 nm) show a good in-plane uniaxial magnetic anisotropy. • Samples with Py layer (>80 nm) show stripe domains and multi-peaks in permeability spectra

Low-frequency magnetic field fluctuations in Venus' solar wind interaction region: Venus Express observations

Directory of Open Access Journals (Sweden)

L. Guicking

2010-04-01

Full Text Available We investigate wave properties of low-frequency magnetic field fluctuations in Venus' solar wind interaction region based on the measurements made on board the Venus Express spacecraft. The orbit geometry is very suitable to investigate the fluctuations in Venus' low-altitude magnetosheath and mid-magnetotail and provides an opportunity for a comparative study of low-frequency waves at Venus and Mars. The spatial distributions of the wave properties, in particular in the dayside and nightside magnetosheath as well as in the tail and mantle region, are similar to observations at Mars. As both planets do not have a global magnetic field, the interaction process of the solar wind with both planets is similar and leads to similar instabilities and wave structures. We focus on the spatial distribution of the wave intensity of the fluctuating magnetic field and detect an enhancement of the intensity in the dayside magnetosheath and a strong decrease towards the terminator. For a detailed investigation of the intensity distribution we adopt an analytical streamline model to describe the plasma flow around Venus. This allows displaying the evolution of the intensity along different streamlines. It is assumed that the waves are generated in the vicinity of the bow shock and are convected downstream with the turbulent magnetosheath flow. However, neither the different Mach numbers upstream and downstream of the bow shock, nor the variation of the cross sectional area and the flow velocity along the streamlines play probably an important role in order to explain the observed concentration of wave intensity in the dayside magnetosheath and the decay towards the nightside magnetosheath. But, the concept of freely evolving or decaying turbulence is in good qualitative agreement with the observations, as we observe a power law decay of the intensity along the streamlines. The observations support the assumption of wave convection through the magnetosheath, but

Transparency of magnetized plasma at the cyclotron frequency

International Nuclear Information System (INIS)

Shvets, G.; Wurtele, J.S.

2002-01-01

Electromagnetic radiation is strongly absorbed by a magnetized plasma if the radiation frequency equals the cyclotron frequency of plasma electrons. It is demonstrated that absorption can be completely canceled in the presence of a magnetostatic field of an undulator, or a second radiation beam, resulting in plasma transparency at the cyclotron frequency. This effect is reminiscent of the electromagnetically induced transparency (EIT) of three-level atomic systems, except that it occurs in a completely classical plasma. Unlike the atomic systems, where all the excited levels required for EIT exist in each atom, this classical EIT requires the excitation of nonlocal plasma oscillation. A Lagrangian description was used to elucidate the physics of the plasma transparency and control of group and phase velocity. This control leads to applications for electromagnetic pulse compression and electron/ion acceleration

High Frequency LLC Resonant Converter with Magnetic Shunt Integrated Planar Transformer

DEFF Research Database (Denmark)

Li, Mingxiao; Ouyang, Ziwei; Andersen, Michael A. E.

2018-01-01

High Frequency LLC requires a smaller resonant inductance which is usually implemented by transformer leakage inductance. However, this small resonant inductance is difficult to deal with a wide input voltage range. This paper proposes a new method to implement a larger resonant inductance by using...... a magnetic shunt integrated into planar transformer. The switching frequency can be greatly narrowed by designing a smaller inductance ratio of magnetizing inductance to resonant inductance. Since this method can well deal with a wide input voltage range without adding extra inductor and increasing the size...... of the transformer, the power density can be improved. The precise leakage inductance calculation method for this transformer and detailed LLC converter design procedure are presented. A 280-380V and 48V-100W half bridge LLC resonant converter with 1 MHz resonant frequency is built to verify the design methodology....

Structural and magnetic properties of NiZn-ferrite thin films prepared by radio frequency magnetron sputtering

International Nuclear Information System (INIS)

Liu Yingli; Li Yuanxun; Zhang Huaiwu; Chen Daming; Mu Chunhong

2011-01-01

Polycrystalline NiZn-ferrite thin films were deposited on Si(100) substrate by rf magnetron sputtering, using targets with a nominal composition of Ni 0.5 Zn 0.5 Fe 2 O 4 . The effects of substrate condition, sputtering pressure, and postannealing on the structure and magnetic properties of thin films have been investigated. Our results show that the preferred orientation of the NiZn spinel film changed from (311) to (400) with increasing the Ar pressure from 0.8 to 1.6 Pa, meanwhile, the grain size also increased. Atomic force microscopy analysis indicates that perfect surface morphology of the film can be obtained at a relatively lower sputtering pressure of 1.0 Pa. The relative percentage of residual oxygen increases significantly on a condition of lower sputtering pressure, and plays an important role in film structure due to the strong molecular adsorption tendency of oxygen on the film surface during the deposition process. A thin film with a typical thickness of 1 μm, a saturation magnetization of 150 emu/cm 3 , and a coercivity of 8.8 kA/m has been obtained after annealing at 800 deg. C, which has the potential application in magnetic integrated circuits.

Nanocomposite permanent magnetic materials Nd-Fe-B type: The influence of nanocomposite on magnetic properties

Directory of Open Access Journals (Sweden)

Talijan Nadežda M.

2005-01-01

Full Text Available The influence on the magnetic properties of nanocristalline ribbons and powders has character of microstructure, between others – the grain size volume of hard and soft magnetic phases and their distribution. Magnetic properties of ribbons and powders depend mainly on their chemical composition and parameters of their heat treatment [1]. Technology of magnets from nanocristalline ribbon consists of the following process: preparing the Nd-Fe- B alloy, preparing the ribbon, powdering of the ribbon, heat treatment of the powder and finally preparing the magnets. Nanocomposite permanent magnet materials based on Nd-Fe- B alloy with Nd low content are a new type of permanent magnetic material. The microstructure of this nanocomposite permanent magnet is composed of a mixture of magnetically soft and hard phases which provide so called exchange coupling effect.

Francisella tularensis detection using magnetic labels and a magnetic biosensor based on frequency mixing

International Nuclear Information System (INIS)

Meyer, Martin H.F.; Krause, Hans-Joachim; Hartmann, Markus; Miethe, Peter; Oster, Juergen; Keusgen, Michael

2007-01-01

A biosensor that uses resonant coils with a special frequency-mixing technique and magnetic beads as detectable labels has been established for the detection of Francisella tularensis, the causative agent for tularemia. The detection principle is based on a sandwich immunoassay using an anti-Ft antibody for immunofiltration immobilized to ABICAP[reg] polyethylene filters, and biotinylated with streptavidin-coated magnetic beads as labels. The linear detection range of this biosensor was found to be 10 4 -10 6 cfu F. tularensis lipopolysaccharide (LPS) per ml. Tested sample matrices were physiological PBS buffer and rabbit serum

Magnetic properties of (misch metal, Nd-Fe-B melt-spun magnets

Directory of Open Access Journals (Sweden)

R. Li

2017-05-01

Full Text Available The effect of replacing Nd with misch metal (MM on magnetic properties and thermal stability has been investigated on melt-spun (Nd1-xMMx13.5Fe79.5B7 ribbons by varying x from 0 to 1. All of the alloys studied crystallize in the tetragonal 2:14:1 structure with single hard magnetic phase. Curie temperature (Tc, coercivity (Hcj, remanence magnetization (Br and maximum energy product ((BHmax all decrease with MM content. The melt-spun MM13.5Fe79.5B ribbons with high ratio of La and Ce exhibit high magnetic properties of Hcj = 8.2 kOe and (BHmax= 10.3 MGOe at room temperature. MM substitution also significantly strengthens the temperature stability of coercivity. The coercivities of the samples with x = 0.2 and even 0.4 exhibit large values close to that of Nd13.5Fe79.5B7 ribbons above 400 K.

Mechanical properties, microstructure and magnetic properties of composite magnet base on SrO.6Fe_2O_3 (SRM)-thermoplastic and thermoset polymer

International Nuclear Information System (INIS)

Grace Tj Sulungbudi; Aloma Karo Karo; Mujamilah; Sudirman

2010-01-01

The use of magnets in industrial applications do not always require high magnetic properties. Therefore, the use of polymer as a matrix that serves as a binder can be applied to obtain lightweight, flexible and cheap composite magnet. This report discuss composite magnet base on SrO.6Fe_2O_3(SRM)-thermoplastic and thermoset polymer. Thermoplastic polymer consist of polypropylene (PP) type of PP2 and PP10 and polyethylene (PE) type of LDPE were used. For thermoset polymer, epoxy and polyester were used. Synthesis of composite magnet based on thermoplastic polymer (PP2, PP10, LDPE) were carried using the blending method, while the thermoset composites magnet using casting method. Thermoplastic composite magnets were prepared with compositions of 50, 41, 38, 33 and 29 % weight of SRM with the blending temperature of 160 °C for LDPE and 180 °C for PP2 and PP10. For thermoset composite magnets, the compositions were 30, 40, 50 and 60 % by weight of SRM. The mechanical test conducted include tensile strength and elongation at break. Microstructure on the surface of the composite materials were observed using SEM (Scanning Electron Microscope) and the magnetic properties were measured using VSM (Vibrating Sample Magnetometer). The SEM results showed the formation of flat shape powder particle with size of 1.6 µm. In general, the mechanical properties of polypropylene polymer composite magnet are better than that using polyethylene (LDPE) binder. For polypropylene binder PP10 is better than PP2. Magnetic properties are not significantly affected by the change of polymer or binder types. (author)

Magnetoresistance and magnetic properties of the double perovskites

International Nuclear Information System (INIS)

Philipp, J.B.; Majewski, P.; Resinger, D.; Gepraegs, S; Opel, M.; Reb, A.; Alff, L.; Gross, R.

2004-01-01

The magnetic double perovskite materials of composition A 2 BB'O 6 with A an alkaline earth ion and B and B' a magnetic and non-magnetic transition metal or lanthanide ions, respectively, have attracted considerable attention due to their interesting magnetic properties ranging from antiferromagnetism to geometrically frustrated spin systems and ferromagnetism. With respect to application in spin electronics, the ferromagnetic double perovskites with BB' = CrW, CrRe, FeMo or FeRe and A = Ca, Ba, Sr are highly interesting due to their in most cases high Curie temperatures well above room temperature and their half-magnetic behaviour. Here, we summarize the structural, magnetotransport, magnetic and optical properties of the ferromagnetic double perovskites and discuss the underlying physics. In particular, we discuss the impact of the steric effects resulting in a distorted perovskite structure, doping effects obtained by a partial replacing of the divalent alkaline earth ions on the A site by a trivalent lanthanide as well as B/B' cationic disorder on the Curie temperature T C , the saturation magnetization and the magnetotransport properties. Our results support the presence of a kinetic energy driven mechanism in the ferromagnetic double perovskites, where ferromagnetism is stabilised by a hybridization of states of the non-magnetic B'- site positioned in between the high spin B-sites. (author)

Transparency of Magnetized Plasma at Cyclotron Frequency; TOPICAL

International Nuclear Information System (INIS)

G. Shvets; J.S. Wurtele

2002-01-01

Electromagnetic radiation is strongly absorbed by a magnetized plasma if the radiation frequency equals the cyclotron frequency of plasma electrons. It is demonstrated that absorption can be completely canceled in the presence of a magnetostatic field of an undulator or a second radiation beam, resulting in plasma transparency at the cyclotron frequency. This effect is reminiscent of the electromagnetically induced transparency (EIT) of the three-level atomic systems, except that it occurs in a completely classical plasma. Unlike the atomic systems, where all the excited levels required for EIT exist in each atom, this classical EIT requires the excitation of the nonlocal plasma oscillation. The complexity of the plasma system results in an index of refraction at the cyclotron frequency that differs from unity. Lagrangian description was used to elucidate the physics and enable numerical simulation of the plasma transparency and control of group and phase velocity. This control naturally leads to applications for electromagnetic pulse compression in the plasma and electron/ion acceleration

Enhancement in magnetic properties of magnesium substituted bismuth ferrite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Xu, Jianlong; Xie, Dan, E-mail: xiedan@mail.tsinghua.edu.cn, E-mail: RenTL@mail.tsinghua.edu.cn; Teng, Changjiu; Zhang, Xiaowen; Zhang, Cheng; Sun, Yilin; Ren, Tian-Ling, E-mail: xiedan@mail.tsinghua.edu.cn, E-mail: RenTL@mail.tsinghua.edu.cn [Institute of Microelectronics, Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084 (China); Zeng, Min; Gao, Xingsen [Institute for Advanced Materials and Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006 (China); Zhao, Yonggang [Department of Physics and State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084 (China)

2015-06-14

We report a potential way to effectively improve the magnetic properties of BiFeO{sub 3} (BFO) nanoparticles through Mg{sup 2+} ion substitution at the Fe-sites of BFO lattice. The high purity and structural changes induced by Mg doping are confirmed by X-ray powder diffractometer and Raman spectra. Enhanced magnetic properties are observed in Mg substituted samples, which simultaneously exhibit ferromagnetic and superparamagnetic properties at room temperature. A physical model is proposed to support the observed ferromagnetism of Mg doped samples, and the superparamagnetic properties are revealed by the temperature dependent magnetization measurements. The improved magnetic properties and soft nature obtained by Mg doping in BFO nanoparticles demonstrate the possibility of BFO nanoparticles to practical applications.

Influence of starting powder milling on magnetic properties of Mn-Zn ferrite

Directory of Open Access Journals (Sweden)

Miodrag M. Milutinov

2017-06-01

Full Text Available In this paper, the influence of additional sieving and milling of starting industrial Mn-Zn powders on magnetic properties was investigated. The starting powder was milled for 60 minutes, followed by sieving through 325 and 400 meshes. The starting and milled powders were used to fabricate toroid shaped samples sintered at 1200°C for 2 hours. Structural parameters of the fabricated samples were analysed by X-ray diffraction and scanning electron microscopy. Complex permeability, core loss density, and hysteresis were measured using the modified watt-meter method. The complex permeability and hysteresis loop were modelled with a new model proposed in the paper. The core loss density was modelled with the Steinmetz empirical equation. The experimental results and calculations show the significance of the additional milling and sieving process on magnetic properties of Mn-Zn ferrite in the frequency range 0.1-10MHz. These processes increase the relative permeability about 3 times and decrease the core loss 4 times by milling of the starting powder.

Exposure estimates based on broadband elf magnetic field measurements versus the ICNIRP multiple frequency rule

International Nuclear Information System (INIS)

Paniagua, Jesus M.; Rufo, Montana; Jimenez, Antonio; Pachon, Fernando T.; Carrero, Julian

2015-01-01

The evaluation of exposure to extremely low-frequency (ELF) magnetic fields using broadband measurement techniques gives satisfactory results when the field has essentially a single frequency. Nevertheless, magnetic fields are in most cases distorted by harmonic components. This work analyses the harmonic components of the ELF magnetic field in an outdoor urban context and compares the evaluation of the exposure based on broadband measurements with that based on spectral analysis. The multiple frequency rule of the International Commission on Non-ionizing Radiation Protection (ICNIRP) regulatory guidelines was applied. With the 1998 ICNIRP guideline, harmonics dominated the exposure with a 55 % contribution. With the 2010 ICNIRP guideline, however, the primary frequency dominated the exposure with a 78 % contribution. Values of the exposure based on spectral analysis were significantly higher than those based on broadband measurements. Hence, it is clearly necessary to determine the harmonic components of the ELF magnetic field to assess exposure in urban contexts. (authors)

Structure and Magnetic Properties of Rare Earth Doped Transparent Alumina

Science.gov (United States)

Limmer, Krista; Neupane, Mahesh; Chantawansri, Tanya

Recent experimental studies of rare earth (RE) doped alumina suggest that the RE induced novel phase-dependent structural and magnetic properties. Motivated by these efforts, the effects of RE doping of alpha and theta alumina on the local structure, magnetic properties, and phase stability have been examined in this first principles study. Although a direct correlation between the magnetic field dependent materials properties observed experimentally and calculated from first principles is not feasible because of the applied field and the scale, the internal magnetic properties and other properties of the doped materials are evaluated. The RE dopants are shown to increase the substitutional site volume as well as increasingly distort the site structure as a function of ionic radii. Doping both the alpha (stable) and theta (metastable) phases enhanced the relative stability of the theta phase. The energetic doping cost and internal magnetic moment were shown to be a function of the electronic configuration of the RE-dopant, with magnetic moment directly proportional to the number of unpaired electrons and doping cost being inversely related.

Effect of {gamma}-ray irradiation on the magnetic properties of NdFeB and Fe-Cr-Co permanent magnets

Energy Technology Data Exchange (ETDEWEB)

Gao, R.S. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Zhen, L. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)]. E-mail: zhenl@hit.edu.cn; Li, G.A. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Xu, C.Y. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Shao, W.Z. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

2006-07-15

The effect of {gamma}-ray irradiation on the magnetic properties of NdFeB and Fe-Cr-Co permanent magnets has been investigated. The magnetic flux loss of two kinds of magnets before and after irradiation was measured. Results show that the effect of {gamma}-ray irradiation on the magnetic properties of sintered NdFeB is not so obvious as that on Fe-Cr-Co magnet. Irradiation-induced damage from {gamma}-ray for the Fe-Cr-Co magnets was characterized for the first time. The decline of permanent magnetic properties of Fe-Cr-Co magnet induced by {gamma}-ray irradiation is reversible except for the maximum energy product (BH){sub max}. The difference of coercivity mechanism between these two kinds of permanent magnets is responsible for the different dependence of magnetic properties loss induced by {gamma}-ray irradiation.

Microstructure characterization and magnetic properties of nano structured materials

International Nuclear Information System (INIS)

Sun, X.C.

2000-01-01

The present thesis deals with the unique microstructural properties and their novel magnetic properties of core-shell Ni-Ce nano composite particles, carbon encapsulated Fe, Co, and Ni nanoparticles and the nano crystallization behavior of typical ferromagnetic Fe 78 Si 9 B 13 ribbons. These properties have intensively been investigated by high resolution transmission electron microscopy (HREM), X-ray diffraction (XRD), scanning electron microscopy (Sem), X-ray energy dispersive spectroscopy (Eds.); selected area electron diffraction pattern (SAED), Ft-IR, differential scanning calorimeter (DSC). In addition, magnetic moments measurements at different temperatures and applied fields have been performed by transmission Moessbauer spectroscopy, superconducting quantum interference device magnetometer (SQUID), and vibrating sample magnetometer (VSM). The present studies may provide the insights for the better understanding of the correlation between the unique microstructure and novel magnetic properties for several magnetic nano structured materials. (Author)

High field high frequency EPR techniques and their application to single molecule magnets

International Nuclear Information System (INIS)

Edwards, R.S.; Hill, S.; Goy, P.; Wylde, R.; Takahashi, S.

2004-01-01

We present details of a new high-field/high-frequency EPR technique, and its application to measurements of single-molecule magnets (SMMs). By using a quasi-optical set-up and microwave sources covering a continuous frequency range from 170 to 600 GHz, in conjunction with a millimetre-wave vector network analyser, we are able to measure EPR to high magnetic fields. For example, a g=2 system will exhibit EPR at about 14 T at a frequency of 400 GHz. We illustrate the technique by presenting details of recent high-frequency experiments on several SMMs which are variations of the well-known SMM Mn 12 -Ac. This material has a spin ground state of S=10 and large uniaxial anisotropy, hence frequencies above 300 GHz are required in order to observe EPR from the ground state

Tailoring the bandgap and magnetic properties by bismuth ...

Indian Academy of Sciences (India)

2017-11-30

Nov 30, 2017 ... interaction between magnetic rare-earth ion and weak ferro- magnetic Cr3+ ions .... (colour online) XRD patterns at RT for compositions x = 0, 0.1 and ..... CrO6 as observed in B1g(3) and B3g(3), which shifts in blue frequency ...

Magnetization of left-handed metamaterials

International Nuclear Information System (INIS)

Kourakis, I; Shukla, P K

2006-01-01

We propose a possible mechanism for the generation of magnetic fields in negative refraction index composite metamaterials. Considering the propagation of a high-frequency modulated amplitude electric field in a left-handed material (LHM), we show that the ponderomotive interaction between the field and low-frequency potential distributions leads to spontaneous generation of magnetic fields, whose form and properties are discussed

Crystallization kinetics and magnetic properties of FeSiCr amorphous alloy powder cores

Energy Technology Data Exchange (ETDEWEB)

Xu, Hu-ping [School of Logistics Engineering, Wuhan University of Technology, Wuhan 430063 (China); Wang, Ru-wu, E-mail: ruwuwang@hotmail.com [National Engineering Research Center For Silicon Steel, Wuhan 430080 (China); College of Materials Science and Metallurgical Engineering, Wuhan University of Science and Technology, Wuhan 430081 (China); Wei, Ding [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Zeng, Chun [National Engineering Research Center For Silicon Steel, Wuhan 430080 (China)

2015-07-01

The crystallization kinetics of FeSiCr amorphous alloy, characterized by the crystallization activation energy, Avrami exponent and frequency factor, was studied by non-isothermal differential scanning calorimetric (DSC) measurements. The crystallization activation energy and frequency factor of amorphous alloy calculated from Augis–Bennett model were 476 kJ/mol and 5.5×10{sup 18} s{sup −1}, respectively. The Avrami exponent n was calculated to be 2.2 from the Johnson–Mehl–Avrami (JMA) equation. Toroid-shaped Fe-base amorphous powder cores were prepared from the commercial FeSiCr amorphous alloy powder and subsequent cold pressing using binder and insulation. The characteristics of FeSiCr amorphous alloy powder and the effects of compaction pressure and insulation content on the magnetic properties, i.e., effective permeability μ{sub e}, quality factor Q and DC-bias properties of FeSiCr amorphous alloy powder cores, were investigated. The FeSiCr amorphous alloy powder cores exhibit a high value of quality factor and a stable permeability in the frequency range up to 1 MHz, showing superior DC-bias properties with a “percent permeability” of more than 82% at H=100 Oe. - Highlights: • The crystallization kinetics of FeSiCr amorphous alloy was investigated. • The FeSiCr powder cores exhibit a high value of Q and a stable permeability. • The FeSiCr powder cores exhibit superior DC-bias properties.

Structural, magnetic and dielectric properties of Pr-modified BiFeO3 multiferroic

International Nuclear Information System (INIS)

Varshney, Dinesh; Sharma, Poorva; Satapathy, S.; Gupta, P.K.

2014-01-01

Graphical abstract: -- Highlights: • BFO and Bi 0.95 Pr 0.05 FeO 3 prepared successfully via solid state reaction route. • XRD confirms rhombohedral structure with space group R3c. • Relaxation process is attributed to thermal motion and hopping of V O 2+ . • Magnetization is enhanced in Bi 0.95 Pr 0.05 FeO 3 sample. • Enhanced magnetization stem from suppression of the spiral spin modulation. -- Abstract: The structural, vibrational, magnetic and dielectric properties of polycrystalline BiFeO 3 and Bi 0.95 Pr 0.05 FeO 3 are investigated by combining X-ray diffraction, Raman scattering spectra, magnetometry and dielectric measurements. Structural symmetry with rhombohedral R3c phase is revealed for both parent and 5% Pr substitution at Bi site, serving no chemical pressure and causes no structural transition from R3c to any other phase is identified from X-ray diffraction patterns and Raman scattering spectra. The shifting of phonon modes towards higher frequency side is attributed to lower atomic mass of Pr ion as compared to Bi ion. The magnetic measurements at room temperature indicate that Pr substitution induces ferromagnetism and discerns large and non-zero remnant magnetization as compare to pristine BiFeO 3 . Both dielectric permittivity and loss factor of Bi 0.95 Pr 0.05 FeO 3 strongly decreases with increased frequency. Significant role of hopping of oxygen ion vacancies in Bi 0.95 Pr 0.05 FeO 3 is inferred from modulus spectra and ac conductivity analysis

Effect of low frequency magnetic fields on the growth of MNP-treated HT29 colon cancer cells

Science.gov (United States)

Spyridopoulou, K.; Makridis, A.; Maniotis, N.; Karypidou, N.; Myrovali, E.; Samaras, T.; Angelakeris, M.; Chlichlia, K.; Kalogirou, O.

2018-04-01

Recent investigations have attempted to understand and exploit the impact of magnetic field-actuated internalized magnetic nanoparticles (MNPs) on the proliferation rate of cancer cells. Due to the complexity of the parameters governing magnetic field-exposure though, individual studies to date have raised contradictory results. In our approach we performed a comparative analysis of key parameters related to the cell exposure of cancer cells to magnetic field-actuated MNPs, and to the magnetic field, in order to better understand the factors affecting cellular responses to magnetic field-stimulated MNPs. We used magnetite MNPs with a hydrodynamic diameter of 100 nm and studied the proliferation rate of MNPs-treated versus untreated HT29 human colon cancer cells, exposed to either static or alternating low frequency magnetic fields with varying intensity (40-200 mT), frequency (0-8 Hz) and field gradient. All three parameters, field intensity, frequency, and field gradient affected the growth rate of cells, with or without internalized MNPs, as compared to control MNPs-untreated and magnetic field-untreated cells. We observed that the growth inhibitory effects induced by static and rotating magnetic fields were enhanced by pre-treating the cells with MNPs, while the growth promoting effects observed in alternating field-treated cells were weakened by MNPs. Compared to static, rotating magnetic fields of the same intensity induced a similar extend of cell growth inhibition, while alternating fields of varying intensity (70 or 100 mT) and frequency (0, 4 or 8 Hz) induced cell proliferation in a frequency-dependent manner. These results, highlighting the diverse effects of mode, intensity, and frequency of the magnetic field on cell growth, indicate that consistent and reproducible results can be achieved by controlling the complexity of the exposure of biological samples to MNPs and external magnetic fields, through monitoring crucial experimental parameters. We

Investigation of Structural, Morphological, Magnetic Properties and Biomedical applications of Cu2+ Substituted Uncoated Cobalt Ferrite Nanoparticles

Directory of Open Access Journals (Sweden)

M. Margabandhu

Full Text Available ABSTRACT In the present work, Cu2+ substituted cobalt ferrite (Co1-xCuxFe2O4, x = 0, 0.3, 0.5, 0.7 and 1 magnetic nanopowders were synthesized via chemical co-precipitation method. The prepared powders were investigated by various characterization methods such as X-ray diffraction analysis (XRD, scanning electron microscope analysis (SEM, vibrating sample magnetometer analysis (VSM and fourier transform infrared spectroscopy analysis (FTIR. The XRD analysis reveals that the synthesized nanopowders possess single phase centred cubic spinel structure. The average crystallite size of the particles ranging from 27-49 nm was calculated by using Debye-scherrer formula. Magnetic properties of the synthesized magnetic nanoparticles are studied by using VSM. The VSM results shows the magnetic properties such as coercivity, magnetic retentivity decreases with increase in copper substitution whereas the saturation magnetization shows increment and decrement in accordance with Cu2+ substitution in cobalt ferrite nanoparticles. SEM analysis reveals the morphology of synthesized magnetic nanoparticles. FTIR spectra of Cu2+ substituted cobalt ferrite magnetic nanoparticles were recorded in the frequency range 4000-400cm-1. The spectrum shows the presence of water adsorption and metal oxygen bonds. The adhesion nature of Cu2+ substituted cobalt ferrite magnetic nanoparticles with bacteria in reviewed results indicates that the synthesized nanoparticles could be used in biotechnology and biomedical applications.

Electrical and magnetic properties of electrodeposited nickel incorporated diamond-like carbon thin films

Energy Technology Data Exchange (ETDEWEB)

Pandey, B., E-mail: pandey.beauty@yahoo.com [Department of Applied Physics, Indian School of Mines, Dhanbad 826004 (India); Das, D. [UGC-DAE CSR, Sector III/LB-8, Bidhan Nagar, Kolkata 700098 (India); Kar, A.K. [Department of Applied Physics, Indian School of Mines, Dhanbad 826004 (India)

2015-05-15

Highlights: • Electrical and magnetic properties of DLC and Ni-DLC thin films are studied. • The ohmicity and conductivity of DLC films rise with nickel addition. • The ohmicity of Ni-DLC is enhanced with increase in dilution of electrolyte. • Dielectric loss is high for Ni-DLC and decreases with frequency till 100 kHz. • (m–H) and (m–T) curves of Ni-DLC indicate superparamagnetic behavior. - Abstract: Nanocomposite diamond-like carbon (DLC) thin films have been synthesized by incorporating nickel (Ni) nanoparticles in DLC matrix with varying concentration of nickel. DLC and Ni-DLC thin films have been deposited on ITO coated glass substrates employing low voltage electrodeposition method. Electrical properties of the samples were studied by measuring current–voltage characteristics and dielectric properties. The current approaches toward an ohmic behavior with metal addition. This tendency of increasing ohmicity is enhanced with increase in dilution of the electrolyte. The conductivity increases with Ni addition and interestingly it continues to increase with dilution of Ni concentration in the electrolyte in the range of our study. Magnetic properties for DLC and Ni-DLC thin film samples were examined by electron paramagnetic resonance (EPR) measurements and Super Conducting Quantum Interference Device (SQUID) measurements. g-Value for DLC is 2.074, whereas it decreases to 2.055 with Ni addition in the electrolyte. This decrement arises from the increased sp{sup 2} content in DLC matrix. The magnetic moment vs. magnetic field (m–H) curves of Ni-DLC indicate superparamagnetic behavior which may be due to ferromagnetic contribution from the incorporated nickel nanoparticles in the DLC matrix. The ZFC curve of Ni-DLC after the blocking temperature shows a combined contribution of ferromagnetic, superparamagnetic and paramagnetic nature of the materials persisting up to 300 K.

Large batch recycling of waste Nd–Fe–B magnets to manufacture sintered magnets with improved magnetic properties

International Nuclear Information System (INIS)

Li, X.T.; Yue, M.; Liu, W.Q.; Li, X.L.; Yi, X.F.; Huang, X.L.; Zhang, D.T.; Chen, J.W.

2015-01-01

The waste Nd–Fe–B sintered magnets up to 500 kg per batch were recycled to manufacture anisotropic sintered magnets by combination of hydrogen decrepitation (HD) and alloying technique. Magnetic properties and thermal stability of both the waste magnets and recycled magnets were investigated. The recycled magnet exhibits magnetic properties with remanence (B r ) of 12.38 kGs, coercivity (H ci ) of 24.89 kOe, and maximum energy product [(BH) max ] of 36.51 MGOe, respectively, which restores 99.20% of B r , 105.65% of H ci , and 98.65% of (BH) max of the waste magnets, respectively. The volume fraction of Nd-rich phase in the recycled magnets is about 10.1 vol.%, which is bigger than that of the waste magnets due to the additive of Nd 3 PrFe 14 B alloy containing more rare earth. The remanence temperature coefficient (α) and coercivity temperature coefficient (β) of the recycled magnets are −0.1155%/K and −0.5099%/K in the range of 288–423 K, respectively, which are comparative to those of the waste magnets. - Highlights: • Large batch recycling of waste Nd–Fe–B sintered magnets were performed. • The recycled magnet restores 99.20% of B r , 105.65% of H ci and 98.65% of (BH) max of the magnet. • The recycled magnets bears bigger volume fraction and better distribution of Nd-rich phase. • The recycled magnets exhibit similar temperature coefficients and maximum working temperature

Enhanced magnetic domain relaxation frequency and low power losses in Zn{sup 2+} substituted manganese ferrites potential for high frequency applications

Energy Technology Data Exchange (ETDEWEB)

Praveena, K., E-mail: praveenaou@gmail.com [Department of Physics, National Taiwan Normal University, Taipei, 11677, Taiwan (China); Chen, Hsiao-Wen [Department of Physics, National Taiwan Normal University, Taipei, 11677, Taiwan (China); Liu, Hsiang-Lin, E-mail: hliu@ntnu.edu.tw [Department of Physics, National Taiwan Normal University, Taipei, 11677, Taiwan (China); Sadhana, K., E-mail: sadhana@osmania.ac.in [Department of Physics, Osmania University, Saifabad, Hyderabad, 500004 (India); Murthy, S.R. [Department of Physics, Osmania University, Hyderabad, 500007 (India)

2016-12-15

Nowadays electronic industries prerequisites magnetic materials, i.e., iron rich materials and their magnetic alloys. However, with the advent of high frequency applications, the standard techniques of reducing eddy current losses, using iron cores, were no longer efficient or cost effective. Current market trends of the switched mode power supplies industries required even low energy losses in power conversion with maintenance of adequate initial permeability. From the above point of view, in the present study we aimed at the production of Manganese–Zinc ferrites prepared via solution combustion method using mixture of fuels and achieved low loss, high saturation magnetization, high permeability, and high magnetic domain relaxation frequency. The as-synthesized Zn{sup 2+} substituted MnFe{sub 2}O{sub 4} were characterized by X-ray diffractometer (XRD) and transmission electron microscopy (TEM). The fractions of Mn{sup 2+}, Zn{sup 2+} and Fe{sup 2+} cations occupying tetrahedral sites along with Fe occupying octahedral sites within the unit cell of all ferrite samples were estimated by Raman scattering spectroscopy. The magnetic domain relaxation was investigated by inductance spectroscopy (IS) and the observed magnetic domain relaxation frequency (f{sub r}) was increased with the increase in grain size. The real and imaginary part of permeability (μ′ and μ″) increased with frequency and showed a maximum above 100 MHz. This can be explained on the basis of spin rotation and domain wall motion. The saturation magnetization (M{sub s}), remnant magnetization (M{sub r}) and magneton number (µ{sub B}) decreased gradually with increasing Zn{sup 2+} concentration. The decrease in the saturation magnetization was discussed with Yafet–Kittel (Y–K) model. The Zn{sup 2+} concentration increases the relative number of ferric ions on the A sites, reduces the A–B interactions. The frequency dependent total power losses decreased as the zinc concentration increased

Magnetic microstructure and magnetic properties of spark plasma sintered NdFeB magnets

Energy Technology Data Exchange (ETDEWEB)

Huang, Y.L., E-mail: hyl1019_lin@163.com [School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063 (China); Wang, Y.; Hou, Y.H.; Wang, Y.L.; Wu, Y.; Ma, S.C. [School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063 (China); Liu, Z.W.; Zeng, D.C. [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Tian, Y.; Xia, W.X. [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Zhong, Z.C., E-mail: zzhong2014@sina.com [School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063 (China)

2016-02-01

Nanocrystalline NdFeB magnets were prepared by spark plasma sintering (SPS) technique using melt-spun ribbons as starting materials. A distinct two-zone structure with coarse grain zone and fine grain zone was formed in the SPSed magnets. Multi-domain particle in coarse grain zone and exchange interaction domain for fine grain zone were observed. Intergranular non-magnetic phase was favorable to improve the coercivity due to the enhancement of domain wall pinning effects and increased exchange-decouple. The remanent polarization of 0.83 T, coercivity of 1516 kA/m, and maximum energy product of 118 kJ/m{sup 3} are obtained for an isotropic magnet. - Highlights: • Nanocrystalline NdFeB magnets were prepared by spark plasma sintering technique. • Multi-domain particle and exchange interaction domain were observed. • Magnetic microstructure and their relation to the properties were investigated.

Molecular gyroscopes and biological effects of weak extremely low-frequency magnetic fields

International Nuclear Information System (INIS)

Binhi, V.N.; Savin, A.V.

2002-01-01

Extremely low-frequency magnetic fields are known to affect biological systems. In many cases, biological effects display 'windows' in biologically effective parameters of the magnetic fields: most dramatic is the fact that the relatively intense magnetic fields sometimes do not cause appreciable effect, while smaller fields of the order of 10-100 μT do. Linear resonant physical processes do not explain the frequency windows in this case. Amplitude window phenomena suggest a nonlinear physical mechanism. Such a nonlinear mechanism has been proposed recently to explain those 'windows'. It considers the quantum-interference effects on the protein-bound substrate ions. Magnetic fields cause an interference of ion quantum states and change the probability of ion-protein dissociation. This ion-interference mechanism predicts specific magnetic-field frequency and amplitude windows within which the biological effects occur. It agrees with a lot of experiments. However, according to the mechanism, the lifetime Γ -1 of ion quantum states within a protein cavity should be of unrealistic value, more than 0.01 s for frequency band 10-100 Hz. In this paper, a biophysical mechanism has been proposed, which (i) retains the attractive features of the ion interference mechanism, i.e., predicts physical characteristics that might be experimentally examined and (ii) uses the principles of gyroscopic motion and removes the necessity to postulate large lifetimes. The mechanism considers the dynamics of the density matrix of the molecular groups, which are attached to the walls of protein cavities by two covalent bonds, i.e., molecular gyroscopes. Numerical computations have shown almost free rotations of the molecular gyroscopes. The relaxation time due to van der Waals forces was about 0.01 s for the cavity size of 28 Aa

High temperature structural and magnetic properties of cobalt nanorods

Energy Technology Data Exchange (ETDEWEB)

Ait Atmane, Kahina [Univ. Paris Diderot, Sorbonne Paris Cite, ITODYS, UMR CNRS 7086, 15 rue J.-A. de Baief, 75205 Paris Cedex 13 (France); Zighem, Fatih [Laboratoire Leon Brillouin, CEA CNRS UMR 12, IRAMIS, CEA-Saclay, 91191 Gif sur Yvette (France); Soumare, Yaghoub [Univ. Paris Diderot, Sorbonne Paris Cite, ITODYS, UMR CNRS 7086, 15 rue J.-A. de Baief, 75205 Paris Cedex 13 (France); Ibrahim, Mona; Boubekri, Rym [Universite de Toulouse, LPCNO, INSA CNRS UMR 5215, 135 av. de Rangueil, 31077 Toulouse Cedex 4 (France); Maurer, Thomas [Laboratoire Leon Brillouin, CEA CNRS UMR 12, IRAMIS, CEA-Saclay, 91191 Gif sur Yvette (France); Margueritat, Jeremie [Univ. Paris Diderot, Sorbonne Paris Cite, ITODYS, UMR CNRS 7086, 15 rue J.-A. de Baief, 75205 Paris Cedex 13 (France); Piquemal, Jean-Yves, E-mail: jean-yves.piquemal@univ-paris-diderot.fr [Univ. Paris Diderot, Sorbonne Paris Cite, ITODYS, UMR CNRS 7086, 15 rue J.-A. de Baief, 75205 Paris Cedex 13 (France); Ott, Frederic; Chaboussant, Gregory [Laboratoire Leon Brillouin, CEA CNRS UMR 12, IRAMIS, CEA-Saclay, 91191 Gif sur Yvette (France); Schoenstein, Frederic; Jouini, Noureddine [LSPM, CNRS UPR 9001, Universite Paris XIII, Institut Galilee, 99 av. J.-B. Clement, 93430 Villetaneuse (France); Viau, Guillaume, E-mail: gviau@insa-toulouse.fr [Universite de Toulouse, LPCNO, INSA CNRS UMR 5215, 135 av. de Rangueil, 31077 Toulouse Cedex 4 (France)

2013-01-15

We present in this paper the structural and magnetic properties of high aspect ratio Co nanoparticles ({approx}10) at high temperatures (up to 623 K) using in-situ X ray diffraction (XRD) and SQUID characterizations. We show that the anisotropic shapes, the structural and texture properties are preserved up to 500 K. The coercivity can be modelled by {mu}{sub 0}H{sub C}=2(K{sub MC}+K{sub shape})/M{sub S} with K{sub MC} the magnetocrystalline anisotropy constant, K{sub shape} the shape anisotropy constant and M{sub S} the saturation magnetization. H{sub C} decreases linearly when the temperature is increased due to the loss of the Co magnetocrystalline anisotropy contribution. At 500 K, 50% of the room temperature coercivity is preserved corresponding to the shape anisotropy contribution only. We show that the coercivity drop is reversible in the range 300-500 K in good agreement with the absence of particle alteration. Above 525 K, the magnetic properties are irreversibly altered either by sintering or by oxidation. - Graphical abstract: We present in this paper the structural and magnetic properties of high aspect ratio Co nanorods ({approx}10) at high temperatures (up to 623 K) using in-situ X-ray diffraction and SQUID characterizations. We show that the anisotropic shapes, the structural and texture properties are preserved up to 500 K. Above 525 K, the magnetic properties are irreversibly altered either by sintering or by oxidation. Highlights: Black-Right-Pointing-Pointer Ferromagnetic Co nanorods are prepared using the polyol process. Black-Right-Pointing-Pointer The structural and texture properties of the Co nanorods are preserved up to 500 K. Black-Right-Pointing-Pointer The magnetic properties of the Co nanorods are irreversibly altered above 525 K.

Adjustability of resonance frequency by external magnetic field and bias electric field of sandwich magnetoelectric PZT/NFO/PZT composites

Energy Technology Data Exchange (ETDEWEB)

Xu, Ling-Fang; Feng, Xing; Sun, Kang; Liang, Ze-Yu; Xu, Qian; Liang, Jia-Yu; Yang, Chang-Ping [Hubei University, Hubei Key Laboratory of Ferro and Piezoelectric Materials and Devices, Faculty of Physics and Electronic Science, Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Wuhan (China)

2017-07-15

Sandwich magnetoelectric composites of PZT/NFO/PZT (PNP) have been prepared by laminating PZT5, NiFe{sub 2}O{sub 4}, and PZT5 ceramics in turn with polyvinyl alcohol (PVA) paste. A systematic study of structural, magnetic and ferroelectric properties is undertaken. Structural studies carried out by X-ray diffraction indicate formation of cubic perovskite phase of PZT5 ceramic and cubic spinel phase of NiFe{sub 2}O{sub 4} ceramic. As increasing the content of PZT5 phase, ferroelectric loops and magnetic loops of PNP composites showed increasing remnant electric polarizations and decreasing remnant magnetic moments separately. Both external magnetic fields and bias voltages could regulate the basal radial resonance frequency of the composites, which should be originated with the transformation and coupling of the stress between the piezoelectric phase and magnetostrictive phase. Such magnetoelectric composite provides great opportunities for electrostatically tunable devices. (orig.)

Structural and magnetic properties of yttrium iron garnet (YIG) and yttrium aluminum iron garnet (YAIG) nanoferrites prepared by microemulsion method

Energy Technology Data Exchange (ETDEWEB)

Akhtar, Majid Niaz, E-mail: majidniazakhtar@ciitlahore.edu.pk [Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Bakar Sulong, Abu [Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Khan, Muhammad Azhar [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Ahmad, Mukhtar [Department of Physics, COMSATS Institute of Information Technology, Islamabad (Pakistan); Murtaza, Ghulam [Centre for Advanced Studies in Physics, G.C. University, Lahore, Pakistan" f Department of Mechanical Engineering, COMSATS Institute of Information Technology Sahiwal Pakistan (Pakistan); Raza, M.R. [Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Department of Mechanical Engineering, COMSATS Institute of Information Technology Sahiwal (Pakistan); Raza, R.; Saleem, M. [Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Kashif, M. [Department of Physics, Govt. College University Faisalabad (Pakistan)

2016-03-01

Yttrium iron garnet (YIG) and yttrium aluminum iron garnet (YAIG) nanoferrite samples were synthesized by microemulsion method. The effect of sintering was examined by heating the samples at 900, 1000, and 1100 °C. The YIG and YAIG samples were then characterized using X-ray diffraction and field-emission scanning electron microscopy. Static and dynamic magnetic properties were measured by evaluating initial permeability, Q factor, and vibrating sample magnetometry properties of YIG and YAIG samples. YIG samples sintered at 1100 °C showed higher initial permeability and Q factor compared with YAIG samples. However, hysteresis loops also showed variations in the saturation magnetization, remanence, and coercivity of YIG and YAIG samples sintered at 900, 1000, and 1100 °C. The observed magnetic parameter such as saturation magnetization, coercivity and initial permeability are strongly affected by increasing temperature. The saturation magnetization and coercivity of YIG and YAIG nanoferrites were found in the range 11.56–19.92 emu/g and 7.30–87.70 Oe respectively. Furthermore, the decreasing trends in the static and magnetic properties of YAIG samples may be due to the introduction of Al ions in the YIG crystal lattice. Thus, YIG and YAIG sintered at 1100 °C can be used for wide-ranging frequency applications. - Highlights: • Static and dynamic magnetic properties of YIG and YAIG nanoferrites were determined. • Saturation magnetization, Q and initial permeability increased in YIG nanoferites. • Possible use of these nanoferrites for sensing and switching applications.

Magnetic properties of nanocrystalline La1-xMnO3+δ manganites: size effects

International Nuclear Information System (INIS)

Markovich, V; Fita, I; Mogilyansky, D; Wisniewski, A; Puzniak, R; Titelman, L; Vradman, L; Herskowitz, M; Gorodetsky, G

2007-01-01

The magnetic properties of nanocrystalline manganites La 1-x MnO 3+δ with particle size of 20 (LMO20), 25 (LMO25), and 30 nm (LMO30), prepared by the citrate method, have been investigated in the temperature range 5-320 K, magnetic field up to 90 kOe and under quasi-hydrostatic pressures up to 14.5 kbar. The studies involve sequential zero-field-cooled magnetization (M) measurements followed by magnetization measurements during cooling in the same magnetic field (H) and complementary measurements of ac susceptibility. Additional measurements of M versus H were carried out at ambient and applied pressures. All nanoparticles exhibit a paramagnetic to ferromagnetic transition (PFT) at a Curie temperature T C >200 K. It was found that the relative volume of the ferromagnetic phase increases for larger particle size and approaches a value of about 93% for LMO30. The real part of the ac susceptibility of sample LMO20 exhibits strong frequency dependence in a wide temperature range below T C , whereas for sample LMO30 only relatively weak frequency dependence was observed. The magnetization of sample LMO30 exhibits a PFT of second order; the type of transition could not be established for the smaller particles. It was found that an applied pressure enhances the T C of La 1-x MnO 3+δ nanoparticles with a pressure coefficient of dT C /dP∼1.9 K kbar -1 for LMO20 and dT C /dP∼1.4 K kbar -1 for LMO25 and LMO30 samples. Peculiar magnetic memory effects observed for sample LMO20 are discussed

Soft magnetic moldable composites: Properties and applications

Energy Technology Data Exchange (ETDEWEB)

Svensson, Leif, E-mail: leif.svensson@iprod.lth.se [Lund University, Division of Production and Materials Engineering, Box 188, 221 00 Lund (Sweden); Frogner, Kenneth, E-mail: kenneth.frogner@iprod.lth.se [Lund University, Division of Production and Materials Engineering, Box 188, 221 00 Lund (Sweden); Jeppsson, Peter, E-mail: peter.jeppsson@iprod.lth.se [Lund University, Division of Production and Materials Engineering, Box 188, 221 00 Lund (Sweden); Cedell, Tord, E-mail: tord.cedell@iprod.lth.se [Lund University, Division of Production and Materials Engineering, Box 188, 221 00 Lund (Sweden); Andersson, Mats, E-mail: mats.andersson@iprod.lth.se [Lund University, Division of Production and Materials Engineering, Box 188, 221 00 Lund (Sweden)

2012-09-15

A new type of electromagnetic soft magnetic material (SMM) is introduced, based on spherical iron powder particles and a suitable polymer binder. A key feature of this material is that it can be cast or molded into almost any 3D shape, hence the denotation soft magnetic moldable composite (SM{sup 2}C). The SM{sup 2}C is compared with a set of reference materials, such as ferrites, laminated steels, and soft magnetic composites, in terms of primary properties such as permeability and loss, and other properties, such as thermal conductivity and manufacturability. The SM{sup 2}C has the obvious disadvantage of relatively low permeability, but offers benefits such as relatively low losses and high potential for close integration into electromagnetic circuits. Some recent SM{sup 2}C applications are illustrated, and design and manufacturing aspects are discussed. - Highlights: Black-Right-Pointing-Pointer A new type of soft magnetic composite is introduced. Black-Right-Pointing-Pointer Properties are compared to other flux core materials. Black-Right-Pointing-Pointer The new material has low losses but also low permeability. Black-Right-Pointing-Pointer Potential benefits in freedom of design and manufacturing issues.

Effect of surfactant for magnetic properties of iron oxide nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Haracz, S. [Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89B, 61-614 Poznań (Poland); Hilgendorff, M. [Freie Universität Berlin, Fachbereich Physik, Arnimalle 14, 14195 Berlin (Germany); Rybka, J.D. [Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89B, 61-614 Poznań (Poland); Giersig, M. [Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89B, 61-614 Poznań (Poland); Freie Universität Berlin, Fachbereich Physik, Arnimalle 14, 14195 Berlin (Germany)

2015-12-01

Highlights: • Dynamic behavior of magnetic nanoparticles. • Synthesis of iron oxide nanoparticles. • Effect of surfactant for magnetic properties. - Abstract: For different medical applications nanoparticles (NPs) with well-defined magnetic properties have to be used. Coating ligand can change the magnetic moment on the surface of nanostructures and therefore the magnetic behavior of the system. Here we investigated magnetic NPs in a size of 13 nm conjugated with four different kinds of surfactants. The surface anisotropy and the magnetic moment of the system were changed due to the presence of the surfactant on the surface of iron oxide NPs.

Microstructure characterization and magnetic properties of nano structured materials

Energy Technology Data Exchange (ETDEWEB)

Sun, X.C

2000-07-01

The present thesis deals with the unique microstructural properties and their novel magnetic properties of core-shell Ni-Ce nano composite particles, carbon encapsulated Fe, Co, and Ni nanoparticles and the nano crystallization behavior of typical ferromagnetic Fe{sub 78}Si{sub 9}B{sub 13} ribbons. These properties have intensively been investigated by high resolution transmission electron microscopy (HREM), X-ray diffraction (XRD), scanning electron microscopy (Sem), X-ray energy dispersive spectroscopy [eds.]; selected area electron diffraction pattern (SAED), Ft-IR, differential scanning calorimeter (DSC). In addition, magnetic moments measurements at different temperatures and applied fields have been performed by transmission Moessbauer spectroscopy, superconducting quantum interference device magnetometer (SQUID), and vibrating sample magnetometer (VSM). The present studies may provide the insights for the better understanding of the correlation between the unique microstructure and novel magnetic properties for several magnetic nano structured materials. (Author)

Impacts of yttrium substitution on FMR line-width and magnetic properties of nickel spinel ferrites

Energy Technology Data Exchange (ETDEWEB)

Ishaque, M., E-mail: ishaqdgk1@gmail.com [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Khan, Muhammad Azhar, E-mail: azhar.khan@iub.edu.pk [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Ali, Irshad; Khan, Hasan M. [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Iqbal, M. Asif [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); College of E & ME, National University of Science and Technology, Islamabad (Pakistan); Islam, M.U. [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Warsi, Muhammad Farooq [Department of Chemistry, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan)

2015-05-15

The influence of yttrium (Y) substitution on ferromagnetic resonance (FMR), initial permeability, and magnetic properties of NiFe{sub 2}O{sub 4} ferrites were investigated. It was observed that the FMR line-width decreases with yttrium contents for the substitution level 0≤×≤0.06. Beyond this, the FMR line-width increases with yttrium contents. The nominal composition NiY{sub 0.12}Fe{sub 1.88}O{sub 4} exhibited the smallest FMR line-width ~282 Oe. A significant change in FMR position of nickel–yttrium (Ni–Y) ferrites was observed and it found to exist between 4150 and 4600 Oe. The saturation magnetization was observed to decrease with the increase of yttrium contents and this was referred to the redistribution of cations on octahedral. The coercivity increased from 15 Oe to 59 Oe by increasing the yttrium concentration. The initial permeability decreased from 110 to 35 at 1 MHz by the incorporation of yttrium and this was attributed to the smaller grains which may obstruct the domain wall movement and impede the domain wall motion. The magnetic loss factors of substituted samples exhibit decreasing behavior in the frequency range 1 kHz to 10 MHz. The smaller FMR line-width and reduced magnetic loss factor of the investigated samples suggest the possible use of these materials in high frequency applications. - Highlights: • Influence of Y{sup 3+} substitution on the properties of nickel ferrites is investigated. • Very small FMR line-width (282 Oe) is exhibited by these substituted ferrites. • Fourfold increase in coercivity was observed for NiY{sub 0.24}Fe{sub 1.76}O{sub 4} ferrites.

Improvement of the microstructure and magnetic properties of sintered NdFeB permant magnets

International Nuclear Information System (INIS)

Vial, F.; Rozendaal, E.; Sagawa, M.

1998-01-01

A correlation between sintered NdFeB process, microstructure of the products at each step of the process and magnetic properties has been established. To increase (BH) max of sintered NdFeB magnets, the total rare-earth content in the alloy has to be decreased and to keep coercivity as high as possible, the unavoidable oxygen pick-up has to be substantially reduced. The composition improvements tend to create a high sensitivity to form abnormal grain growth which can potentially occur during the sintering operation. Special attention has been given to characterising, understanding the mechanisms and solving this defect which could affect the magnetic properties. In addition, the composition and each step of the process have been optimised to improve magnetic properties, thermal stability and corrosion resistance of the NdFeB permanent magnets. These collaborative studies have resulted in a significant improvement of both remanence and coercivity of the sintered NdFeB permanent magnets, covering a wide coercivity range from 800 to 2500 kA/m (10 to 35 kOe) with respective associated energy products of 400 to 270 kJ/m3 (52 to 35 MGOe). (orig.)

Modulation of electromagnetic and absorption properties in 18-26.5 GHz frequency range of strontium hexaferrites with doping of cobalt-zirconium

Science.gov (United States)

Pubby, Kunal; Narang, Sukhleen Bindra; Kaur, Prabhjyot; Chawla, S. K.

2017-05-01

Hexaferrite nano-particles of stoichiometric composition {{Sr}}{({{CoZr}})_x}{{F}}{{{e}}_{12 - 2x}}{{{O}}_{19}}, with x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 were prepared using sol-gel auto-combustion route owing to its advantages such as low sintering temperature requirement, homogeneity and uniformity of grains. Tartaric acid as a fuel was utilized to complete the chemical reaction. The goal of this study is to analyse the effect of co-substitution of cobalt and zirconium on the electromagnetic and absorption properties of pure {{SrF}}{{{e}}_{12}}{{{O}}_{19}} hexaferrite. The properties were measured on the rectangular pellets of thickness 2.5 mm for K-frequency band using Vector Network Analyzer. The doping of Co-Zr has resulted in increase in real as well as imaginary parts of permittivity. The values of real permittivity lie in the range 3.6-7.0 for all the composition. The real part of permeability remains in range 0.7-1.6 in the studied frequency band for all the samples and shows slightly increasing trend with frequency. The maximum values of dielectric loss tangent peak (3.04) and magnetic loss tangent peak (2.34), among all the prepared compositions, have been observed for composition x = 0.2. Compositions with x = 0.6 and x = 0.0 also have high dielectric and magnetic loss peaks. Dielectric loss peaks are attributed to dielectric resonance and magnetic loss peaks are attributed to natural resonance. Experimentally determined reflection loss results show that all six compositions of prepared series have high values of absorption to propose them as single-layer absorbers in 18-26.5 GHz frequency range. The composition with x = 0.2 has maximum absorption capacity with reflection loss peak of -37.2 dB at 24.3 GHz frequency. The undoped composition also has high absorption peak (-25.46 dB), but -10 dB absorption bandwidth is minimum (2.2 GHz) out of the present series. Maximum absorption bandwidth is obtained for x = 1.0 (4.1 GHz). Other doped compositions also

Modulation of electromagnetic and absorption properties in 18-26.5 GHz frequency range of strontium hexaferrites with doping of cobalt-zirconium

Energy Technology Data Exchange (ETDEWEB)

Pubby, Kunal; Narang, Sukhleen Bindra [Guru Nanak Dev University, Department of Electronics Technology, Amritsar (India); Kaur, Prabhjyot; Chawla, S.K. [Guru Nanak Dev University, Department of Chemistry, Centre for Advanced Studies-I, Amritsar (India)

2017-05-15

Hexaferrite nano-particles of stoichiometric composition Sr(CoZr){sub x}Fe{sub 12-2x}O{sub 19}, with x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 were prepared using sol-gel auto-combustion route owing to its advantages such as low sintering temperature requirement, homogeneity and uniformity of grains. Tartaric acid as a fuel was utilized to complete the chemical reaction. The goal of this study is to analyse the effect of co-substitution of cobalt and zirconium on the electromagnetic and absorption properties of pure SrFe{sub 12}O{sub 19} hexaferrite. The properties were measured on the rectangular pellets of thickness 2.5 mm for K-frequency band using Vector Network Analyzer. The doping of Co-Zr has resulted in increase in real as well as imaginary parts of permittivity. The values of real permittivity lie in the range 3.6-7.0 for all the composition. The real part of permeability remains in range 0.7-1.6 in the studied frequency band for all the samples and shows slightly increasing trend with frequency. The maximum values of dielectric loss tangent peak (3.04) and magnetic loss tangent peak (2.34), among all the prepared compositions, have been observed for composition x = 0.2. Compositions with x = 0.6 and x = 0.0 also have high dielectric and magnetic loss peaks. Dielectric loss peaks are attributed to dielectric resonance and magnetic loss peaks are attributed to natural resonance. Experimentally determined reflection loss results show that all six compositions of prepared series have high values of absorption to propose them as single-layer absorbers in 18-26.5 GHz frequency range. The composition with x = 0.2 has maximum absorption capacity with reflection loss peak of -37.2 dB at 24.3 GHz frequency. The undoped composition also has high absorption peak (-25.46 dB), but -10 dB absorption bandwidth is minimum (2.2 GHz) out of the present series. Maximum absorption bandwidth is obtained for x = 1.0 (4.1 GHz). Other doped compositions also have high absorption bandwidth

The magnetic field dependent dynamic properties of magnetorheological elastomers based on hard magnetic particles

Science.gov (United States)

Wen, Qianqian; Wang, Yu; Gong, Xinglong

2017-07-01

In this study, novel magnetorheological elastomers based on hard magnetic particles (H-MREs) were developed and the magnetic field dependent dynamic properties of the H-MREs were further investigated. The storage modulus of H-MREs could not only be increased by increasing magnetic field but also be decreased by the increasing magnetic field of opposite orientation. For the anisotropic H-MREs with 80 wt% NdFeB particles, the field-induced increasing and decreasing modulus was 426 kPa and 118 kPa respectively. Moreover, the dynamic performances of H-MREs significantly depended on the pre-structure magnetic field, magnetizing field and test magnetic field. The H-MREs were initially magnetized and formed the chain-like microstructure by the pre-structure magnetic field. The field-induced increasing and decreasing modulus of H-MREs both raised with increasing of the magnetizing field. When the magnetizing field increased from 400 to 1200 kA m-1, the field induced decreasing modulus of the 80 wt% isotropic H-MREs raised from 3 to 47 kPa. The magnetic field dependent curves of H-MREs’ storage modulus were asymmetric if the magnetizing field was higher than the test magnetic field. Based on the dipolar model of MREs and magnetic properties of hard magnetic material, a reasonable explanation was proposed to understand the H-MREs’ field dependent mechanical behaviors.

Microstructure, magnetic properties and magnetic hardening in 2:17 Sm-Co magnets

International Nuclear Information System (INIS)

Tang, W.; Zhang, Y.; Hadjipanayis, G.C.

2002-01-01

A comprehensive and systematic study has been made on Sm(Co,Fe,M,L) z magnets (M=Cu or Ni, and L=Zr or Ti) to completely understand the effects of composition and processing on the microstructure and magnetic properties of magnets. Ti-containing magnets do not have a lamellar phase but exhibit only a cellular microstructure, resulting in a much lower coercivity (below 10 kOe). Ni-containing magnets exhibit a perfect cellular/lamellar microstructure, but without a large domain wall energy gradient at the interface of the 2:17 and 1:5 phases, leading to a low coercivity. Only in the magnets containing both Cu and Zr, a uniform and stable cellular/lamellar microstructure with a high domain wall energy gradient across the 1:5 phase is formed, resulting in high coercivity. These results indicate that the conditions for effective magnetic hardening are: (1) Formation of a cellular/lamellar microstructure, and (2) establishment of a domain wall energy gradient at the cell boundaries. Based on all of these experimental results, the magnetization reversal mechanism of 2:17 Sm-Co magnets can be explained by both the domain wall pinning and nucleation models. The nucleation mechanism holds at any temperature in the Cu-rich magnets, and only above the Curie temperature of the 1:5 phase in the alloys with the lower Cu content. In these cases, the 2:17 cells become magnetically decoupled. (orig.)

Magnetic properties of high temperature superconductors and their interaction with high energy permanent magnets

International Nuclear Information System (INIS)

Agarwala, A.K.

1990-01-01

Magnetic properties of sintered samples of YBCO ceramic superconductors at various temperatures were measured using a vibrating sample magnetometer (VSM). Also, measurements of forces experienced by a well characterized rare earth-transition metal (RE-TM) permanent magnet (PM) interacting with the superconducting YBCO sample cooled in liquid nitrogen, were performed. Based upon the observed hysteretic magnetization properties of these high temperature superconductors (HTS), the HTS-PM interaction force at liquid nitrogen temperature was calculated from first principle, and finally correlated to the force measurement results. With this analysis, magnetic forces between the same HTS and PM system including the levitation as well as suspension effects at liquid-helium temperature are predicted

Dynamical properties of magnetized two-dimensional one-component plasma

Science.gov (United States)

Dubey, Girija S.; Gumbs, Godfrey; Fessatidis, Vassilios

2018-05-01

Molecular dynamics simulation are used to examine the effect of a uniform perpendicular magnetic field on a two-dimensional interacting electron system. In this simulation we include the effect of the magnetic field classically through the Lorentz force. Both the Coulomb and the magnetic forces are included directly in the electron dynamics to study their combined effect on the dynamical properties of the 2D system. Results are presented for the velocity autocorrelation function and the diffusion constants in the presence and absence of an external magnetic field. Our simulation results clearly show that the external magnetic field has an effect on the dynamical properties of the system.

Francisella tularensis detection using magnetic labels and a magnetic biosensor based on frequency mixing

Energy Technology Data Exchange (ETDEWEB)

Meyer, Martin H.F. [Institute for Pharmaceutical Chemistry, Philipps-Universitaet Marburg (Germany); Krause, Hans-Joachim [Institute of Bio-and Nanosystems (IBN-2), Research Center Juelich (Germany); Hartmann, Markus [Institute for Pharmaceutical Chemistry, Philipps-Universitaet Marburg (Germany); Miethe, Peter [SENOVA GmbH, Jena (Germany); Oster, Juergen [chemagen GmbH, Baesweiler (Germany); Keusgen, Michael [Institute for Pharmaceutical Chemistry, Philipps-Universitaet Marburg (Germany)]. E-mail: Keusgen@staff.uni-marburg.de

2007-04-15

A biosensor that uses resonant coils with a special frequency-mixing technique and magnetic beads as detectable labels has been established for the detection of Francisella tularensis, the causative agent for tularemia. The detection principle is based on a sandwich immunoassay using an anti-Ft antibody for immunofiltration immobilized to ABICAP[reg] polyethylene filters, and biotinylated with streptavidin-coated magnetic beads as labels. The linear detection range of this biosensor was found to be 10{sup 4}-10{sup 6} cfu F. tularensis lipopolysaccharide (LPS) per ml. Tested sample matrices were physiological PBS buffer and rabbit serum.

Magnetic properties of TbTiGe

International Nuclear Information System (INIS)

Prokes, K.; Tegus, O.; Brueck, E.; Gortenmulder, T.J.; Boer, F.R. de; Buschow, K.H.J.

2001-01-01

We have studied the magnetic properties of the compound TbTiGe by means of neutron diffraction in the temperature range 1.7-310 K. We also report on magnetization measurements made at different temperatures and fields. The compound TbTiGe adopts the tetragonal CeFeSi-structure type and orders antiferromagnetically at T N =286 K. The structure is collinear antiferromagnetic in the whole temperature range below T N , with the magnetic moments aligned along the tetragonal c-axis. The uncommon shape of the temperature dependence of the magnetization observed in our sample is attributed to small amounts of the ferromagnetic low-temperature modification of TbTiGe

Effects of low-frequency repetitive transcranial magnetic stimulation on event-related potential P300

Science.gov (United States)

Torii, Tetsuya; Sato, Aya; Iwahashi, Masakuni; Iramina, Keiji

2012-04-01

The present study analyzed the effects of repetitive transcranial magnetic stimulation (rTMS) on brain activity. P300 latency of event-related potential (ERP) was used to evaluate the effects of low-frequency and short-term rTMS by stimulating the supramarginal gyrus (SMG), which is considered to be the related area of P300 origin. In addition, the prolonged stimulation effects on P300 latency were analyzed after applying rTMS. A figure-eight coil was used to stimulate left-right SMG, and intensity of magnetic stimulation was 80% of motor threshold. A total of 100 magnetic pulses were applied for rTMS. The effects of stimulus frequency at 0.5 or 1 Hz were determined. Following rTMS, an odd-ball task was performed and P300 latency of ERP was measured. The odd-ball task was performed at 5, 10, and 15 min post-rTMS. ERP was measured prior to magnetic stimulation as a control. Electroencephalograph (EEG) was measured at Fz, Cz, and Pz that were indicated by the international 10-20 electrode system. Results demonstrated that different effects on P300 latency occurred between 0.5-1 Hz rTMS. With 1 Hz low-frequency magnetic stimulation to the left SMG, P300 latency decreased. Compared to the control, the latency time difference was approximately 15 ms at Cz. This decrease continued for approximately 10 min post-rTMS. In contrast, 0.5 Hz rTMS resulted in delayed P300 latency. Compared to the control, the latency time difference was approximately 20 ms at Fz, and this delayed effect continued for approximately 15 min post-rTMS. Results demonstrated that P300 latency varied according to rTMS frequency. Furthermore, the duration of the effect was not similar for stimulus frequency of low-frequency rTMS.

Magnetic properties of the binary Nickel/Bismuth alloy

Energy Technology Data Exchange (ETDEWEB)

Keskin, Mustafa; Şarlı, Numan, E-mail: numansarli82@gmail.com

2017-09-01

Highlights: • We model and investigate the magnetic properties of the Ni/Bi alloy within the EFT. • Magnetizations of the Ni/Bi alloy are observed as Bi1 > Bi2 > Ni/Bi > Ni at T < Tc. • Magnetization of the Bi1 is dominant and Ni is at least dominant T < Tc. • Total magnetization of the Ni/Bi alloy is close to those of Ni at T < Tc. • Hysteresis curves are overlap at T < 0.1 and they behave separately at T > 0.1. - Abstract: Magnetic properties of the binary Nickel/Bismuth alloy (Ni/Bi) are investigated within the effective field theory. The Ni/Bi alloy has been modeled that the rhombohedral Bi lattice is surrounded by the hexagonal Ni lattice. According to lattice locations, Bi atoms have two different magnetic properties. Bi1 atoms are in the center of the hexagonal Ni atoms (Ni/Bi1 single layer) and Bi2 atoms are between two Ni/Bi1 bilayers. The Ni, Bi1, Bi2 and Ni/Bi undergo a second-order phase transition from the ferromagnetic phase to paramagnetic phase at Tc = 1.14. The magnetizations of the Ni/Bi alloy are observed as Bi1 > Bi2 > Ni/Bi > Ni at T < Tc; hence the magnetization of the Bi1 is dominant and Ni is at least dominant. However, the total magnetization of the Ni/Bi alloy is close to magnetization of the Ni at T < Tc. The corcivities of the Ni, Bi1, Bi2 and Ni/Bi alloy are the same with each others, but the remanence magnetizations are different. Our theoretical results of M(T) and M(H) of the Ni/Bi alloy are in quantitatively good agreement with the some experimental results of binary Nickel/Bismuth systems.

Structural and magnetic properties of Fe76P5(Si0.3B0.5C0.2)19 amorphous alloy

International Nuclear Information System (INIS)

Lavorato, G.C.; Fiore, G.; Tiberto, P.; Baricco, M.; Sirkin, H.; Moya, J.A.

2012-01-01

Highlights: ► Fe 76 P 5 (Si 0.3 B 0.5 C 0.2 ) 19 amorphous alloy in ribbons and 1 mm and 2 mm rod samples. ► Good glass forming ability with ΔT = 50 K and γ = 0.37 and off-eutectic composition. ► Good soft magnetic properties with magnetization saturation of 1.44 T. ► Geometrical factors are the primary causes of magnetic losses in frequencies above 10 Hz. - Abstract: Recently, bulk amorphous alloys were produced in the Fe–B–Si–P–C system with high glass forming ability, excellent magnetic properties and the advantage of containing no expensive glass-forming elements, such as Ga, Y, Cr or Nb, having, therefore, a good perspective of commercial applications. In the present work, the Fe 76 P 5 (Si 0.3 B 0.5 C 0.2 ) 19 amorphous alloy prepared by two quenching techniques has been studied. Amorphous ribbons of about 40 μm thick were obtained by planar-flow casting together with cylinders having 1 and 2 mm diameter produced by copper mold injection casting. All the samples appear fully amorphous after X-ray diffraction analysis. A comprehensive set of thermal data (glass, crystallization, melting and liquidus temperatures) were obtained as well as a description of the melting and solidification processes. Mechanical microhardness tests showed that the samples have a hardness of 9.7 ± 0.3 GPa. Good soft-magnetic properties were obtained, including a high magnetization of 1.44 T and a low coercivity (4.5 A/m for ribbons and 7.5 A/m in the case of 1 mm rod samples, both in as-cast state). Thermomagnetic studies showed a Curie temperature around 665 K and the precipitation of new magnetic phases upon temperatures of 1000 K. Furthermore, the frequency dependence of magnetic losses at a fixed peak induction was studied. The results suggest the occurrence of a fine magnetic domain structure in bulk samples. The good soft magnetic properties of the bulk metallic glass obtained by copper mold casting for this particular Fe-based composition suggests possible

Magnetic properties of nanocrystalline KNbO3

International Nuclear Information System (INIS)

Golovina, I. S.; Shanina, B. D.; Kolesnik, S. P.; Geifman, I. N.; Andriiko, A. A.

2013-01-01

Newly synthesized undoped and iron-doped nanoscale powders of KNbO 3 are investigated using magnetic resonance and static magnetization methods in order to determine how the crystal size and doping affect the structure of magnetic defects and material properties. Although the bulk crystals of KNbO 3 are nonmagnetic, the undoped KNbO 3 powder with average particle size of 80 nm exhibits magnetic properties. The ferromagnetic resonance signal and the magnetization curve registered on the powder are thoroughly analyzed. It is concluded that the appearance of the defect driven ferromagnetism in the undoped powder is due to the nano-size of the particles. This effect disappears in the iron-doped KNbO 3 powder with particle sizes above 300 nm. In case of low doping ( eff  = 4.21 is found out in the KNbO 3 :Fe powder. Such a signal has not been observed in the bulk crystals of KNbO 3 :Fe. We suppose that this signal corresponds to individual paramagnetic Fe 3+ ions having rhombic symmetry

Design of the ITER high-frequency magnetic diagnostic coils

International Nuclear Information System (INIS)

Toussaint, M.; Testa, D.; Baluc, N.; Chavan, R.; Fournier, Y.; Lister, J.B.; Maeder, T.; Marmillod, P.; Sanchez, F.; Stoeck, M.

2011-01-01

This paper is an overview of work carried out on the design of the ITER high-frequency magnetic diagnostic coil (HF sensor). In the first part, the ITER requirements for the HF sensor are presented. In the second part, the ITER reference design of the HF sensor has been assessed and showed some potential weaknesses, which led us to the conclusion that alternative designs could usefully be examined. Several options have been explored, and are presented in the third part: (a) direct laser cutting a metallic tube, (b) stacking of plane windings manufactured from a tungsten plate by electrical discharge machining, (c) coil using the conventional spring manufacture. In the fourth part, sensors using the low temperature co-fired ceramic technology (LTCC) are presented: (d) monolithic 1D magnetic flux sensors based on LTCC technology, and (e) monolithic 3D magnetic flux sensors based on the same LTCC technology. The solution which showed the best results is the monolithic 3D magnetic flux sensor based on LTCC.

The magnetic properties of powdered and compacted microcrystalline permalloy

International Nuclear Information System (INIS)

Kollar, P.; Oleksakova, D.; Fuezer, J.; Kovac, J.; Roth, S.; Polanski, K.

2007-01-01

The aim of this work is to investigate the magnetic properties of powdered and compacted microcrystalline Ni-Fe (81 wt% of Ni) permalloy. It was found by investigating the influence of mechanical milling on the magnetic properties of powder samples prepared by milling of the ribbon that the alloy remains a solid solution with stable structure during the whole milling process. With decreasing particle size the rotation of magnetization vector gradually becomes dominant magnetization process and thus coercivity increases. After compaction of the powder by uniaxial hot pressing the magnetic contact between powder particles is recreated and for resulting bulk the displacement of the domain walls becomes dominant magnetization process with coercivity of 11 A/m (comparable with the coercivity of conventional permalloy)

Growth and magnetic properties dependence of the Co–Cu/Cu films electrodeposited under high magnetic fields

Energy Technology Data Exchange (ETDEWEB)

Franczak, Agnieszka, E-mail: agnieszka.franczak@mtm.kuleuven.be [Laboratoire d’Ingénierie et Sciences des Matériaux (LISM EA 4695), Université de Reims Champagne-Ardenne, UFR Sciences et Naturelles, Bat. 6, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2 (France); Department of Materials Science (MTM), KU Leuven, Kasteelpark Arenberg 44, 3001 Haverlee (Leuven) (Belgium); Levesque, Alexandra [Laboratoire d’Ingénierie et Sciences des Matériaux (LISM EA 4695), Université de Reims Champagne-Ardenne, UFR Sciences et Naturelles, Bat. 6, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2 (France); Zabinski, Piotr [Laboratory of Physical Chemistry and Electrochemistry, Faculty of Non-Ferrous Metals, AGH University of Science and Technology, al. A. Mickiewicza 30, 30059 Krakow (Poland); Li, Donggang [Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, 314 Box, 110004 Shenyang (China); Czapkiewicz, Maciej [Department of Electronics, AGH University of Science and Technology, al. A. Mickiewicza 30, 30059 Krakow (Poland); Kowalik, Remigiusz [Laboratory of Physical Chemistry and Electrochemistry, Faculty of Non-Ferrous Metals, AGH University of Science and Technology, al. A. Mickiewicza 30, 30059 Krakow (Poland); Bohr, Frédéric [Laboratoire d’Ingénierie et Sciences des Matériaux (LISM EA 4695), Université de Reims Champagne-Ardenne, UFR Sciences et Naturelles, Bat. 6, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2 (France); and others

2015-07-15

The present work is focused on the investigations of magnetic properties dependence on microstructure of Co–Cu/Cu films electrodeposited under superimposed high magnetic field. The experimental results indicate a strong effect of an external magnetic field on the morphology of deposited films, more precisely on the Co:Cu ratio that determines the film growth. It is shown that the Co–Cu/Cu films electrodeposited without superimposed magnetic field consisted of two clearly visible features: compact film with incorporated granular particles. Under a superimposed external high magnetic field the privilege growth of the particles was induced. As a consequence, development of the well-defined branched structure of Co–Cu/Cu film was observed. In contrary, the phase compositional investigations do not reveal any changes in the phase formation during electrodeposition under magnetic field conditions. Thus, it is assumed that a strong growth of Co–Cu/Cu films in (111) direction under magnetic or non-magnetic electrodeposition conditions is related with the growth of Cu (111) plane and embedded into it some of the Co fcc atoms of same (111) orientation, as well as the Co hcp atoms that grows in the (002) direction. This non-equilibrium growth of Co–Cu/Cu films under magnetic deposition conditions affects strongly the magnetic properties of deposited films, revealing that films obtained under magnetic fields higher than 3 T were no more magnetic materials. - Highlights: • Co–Cu/Cu electrodeposits were obtained at elevated temperature under HMFs. • The effects of HMFs on microstructure and magnetic properties were investigated. • Interesting morphological changes due to HMFs has been observed. • Changes in Co:Cu ratio due to HMFs modified the magnetic properties of deposits.

Growth and magnetic properties dependence of the Co–Cu/Cu films electrodeposited under high magnetic fields

International Nuclear Information System (INIS)

Franczak, Agnieszka; Levesque, Alexandra; Zabinski, Piotr; Li, Donggang; Czapkiewicz, Maciej; Kowalik, Remigiusz; Bohr, Frédéric

2015-01-01

The present work is focused on the investigations of magnetic properties dependence on microstructure of Co–Cu/Cu films electrodeposited under superimposed high magnetic field. The experimental results indicate a strong effect of an external magnetic field on the morphology of deposited films, more precisely on the Co:Cu ratio that determines the film growth. It is shown that the Co–Cu/Cu films electrodeposited without superimposed magnetic field consisted of two clearly visible features: compact film with incorporated granular particles. Under a superimposed external high magnetic field the privilege growth of the particles was induced. As a consequence, development of the well-defined branched structure of Co–Cu/Cu film was observed. In contrary, the phase compositional investigations do not reveal any changes in the phase formation during electrodeposition under magnetic field conditions. Thus, it is assumed that a strong growth of Co–Cu/Cu films in (111) direction under magnetic or non-magnetic electrodeposition conditions is related with the growth of Cu (111) plane and embedded into it some of the Co fcc atoms of same (111) orientation, as well as the Co hcp atoms that grows in the (002) direction. This non-equilibrium growth of Co–Cu/Cu films under magnetic deposition conditions affects strongly the magnetic properties of deposited films, revealing that films obtained under magnetic fields higher than 3 T were no more magnetic materials. - Highlights: • Co–Cu/Cu electrodeposits were obtained at elevated temperature under HMFs. • The effects of HMFs on microstructure and magnetic properties were investigated. • Interesting morphological changes due to HMFs has been observed. • Changes in Co:Cu ratio due to HMFs modified the magnetic properties of deposits

Ultrathin magnetic structures II measurement techniques and novel magnetic properties

CERN Document Server

Heinrich, Bretislav

2006-01-01

The ability to understand and control the unique properties of interfaces has created an entirely new field of magnetism, with profound impact in technology and serving as the basis for a revolution in electronics. Our understanding of the physics of magnetic nanostructures has also advanced significantly. This rapid development has generated a need for a comprehensive treatment that can serve as an introduction to the field for those entering it from diverse fields, but which will also serve as a timely overview for those already working in this area. The four-volume work Ultra-Thin Magnetic

On the room temperature multiferroic BiFeO3: magnetic, dielectric and thermal properties

Science.gov (United States)

Lu, J.; Günther, A.; Schrettle, F.; Mayr, F.; Krohns, S.; Lunkenheimer, P.; Pimenov, A.; Travkin, V. D.; Mukhin, A. A.; Loidl, A.

2010-06-01

Magnetic dc susceptibility between 1.5 and 800 K, ac susceptibility and magnetization, thermodynamic properties, temperature dependence of radio and audio-wave dielectric constants and conductivity, contact-free dielectric constants at mm-wavelengths, as well as ferroelectric polarization are reported for single crystalline BiFeO3. A well developed anomaly in the magnetic susceptibility signals the onset of antiferromagnetic order close to 635 K. Beside this anomaly no further indications of phase or glass transitions are indicated in the magnetic dc and ac susceptibilities down to the lowest temperatures. The heat capacity has been measured from 2 K up to room temperature and significant contributions from magnon excitations have been detected. From the low-temperature heat capacity an anisotropy gap of the magnon modes of the order of 6 meV has been determined. The dielectric constants measured in standard two-point configuration are dominated by Maxwell-Wagner like effects for temperatures T > 300 K and frequencies below 1 MHz. At lower temperatures the temperature dependence of the dielectric constant and loss reveals no anomalies outside the experimental errors, indicating neither phase transitions nor strong spin phonon coupling. The temperature dependence of the dielectric constant was measured contact free at microwave frequencies. At room temperature the dielectric constant has an intrinsic value of 53. The loss is substantial and strongly frequency dependent indicating the predominance of hopping conductivity. Finally, in small thin samples we were able to measure the ferroelectric polarization between 10 and 200 K. The saturation polarization is of the order of 40 μC/cm2, comparable to reports in literature.

Electronic and magnetic properties of ultrathin rhodium nanowires

CERN Document Server

Wang Bao Lin; Ren-Yun; Sun Hou Qian; Chen Xiao Shuang; Zhao Ji Jun

2003-01-01

The structures of ultrathin rhodium nanowires are studied using empirical molecular dynamics simulations with a genetic algorithm. Helical multishell cylindrical and pentagonal packing structures are found. The electronic and magnetic properties of the rhodium nanowires are calculated using an spd tight-binding Hamiltonian in the unrestricted Hartree-Fock approximation. The average magnetic moment and electronic density of states are obtained. Our results indicate that the electronic and magnetic properties of the rhodium nanowires depend not only on the size of the wire but also on the atomic structure. In particular, centred pentagonal and hexagonal structures can be unusually ferromagnetic.

Soft Magnetic Multilayered Thin Films for HF Applications

Science.gov (United States)

Loizos, George; Giannopoulos, George; Serletis, Christos; Maity, Tuhin; Roy, Saibal; Lupu, Nicoleta; Kijima, Hanae; Yamaguchi, Masahiro; Niarchos, Dimitris

Multilayered thin films from various soft magnetic materials were successfully prepared by magnetron sputtering in Ar atmosphere. The magnetic properties and microstructure were investigated. It is found that the films show good soft magnetic properties: magnetic coercivity of 1-10 Oe and saturation magnetization higher than 1T. The initial permeability of the films is greater than 300 and flattens up to 600 MHz. The multilayer thin film properties in combination with their easy, fast and reproducible fabrication indicate that they are potential candidates for high frequency applications.

Study on magnetic property and fracture behavior of magnetic materials

International Nuclear Information System (INIS)

Miya, Kenzo; Demachi, Kazuyuki; Aoto, Kazumi; Nagae, Yuji

2002-04-01

Establishment of evaluation methods of material degradation before crack initiation is needed very much to enhance the reliability of structural components. We remark magnetic methods in this report. Our objectives are to reveal the relation between degradation and magnetic property and to develop evaluation methods of material degradation, especially plastic deformation and stress corrosion cracking (SCC). In the former part of this report, evaluation methods for plastic deformation are discussed. At first, the study that shows the relation between the magnetic flux leakage and plastic deformation is reviewed. We developed the inverse analysis method of magnetization to specify the degradation distribution. Moreover, we propose inverse analysis of magnetic susceptibility for quantitative evaluation. In the latter part, the topic is SCC. We measured the magnetic flux leakage from the sample induced a SCC crack (Inconel 600). Inconel 600 is a paramagnetic material at room temperature but the sample shows ferromagnetic and the magnetic flux leakage was changed near the SCC crack. The possibility of detection of a SCC crack is shown by the inverse analysis result from the magnetic flux leakage. Finally, it is recognized by observation of the micro magnetic distributions by using a magnetic force microscope that the magnetization has relation with chromium depletion near grain boundaries and it is weak near the SCC crack. From these results, the magnetic method is very effective for evaluation of degradation. (author)

Properties of barium strontium titanate at millimeter wave frequencies

Energy Technology Data Exchange (ETDEWEB)

Osman, Nurul [Department of Physics, Universiti Putra Malaysia (Malaysia); Free, Charles [Department of Engineering and Design, University of Sussex (United Kingdom)

2015-04-24

The trend towards using higher millimetre-wave frequencies for communication systems has created a need for accurate characterization of materials to be used at these frequencies. Barium Strontium Titanate (BST) is a ferroelectric material whose permittivity is known to change as a function of applied electric field and have found varieties of application in electronic and communication field. In this work, new data on the properties of BST characterize using the free space technique at frequencies between 145 GHz and 155 GHz for both thick film and bulk samples are presented. The measurement data provided useful information on effective permittivity and loss tangent for all the BST samples. Data on the material transmission, reflection properties as well as loss will also be presented. The outcome of the work shows through practical measurement, that BST has a high permittivity with moderate losses and the results also shows that BST has suitable properties to be used as RAM for high frequency application.

Frequency Noise Properties of Lasers for Interferometry in Nanometrology

Directory of Open Access Journals (Sweden)

Ondřej Číp

2013-02-01

Full Text Available In this contribution we focus on laser frequency noise properties and their influence on the interferometric displacement measurements. A setup for measurement of laser frequency noise is proposed and tested together with simultaneous measurement of fluctuations in displacement in the Michelson interferometer. Several laser sources, including traditional He-Ne and solid-state lasers, and their noise properties are evaluated and compared. The contribution of the laser frequency noise to the displacement measurement is discussed in the context of other sources of uncertainty associated with the interferometric setup, such as, mechanics, resolution of analog-to-digital conversion, frequency bandwidth of the detection chain, and variations of the refractive index of air.

Influences of Laser Spot Welding on Magnetic Property of a Sintered NdFeB Magnet

Directory of Open Access Journals (Sweden)

Baohua Chang

2016-08-01

Full Text Available Laser welding has been considered as a promising method to join sintered NdFeB permanent magnets thanks to its high precision and productivity. However, the influences of laser welding on the magnetic property of NdFeB are still not clear. In the present paper, the effects of laser power on the remanence (Br were experimentally investigated in laser spot welding of a NdFeB magnet (N48H. Results show that the Br decreased with the increase of laser power. For the same welding parameters, the Br of magnets, that were magnetized before welding, were much lower than that of magnets that were magnetized after welding. The decrease in Br of magnets after laser welding resulted from the changes in microstructures and, in turn, the deterioration of magnetic properties in the nugget and the heat affected zone (HAZ in a laser weld. It is recommended that the dimensions of nuggets and HAZ in laser welds of a NdFeB permanent magnet should be as small as possible, and the magnets should be welded before being magnetized in order to achieve a better magnetic performance in practical engineering applications.

Magnetic tunnel structures: Transport properties controlled by bias, magnetic field, and microwave and optical radiation

International Nuclear Information System (INIS)

Volkov, N.V.; Eremin, E.V.; Tarasov, A.S.; Rautskii, M.V.; Varnakov, S.N.; Ovchinnikov, S.G.; Patrin, G.S.

2012-01-01

Different phenomena that give rise to a spin-polarized current in some systems with magnetic tunnel junctions are considered. In a manganite-based magnetic tunnel structure in CIP geometry, the effect of current-channel switching was observed, which causes bias-driven magnetoresistance, rf rectification, and the photoelectric effect. The second system under study, ferromagnetic/insulator/semiconductor, exhibits the features of the transport properties in CIP geometry that are also related to the current-channel switching effect. The described properties can be controlled by a bias, a magnetic field, and optical radiation. At last, the third system under consideration is a cooperative assembly of magnetic tunnel junctions. This system exhibits tunnel magnetoresistance and the magnetic-field-driven microwave detection effect.

Magnetic properties of epitaxial bismuth ferrite-garnet mono- and bilayers

International Nuclear Information System (INIS)

Semuk, E.Yu.; Berzhansky, V.N.; Prokopov, A.R.; Shaposhnikov, A.N.; Karavainikov, A.V.; Salyuk, O.Yu.; Golub, V.O.

2015-01-01

Magnetic properties of Bi 1.5 Gd 1.5 Fe 4.5 Al 0.5 O 12 (84 nm) and Bi 2.8 Y 0.2 Fe 5 O 12 (180 nm) films epitaxially grown on gallium-gadolinium garnet (GGG) single crystal (111) substrate as well as Bi 1.5 Gd 1.5 Fe 4.5 Al 0.5 O 12 /Bi 2.8 Y 0.2 Fe 5 O 12 bilayer were investigated using ferromagnetic resonance technique. The mismatch of the lattice parameters of substrate and magnetic layers leads to formation of adaptive layers which affect on the high order anisotropy constant of the films but practically do not affect on uniaxial perpendicular magnetic anisotropy The magnetic properties of the bilayer film were explained in supposition of strong exchange coupling between magnetic layers taking into account film-film and film-substrate elastic interaction. - Highlights: • Magnetic parameters of epitaxial Bi-YIG films and bilayers on GGG substrate. • Adaptive layers affect on high order magnetic anisotropy. • Magnetic properties of bilayers are result of strong exchange interaction

Magnetic properties of bimetallic nanoislands deposited on Pt(111)

Energy Technology Data Exchange (ETDEWEB)

Bornemann, Sven; Minar, Jan; Mankovsky, Sergey; Ebert, Hubert [Department Chemie und Biochemie, LMU Muenchen, 81377 Muenchen (Germany); Ouazi, Safia; Rusponi, Stefano; Brune, Harald [Institute of Condensed Matter Physics, EPF Lausanne (Switzerland); Staunton, Julie B. [Department of Physics, University of Warwick (United Kingdom)

2010-07-01

In recent years, magnetic nanostructures on surfaces have been the subject of intense research activities which are driven by fundamental as well as practical interests. One of the central questions for future applications is how the magnetic properties like the magnetic anisotropy evolve in-between single magnetic adatoms and submonolayer magnetic particle arrays. Experimentalists have succeeded in assembling surface supported single domain particles where the magnetic moments of all atoms form a so-called macrospin and it is commonly believed that the special magnetic characteristics of such structures are mainly due to their exposed low-coordinated edge atoms. For some of these novel systems, however, unexpected low anisotropies or reduced magnetic moments are observed which makes it difficult to find promising candidates for real life technical applications. To support these experimental efforts the fully relativistic spin-polarized KKR method has been applied to investigate the influence of spin-orbit coupling on the magnetic properties of various FeCo nanostructures deposited on Pt(111). The discussion focuses on interface and alloy contributions to the magnetic anisotropy in these systems.

Room temperature magnetic and dielectric properties of cobalt doped CaCu3Ti4O12 ceramics

Science.gov (United States)

Mu, Chunhong; Song, Yuanqiang; Wang, Haibin; Wang, Xiaoning

2015-05-01

CaCu3Ti4-xCoxO12 (x = 0, 0.2, 0.4) ceramics were prepared by a conventional solid state reaction, and the effects of cobalt doping on the room temperature magnetic and dielectric properties were investigated. Both X-ray diffraction and energy dispersive X-ray spectroscopy confirmed the presence of Cu and Co rich phase at grain boundaries of Co-doped ceramics. Scanning electron microscopy micrographs of Co-doped samples showed a striking change from regular polyhedral particle type in pure CaCu3Ti4O12 (CCTO) to sheet-like grains with certain growth orientation. Undoped CaCu3Ti4O12 is well known for its colossal dielectric constant in a broad temperature and frequency range. The dielectric constant value was slightly changed by 5 at. % and 10 at. % Co doping, whereas the second relaxation process was clearly separated in low frequency region at room temperature. A multirelaxation mechanism was proposed to be the origin of the colossal dielectric constant. In addition, the permeability spectra measurements indicated Co-doped CCTO with good magnetic properties, showing the initial permeability (μ') as high as 5.5 and low magnetic loss (μ″ < 0.2) below 3 MHz. And the interesting ferromagnetic superexchange coupling in Co-doped CaCu3Ti4O12 was discussed.

ZERO-FIELD NUCLEAR MAGNETIC RESONANCE FOR STUDY OF ANTIFERROMAGNETIC PROPERTIES OF FeF3 MATERIALS

Directory of Open Access Journals (Sweden)

G. R. F. Suwandi

2016-01-01

Full Text Available Nuclear Magnetic Resonance (NMR has been used as a research tool in many fields. In this study, the magnetic properties, especially anti-ferromagnetic properties of FeF3 materials were investigated. Zero-field custom-built NMR method was used to investigate the anti-ferromagnetic properties in the materials. Experiments have been carried out by varying the sample temperatures from 8 K to 220 K. Ordinary spin echo pulse sequence 90⁰RF–τ–180⁰RF were used. Using Fast Fourier Transform, the signals in NMR spectrum were analyzed and the peak showed the resonance frequency. The result showed that resonance frequencies decrease with increasing in temperature. The frequency of the spectrum was around 85.41 MHz in the zero-temperature limit, and this corresponds with Fe hyperfine field at zero-temperature limit was 2.14 T. The temperature dependence of the local magnetization does not fit T2 Bloch’s Law very well. Instead, it fits the exponential form having an energy gap in the dispersion relation of the spin wave. It is obtained from the result that FeF3 is antiferromagnetic materials with energy gap of 11.466 meV and anisotropy energy of 1.045 meV.Nuclear Magnetic Resonance (NMR telah banyak digunakan sebagai “research tool” pada berbagai bidang kajian di fisika. Pada studi ini, akan dilakukan eksperimen untuk menguji sifat magnetik, khususnya antiferromagnetik pada material FeF3. Telah dilakukan eksperimen dengan memvariasikan temperatur pada sampel dari 8 K hingga 220 K. Pulse sequence yang digunakan adalah 90⁰RF–τ–180⁰RF. Dengan memanfaatkan Fast Fourier Transform, sinyal echo ini dapat dianalisis dalam bentuk spektrum NMR dengan puncak spektrum menunjukkan frekuensi resonansinya. Diperoleh bahwa frekuensi resonansi akan menurun seiring dengan kenaikan temperatur. Posisi frekuensi pada temperatur 0 K adalah sebesar 85,41 MHz, hal ini memperlihatkan bahwa medan hyperfine dari Fe sebesar 2,14 T pada temperatur 0 K. Kurva

A comparative study of magnetic properties of MnFe2O4 nanoparticles prepared by thermal decomposition and solvothermal methods

Directory of Open Access Journals (Sweden)

B Aslibeiki

2017-09-01

Full Text Available A comparative study of magnetic properties of MnFe2O4 ferrite nanoparticles prepared by two different methods has been reported. The first sample (S1 was synthesized by thermal decomposition of metal nitrates. And the second sample (S2 was prepared by solvothermal method using Tri-ethylene glycol (TEG. Magnetic hysteresis loops at 300 and 5 K; magnetization and AC susceptibility measurements versus temperature confirmed the effective role of TEG on the magnetic properties of nanoparticles. The results showed that, at 300 K the saturation magnetization (MS of S2 sample is 46% greater than that of S1 sample. At 5 K, the difference in MS of the samples raised to 60%. AC susceptibility measurements at different frequencies and also magnetization versus temperature under field cooling and zero field cooling processes revealed that, the TEG molecules influence the surface spins order of S2 sample. The sample S1 showed strongly interacting superspin glass state, while the sample S2 consists of weakly interacting superparamagnetic nanoparticles.

Nano-Scale Devices for Frequency-Based Magnetic Biosensing

Science.gov (United States)

2017-01-31

show the basic measurement setup (the field is applied perpendicular to the disk plane). A radiofrequency signal is injected across the disk (disks...shown in Fig. 7(a). A spectrum analyser (S.A.) (or a high frequency oscilloscope) is used to measure the radiofrequency STO output signal with Fig...crystals and, via electrical measurements , in magnetic-vortex-containing, isolated micro- and nano-devices. Via micromagnetic simulations, we have largely

Exponential frequency spectrum and Lorentzian pulses in magnetized plasmas

International Nuclear Information System (INIS)

Pace, D. C.; Shi, M.; Maggs, J. E.; Morales, G. J.; Carter, T. A.

2008-01-01

Two different experiments involving pressure gradients across the confinement magnetic field in a large plasma column are found to exhibit a broadband turbulence that displays an exponential frequency spectrum for frequencies below the ion cyclotron frequency. The exponential feature has been traced to the presence of solitary pulses having a Lorentzian temporal signature. These pulses arise from nonlinear interactions of drift-Alfven waves driven by the pressure gradients. In both experiments the width of the pulses is narrowly distributed resulting in exponential spectra with a single characteristic time scale. The temporal width of the pulses is measured to be a fraction of a period of the drift-Alfven waves. The experiments are performed in the Large Plasma Device (LAPD-U) [W. Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] operated by the Basic Plasma Science Facility at the University of California, Los Angeles. One experiment involves a controlled, pure electron temperature gradient associated with a microscopic (6 mm gradient length) hot electron temperature filament created by the injection a small electron beam embedded in the center of a large, cold magnetized plasma. The other experiment is a macroscopic (3.5 cm gradient length) limiter-edge experiment in which a density gradient is established by inserting a metallic plate at the edge of the nominal plasma column of the LAPD-U. The temperature filament experiment permits a detailed study of the transition from coherent to turbulent behavior and the concomitant change from classical to anomalous transport. In the limiter experiment the turbulence sampled is always fully developed. The similarity of the results in the two experiments strongly suggests a universal feature of pressure-gradient driven turbulence in magnetized plasmas that results in nondiffusive cross-field transport. This may explain previous observations in helical confinement devices, research tokamaks, and arc plasmas.

Magnetic and physical-mechanical properties of polymer composites with soft magnetic fillers

International Nuclear Information System (INIS)

Usakova, M.; Usak, E.; Olah, V.; Rekosova, J.

2013-01-01

In this paper the influence of soft magnetic ferrite fillers on magnetic and physical-mechanical properties of the prepared composite samples based in natural rubber matrix was studied. The soft magnetic ferrite materials with the chemical composition Mn_0_._3_7Zn_0_._5_7Fe_2_._0_6O_4 and Ni_0_._3_3Zn_0_._6_7Fe_2O_4 were used as magnetic filler in various concentrations. Further, the effect of thermo-oxidative ageing on the prepared composite materials was investigated. Magneto-rheological elastomers are solid analogues to magneto-rheological fluids. These materials are considered as smart materials comprising of micro- or submicro-sized magnetic particles dispersed in non-magnetic matrix. (authors)

The influence of low frequency magnetic field upon cultivable plant physiology

International Nuclear Information System (INIS)

Rochalska, M.

2008-01-01

The 16 Hz frequency and 5 mT magnetic flux density as well as alternating magnetic field influence the field germination physiological yield-forming features and the yield of sugar have been investigated. The profitable influence of the investigated factor at physiological yield-forming features, causing an increase in sugar beet root and leaf yield, was shown. The beneficial influence on the yield is especially clear in unfavourable weather conditions. (author)

Extremely low-frequency magnetic fields and risk of childhood leukemia

DEFF Research Database (Denmark)

Schüz, Joachim; Dasenbrock, Clemens; Ravazzani, Paolo

2016-01-01

Exposure to extremely low-frequency magnetic fields (ELF-MF) was evaluated in an International Agency for Research on Cancer (IARC) Monographs as "possibly carcinogenic to humans" in 2001, based on increased childhood leukemia risk observed in epidemiological studies. We conducted a hazard assess...

Effect of magnetic field on the physical properties of water

Science.gov (United States)

Wang, Youkai; Wei, Huinan; Li, Zhuangwen

2018-03-01

In this study, the effect of magnetic field (MF) on the partial physical properties of water are reported, tap water (TW) and 4 types of magnetized water (MW) were measured in the same condition. It was found that the properties of TW were changed following the MF treatment, shown as the increase of evaporation amount, the decrease of specific heat and boiling point after magnetization, the changes depend on the magnetization effect. In addition, magnetic field strength (MFS) has a marked influence on the magnetization effect, the optimal magnetizing condition was determined as the MFS of 300 mT. The findings of this study offered a facile approach to improve cooling and power generation efficiency in industrial.

Transmission of Mössbauer rays through ferromagnets in radio-frequency magnetic field

International Nuclear Information System (INIS)

Dzyublik, A. Ya.; Sadykov, E. K.; Petrov, G. I.; Arinin, V. V.; Vagizov, F. G.; Spivak, V. Yu.

2013-01-01

The transmission of Mössbauer radiation through a thick ferromagnetic crystal, exposed to a radio-frequency (rf) magnetic field, is studied. The quantum-mechanical dynamical scattering theory is developed, taking into account the periodical reversals of the magnetic field at the nuclei. The Mössbauer forward scattering (FS) spectra of the weak ferromagnet FeBO 3 placed into rf field are measured. It is found that the coherent gamma wave in the crystal absorbs or emits only couples of the rf photons. As a result, the FS spectra consist of equidistant lines spaced by twice the frequency of the rf field in contrast to the absorption spectra

Structure and phase formation behavior and dielectric and magnetic properties of lead iron tantalate-lead zirconate titanate multiferroic ceramics

International Nuclear Information System (INIS)

Wongmaneerung, R.; Tipakontitikul, R.; Jantaratana, P.; Bootchanont, A.; Jutimoosik, J.; Yimnirun, R.; Ananta, S.

2016-01-01

Highlights: • The multiferroic ceramics consisted of PFT and PZT. • Crystal structure changed from cubic to mixedcubic and tetragonal with increasing PZT content. • Dielectric showed the samples underwent a typical relaxor ferroelectric behavior. • Magnetic properties showed very interesting behavior with square saturated magnetic hysteresis loops. - Abstract: Multiferroic (1 − x)Pb(Fe_0_._5Ta_0_._5)O_3–xPb(Zr_0_._5_3Ti_0_._4_7)O_3 (or PFT–PZT) ceramics were synthesized by solid-state reaction method. The crystal structure and phase formation of the ceramics were examined by X-ray diffraction (XRD). The local structure surrounding Fe and Ti absorbing atoms was investigated by synchrotron X-ray Absorption Near-Edge Structure (XANES) measurement. Dielectric properties were studied as a function of frequency and temperature using a LCR meter. A vibrating sample magnetometer (VSM) was used to determine the magnetic hysteresis loops. XRD study indicated that the crystal structure of the sample changed from pure cubic to mixed cubic and tetragonal with increasing PZT content. XANES measurements showed that the local structure surrounding Fe and Ti ions was similar. Dielectric study showed that the samples underwent a typical relaxor ferroelectric behavior while the magnetic properties showed very interesting behavior with square saturated magnetic hysteresis loops.

Biological effects of exposure to low frequency electric and magnetic fields

International Nuclear Information System (INIS)

Ahnstroem, G.

1992-10-01

The biological effects of exposure to low frequency electric and magnetic fields are reviewed with the objective of summarizing effects directly relevant to considerations of the health and safety of exposed people

The effect of boron doping on crystal structure, magnetic properties and magnetocaloric effect of DyCo{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Wang, C.L., E-mail: wangchaolun2004@163.com [The Ames Laboratory U.S. Department of Energy, Iowa State University, Ames, IA 50011-3020 (United States); School of Materials Science and Engineering, University of Science and Technology of Beijing, Beijing 100083 (China); Liu, J. [The Ames Laboratory U.S. Department of Energy, Iowa State University, Ames, IA 50011-3020 (United States); Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011-2300 (United States); Mudryk, Y.; Gschneidner, K.A. [The Ames Laboratory U.S. Department of Energy, Iowa State University, Ames, IA 50011-3020 (United States); Long, Y. [School of Materials Science and Engineering, University of Science and Technology of Beijing, Beijing 100083 (China); Pecharsky, V.K. [The Ames Laboratory U.S. Department of Energy, Iowa State University, Ames, IA 50011-3020 (United States); Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011-2300 (United States)

2016-05-01

The magnetic properties and magnetic entropy changes of DyCo{sub 2}B{sub x} (x=0, 0.05, 0.1, and 0.2) alloys were investigated. The Curie temperature (T{sub C}) increases with increasing B concentration. The frequency dependence of ac magnetic susceptibility of DyCo{sub 2} caused by the narrow domain wall pinning effect is depressed by B doping, but the coercivity and the magnetic viscosity are prominently increased in the B doped alloys. The magnetic transition nature of DyCo{sub 2}B{sub x} changes from the first-order to the second-order with increasing x, which leads to the decrease of the maximum magnetic entropy change. However, the relative cooling power (RCP) of DyCo{sub 2} and the B doped alloys remains nearly constant. - Highlights: • The discrepancy between the ZFC and FCC curves of DyCo{sub 2}B{sub x} is enhanced in the B doped samples, while the frequency dependence of the ac magnetic susceptibility is depressed. • The Curie temperature, coercivity and viscosity of DyCo{sub 2}B{sub x} are increased by B doping • The magnetic transition nature of the B doped samples is changed from first order to second order, leading to the decrease of magnetic entropy change. However, the relative cooling power of DyCo{sub 2}B{sub 0.05} is increased about 18%.

Magnetic and electrical properties of ITER vacuum vessel steels

International Nuclear Information System (INIS)

Mergia, K.; Apostolopoulos, G.; Gjoka, M.; Niarchos, D.

2007-01-01

Full text of publication follows: Ferritic steel AISI 430 is a candidate material for the lTER vacuum vessel which will be used to limit the ripple in the toroidal magnetic field. The magnetic and electrical properties and their temperature dependence in the temperature range 300 - 900 K of AISI 430 ferritic stainless steels are presented. The temperature variation of the coercive field, remanence and saturation magnetization as well as electrical resistivity and the effect of annealing on these properties is discussed. (authors)

Tunable Magnetic Resonance in Microwave Spintronics Devices

Science.gov (United States)

Chen, Yunpeng; Fan, Xin; Xie, Yunsong; Zhou, Yang; Wang, Tao; Wilson, Jeffrey D.; Simons, Rainee N.; Chui, Sui-Tat; Xiao, John Q.

2015-01-01

Magnetic resonance is one of the key properties of magnetic materials for the application of microwave spintronics devices. The conventional method for tuning magnetic resonance is to use an electromagnet, which provides very limited tuning range. Hence, the quest for enhancing the magnetic resonance tuning range without using an electromagnet has attracted tremendous attention. In this paper, we exploit the huge exchange coupling field between magnetic interlayers, which is on the order of 4000 Oe and also the high frequency modes of coupled oscillators to enhance the tuning range. Furthermore, we demonstrate a new scheme to control the magnetic resonance frequency. Moreover, we report a shift in the magnetic resonance frequency as high as 20 GHz in CoFe based tunable microwave spintronics devices, which is 10X higher than conventional methods.

Magnetic and electromagnetic properties of Pr doped strontium ferrite/polyaniline composite film

Energy Technology Data Exchange (ETDEWEB)

Huang, Ying; Li, Yuqing; Wang, Yan, E-mail: wangyan287580632@126.com

2014-11-15

This paper reported three acid (including hydrochloric acid HCl, p-toluenesulfonic acid PTS and D-camphor-10-acid CSA) doped SrPr{sub 0.2}Fe{sub 11.8}O{sub 19}/PANI composite film and the HCl–PANI film prepared by a sol–gel method and in-situ oxidative polymerization. The characteristics of the film phase structure, surface morphology, conductivity and magnetic and electromagnetic properties were studied by using XRD, XPS, FESEM, four-probe tester, VSM and Vector Network Analyzer. The resistivity of organic acid doped composite films is higher than that of the HCl doped one. The saturation and remanent magnetization of PTS and HCl doped composite films are greater than the CSA-doped one; however, the coercivity of the three acid doped composite films is basically 5546 Oe. The saturation magnetization, remanent magnetization and coercivity of SrPr{sub 0.2}Fe{sub 11.8}O{sub 19} film are greater than those of the SrPr{sub 0.2}Fe{sub 11.8}O{sub 19}–PANI composite film. In the frequency range of 8–12 GHz, the dielectric loss of HCl–PANI film is the maximum, and the dielectric loss of SrPr{sub 0.2}Fe{sub 11.8}O{sub 19} film is the minimum; the magnetic loss of the four films is in descending order as SrPr{sub 0.2}Fe{sub 11.8}O{sub 19} film, PrSrM/(HCl–PANI) composite film, PrSrM/(CSA–PANI) and HCl–PANI film. - Highlights: • Synthesizing three acid doped SrPr{sub 0.2}Fe{sub 11.8}O{sub 19}/PANI composite films. • By sol–gel method and in-situ oxidative polymerization. • With excellent magnetic and electromagnetic properties. • The particular coating structure of PANI and Sr-ferrite. • Great interest for magnetic material and microwave absorbers.

High Frequency Amplitude Detector for GMI Magnetic Sensors

Directory of Open Access Journals (Sweden)

Aktham Asfour

2014-12-01

Full Text Available A new concept of a high-frequency amplitude detector and demodulator for Giant-Magneto-Impedance (GMI sensors is presented. This concept combines a half wave rectifier, with outstanding capabilities and high speed, and a feedback approach that ensures the amplitude detection with easily adjustable gain. The developed detector is capable of measuring high-frequency and very low amplitude signals without the use of diode-based active rectifiers or analog multipliers. The performances of this detector are addressed throughout the paper. The full circuitry of the design is given, together with a comprehensive theoretical study of the concept and experimental validation. The detector has been used for the amplitude measurement of both single frequency and pulsed signals and for the demodulation of amplitude-modulated signals. It has also been successfully integrated in a GMI sensor prototype. Magnetic field and electrical current measurements in open- and closed-loop of this sensor have also been conducted.

Microstructure and Magnetic Properties of Magnetic Material Fabricated by Selective Laser Melting

Science.gov (United States)

Jhong, Kai Jyun; Huang, Wei-Chin; Lee, Wen Hsi

Selective Laser Melting (SLM) is a powder-based additive manufacturing which is capable of producing parts layer-by-layer from a 3D CAD model. The aim of this study is to adopt the selective laser melting technique to magnetic material fabrication. [1]For the SLM process to be practical in industrial use, highly specific mechanical properties of the final product must be achieved. The integrity of the manufactured components depend strongly on each single laser-melted track and every single layer, as well as the strength of the connections between them. In this study, effects of the processing parameters, such as the space distance of surface morphology is analyzed. Our hypothesis is that when a magnetic product is made by the selective laser melting techniques instead of traditional techniques, the finished component will have more precise and effective properties. This study analyzed the magnitudes of magnetic properties in comparison with different parameters in the SLM process and compiled a completed product to investigate the efficiency in contrast with products made with existing manufacturing processes.

Magnetic properties of heavy-fermion superconductors

International Nuclear Information System (INIS)

Rauchschwalbe, U.

1986-01-01

In the present thesis the magnetic properties of heavy-fermion superconductors are investigated. The magnetoresistance and the critical magnetic fields show a variety of anomalous phenomena. The Kondo lattices CeCu 2 Si and CeAl 3 are analysed by magnetoresistance and the field dependence of the resistivitis of UBe 13 , UPt 3 , URu 2 Si 2 and CeRu 3 Si are measured for temperatures < or approx. 1 K. (BHO)

Magnetoliposomes for controlled drug release in the presence of low-frequency magnetic field

KAUST Repository

Nappini, Silvia

2010-01-01

In this work we have studied the effect of a low-frequency alternating magnetic field (LF-AMF) on the permeability of magnetoliposomes, i.e. liposomes including magnetic nanoparticles within their water pool. Large unilamellar liposomes loaded with magnetic cobalt ferrite nanoparticles (CoFe 2O4) have been prepared and characterized. Structural characterization of the liposomal dispersion has been performed by dynamic light scattering (DLS). The enhancement of liposome permeability upon exposure to LF-AMF has been measured as the self-quenching decrease of a fluorescent hydrophilic molecule (carboxyfluorescein, CF) entrapped in the liposome pool. Liposome leakage has been monitored as a function of field frequency, time of exposure and concentration, charge and size of the embedded nanoparticles. The results show that CF release from magnetoliposomes is strongly promoted by LF-AMF, reasonably as a consequence of nanoparticle motions in the liposome pool at the applied frequency. CF release as a function of time in magnetoliposomes unexposed to magnetic field follows Fickian diffusion, while samples exposed to LF-AMF show zero-order kinetics, consistently with an anomalous transport, due to an alteration of the bilayer permeability. These preliminary results open up new perspectives in the use of these systems as carriers in targeted and controlled release of drugs. © The Royal Society of Chemistry 2010.

Electronic and magnetic properties of MnAu nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, Safi 46000 (Morocco); LMPHE (URAC 12), Faculty of Science, Mohammed V-Agdal University, Rabat (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 (France); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Benyoussef, A. [LMPHE (URAC 12), Faculty of Science, Mohammed V-Agdal University, Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Mounkachi, O; El moussaoui, H. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco)

2014-03-15

Self-consistent ab initio calculations, based on DFT (Density Functional Theory) approach and using FLAPW (Full potential Linear Augmented Plane Wave) method, are performed to investigate both electronic and magnetic properties of the MnAu nanoparticles. Polarized spin is included in calculations within the framework of the antiferromagnetic. The Mn magnetic moments where considered to be along c axes. Obtained data from ab initio calculations are used as input for the high temperature series expansions (HTSEs) calculations to compute other magnetic parameters. The zero-field high temperature static susceptibility series of the magnetic moment (m) and nearest-neighbour Heisenberg and XY models on a MnAu nanoparticles is thoroughly analyzed by means of a power series coherent anomaly method (CAM) for different nanoparticles. The exchanges interactions between the magnetic atoms are obtained for MnAu nanoparticles. - Highlights: • The electronic properties of the MnAu nanoparticles are studied using the DFT and FLAPW. • Magnetic moment is computed. • The ab initio calculations are used as input for HTSEs to compute other magnetic parameters. • The exchanges interactions and blocking temperature are obtained for MnAu nanoparticles.

Electronic and magnetic properties of MnAu nanoparticles

International Nuclear Information System (INIS)

Masrour, R.; Hlil, E.K.; Hamedoun, M.; Benyoussef, A.; Mounkachi, O; El moussaoui, H.

2014-01-01

Self-consistent ab initio calculations, based on DFT (Density Functional Theory) approach and using FLAPW (Full potential Linear Augmented Plane Wave) method, are performed to investigate both electronic and magnetic properties of the MnAu nanoparticles. Polarized spin is included in calculations within the framework of the antiferromagnetic. The Mn magnetic moments where considered to be along c axes. Obtained data from ab initio calculations are used as input for the high temperature series expansions (HTSEs) calculations to compute other magnetic parameters. The zero-field high temperature static susceptibility series of the magnetic moment (m) and nearest-neighbour Heisenberg and XY models on a MnAu nanoparticles is thoroughly analyzed by means of a power series coherent anomaly method (CAM) for different nanoparticles. The exchanges interactions between the magnetic atoms are obtained for MnAu nanoparticles. - Highlights: • The electronic properties of the MnAu nanoparticles are studied using the DFT and FLAPW. • Magnetic moment is computed. • The ab initio calculations are used as input for HTSEs to compute other magnetic parameters. • The exchanges interactions and blocking temperature are obtained for MnAu nanoparticles

Magnetic properties and thermodynamics in a metallic nanotube

International Nuclear Information System (INIS)

Jiang, Wei; Li, Xiao-Xi; Guo, An-Bang; Guan, Hong-Yu; Wang, Zan; Wang, Kai

2014-01-01

A metallic nanotube composed of the ferromagnetic spin-3/2 inner shell and spin-1 outer shell with a ferrimagnetic interlayer coupling has been studied by using the effective-field theory with correlations (EFT). With both existence of the magnetic anisotropy and transverse field, we have studied effects of them on the magnetic properties and the thermodynamics. Some interesting phenomena have been found in the phase diagrams. At low temperature, the magnetization curves present different behaviors. Two compensation points have been found for the certain values of the system parameters in the system. The research results of metallic nanotubes may have potential applications in the fields of biomedicine and molecular devices. - Highlights: • A hexagonal metallic nanotube is composed of spin-3/2 inner layer and spin-1 outer layer. • Various types of magnetization curves depend on physical parameters and temperature. • We study the effects of physical parameters on the magnetic properties and thermodynamics

Magnetic nanoparticles: surface effects and properties related to biomedicine applications.