Negative magnetoresistance of polymer nanocomposites on the basis of PP + Fe3O4 and PVDF + Fe3O4 in the magnetic field

In the present study, the influence of the temperature–time mode of crystallization (TTC) on the electrophysical properties of polymer-based PP + Fe3O4 nanocomposite materials was investigated. Also, the effect of the temperature-time mode of crystallization of nanocomposites on the negative magnetoresistance (NMR) effect that observed in this material was investigated. It was found that dielectric permittivity of polymer nanocomposites rises with increasing of cooling rate. The cooling rate of nanocomposites after hot-pressing also affects the NMR effect of these materials. The conductivity of the material under the influence of magnetic field improves with increasing of its cooling rate, which leads to increasing of NMR effect.

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DEPHASING IN PRESENCE OF A MAGNETIC FIELD

International Journal of Nanoscience ◽

10.1142/s0219581x07004675 ◽

2007 ◽

Vol 06 (03n04) ◽

pp. 261-264 ◽

Cited By ~ 3

Author(s):

A. V. GERMANENKO ◽

V. A. LARIONOVA ◽

I. V. GORNYI ◽

G. M. MINKOV

Keyword(s):

Magnetic Field ◽

Relaxation Time ◽

Relaxation Rate ◽

Negative Magnetoresistance ◽

Phase Relaxation ◽

Quasi Momentum ◽

Fitting Procedure ◽

Electron Interference ◽

Momentum Relaxation ◽

The Magnetic Field

Effect of the magnetic field on the rate of phase breaking is studied. It is shown that the magnetic field resulting in the decrease of phase relaxation rate [Formula: see text] makes the negative magnetoresistance due to suppression of the electron interference to be smoother in shape and lower in magnitude than that found with constant [Formula: see text]-value. Nevertheless our analysis shows that experimental magnetoconductance curves can be well fitted by the Hikami–Larkin–Nagaoka expression.1 The fitting procedure gives the value of τ/τϕ, where τ is the quasi-momentum relaxation time, which is close to the value of τ/τϕ(B = 0) with an accuracy of 25% or better when the temperature varies within the range from 0.4 to 10 K. The value of the prefactor α found from this procedure lies within the interval 0.9–1.2.

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ALIGNMENT OF CARBON NANOTUBES USING MAGNETIC NANOPARTICLES

International Journal of Nanoscience ◽

10.1142/s0219581x09006067 ◽

2009 ◽

Vol 08 (03) ◽

pp. 251-259 ◽

Cited By ~ 2

Author(s):

S. ALDAJAH ◽

J. CHATTERJEE ◽

M. ALRAWADEH ◽

A. KOSURI ◽

Y. HAIK

Keyword(s):

Magnetic Field ◽

Carbon Nanotubes ◽

Polymer Nanocomposites ◽

Electronic Transport ◽

Basic Research ◽

Sem Analysis ◽

Matrix Interface ◽

Field Emission Properties ◽

Alignment Problem ◽

The Magnetic Field

Carbon nanotubes are driving scientific research nowadays. This field has several important directions in basic research, including chemistry, electronic transport, mechanical, and field emission properties. The most eye-catching features of carbon nanotubes are their electronic, mechanical, optical, and chemical characteristics, which open a way to future applications. One of the most important applications of nanotubes based on their properties will be as reinforcements in composite materials. One of the biggest concerns to nanotube industry is the alignment problem which has limited the usage and utilizations of carbon nanotubes in composites. The ability to impose a preferred alignment of carbon nanotubes in a composite will increase the effectiveness of utilizing nanotubes in composite applications. The alignment of nanotubes will maximize the interfacial bonding across the nanotube matrix interface. In this research, we developed a methodology and a process to align nanotubes in polymer nanocomposites by means of a magnetic field. By doing so, we will get a very strong nanocomposite that can be used in the composites industry. The proposed mechanism aims at aligning the carbon nanotubes by means of nanomagnetic particles that are adsorbed on the nanotube surfaces and by applying an external magnetic field. SEM analysis have shown that nanomagnetic particles with the assistance of the magnetic field were able to align the carbon nanotubes in the desired direction.

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Cyclotron resonance in copper by a calorimetric method

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1967.0040 ◽

1967 ◽

Vol 296 (1447) ◽

pp. 476-497 ◽

Cited By ~ 5

Keyword(s):

Magnetic Field ◽

Cyclotron Resonance ◽

Skin Depth ◽

Negative Magnetoresistance ◽

Calorimetric Method ◽

Substitution Method ◽

Resonant Orbits ◽

Retardation Effects ◽

The Magnetic Field

Azbel’-Kaner cyclotron resonance in copper at 136 Gc/s has been observed by a calorimetric method. Masses are presented with the magnetic field lying in a (112) plane and tipping effects investigated with the magnetic field along a <111> direction. Beyond a certain tip angle, the absorption exhibits a pronounced ‘negative magnetoresistance’ due to the removal of non-stationary resonant orbits by tipping from the skin depth, and at smaller tip angles the resonant minima shift to lower fields as expected. The spectrometer was calibrated by a substitution method and the amplitude of the oscillations compared with theoretical estimates. Finally, a pronounced rise in absorption at low fields was observed, and arguments are presented that this is due to retardation effects.

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Negative Magnetoresistance in (Bi,Pb)2Sr3Co2O9 Layered Cobalt Oxides

MRS Proceedings ◽

10.1557/proc-494-119 ◽

1997 ◽

Vol 494 ◽

Cited By ~ 7

Author(s):

I. Tsukada ◽

T. Yamamoto ◽

M. Takagi ◽

T. Tsubone ◽

K. Uchinokura

Keyword(s):

Magnetic Field ◽

Magnetic Properties ◽

Parent Compound ◽

Resistivity Measurement ◽

Double Exchange ◽

Negative Magnetoresistance ◽

Hole Doping ◽

Metallic Behavior ◽

Pb Substitution ◽

The Magnetic Field

ABSTRACTTransport and magnetic properties of layered cobalt oxide (BiPb)2Sr3Co2O9 are investigated in detail under magnetic field up to 8 T. Parent compound, Bi2Sr3Co2O9, is a typical band insulator with Co ions being in a low-spin 3+ state because of the well-separated dε and dγ levels possibly due to a strong crystal field. We have tried to introduce holes mainly by Pb substitution for Bi. The hole-doped sample shows metallic behavior in a resistivity measurement between 300 and 30 K. Below 30 K, however, the resisitivity increases. Under the magnetic field the resistivity is strongly suppressed in this region. We observed more than 30% resistivity drop at 2 K under H = 8 T, which is comparable to insulating (La,Sr)CoO3 system. We discuss the mechanism of hole doping and the origin of negative magnetoresistance with tranport and magnetic properties, and point out that the conventional double-exchange mechanism cannot be applied to this system. This means that some new mechanism is necessary to explain this phenomenon.

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Observing the galactic magnetic field

Symposium - International Astronomical Union ◽

10.1017/s0074180900101251 ◽

1967 ◽

Vol 31 ◽

pp. 375-380

Author(s):

H. C. van de Hulst

Keyword(s):

Magnetic Field ◽

Fair Agreement ◽

Solar Neighbourhood ◽

Galactic Magnetic Field ◽

The Magnetic Field

Various methods of observing the galactic magnetic field are reviewed, and their results summarized. There is fair agreement about the direction of the magnetic field in the solar neighbourhood:l= 50° to 80°; the strength of the field in the disk is of the order of 10-5gauss.

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Evolution of Large-Scale Coronal Structures

International Astronomical Union Colloquium ◽

10.1017/s0252921100024945 ◽

1994 ◽

Vol 144 ◽

pp. 29-33

Author(s):

P. Ambrož

Keyword(s):

Magnetic Field ◽

Field Line ◽

Large Scale ◽

Coronal Magnetic Field ◽

Source Surface ◽

Solar Cycles ◽

Characteristic Relationship ◽

The Magnetic Field ◽

Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

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Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

International Astronomical Union Colloquium ◽

10.1017/s0252921100064630 ◽

2000 ◽

Vol 179 ◽

pp. 263-264

Author(s):

K. Sundara Raman ◽

K. B. Ramesh ◽

R. Selvendran ◽

P. S. M. Aleem ◽

K. M. Hiremath

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Magnetic Flux ◽

Ultra Violet ◽

Active Regions ◽

Morphological Properties ◽

Energy Storage And Conversion ◽

The Sun ◽

X Rays ◽

The Magnetic Field

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.

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On the Configuration of the Magnetic Field of β CrB

International Astronomical Union Colloquium ◽

10.1017/s0252921100080933 ◽

1976 ◽

Vol 32 ◽

pp. 613-622

Author(s):

I.A. Aslanov ◽

Yu.S. Rustamov

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Radial Velocity ◽

Magnetic Field Strength ◽

Complex Shape ◽

Rotation Period ◽

Field Variation ◽

Magnetic Field Variation ◽

Secular Variations ◽

The Magnetic Field

SummaryMeasurements of the radial velocities and magnetic field strength of β CrB were carried out. It is shown that there is a variability with the rotation period different for various elements. The curve of the magnetic field variation measured from lines of 5 different elements: FeI, CrI, CrII, TiII, ScII and CaI has a complex shape specific for each element. This may be due to the presence of magnetic spots on the stellar surface. A comparison with the radial velocity curves suggests the presence of a least 4 spots of Ti and Cr coinciding with magnetic spots. A change of the magnetic field with optical depth is shown. The curve of the Heffvariation with the rotation period is given. A possibility of secular variations of the magnetic field is shown.

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Materials for Electron Beam Information Storage

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100062671 ◽

1969 ◽

Vol 27 ◽

pp. 152-153 ◽

Cited By ~ 1

Author(s):

D. E. Speliotis

Keyword(s):

Magnetic Field ◽

Electron Beam ◽

Recent Literature ◽

Electron Beams ◽

Information Storage ◽

The Subject ◽

The Magnetic Field

The interaction of electron beams with a large variety of materials for information storage has been the subject of numerous proposals and studies in the recent literature. The materials range from photographic to thermoplastic and magnetic, and the interactions with the electron beam for writing and reading the information utilize the energy, or the current, or even the magnetic field associated with the electron beam.

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