scholarly journals Clarification of the Magnetocapacitance Mechanism for Fe3O4-PDMS Nanocomposites

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Chen Guobin ◽  
Yang Hui ◽  
Zhang Xiaoming ◽  
Liu Jun ◽  
Tang Jun
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Magnetic Property ◽  
Preparation Method ◽  
Volume Fraction ◽  
Magnetic Interaction ◽  
Mechanical Parameters ◽  
Measurement Results

We mainly focused on the magnetocapacitance effect of Fe3O4-PDMS nanocomposites. We also proposed the preparation method and measured microstructures, magnetic properties, and magnetocapacitance value of the nanocomposites. The magnetocapacitance measurement results show that the nanocomposites have magnetocapacitance property, the magnetocapacitance with magnetic field depends on the magnetic property, and the value at the same magnetic field is increasing with the volume fraction of Fe3O4nanoparticles. The magnetocapacitance model is proposed to explain this phenomenon by analyzing the magnetic interaction between particles and the viscoelasticity of PDMS. We also calculated the theoretical capacitance value of all samples using the magnetization of nanoparticles and mechanical parameters of PDMS. From the theoretical values, it is concluded that the model we proposed can well explain the magnetocapacitance effect of Fe3O4-PDMS nanocomposites.

WANG–LANDAU SIMULATION ON THERMODYNAMIC AND MAGNETIC PROPERTIES OF HONEYCOMB LATTICE

2011 ◽  
Vol 25 (26) ◽  
pp. 3435-3442
Author(s):  
XIAOYAN YAO
Keyword(s):  
Magnetic Field ◽  
Monte Carlo Simulation ◽  
Magnetic Properties ◽  
Free Energy ◽  
Magnetic Susceptibility ◽  
Magnetic Property ◽  
Ground State ◽  
Antiferromagnetic Order ◽  
Honeycomb Lattice ◽  
Antiferromagnetic Ising Model

Wang–Landau algorithm of Monte Carlo simulation is performed to understand the thermodynamic and magnetic properties of antiferromagnetic Ising model on honeycomb lattice. The internal energy, specific heat, free energy and entropy are calculated to present the thermodynamic behavior. For magnetic property, the magnetization and magnetic susceptibility are discussed at different temperature upon different magnetic field. The antiferromagnetic order is confirmed to be the ground state of the system, and it can be destroyed by a large magnetic field.

scholarly journals The direction of magnetisation of single ferromagnetic crystals

1930 ◽  
Vol 130 (812) ◽  
pp. 167-181 ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Crystalline Structure ◽  
Magnetic Interaction ◽  
Effective Field ◽  
Quadrupole Moments ◽  
Cubic Crystals ◽  
Cubic Structure ◽  
Dipole Energy ◽  
Satisfactory Theory

The study of the magnetisation of single crystals of ferromagnetic substances has shown that there are definite relations between magnetic properties and crystalline structure. One of the most important, the relation between the crystalline structure and the direction of magnetisation, will be studied in this paper. It is well known that on applying a magnetic field to a crystal the direction of the magnetisation produced does not, in general, coincide with that of the field (here and elsewhere, unless the external field is specifically mentioned, the effective field is to be understood). The phenomenon has been extensively studied experimentally, but hitherto there has been no entirely satisfactory theory. A theory, at least partially successful, was proposed by Mahajani, who assumed that the elementary magnets are electron orbits. Owing to their magnetic interaction, these magnets posses a mutual potential energy which in general depends upon their orientation, and hence leads to deviations between the directions of magnetisation and field. In the case of non-cubic crystals, it is sufficient to consider the elementary magnets as simple dipoles, but in the case of cubic crystals, the dipole energy is independent of the orientation of the dipoles, and it becomes necessary to consider the quadrupole moments. Mahajani showed that this theory accounts qualitatively for the various effects observed in iron (with a cubic structure) and pyrrhotite (with a non-cubic structure).

scholarly journals Ферромагнетизм в гетероструктуре ферромагнитная пленка железо-иттриевого граната/ферромагнитный интерметаллид

2020 ◽  
Vol 62 (9) ◽  
pp. 1488
Author(s):  
Т.А. Шайхулов ◽  
Г.А. Овсянников ◽  
К.И. Константинян ◽  
А.А. Климов ◽  
В.В. Демидов ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Yttrium Iron Garnet ◽  
Spin Current ◽  
Magnetic Interaction ◽  
Yttrium Iron ◽  
Elastic Stresses ◽  
Giant Magnetostriction ◽  
Iron Garnet ◽  
Rare Earth Intermetallic

Abstract We report on the investigations of the magnetic properties and ferromagnetic resonance in the heterostructure consisting of an epitaxial yttrium iron garnet (Y_3Fe_5O_12) film and a nanometer rare-earth intermetallic superlattice comprised of the (TbCo_2/FeCo)_ n exchange-coupled layers. The (TbCo_2/FeCo)_ n superlattice exhibits the giant magnetostriction and the controlled magnetic anisotropy induced by a magnetic field or elastic stresses. The magnetic interaction of the films in the (TbCo_2/FeCo)_ n /Y_3Fe_5O_12 heterostructure has been experimentally established and the spin current flowing through their interface has been detected.

scholarly journals A distinct magnetic property of the inner penumbral boundary

2020 ◽  
Vol 638 ◽  
pp. A28 ◽  
Author(s):  
Jan Jurčák ◽  
Markus Schmassmann ◽  
Matthias Rempel ◽  
Nazaret Bello González ◽  
Rolf Schlichenmaier
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Magnetic Property ◽  
Potential Field ◽  
Magnetic Energy ◽  
Vertical Component ◽  
Flux Rope ◽  
Field Configuration ◽  
The Magnetic Field ◽  
Upper Boundary

Context. Analyses of sunspot observations revealed a fundamental magnetic property of the umbral boundary: the invariance of the vertical component of the magnetic field. Aims. We analyse the magnetic properties of the umbra-penumbra boundary in simulated sunspots and thus assess their similarity to observed sunspots. We also aim to investigate the role of the plasma β and the ratio of kinetic to magnetic energy in simulated sunspots in the convective motions because these quantities cannot be reliably determined from observations. Methods. We used a set of non-gray simulation runs of sunspots with the MURaM code. The setups differed in terms of subsurface magnetic field structure and magnetic field boundary imposed at the top of the simulation domain. These data were used to synthesize the Stokes profiles, which were then degraded to the Hinode spectropolarimeter-like observations. Then, the data were treated like real Hinode observations of a sunspot, and magnetic properties at the umbral boundaries were determined. Results. Simulations with potential field extrapolation produce a realistic magnetic field configuration on the umbral boundaries of the sunspots. Two simulations with a potential field upper boundary, but different subsurface magnetic field structures, differ significantly in the extent of their penumbrae. Increasing the penumbra width by forcing more horizontal magnetic fields at the upper boundary results in magnetic properties that are not consistent with observations. This implies that the size of the penumbra is given by the subsurface structure of the magnetic field, that is, by the depth and inclination of the magnetopause, which is shaped by the expansion of the sunspot flux rope with height. None of the sunspot simulations is consistent with the observed properties of the magnetic field and the direction of the Evershed flow at the same time. Strong outward-directed Evershed flows are only found in setups with an artificially enhanced horizontal component of the magnetic field at the top boundary that are not consistent with the observed magnetic field properties at the umbra-penumbra boundary. We stress that the photospheric boundary of simulated sunspots is defined by a magnetic field strength of equipartition field value.

A Research on Magnetic Properties of Ferromagnetic Liquid γ–Fe2O3

2012 ◽  
Vol 246-247 ◽  
pp. 1091-1095
Author(s):  
An Rong Wang ◽  
Hai Yan Huang ◽  
Chun Jun Shu
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Saturation Magnetization ◽  
Interaction Energy ◽  
Self Assembly ◽  
Volume Fraction ◽  
Chemical Precipitation ◽  
Ring Structure ◽  
Heat Energy ◽  
Chemical Coprecipitation

This paper explains how to make ferrimagnetic ferrofluid r-Fe2O3with chemical precipitation. First, ferrimagnetic nanoparticle r-Fe2O3is produced with chemical coprecipitation. Then, the ferrofluid r-Fe2O3is synthesized by Massart method. Without magnetic field, the interaction energy of two r-Fe2O3particles is about 1.92×10-19J, which is more than heat energy and is easy to form a reunion. There exist ring-like structure in ferrofluidr-Fe2O3, which has no contribution to the saturation magnetization. The saturation magnetization is less than the theoretical value. The bigger the volume fraction, the more self-assembly ring structure, the less possible it is to crack in the process of dilution and magnetization.

Effect of Continuous Annealing Parameters on the Microstructure and Magnetic Property of Cold Rolled Dual Phase Steel

2012 ◽  
Vol 476-478 ◽  
pp. 241-247 ◽  
Author(s):  
Li Gao ◽  
Qiu Hong Song ◽  
Jun Ting Yuan
Keyword(s):  
Magnetic Properties ◽  
Magnetic Property ◽  
Dual Phase Steel ◽  
Volume Fraction ◽  
Annealing Process ◽  
Continuous Annealing ◽  
Dual Phase ◽  
Quenching Temperature ◽  
Dp Steel ◽  
Cold Rolled

The effect of continuous annealing parameters on the microstructure and magnetic property of cold rolled dual phase steel (DP steel) are investigated. Correlations of microstructure, magnetic properties and continuous annealing parameters are revealed. The mechanism of the magnetic property varying with continuous annealing process is also discussed. The results show that recrystallization is almost completed when heating to 740°C. For the DP steel soaked in the range of 770°C-830°C and quenched in different temperature, the TEM results indicate its microstructure mainly consists of the ferrite and martensite phase. The martensite volume fraction increases gradually with increasing the soaking and quenching temperature. It is found that magnetic properties of dual phase steel are very sensitive to continuous annealing process. With rising soaking and quenching temperature, the coercivity and hysteresis loss increase obviously, whereas the maximum permeability and the remanent induction tend to decrease.

TRANSPORT AND MAGNETIC PROPERTIES OF Bi BASED MULTIPHASE SUPERCONDUCTORS

1999 ◽  
Vol 13 (29n31) ◽  
pp. 3741-3743 ◽  
Author(s):  
P. Vašek ◽  
I. Janeček
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Electrical Resistivity ◽  
Magnetic Susceptibility ◽  
Volume Fraction ◽  
The Other ◽  
Hall Voltage ◽  
X Ray Diffraction ◽  
X Ray ◽  
Effective Medium Approach

A series of (Bi,Pb)SrCuCaO samples with varying volume fraction of the 2223 phase (determined by X-ray diffraction) has been prepared. Temperature dependence of the resistance, Hall effect and magnetic susceptibility has been measured. Neither susceptibility (both dc and ac) nor electrical resistivity in magnetic field reveal the presence of the low temperature (2212) phase. On the other hand the Hall voltage in the mixed state is very sensitive to the presence of different phases. Obtained results have been discussed within the frame of the effective medium approach and related to the growth mechanism of the 2223 phase.

Investigation of the Structure and Magnetic Properties of Bulk Amorphous FeCoYB Alloy

2017 ◽  
Vol 68 (9) ◽  
pp. 2162-2165 ◽  
Author(s):  
Katarzyna Bloch ◽  
Mihail Aurel Titu ◽  
Andrei Victor Sandu
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Hyperfine Field ◽  
Irreversible Processes ◽  
Magnetization Process ◽  
Casting Method ◽  
The Core ◽  
Injection Casting ◽  
Core Losses ◽  
Microstructural Studies

The paper presents the results of structural and microstructural studies for the bulk Fe65Co10Y5B20 and Fe63Co10Y7B20 alloys. All the rods obtained by the injection casting method were fully amorphous. It was found on the basis of analysis of distribution of hyperfine field induction that the samples of Fe65Co10Y5B20 alloy are characterised with greater atomic packing density. Addition of Y to the bulk amorphous Fe65Co10Y5B20 alloy leads to the decrease of the average induction of hyperfine field value. In a strong magnetic field (i.e. greater than 0.4HC), during the magnetization process of the alloys, where irreversible processes take place, the core losses associated with magnetization and de-magnetization were investigated.

scholarly journals Jet Impingement Heat Transfer of Confined Single and Double Jets with Non-Newtonian Power Law Nanofluid under the Inclined Magnetic Field Effects for a Partly Curved Heated Wall

2021 ◽  
Vol 13 (9) ◽  
pp. 5086
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop ◽  
Ali J. Chamkha
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Particle Size ◽  
Aspect Ratio ◽  
Power Law ◽  
Volume Fraction ◽  
Inclined Magnetic Field ◽  
Magnetic Field Effects ◽  
Power Law Nanofluid ◽  
Power Law Index

Single and double impinging jets heat transfer of non-Newtonian power law nanofluid on a partly curved surface under the inclined magnetic field effects is analyzed with finite element method. The numerical work is performed for various values of Reynolds number (Re, between 100 and 300), Hartmann number (Ha, between 0 and 10), magnetic field inclination (γ, between 0 and 90), curved wall aspect ratio (AR, between 01. and 1.2), power law index (n, between 0.8 and 1.2), nanoparticle volume fraction (ϕ, between 0 and 0.04) and particle size in nm (dp, between 20 and 80). The amount of rise in average Nusselt (Nu) number with Re number depends upon the power law index while the discrepancy between the Newtonian fluid case becomes higher with higher values of power law indices. As compared to case with n = 1, discrepancy in the average Nu number are obtained as −38% and 71.5% for cases with n = 0.8 and n = 1.2. The magnetic field strength and inclination can be used to control the size and number or vortices. As magnetic field is imposed at the higher strength, the average Nu reduces by about 26.6% and 7.5% for single and double jets with n greater than 1 while it increases by about 4.78% and 12.58% with n less than 1. The inclination of magnetic field also plays an important role on the amount of enhancement in the average Nu number for different n values. The aspect ratio of the curved wall affects the flow field slightly while the average Nu variation becomes 5%. Average Nu number increases with higher solid particle volume fraction and with smaller particle size. At the highest particle size, it is increased by about 14%. There is 7% variation in the average Nu number when cases with lowest and highest particle size are compared. Finally, convective heat transfer performance modeling with four inputs and one output is successfully obtained by using Adaptive Neuro-Fuzzy Interface System (ANFIS) which provides fast and accurate prediction results.

Effects of uniform or non-uniform heating at bottom wall on MHD mixed convection in a porous cavity saturated by nanofluid

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Subramanian Muthukumar ◽  
Selvaraj Sureshkumar ◽  
Arthanari Malleswaran ◽  
Murugan Muthtamilselvan ◽  
Eswari Prem
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Transfer Rate ◽  
Hartmann Number ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Darcy Number ◽  
Bottom Wall ◽  
Uniform Heating ◽  
The Magnetic Field

Abstract A numerical investigation on the effects of uniform and non-uniform heating of bottom wall on mixed convective heat transfer in a square porous chamber filled with nanofluid in the appearance of magnetic field is carried out. Uniform or sinusoidal heat source is fixed at the bottom wall. The top wall moves in either positive or negative direction with a constant cold temperature. The vertical sidewalls are thermally insulated. The finite volume approach based on SIMPLE algorithm is followed for solving the governing equations. The different parameters connected with this study are Richardson number (0.01 ≤ Ri ≤ 100), Darcy number (10−4 ≤ Da ≤ 10−1), Hartmann number (0 ≤ Ha ≤ 70), and the solid volume fraction (0.00 ≤ χ ≤ 0.06). The results are presented graphically in the form of isotherms, streamlines, mid-plane velocities, and Nusselt numbers for the various combinations of the considered parameters. It is observed that the overall heat transfer rate is low at Ri = 100 in the positive direction of lid movement, whereas it is low at Ri = 1 in the negative direction. The average Nusselt number is lowered on growing Hartmann number for all considered moving directions of top wall with non-uniform heating. The low permeability, Da = 10−4 keeps the flow pattern same dominating the magnetic field, whereas magnetic field strongly affects the flow pattern dominating the high Darcy number Da = 10−1. The heat transfer rate increases on enhancing the solid volume fraction regardless of the magnetic field.

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