Time Variation Of Magnetic Field Research Articles

Transient magnetic hybridization of spin and orbital degrees of freedom in two-dimensional quantum rings

We consider the effects of interaction of a two-dimensional charged quantum ring with an ultra-short transient perpendicular magnetic field of duration below 10 ps. According to Faraday law, the time variations of magnetic field generate the rotational electric field in the ring, which however, as we show in a paper, can not induce the charge current along the channel of circular ring. It is because the magnetic field preserves the rotational symmetry of the confinement, and thus, can not mix the states of different angular momenta, albeit, the weak radial oscillations of the charge current can be still induced. We show, that the azimuthal component of charge current can be actually generated by an ultra-short magnetic pulse, provided that, the rotational symmetry of the ring is lifted by an in-plane electric field or when a spin-orbit interaction is taken into account. In both cases, the mixing of the angular momentum states is activated by the off-diagonal terms in Hamiltonian matrix. In the latter case, the change of angular momentum of the electron is accompanied by a rotation of its spin, and therefore, depending on an initial polarization of magnetic pulse, the final excitation energy may have a monotonic or an oscillatory character for a longer pulse duration. We conclude that proposed mechanism of fast excitation of charge carriers confined in quantum ring with an ultra-fast magnetic pulse can be applied for an ensemble of self-organized quantum rings, since, these are not usually perfectly circular while the strength of Dresselhaus spin-orbit interaction can be determined in advance, during their fabrication. Additionally, it allows for excitation of charge carriers without heating the sample what takes place if it is irradiated by a laser beam.

Particle modelling of low-pressure radio-frequency magnetron discharges including the effects of self-induced electromagnetic fields

Modelling of radio-frequency (RF) magnetron discharges is performed using a particle-in-cell/Monte Carlo technique in the case of low-pressure argon gas at 4 mTorr and high external magnetic field in order to self-maintain the discharge and to generate an energetic quasi-ion beam required for cathode sputtering applications. An emphasis is made, for the first time in the literature in the case of low-pressure RF discharges, on the development of a particle model coupled with the full set of electromagnetic field equations. The aim is to analyse the effect on the RF plasma features of the plasma-induced magnetic field resulting from the coupling of the Maxwell–Ampere equation. We also analysed the effect of the electric field due to the time variation of magnetic field resulting from the coupling of the Maxwell–Faraday equation. For the present asymmetrical plasma reactor, the mean relative difference on, for instance, the ion density with and without the consideration of plasma-induced magnetic and electric fields due to the time variation of the magnetic field can reach about 2.5% in the region of the plasma bulk and about 10% in the lateral sheath. The effects of these two induced electromagnetic fields are in fact higher in the regions where the radial magnetic field generated by the external magnets belonging to the magnetron configuration is low. These non-negligible relative differences clearly show the importance of rigorously taking into account, beyond the usual Poisson's equation for the space charge electric field, the full set of electromagnetic Maxwell equations for a more accurate modelling of these low-pressure discharges, particularly when the total current density reaches a few mA cm−2.

Optical extinction change of magnetic nanoparticle suspension under pulsed magnetic field

We investigated the optical extinction change of γ-Fe2O3 magnetic nanoparticle suspension induced by a pulsed magnetic field. The Extinction decrease accompanied by a pulsed magnetic field showed clear relationship with the magnetization of magnetic nanoparticle. However, there observed a different response to the magnetic field between increasing and decreasing of the magnetic field. This indicated that the extinction change followed the time variation of magnetic field with some time constant. The time constant was estimated to be 4.5 μs, but it was different from either of rotational Brownian relaxation (0.23 μs) and Neel relaxation (10 ns) of individual particle. It was thought that the optical density decrease might be attributed to the decrease of Rayleigh scattering cross section by the rotation of the magnetic nanoparticle aggregates.

813 磁場の正弦的時間変動を受ける導体長方形柱の電磁熱弾性問題 : 非定常熱弾性挙動に及ぼす外部磁場の変動周波数の効果(GS-3 熱応力・熱弾性(1))

813 磁場の正弦的時間変動を受ける導体長方形柱の電磁熱弾性問題 : 非定常熱弾性挙動に及ぼす外部磁場の変動周波数の効果(GS-3 熱応力・熱弾性(1))

1211 磁場の時間変動を受ける導体円柱の電磁熱弾性問題(GS-3 電磁熱弾性)

1211 磁場の時間変動を受ける導体円柱の電磁熱弾性問題(GS-3 電磁熱弾性)

P49 磁場の時間変動を受ける導体円柱の応力と変形(OS12)

P49 磁場の時間変動を受ける導体円柱の応力と変形(OS12)

1209 磁場の時間変動を受ける導体無限平板の一次元動的電磁熱弾性問題(GS-3 電磁熱弾性)

1209 磁場の時間変動を受ける導体無限平板の一次元動的電磁熱弾性問題(GS-3 電磁熱弾性)

903 磁界の周期的変動を受ける導体中空円筒の動的電磁熱弾性問題(OS-5 周期的熱応力変動,研究発表講演)

In the present article, a theoretical treatment of magnetothermoelastic stresses and deformation by cyclic time variation of magnetic field is dealt with in a conducting hollow circular cylinder subjected to both internal heat generation due to eddy current loss and Lorentz force. Assuming that uniform magnetic field whose intensity varies sinusoidally in time acts on the hollow circular cylinder in the direction parallel to its outer surface, plane axisymmetrical magnetic field and the associated eddy current in the hollow circular cylinder due to electromagnetic induction have been formulated based on the theory of quasi-stationary electromagnetic field. Therefore, dynamic solutions of stresses and deformation in a conducting hollow circular cylinder, which are subjected to both plane axisymmetrical temperature change due to eddy current loss and Lorentz force, have been analyzed under plane strain condition. Comparing numerical results of dynamic solutions with those of quasi-static ones, we discuss an effect of the inertial force on stress and displacement in the hollow cylinder.

磁界の周期的時間変動を受ける導体中空円筒の電磁熱弾性問題 : 一般化平面ひずみ条件による解析(OS3-8 先進材料の機能性発現,OS3 先端機能性構造材料の力学的挙動に関する数理解析とマルチスケールアナリシスへの進展)

In the present article, a theoretical treatment of magnetothermoelastic stresses and deformation by cyclic time variation of magnetic field is dealt with in a conducting hollow circular cylinder subjected to both internal heat generation due to eddy current loss and Lorentz force. Assuming that uniform magnetic field whose intensity varies sinusoidally in time acts on the hollow circular cylinder in the direction parallel to its outer surface, plane axisymmetrical magnetic field and the associated eddy current in the hollow circular cylinder due to electromagnetic induction have been formulated based on the theory of quasi-stationary electromagnetic field. Therefore, stresses and deformation in a conducting hollow circular cylinder, which are subjected to both plane axisymmetrical temperature change due to eddy current loss and Lorentz force, have been analyzed under generalized plane strain condition. Carrying out numerical calculations, we examine the effects of the frequency in cyclic variation of magnetic field on the electro-magnetic field and radius ratio of the hollow circular cylinder, current density, temperature change and stress and deformation in the hollow circular cylinder.

524 磁界の周期的時間変動を受ける導体中空円筒の電磁熱弾性問題(OS-4 熱弾性・等温弾性(2))

In the present article, a theoretical treatment of magnetothermoelastic stresses and deformation by cyclic time variation of magnetic field is dealt with in a conducting hollow circular cylinder subjected to both internal heat generation due to eddy current loss and Lorentz force. Assuming that uniform magnetic field whose intensity varies sinusoidally in time acts on the hollow circular cylinder in the direction parallel to its outer surface, plane axisymmetrical magnetic field and the associated eddy current in the hollow circular cylinder due to electromagnetic induction have been formulated based on the theory of quasi-stationary electromagnetic field. Therefore, stresses and deformation in a conducting hollow circular cylinder, which are subjected to both plane axisymmetrical temperature change due to eddy current loss and Lorentz force, have been analyzed under plane strain condition. Carrying out numerical calculations, we examine the effects of the frequency in cyclic variation of magnetic field on the electro-magnetic field and radius ratio of the hollow circular cylinder, current density, temperature change and stress and deformation in the hollow circular cylinder.

816 磁界の周期的時間変動を受ける導体円柱の動的電磁熱弾性解析

In the present article, a theoretical treatment of dynamic behaviors for magnetothermoelastic stresses and deformation is dealt with in a conducting solid circular cylinder subjected to both internal heat generation due to eddy current loss and Lorentz force by cyclic time variation of magnetic field. Assuming that uniform magnetic field whose intensity varies sinusoidally in time acts on the cylinder in the direction parallel to its surface, plane axisymmetrical magnetic field and the associated eddy current in the cylinder due to electromagnetic induction have been formulated based on the theory of quasi-stationary electromagnetic field. Therefore, dynamic behaviors of magnetothermoelastic stresses and deformations in a conducting solid cylinder, which are subjected to both plane axisymmetrical temperature change due to eddy current loss and Lorentz force, have been analyzed under plane strain condition. Comparing numerical results of dynamic behaviors for magnetothermoelastic stresses and deformation in the cylinder with those of quasi-static one, an effect of frequency in cyclic time variation of magnetic field has been investigated.

Equivalent Circuit Parameter Calculation of Interior Permanent Magnet Motor Involving Iron Loss Resistance Using Finite Element Method.

In this paper, we propose a method to calculate the equivalent circuit parameters of interior permanent magnet motors including iron loss resistance using the finite element method. First, the finite element analysis considering harmonics and magnetic saturation is carried out to obtain time variations of magnetic fields in the stator and the rotor core. Second, the iron losses of the stator and the rotor are calculated from the results of the finite element analysis with the considerations of harmonic eddy current losses and the minor hysteresis losses of the core. As a result, we obtain the equivalent circuit parameters i.e. the d-q axis inductance and the iron loss resistance as functions of operating condition of the motor. The proposed method is applied to an interior permanent magnet motor to calculate the characteristics based on the equivalent circuit obtained by the proposed method. The calculated results are compared with the experimental results to verify the accuracy.