Effect of a magnetic field on the conduction mechanism in Silicon PN junctions

The influence of a weak magnetic field on the electric current across silicon P⁺N junctions has been studied. The theoretical analysis considers two types of diodes: diodes with short base and diodes with long base and the magnetic field is assumed to be perpendicular to the direction of the electric current across the junction. The results show that the variation of the current is directly related to the variation of the hole diffusion coefficient, which is then calculated in the approximation of a P-type silicon material. The relative variation of the diffusion coefficient was found B² dependent. Experimental investigations have then been carried out in order to validate the theoretical calculations. The experimental results were in good agreement with the theoretical development when taking into account the two types of holes in the diffusion mechanism in silicon.     

Structural,morphological, optical,and magnetic properties of Ni-doped CuO nanostructures prepared by a rapid microwave combustion method

In the present paper, we report a facile and rapid microwave-assisted combustion synthesis method for the preparation of pure and Ni-doped CuO nanostructures with different weight ratios (0.5, 1.0, 1.5, and 2.0 at wt% of Ni). The structure and morphology of the pure and Ni-doped CuO samples were investigated by X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), energy dispersive x-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and vibrating sample magnetometry (VSM). XRD patterns refined by the Rietveld method indicated the formation of single-phase monoclinic structure and also confirmed that Ni ions are successfully doped into CuO crystal lattice by occupying Cu ionic sites. Interestingly, the morphology was found to transform substantially from nanoflowers to nanoparticles with close-packed periodic array, and then into nanocrystals with the variation of Ni content. The optical band gap estimated using DRS was found to be 3.9 eV for pure CuO and then increases up to 4.3 eV with increasing Ni content. PL spectra at room temperature showed a strong green emission band, and thereby confirmed the above results. Magnetic measurements reveal a room temperature ferromagnetism (RTFM) with an optimum value of saturation magnetization of 1.3140×10⁻³ emu/g for 2.0 wt% of Ni.     

螺线型爆磁压缩发生器工程计算

根据发生器的等效电路模型,建立了单级爆磁压缩发生器运行时的电路方程;建立了接触磁通损失模型并推导了磁通损失等效电阻计算公式。根据电路方程和发生器电阻、电感和磁通损失等效电阻的计算公式编制了一个计算程序,利用该程序对文献介绍的某分段变螺距的圆柱型爆磁压缩发生器进行了计算,结果表明,该计算程序能很好地预测发生器的性能并验证接触磁通损失模型的可行性。     

带误差补偿的二位置寻北仪设计

带误差补偿的二位置寻北仪系统包括电源、转机结构、控制电路、计数器等.其补偿算法推导基于陀螺和加速度计一次误差补偿模型,以降低陀螺随机漂移及加速度计的零位漂移对寻北精度的影响.同时再利用由典型静态误差源产生的寻北误差与方位角三角函数成正比或为常值,以罗差修正寻北结果进一步提高寻北精度.     

Tuning optical,electrical and magnetic properties of fiber structured ZnO film by deposition temperature and precursor concentration

Highly transparent ZnO films were deposited on glass substrates using zinc acetate solution through cost effective spray pyrolysis method. A comprehensive study was carried out to understand the effects of deposition temperature and precursor concentrations on structure, surface morphology, optical, electrical and magnetic properties of the deposited films. All deposited films were polycrystalline in nature with hexagonal wurtzite structure. The films were preferentially oriented along (1 0 1) plane up to 723 K beyond which orientation changed to (0 0 2) plane. Irrespective of precursor concentration used, the films deposited at 673 K and 723 K showed fibrous structure. The films deposited at higher temperature led to enhanced transmittance and optical energy band gap. With higher precursor concentrations the transmittance decreased while the band gap increased. Photoluminescence studies revealed the presence of various defects leading to emission in the visible region apart from band to band transition near UV region. Lowest electrical resistivity was obtained for films deposited at 723 K which is of the order 10² Ω cm. At room temperature, all deposited films were diamagnetic while they were paramagnetic at 5 K.     

Introducing immobilized metal phthalocyanines as spin-injection and detection layers in organic spin-valves: Spin-tunneling and spin-transport regimes

In (organic) spin-valve devices, two ferromagnetic electrodes having different coercive fields are used to achieve an anti-parallel configuration necessary to enforce spin-flip of electrons within the semiconductor spacer layer. Here we report a use of immobilized magnetic organic molecules as spin-injection and spin-detection layers to form pre-fabricated spin-valve devices. While immobilized manganese- and nickel-phthalocyanines were used as spin-injection and spin-detection layers both, copper phthalocyanine acted as the spacer layer in the all-organic spin-valve devices.In the current-voltage characteristics of parallel and anti-parallel configurations, the electrical resistance was always higher for the latter one implying positive magnetoresistance in the material. By lowering thickness of the spacer layer down to a monolayer region, a tunneling regime could be achieved; spin-flip process in organic spin-valves has been found to be facile in the tunneling regime as compared to that during the spin-transport process through a thicker spacer layer.     

Syntheses,Properties, and Potential Applications of Multicomponent Magnetic Nanoparticles

Multicomponent hybrid nanostructures that contain two or more nanometer‐scale components have attracted much attention recently owing to the synergistic properties induced by interactions between these different nanometer‐scale objects. Herein, we give an overview of the efforts to synthesize multicomponent nanoparticles with at least one component being magnetic, and focus on our recent developments. The syntheses are based on heterogeneous nucleation and growth of a second and third component onto seed nanoparticles. These multicomponent nanoparticles show interesting magnetic, magneto‐optical, plasmonic, and semiconducting properties that can be modulated by interfacial interactions between different nanocomponents. This opens up a new avenue to advanced multifunctional nanomaterials for device concepts and applications.     

Magnetic levitation with unlimited omnidirectional rotation range

We have realized a magnetic levitation device in which the motion of a levitated body can be stably controlled in any orientation, with no limits on its spatial rotation range. The system consists of a planar array of cylindrical coils on a fixed base, a levitated frame containing disc magnets and LED position markers, and an optical motion tracking sensor for feedback control of levitation. This system combines the capabilities of fine positioning, vibration isolation, and a spherical motor, with potential applications in omnidirectional antenna and camera pointing, user interaction, manipulation, and simulated spaceflight dynamics and control. The device design is presented including the magnet and coil configuration, analysis and control methods, and position and rotation trajectory control results.The system development process consisted of numerical analysis of electromagnetic forces and torques between coils and magnets, to find the maximum required coil currents for levitation and the condition numbers of the transformation matrices between coil currents and forces and torques generated on the levitated body, for various configurations of coils and magnets, over their full 3D translation and rotation ranges. As a result, a magnetic levitation setup consisting of an array of 27 coils and a levitated object with six disk-shaped permanent magnets was selected. The setup achieved levitation in six degrees of freedom and unlimited rotation about any axis at a fixed height of 40 mm (a 4 mm minimum height above the coil array). The performance was verified with levitated trajectory following rotation command experiments in roll, pitch, yaw, and including 360° rotations about non-principal axes.     

真空灭弧室横向磁场触头间磁吹力的计算分析

对螺旋槽型和杯状型两种横磁触头进行了研究,仿真分析了不同电弧位置和触头结构参数下触头间磁场的分布,同时计算分析了触头间电弧所受的磁吹力,可为横向磁场触头的研究与应用提供参考。     

Electromodulation and magnetomodulation of exciton dissociation in electron donor (starburst amine) : electron acceptor (bathocuproine) system

Electric field dependencies of electromodulated photoluminescence and photocurrents as well as the magnetic field effects on photocurrents, photovoltaic characteristics, electromodulated photoluminescence and photoluminescence have been investigated in vacuum evaporated films of m-MTDATA:BCP (4,4′,4″-tris(N-(3-methylphenyl)-N-phenylamino)triphenylamine and bathocuproine) system. The electromodulation processes do remain in accordance with Onsager as well as with the Sano–Tachiya–Noolandi–Hong formalisms of electron–hole pair separation. While the electromodulated photocurrents are due to operation of both long-radius and short-radius e–h pairs, the electromodulated photoluminescence quenching is related to merely short-radius fraction of the e–h pairs involved in the exciplex creation process. The photocurrents, photovoltaic characteristics, photoluminescence and electromodulated photoluminescence are influenced by external magnetic field of the hyperfine coupling (HFC) scale which modulates the singlet–triplet intersystem crossing of long-radius e–h pairs.