Effect of C layer on the structures and magnetic properties of (0 0 1)-oriented [C/CoPt]n/Ag films

CoPt/Ag and [C/CoPt]n/Ag thin films have been prepared onto the glass substrates by magnetron sputtering. We investigated the evolution of texture and magnetic properties of CoPt/Ag and [C/CoPt]n/Ag films. The results show that C-doping plays an important role in improving (0 0 1) texture, improving the order parameter S, reducing the intergrain interactions, and making the magnetization reversal mechanism more close to Stoner-Wolfarth rotational mechanism. The growth mechanism of (0 0 1) texture also seems to be related strongly to the films thickness. Our results show that the highly (0 0 1)-oriented films with ordered fct phase have a significant potential for the perpendicular media of extremely high-density recording.     

非保守力学系统Nielsen方程的形式不变性

研究非保守力学系统Nielsen方程的形式不变性.给出非保守力学系统Nielsen方程的形式不变性的定义和判据,研究形式不变性和Noether对称性的关系,并举例说明结果的应用 关键词： 非保守力学系统 Nielsen方程 形式不变性 Noether对称性     

二维光电位置敏感器件的非线性修正

根据二维光电位置敏感器件 (PSD)的工作原理 ,分析了影响PSD线性度的主要因素 ,提出了一种用神经网络对PSD进行非线性修正的方法。以PSD的输入输出数据对作为样本训练的神经网络 ,利用神经网络所具有地能够以任意精度逼近非线性函数的能力 ,实现PSD的输出与实际光点位置之间的映射 ,在神经网络的输出端得到线性响应。该方法的优点是不需要很大的数据存储量即可得到很好的修正效果。结果表明 ,修正后的PSD能在较宽的位置范围内输出高线性度的信号     

Drift of Spiral Waves in Complex Ginzburg-Landau Equation

The spontaneous drift of the spiral wave in a finite domain in the complex Ginzburg-Landau equation is investigated numerically. By using the interactions between the spiral wave and its images, we propose a phenomenological theory to explain the observations.     

掺铥氟磷玻璃的结构、热学性质和光谱性质

制备了不同Al(PO3)3含量的掺铥系列氟磷玻璃,研究了其结构、热稳定性和光谱性质。随着Al(PO3)3含量的增加,该系列玻璃的密度降低,折射率增加,差热分析表明,转变温度、析晶起始温度、析晶峰温度和熔化温度增加。Al(PO3)3摩尔浓度在7%~9%时析晶稳定性最佳。采用归一化的拉曼光谱分析了材料的结构和声子状况,对于该系列氟磷玻璃,Al(PO3)3含量的增加不会影响声子能量,但使声子密度增大。测试了样品的吸收光谱,Tm3 的3H6→3F4在第三通信窗口的L波段有明显吸收。与在其它玻璃基质中相比,Tm3 的3F4能级对应能量偏高,3H4能级对应能量偏低,使得3H4→3F4跃迁波长较大,接近于增益迁移光纤放大器的放大波长。扎得奥菲而特(Judd-Ofelt)理论分析表明随着Al(PO3)3含量增加,离子强度参量Ω2增大,Ω6保持相对稳定,Tm3 的能级寿命降低。     

Liquid phase oxidation of p-chlorotoluene to p-chlorobenzaldehyde over cobalt-doped mesoporous titania with a crystalline framework

Cobalt-doped mesoporous titania with a crystalline framework synthesized by surfactant templating method presented highly selective (99%) and reasonable conversion rate (49%) of catalytic oxidation of para-chlorotoluene to para-chlorobenzaldehyde in acetic acid using aqueous hydrogen peroxide as oxidant for the first time. Recycling of the catalyst indicates that the catalyst can be used a number of times without losing its activity to a greater extent. By contrast, cobalt-doped mesoporous titania without a crystalline structure and cobalt doped the commercial titania, Degussa P25 prepared by impregnation method with the similar concentration of cobalt were found inactive. The effects of catalyst concentration, reaction time, reaction temperature, and solvents on the performance of the catalyst were also investigated.     

A study of the effect of ZrO2 on the magnetic properties of FePt/ZrO2 multilayer

Fe_xPt_100−x(30 nm) and [Fe_xPt_100−x(3 nm)/ZrO₂]₁₀ (x = 37, 48, 57, 63, 69) films with different ZrO₂ content were prepared by RF magnetron sputtering technique, then were annealed at 550 °C for 30 min. This work investigates the effect of ZrO₂ doping on the microstructural evolution, magnetic properties, grain size, as well as the ordering kinetics of FePt alloy films. The as-deposited films behaved a disordered state, and the ordered L1₀ structure was obtained by post-annealing. The magnetic properties of the films are changed from soft magnetism to hard magnetism after annealing. The variation of the largest coercivities of [Fe_xPt_100−x/ZrO₂]₁₀ films with the Fe atomic percentage, x and differing amounts of ZrO₂ content reveals that as we increase the ZrO₂ content we must correspondingly increase the amount of Fe. This phenomenon suggests that the Zr or O atoms of ZrO₂ preferentially react with the Fe atoms of FePt alloy to form compounds. In addition, introducing the nonmagnetic ZrO₂ can reduce the intergrain exchange interactions of the FePt/ZrO₂ films, and the interactions are decreased as the ZrO₂ content increases, the dipole interactions are observed in FePt/ZrO₂ films as the ZrO₂ content is more than 15%.     

The Tolerance of All-Optical Switching Based on Cascaded Second-Order Nonlinearity in PPLN APE Waveguide

Based on solving the couple mode equation numerically, the characterization of the signal power on the gate power was analyzed. And the relationship of the tolerance of the grating period and the bulk temperature on the interaction length was analyzed.     

Nonvolatile photorefractive holographic recording in Sc:Ce:Cu:LiNbO3

In this paper experimental studies of nonvolatile photorefractive holographic recording in Ce:Cu:LiNbO₃ crystals doped with Sc(0,1,2,3 mol%) were carried out. The Sc:Ce:Cu:LiNbO₃ crystals were grown by the Czochralski method and oxidized in Nb₂O₅ powders. The nonvolatile holographic recording in Sc:Ce:Cu:LiNbO₃ crystals was realized by the two-photon fixed method. We found that the recording time of Sc:Ce:Cu:LiNbO₃ crystal became shorter with the increase of Sc doping concentration, especially doping with Sc(3 mol%), which exceeds the so-called threshold, and there was little loss of nonvolatile diffraction efficiencies between Sc(3 mol%):Ce:Cu:LiNbO₃ and Ce:Cu:LiNbO₃ crystals.     

Propagation of elegant Laguerre–Gaussian beams through an annular apertured paraxial ABCD optical system

Based on the generalized Huygens–Fresnel diffraction integral and the expansion of the hard aperture function into a finite sum of complex Gaussian functions, the approximate analytical expression of elegant Laguerre–Gaussian beams passing through a paraxial ABCD optical system with an annular aperture is derived. Meanwhile, the corresponding closed-forms for the unapertured, circular apertured or circular black screen cases are also given. The obtained results provide more convenience for studying their propagation and transformation than the usual way by using diffraction integral formula directly. Some numerical examples are given to illustrate the propagation properties of elegant Laguerre–Gaussian beams.