立方星剩磁在轨辨识与主动补偿技术

立方星的姿态测量与控制系统常采用磁测磁控结合偏置动量轮的方案,整星剩磁干扰力矩是影响姿态控制精度的重要因素之一。提出了一种利用磁强计实现剩磁矩在轨辨识与利用磁力矩器实现剩磁矩主动补偿的新方案:基于磁强计输出和卫星姿态动力学建立了剩磁矩在轨辨识模型,并利用采样滤波器(UKF)提高单磁强计条件下的辨识效果;把控制对象简化成线性定常系统,分析了剩磁干扰力矩对姿态的影响数学模型,并针对磁力矩器和磁强计分时工作的特点,基于叠加性原理提出了基于角速度的剩磁矩主动补偿算法。仿真研究表明,在1000 s内剩磁矩在轨辨识精度为0.001 A×m~2量级,主动补偿后,偏航角、滚动角与俯仰角控制误差分别从4.3°、4.6°与2.1°均减少至0.4°以内。提出的方法为类似配置卫星减少剩磁干扰力矩的影响提供了一种新思路。     

Mössbauer study of the transition metal phosphorus trichalcogenide FePS3 and spin glass Mn0.5Fe0.5PS3

The transition metal phosphorus trichalcogenides MnPS₃ and the FePS₃ are CdCl₂ type layered compounds, where the transition metal ions form a hexagonal lattice. While these compounds order anti-ferromagnetically at low temperature, the magnetic structures are different. We have reported that these mixtures Mn_0.5Fe_0.5PS₃ is a spin glass with a glass transition temperature T _g=33.7 K. Then, in this work, we report that the results of the temperature variation of the ⁵⁷Fe Mössbauer spectra of FePS₃ and Mn_0.5Fe_0.5PS₃, in detail. In the anti-ferromagnetic state of FePS₃, the hyperfine magnetic field H _int increases with decreasing temperature and the Isomer shift I. S. increases slightly with decreasing temperature. However in Mn_0.5Fe_0.5PS₃, the two broadened peaks are observed and the two peaks became a single peak with decreasing temperature at about 50.0 K, which is higher than T _g=33.7 K. In the spin glass Mn_0.5Fe_0.5PS₃, the Mössbauer spectra suggest that the magnetic interactions exist far above T _g.     

纳米晶永磁Pr2Fe14B微磁学有限元法的模拟计算研究

根据实验数据，构造了接近实际纳米晶永磁Pr2Fe14B的样品，用微磁学有限元法进行了模拟计算.计算结果表明，晶界处各向异性的下降会导致矫顽力减小、剩磁值增大，而晶界处交换作用常数的减小则会使剩磁值减小、矫顽力增大.通过对实验样品的模拟研究发现，晶界处各向异性和交换作用常数的共同减小能够同时拟合出真实的矫顽力和剩磁值.模拟计算与实验在退磁曲线形状上的差距则说明模拟还存在不足. 关键词： 纳米晶永磁 磁滞回线 矫顽力 剩磁     

Ultrafast pulsed laser deposition as a method for the synthesis of innovative magnetic films

Exchange-coupled monocomponent magnetic films constituted of disk-shaped Ni and Fe nanoparticles were produced by ultrafast pulsed laser deposition, in vacuum. These films show a peculiar cauliflower-like structure, made of granular agglomerates of nanoparticles sticking to one another with a significant shape and orientation anisotropy. Both as-deposited Ni and Fe films present hysteresis loops with a high in-plane remanence ratio (0.61 and 0.81 at 250 K, respectively), relatively low values of the saturation and coercive fields and a steep slope near coercivity. At temperature of 10 K and 250 K, the magnetization curves confirm the strong influence of the production technique on the topologic structure of these films, and consequently on their magnetic properties. In perspective, the striking and intriguing properties of these nanogranular films appear very promising for potential application as permanent magnets and in data storage technology.     

Angular dependence of the coercivity and remanence of ordered arrays of Co nanowires

The angular dependence of the coercivity and remanence of ordered hexagonal arrays of Co nanowires prepared using anodic aluminum oxide templates was investigated. The experimental evolution of coercivity as a function of the angle, in which the external field is applied, is interpreted considering micromagnetic simulations. Depending on the angle between the axis of the wire and the applied magnetic field direction our results show that the magnetization reversal mode changes from vortex to a transverse domain wall. Besides, we observed that the dipolar interactions cause a reduction in coercive fields, mainly in the direction of easy magnetization of the nanowires. Good agreement between numerical and experimental data is obtained.     

Synthesis and magnetic properties of hard/soft SrFe12O19/Ni0.7Zn0.3Fe2O4 nanocomposite magnets

Magnetic nanocomposite SrFe₁₂O₁₉/Ni_0.7Zn_0.3Fe₂O₄ powders with different weight fractions of the Ni_0.7Zn_0.3Fe₂O₄ soft ferrite were synthesized by a combination of the sol–gel self-propagation and glyoxilate precursor methods. The results of magnetic measurements revealed the higher Mr/Ms ratio for the nanocomposites than that for the single phase SrFe₁₂O₁₉ which proves the existence of the intergrain exchange coupling between hard and soft magnetic phases with the exchange spring behavior. The highest Mr/Ms ratio of 0.63 was obtained in the composite consisting of 80 wt% of SrFe₁₂O₁₉ and 20 wt% Ni_0.7Zn_0.3Fe₂O₄. The microstructural studies of this sample exhibited the average dimensions of hard and soft phases about 20 nm and 15 nm, respectively which are small enough for strong exchange coupling according to the theoretical studies. The variations of the reduced remanence (Mr/Ms) with increasing the weight fraction of the soft phase could be also explained by the role of the exchange and dipolar interactions in tuning the magnetic properties of the nanocomposites.     

2维全自动亥姆霍兹线圈磁块测量方法

在波荡器和扭摆器的研制过程中,为提高磁块的测量效率和精度,提出了2维全自动亥姆霍兹线圈磁块测量方法。通过理论推导得到仅采用2维全自动旋转而不需要3维旋转就可以实现磁块的全自动测量,降低了磁块全自动测量的实现难度。根据该方法的理论,已成功研制出一台2维全自动亥姆霍兹线圈测量装备,并在上海光源的磁块测量中使用。系统地给出2维全自动亥姆霍兹线圈磁块的测量理论和方法,并对测量误差进行了分析,该系统实现了磁块剩磁测量的高效率、高精度和高重复性,可以在30 s内完成单磁块的测量,重复性和精度均好于510-4。     

自由落体重力加速度测量实验的误差分析与改进措施

本文分析了自由落体重力加速度测量实验中，初速度为零时的测量误差形成的三个原因，并对此提出了改进的方法，使实验得到满意的结果。     

纳米复合稀土永磁材料：稀土永磁领域的新方向

纳米复合稀土永磁材料是近几年来在稀土永磁材料研究中发展起来的新兴领域，它可能是发展新一代稀土永磁材料的重要途径，文章简要综述了它的理论与实验方面的最新进展。     

上海光源首批波荡器永磁块研制

介绍了上海光源2台混合型真空室内波荡器IVU25用636件Sm2Co17永磁块(规格为65 mm×25 mm×8.965 mm)和1台APPLE-Ⅱ型椭圆极化波荡器EPU100用668件NdFeB永磁块(规格为35 mm×35 mm×25 mm)的研制情况。指出了影响剩磁离散性、磁化偏角、机械尺寸精度等技术要求的基本因素,并对其原理进行了分析。研制的Sm2Co17和NdFeB永磁块的磁性能、磁场品质、机械尺寸精度等满足了上海光源首批波荡器插入件技术要求。