Physical,structural and topographical aspects of Zn1−xCoxSe thin films

In the present study, Zn_1−xCo_xSe (0≤x≤0.275) thin films were synthesized via a chemical route and characterized through the physical, compositional, structural and morphological properties. The change in colour appearance from ash-grey to charcoal-black suggested integration of Co²⁺ into ZnSe host lattice. Similar conclusions on the colour appearance were drawn from colorimetric studies. The hydrophobic nature of the as-obtained sample surface was revealed in wettability measurements. Zn²⁺, Co²⁺ and Se^2- states of constituents in the thin films were found in the elemental analysis. Formation of ternary alloy was confirmed by shift in (111) X-ray diffraction peak. The surface topography was analysed by an atomic force microscopy (AFM). A variety of AFM parameters were determined to study the effect of Co²⁺ addition onto the surface topography. Magnetic mapping of the surface topography concluded the existence of magnetic domains of irregular sizes and shapes.     

退火条件对注Mn GaAs结构的影响

通过离子注入在半绝缘GaAs衬底中掺引入Mn杂质,进行不同温度的退火后,在样品中形成了磁性MnAs粒子.利用原子力显微镜和磁力显微镜对样品的表面进行分析,发现退火条件会影响样品磁性粒子的分布.运用二次离子质谱仪测量了样品中Mn的深度分布,发现退火温度对样品中Mn的分布有很大影响.     

电子束诱导沉积钴微米线及其铁磁性

通过电子束诱导沉积的方法制备了钴(Co)微米线,并利用扫描电子显微镜(SEM)、原子力/磁力显微镜(AFM/MFM)以及物性测量系统(PPMS)等手段对Co微米线的沉积尺寸、微结构、铁磁性和电学性质进行了测试和分析。研究结果表明:Co微米线轮廓清晰、均匀性好。在不同的沉积条件下,微米线的实际长度与设定长度基本一致;实际宽度数据呈类梯形分布,半高宽是设定值的2~10倍;实际厚度低于设定厚度的60%。沉积电流对Co微米线的铁磁特性有重要影响。当沉积电流大于0.5 nA时,样品呈现出良好的铁磁特性。另外,电学性能测试结果显示Co微米线呈现绝缘特性。成功制备了室温铁磁绝缘Co微米线,这将有助于深入开展微纳尺度的结构与器件的研究和应用。     

Enhancement of the Magnetic Coupling in Exfoliated CrCl3 Crystals Observed by Low-Temperature Magnetic Force Microscopy and X-ray Magnetic Circular Dichroism

Magnetic crystals formed by 2D layers interacting by weak van der Waals forces are currently a hot research topic. When these crystals are thinned to nanometric size, they can manifest strikingly different magnetic behavior compared to the bulk form. This can be the result of, for example, quantum electronic confinement effects, the presence of defects, or pinning of the crystallographic structure in metastable phases induced by the exfoliation process. In this work, an investigation of the magnetism of micromechanically cleaved CrCl₃ flakes with thickness >10 nm is performed. These flakes are characterized by superconducting quantum interference device magnetometry, surface-sensitive X-ray magnetic circular dichroism, and spatially resolved magnetic force microscopy. The results highlight an enhancement of the CrCl₃ antiferromagnetic interlayer interaction that appears to be independent of the flake size when the thickness is tens of nanometers. The estimated exchange field is 9 kOe, representing an increase of ≈900% compared to the one of the bulk crystals. This effect can be attributed to the pinning of the high-temperature monoclinic structure, as recently suggested by polarized Raman spectroscopy investigations in thin (8–35 nm) CrCl₃ flakes.     

Effect of Ni doping on the microstructure and high Curie temperature ferromagnetism in sol–gel derived titania powders

Undoped, 0.05 and 0.5 mol% Ni-doped TiO₂ powders were prepared by a modified sol–gel route. The doping effects on the microstructure and magnetism for the powdered samples have been systematically investigated. Doping of Ni in TiO₂ inhibited rutile crystal growth. The probable reason for this is discussed on the basis of band calculation based analysis of electronic structures of 3d transition metal-doped TiO₂ and the energetic, transformation kinetics and phase stability of anatase over rutile as the function of particle size. Room temperature ferromagnetism (RTFM) with the saturation magnetization of 12 m emu g⁻¹ and Curie temperature as high as 820 K is observed only in case of 0.05 mol% Ni:TiO₂ powdered sample, whereas undoped TiO₂ was diamagnetic and 0.5 mol% Ni:TiO₂ was paramagnetic in nature. The role of any magnetic impurity or any Ni metal in the origin of the RTFM has been ruled out by energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and high resolution TEM (HRTEM) analysis, whereas magnetic force microscopy (MFM) established the presence of magnetic domains, supporting the intrinsic diluted magnetic semiconductor behavior. The observed ferromagnetism has been attributed to the spin ordering through exchange interaction between holes trapped in oxygen orbitals adjacent to Ni substitutional sites.     

基于多层流模型的一回路报警元件分析算法研究

针对一回路发生故障时报警元件多、信息量大的特点,本文采用了基于多层流模型的方法来分析报警元件,并对警报算法进行了分析。该算法采用因果图原理对报警部件进行深度优先搜索,确定故障报警元件及报警传播路径。基于多层流模型的报警分析系统可作为运行支持系统的子系统来辅助运行人员决策。     

一种基于MFM的传感器优化配置方法

为了解决大型流程工业系统状态监测故障诊断系统的传感器优化配置问题,基于多级流模型(MFM)的传感器优化配置,在多级流模型分析的基础上,提出了一种改进的失效模式与影响分析(FMEA)方法.以故障可检测性及可分辨性作为约束函数,利用测点-故障敏感度、传感器可靠性及成本系数构造了一种新的复合优化目标函数,建立传感器优化配置模型并给出了优化算法,最后给出了电站除氧器实例.分析结果表明该方法的可行性和有效性.     

High-resolution force microscopy of in-plane magnetization

We have shown for the first time, in previous studies, that the force microscope fitted with a magnetic tip could be used to image magnetic domains in TbFe thin films. In this report we show that the information provided by the magnetic force microscope can also include a measurement of the component of magnetization in the sample which is parallel to the surface. Measurements were taken with a magnetized tip tilted at 45° with respect to the surface normal. In a first experiment, we imaged 1 μm diameter domains thermomagnetically written in a TbFe thin film. In a second measurement, we imaged a series of alternating domains in a thin film Co-alloy disc which was decorated with small magnetized particles, allowing unambiguous identification of the domain boundaries. In both cases we interpret the asymmetric portion of the images to the in-plane component of the sample magnetization.     

多模式失效的机械零件可靠度计算新理论

解决了长期未能解决的机械零件多模式相关的可靠度定量计算难题,提出了多模失效的机械零件可靠度值在独立假设理论计算值和薄弱环节理论计算值之间,而且是一个连续过程,随主次失效模式相关系数ρ12呈线性变化,给出了可靠度计算数学模型,并采用O.Ditlevsen理论给出了科学严谨的理论证明,同时给出了传动轴可靠度算例。