Magnetization Reversal Mechanism for CoFeB Ferromagnetic Nanotube Arrays

CoFeB nanotube arrays are fabricated in anodic aluminum oxide （AAO） membranes and track etched polycarbonate （PCTE） membranes by using an electrochemical method, and their magnetic properties are investigated by vibrating sample magnetometry. The coercivity Hc and remanent squareness SQ of these CoFeB nanotube arrays are derived from hysteresis loops as a function of angle between the field and tube axis, The He（8） curves for CoFeB nanotube arrays in AAO and PCTE membranes show M-type variation, while they change shape from M to mountain-type as the tube length increases. However, the overall easy axis perpendicular to tube axis does not change with tube length. The different angular dependences are attributed to different magnetization reversal mechanisms.     

Neutron Spectroscopy of Norbornane

Results of inelastic incoherent neutron scattering (IINS) on norbornane are reported. The IINS spectra in the low-temperature phases display low-frequency internal vibration modes very well. The assignment of these modes is proposed in reference to the results of the calculations of the structure and dynamics of isolated molecules by semi-empirical quantum chemistry methods.     

Electronic Transport in Magnetic Domain-wall Structure

The resistivity due to the domain wall in the presence of impurities in a ferromagnetic metallic wire is calculated based on the linear response theory. Assuming the local spin distribution to be spin-spiral the modification of the band structure has been obtained exactly. With this modified band structure we calculate the conductivity of the system as a function of electronic filling and show that the domain-wall contribution to the resistance can be positive or negative depending on the dimensionality, the position of the Fermi energy on the band structure and the strength of the electron local spin interaction of the system.     

Letter: Behavior of Magnetic Tubes in Neutron Star's Interior

It is found from Maxwell's equations that the magnetic field lines are good analogues of relativistic strings. It is shown that the superconducting current in the neutron star's interior causes local rotation of magnetic flux tubes carrying quantized flux.     

Neutron Scattering on Magnetic Materials Under Extreme Conditions

Many materials exhibit various magnetic phenomena as a function of magnetic field, temperature and/or pressure. Usually, bulk magnetic measurements provide first information on the magnetic state of the material by measuring their response on the applied magnetic field. However, it is necessary to investigate materials also on a microscopic scale. This is often done by means of neutron scattering. In this contribution we discuss basic ideas of this method and we report on few experimental results obtained with a split-pair coil 14.5 T superconducting magnet which can be combined with dilution stick offering temperatures as low as 30 mK and/or with a small clamped-type pressure cell which offers pressure up to 1.0 GPa.     

银纳米粒子对组装阵列中耦联分子拉曼散射的影响

分别用硼氢化钠和氢气还原法制备了两种不同的银溶胶(I和II),并采用自组装技术将银纳米粒子组装到对巯基苯胺(PATP)修饰的光滑银基底表面,形成银纳米粒子亚单层二维阵列。比较两种阵列中PATP的表面增强拉曼光谱发现,溶胶II所得阵列中的PATP的b2振动得到了较大的增强,即存在较大程度的电荷转移,说明银纳米粒子的性质直接影响了耦联分子的光谱特征。对溶胶Ⅰ进行离心处理,组装,得到的拉曼特征与阵列II类似。就溶胶II的银纳米粒子而言,组装结构中可能形成Ag-N化学键,从而导致更强的氨基与银粒子的相互作用。     

Magnetic Properties of Monocrystal 57Fe/V Multilayers Investigated by CEMS,Nuclear Resonance Reflectivity in the Time Domain and Polarized Neutron Scattering

Hyperfine Interactions - We have performed a depth selective investigation of monocrystalline samples with composition [57Fe(10 ML)/V(5 ML)]20 and [57Fe(7 ML)/V(10 ML)]29 by means of synchrotron...     

Field-and Current-Driven Magnetization Reversal and Dynamic Properties of CoFeB-MgO-Based Perpendicular Magnetic Tunnel Junctions

We report a perpendicular magnetic tunnel junction(p MTJ) cell with a tunnel magnetoresistance(TMR) ratio of nearly 200% at room temperature based on Co Fe B/Ta/Co Fe B as the free layer(FL) and a synthetic antiferromagnetic(SAF) multilayer [Pt/Co]/Ru/[Pt/Co]/Ta/Co Fe B as the reference layer(RL). The field-driven magnetization switching measurements show that the p MTJs exhibit an anomalous TMR hysteresis loop. The spin-polarized layer Co Fe B of SAF-RL has a lower critical switching field than...     

Diffusion Studies with Synchrotron Radiation and with Neutron Scattering

With scattering methods we are able to detect the elementary diffusion jump. This is a report on investigations with methods working in the time domain, i.e., nuclear resonant scattering of synchrotron radiation and neutron spin echo. The accent of this paper is on diffusion in ordered alloys. We finish with an outlook on what will be possible with the upcoming potential of future synchrotron sources. This revised version was published online in August 2006 with corrections to the Cover Date.     

共振光散射法测定三聚氰胺

应用共振散射光谱技术建立三聚氰胺检测新方法。三聚氰胺可使甲醇体系在567nm处的共振散射光明显增强。在优化实验条件下,体系的ΔI值与三聚氰胺的浓度在0.7—16.0mg/L之间具有良好的线性关系,线性方程为ΔIRLS=40.53C(mg/L)-2.64,r=0.9993;检出限为0.21mg/L;样品加标回收率为92.6%—102.3%。方法灵敏,操作简便,分析成本低,用于奶粉中三聚氰胺的测定,结果满意。     

Magnetization Reversal of Single-Molecular Magnets by a Spin-Polarized Current

We study the magnetization reversal of single-molecular magnets by a spin-polarized current in the framework of the spinor Boltzmann equation. Because of the spin–orbit coupling, the spin-polarized current will impose a non-zero spin transfer torque on the single-molecular magnets, which will induce the magnetization switching of the latter. Via the s–d exchange interaction between the conducting electrons and single-molecular magnets,we can investigate the magnetization dynamics of single-molec...     

共振散射光谱法测定痕量的美他环素

在pH为11.82的B-R缓冲溶液中,美他环素与溴化十六烷基吡啶反应形成离子缔合物,导致体系的共振散射强度急剧增强,并在300nm、429nm处产生两个新的散射峰。研究了体系的光谱特征、反应的适宜条件和共存物质的影响。在最强散射波长429nm处,美他环素的浓度在0.02—12.0μg·mL^-1范围内与体系的散射强度呈现良好的线性关系,其回归方程为ΔI429nm=8.845C＋1.600（μg·mL^-1,r=0.9969）,检出限为7.5ng·mL^-1（3σ）,据此,建立了一种测定痕量美他环素的共振散射光谱法。该方法操作简便、灵敏度高,已用于美他环素胶囊和片剂的快速检测,结果满意。     

Effect of a Soft Magnetic Phase on the Processes of Magnetization Reversal of a Hard/Soft Magnetic Bilayer

Physics of the Solid State - Magnetization reversal of a hard/soft magnetic bilayer in an external magnetic field has been studied by the Monte Carlo method. The magnetization reversal curves of a...     

中子散射对快中子照相质量影响的分析

通过一内空的圆柱体模型，对在快中子照相时由样品引起的散射中子强度与样品形状和探测距离之间的关系进行模拟，并用^241Am—Be作中子源对散射中子的影响进行实验验证。结果表明，在快中子照相时，由样品引起的散射中子的强度与探测距离以及样品形状有关。对于同一样品，探测距离增加，散射中子的影响则降低。The relationships between intensities of scattered neutrons by specimens and their shapes and detecting distances have been simulated using a hollow cylinder model, and the results were validated by experiments of fast neutron imaging using ^241Am-Be neutron source. The results showed that the intensities of scattered neutrons are closely related to the detecting distances and sample＇ s shapes. The influences of scattered neutronns in fast neutron imaging will be reduced while detecting distances increased.     

Investigation of Plastically Deformed TRIP-Composites by Neutron Diffraction and Small-Angle Neutron Scattering Methods

The main parameters of the microstructure of TRIP (TRansformation Induced Plasticity) composites with an austenitic matrix and a ZrO₂ zirconium-dioxide reinforcing phase subjected to plastic deformation of different degrees (compressive uniaxial load) are studied by neutron diffraction and small-angle neutron scattering. A series of composite material samples with different contents of the ZrO₂ ceramic phase (0, 10, 20, 30, and 100 wt %) are prepared by the powder metallurgy method using hot pressing. In the region of plastic deformation at load values above 650 MPa, two phases are observed in the austenitic matrix: cubic α'-martensite and hexagonal ε-martensite. Data on the lattice strains of the observed phases, dislocation density in the austenitic matrix, and characteristic sizes of the martensitic-phase particles are obtained.     

Scattering by random rough surfaces: Study of direct and inverse problem

In order to study the problems of scattering by rough metallic surfaces, we have used Maxwell’s equations in covariant form within the framework of a non-orthogonal coordinates system adapted to the geometry of the problem. Electromagnetic fields are written in Fourier’s integral form. The solution is found by using a perturbation method applied to the smooth surface problem; this is fully justified when the defects are of small magnitude.For the direct problem, the mean value of diffraction intensity is obtained for random rough surfaces of finite conductivity by computer simulation.In the case of the inverse problem, the reconstruction of the profile of the metal surface from values of the diffraction intensity, obtained by simulation, is found using an iterative algorithm.     

生物大分子的共振光散射光谱

共振光散射技术是一项在普通荧光分光光度计上可实现分析领域中应用的新技术。本文阐述了共振光散射的基本原理 ,分类介绍了在生物大分子研究和测定方面的应用 ,分析了共振散射体系的新发展。     

Neutron diffraction studies of hydrogen-bonded ices at high pressure

Abstract

The development of the Paris-Edinburgh cell has extended the pressure range for neutron diffraction by a full order of magnitude to 30 GPa. This advance has provided a wealth of new information on the high-pressure behaviour of ices such as water-ice, ammonia, methane and hydrogen sulphide. We have now put in place technique developments to permit loading of water-gas mixtures into the Paris-Edinburgh cell.     

Effect of Exchange Interaction Constants on the Magnetization Reversal in a Hard/Soft Magnetic Bilayer Model

Journal of Experimental and Theoretical Physics - A model is developed to study a hard/soft magnetic bilayer in an external magnetic field by the Monte Carlo method. The influence of the constants...