磁流变智能液场致微结构变化的Monte Carlo模拟

从磁流变液中存在的各种相互作用势出发，对Ｎ＝１００个球形羰基铁颗粒均匀分布于一正方形二维体系之中的物理模型，利用ＭｏｎｔｅＣａｒｌｏ方法和Ｍｅｔｒｏｐｌｉｓ算法着重计算了磁流变智能液的场致微结构变化。计算结果表明，磁流变液（ＭＲＦ）的流变效应在外磁场中的变化是由于其ＭＲＦ中磁性颗粒的成链团簇有序化所致。这与磁流变液在外磁场中熵的下降和对ＭＲＦ的光学显微镜观察结果是一致的。     

电极/水溶液界面的SERS研究Ⅰ.Cu/1.0M的Na_2SO_4和NaCl溶液体系

电极／水溶液界面的ＳＥＲＳ研究Ⅰ．Ｃｕ／１．０Ｍ的Ｎａ２ＳＯ４和ＮａＣｌ溶液体系陈燕霞黄开启田中群（厦门大学化学系固体表面物理化学国家重点实验室物理化学研究所厦门３６１００５）ＳＥＲＳＳｔｕｄｉｅｓｏｆＥｌｅｃｔｒｏｄｅ／ＥｌｅｃｔｒｏｌｙｔｅＳｏ...     

ELECTRON MOMENTUM SPECTRA OF EXCITED He(2~1S) AND He(2~3S)

ＥＬＥＣＴＲＯＮＭＯＭＥＮＴＵＭＳＰＥＣＴＲＡＯＦＥＸＣＩＴＥＤＨｅ（２１Ｓ）ＡＮＤＨｅ（２３Ｓ）ＣｈｅｎＺｈａｎｇｊｉｎＳｈｉＱｉｃｕｎＣｈｅｎＪｉＸｕＫｅｚｕｎＤｅｐａｒｔｍｅｎｔｏｆＭｏｄｅｒｎＰｈｙｓｉｃｓ，ＵｎｉｖｅｒｓｉｔｙｏｆＳｃｉｅｎ...     

水杨酸分子NIR－FT－SERS与VIS－SERS的比较研究

水杨酸分子ＮＩＲ－ＦＴ－ＳＥＲＳ与ＶＩＳ－ＳＥＲＳ的比较研究方炎，汪媛，胡凤霞（首都师范大学实验中心，首都师范大学综合所北京１０００３７）ＴｈｅＣｏｍｐａｒｉｓｏｎｏｆＶＩＳ－ＳＥＲＳｔｏＮＩＲ－ＦＴ－ＳＥＲＳｏｆＭｏｌｅｃｕｌｅｓＡｄｓｏｒｂｅｄｏ...     

电极/水溶液界面的SERS研究Ⅱ.Ag/MgSo_4体系——一种可能的检测界面pH值的方法

电极／水溶液界面的ＳＥＲＳ研究Ⅱ．Ａｇ／ＭｇＳｏ４体系——一种可能的检测界面ｐＨ值的方法陈燕霞黄开启田中群（厦门大学化学系固体表面物理化学国家重点实验室物理化学研究所厦门３６１００５）ＳＥＲＳＳｔｕｄｉｅｓｏｆＥｌｅｃｔｒｏｄｅ／Ｅｌｅｃｔｒｏｌｙ...     

MARTIN MARETTA EOSS（EOTAS／NVPS）

ＭＡＲＴＩＮ　ＭＡＲＥＴＴＡ　ＥＯＳＳ（ＥＯＴＡＳ／ＮＶＰＳ）１９９１年９月，ＭａｒｔｉｎＭａｒｉｅｔｔａ公司接收３亿美元的合同，为美军的ＲＡＨ—６６Ｃｏｍａｎｃｈｅ轻型直升机研制光电传感器系统（ＥＯＳＳ）（前身是目标搜索系统／夜视领航传感器（ＴＡＳ...     

格点定模SU（2）－Higgs模型的解析计算

对格点上基础表示的定模Ｈｉｇｇｓ场与ＳＵ（２）规范场耦合系统的相图进行解析计算至累积展开的第四级，用扫瞄确定变分参数的方法，得到与ＭｏｎｔｅＣａｒｌｏ模拟很好符合的相图．计算了Ｎ＿τ＝１的有限温度情形下ＳＵ（２）－Ｈｉｇｇｓ系统和纯ＳＵ（２）模型的Ｐｏｌｙａｋｏｖ线＜Ｌ＞，对后者得到迄今最佳的近似解析结果βｃ。     

激光散射研究聚甲基丙烯酸烷基磺酸钠／氯化钠水溶液的性质

本文用激光散射技术研究了具有不同长度烷基侧链的聚甲基丙烯酸烷基磺酸钠（ＰＳＳＲＭＡ）在０．１ＭＮａＣｌ水溶液中的性质。用静态光散射测定了这一系列聚合物的重均分子量Ｍ＿ｗ，均方半径Ｒ＿ｇ以及第二维利系数Ａ＿２．用动态光散射测定了光强的时间相关函数，运用Ｌａｐｌａｃｅ反演得到线宽分布Ｇ（Г）。当高聚物溶液的浓度大于１０￣（－３）ｇ／ｍＬ时，特性平均线宽〈Г〉迅速增加、表面张力降低；在２５℃－４７℃的范围内，〈Г〉随温度增加；烷基侧链越长，在０．１ＭＮａＣｌ水溶液中ＰＳＳＲＭＡ的分子排列更紧密。静态与动态光散射的结果建立以下方程：Ｄ＝ｋ＿ＤＭ￣ａ＿Ｄ，当α＿Ｄ～０．５６，对应于不同侧链，Ｋ＿Ｄ在１．５４×～１０￣（－４）－２．０７×１０￣（－４）（ｍＬ／ｇ）时，从线宽分布Ｇ（Г）得到ＰＳＳＲＭＡ的分子量分布。     

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１Ｇａｍｍａｒａｙａｓｔｒｏｎｏｍｙａｔｈｉｇｈｅｎｅｒｇｉｅｓ（Ｃ．Ｍ．Ｈｏｆｆｍａｎ,Ｃ．Ｓｉｎｎｉｓ,Ｐ．Ｆｌｅｕｒｙｅｔａｌ．Ｒｅｖ．Ｍｏｄ．Ｐｈｙｓ．,１９９９,７１：８９７—９３６）２ＳｅａｒｃｈｅｓｆｏｒｓｕｐｅｒｓｙｍｍｅｔｒｉｃｐａｒｔｉｃｌｅｓａｔｔｈｅＴｅｖａｔｒｏｎｃｏｌｌｉｄｅｒ（Ｍ．Ｃａｒｅｎａ,Ｒ．Ｃｕｌｂｅｒｔｓｏｎ,Ｈ．Ｆｒｉｓｃｈｅｔａｌ．Ｒｅｖ．Ｍｏｄ．Ｐｈｙｓ．,１９９９,７１：９３７—９８１）３Ｂｒａｎｅｄｙｎａｍｉｃｓａｎｄｇａｕｇｅｔｈｅｏｒｙ（Ａ…     

GaAs／GaAlAs多量子阱反射型光调制器及自电光效应器件

采用分子束外延技术生长含有大周期数的ＧａＡｓ／ＧａＡｌＡｓ多量子阶（ＭＱＷ）及分布布喇格反射器（ＤＢＲ）的ＰＩＮ结构器件。研究了量子限制斯塔克效应（ＱＣＳＥ），分布布喇格反射及非对称腔模（ＡＳＦＰ）效应对光的反射调制作用及这三种效应的兼容性对光调制及逻辑器件的重要影响。给出我们研制的反射型光调制器及自电光效应器件的实验结果。对于常通型及常闭型调制器，其两态衬比度可达１０ｄＢ。所研制的ＳＥＥＤ器件，其导通光能耗低于１０ｆＪ／（μｍ）￣２，实现其光学双稳态及Ｒ－Ｓ光触发器工作。     

Ion-beam induced changes in magnetic and microstructural properties of thin iron films

Changes in magnetic and structural properties of 60–82 nm iron films induced by heavy-ion implantation were studied using the magneto-optical Kerr effect, M?ssbauer spectroscopy, Rutherford backscattering spectroscopy, X-ray diffraction, and X-ray absorption fine structure. The influence of ion-beam parameters (ion mass, fluence) and of sample parameters (external magnetic field and stress during implantation) were investigated. The Fe films, some of them containing a thin ⁵⁷Fe marker layer for M?ssbauer spectroscopy, were deposited on Si(100) substrates, by electron-beam and effusion-cell evaporation. The films were irradiated with ²⁰Ne, ⁵⁶Fe, ⁸⁶Kr and ¹³²Xe ions at energies chosen so that the implantation profiles peaked near the middle of the Fe films. The as-deposited films were magnetically isotropic and had a high coercivity. After ion implantation, the coercivity decreased and magnetic anisotropy developed. Both changes correlated with a decrease in the internal film stress. External mechanical stress applied during the irradiation had hardly any influence on the magnetic texture, opposite to an external magnetic field applied during or before ion implantation. The results are compared with those obtained for ion-irradiated polycrystalline Ni films and epitaxial Fe films and discussed with respect to the role of radiation-induced extended defects as pinning centers.     

Fe掺杂ZnSe团簇结构和磁性质

采用密度泛函理论研究了Fe原子单掺杂和双掺杂(ZnSe)12团簇的结构、电子性质和磁性质.我们考虑了三种掺杂方式:替代掺杂,外掺杂和内掺杂.单掺杂时,外掺杂团簇是最稳定结构;而双掺杂时,内掺杂团簇是最稳定结构.团簇磁矩主要来自Fe-3d态的贡献,4s和4p态也贡献了一小部分磁矩.由于轨道杂化,相邻的Zn和Se原子上也产生少量自旋.不同掺杂团簇的总磁矩不同,在可调磁矩的磁性材料领域有潜在应用价值.     

Comparative study of core–shell iron/iron oxide gold covered magnetic nanoparticles obtained in different conditions

In this study, we report the synthesis and characterization of the core–shell Fe covered with Au shells nanoparticles with mean diameters between 5 and 8 nm. The inverse micelles method was utilized to produce the samples. X-ray diffraction studies show that both core–shell systems have the expected crystalline structure. High resolution transmission electron microscopy and atomic emission spectroscopy techniques give additional information concerning the structure and composition of nanoparticles. An intermediate shell of amorphous oxidized iron was found between the magnetic Fe core and the external gold shell. The magnetic behavior of different core–shell samples shows no hysteresis loop indicating the superparamagnetic behavior of Fe@Au systems. The superparamagnetic behavior is also evidenced from FC and ZFC dependences of the magnetization versus temperature. By using the temperature dependence of the thermoremanent magnetization combined with magnetization versus applied magnetic field, the effective anisotropy constant was determined. The Fe/Au interface contribution to the effective anisotropy constant was calculated and discussed in relation with the combined shape and stress anisotropies.     

Heavy Ion Irradiated Ferromagnetic Films: The Cases of Cobalt and Iron

Polycrystalline, e-gun deposited Co, Fe and Co/Fe films, tens of nanometers thick, have been irradiated with Ne, Kr, Xe and/or Fe ions to fluences of up to 5 × 10¹⁶ ions/cm². Changes in the magnetic texture induced by the implanted ions have been measured by means of hyperfine methods, such as Magnetic Orientation Mössbauer Spectroscopy (Fe), and by Magneto-Optical Kerr Effect and Vibrating Sample Magnetometry. In Co and CoFe an hcp → fcc phase transition has been observed under the influence of Xe-ion implantation. For 10¹⁶ Xe-ions/cm², ion beam mixing in the Co/Fe system produces a soft magnetic material with uniaxial anisotropy. The effects have been correlated with changes in the microstructure as determined via X-ray diffraction. The influences of internal and external strain fields, an external magnetic field and pre-magnetization have been studied. A comprehensive understanding of the various effects and underlying physical reasons for the modifications appears to emerge from these investigations.     

Fe掺杂ZnTe团簇结构和磁性质

本文采用第一性原理密度泛函理论系统的研究了Fe原子单掺杂和双掺杂(ZnTe)12团簇的结构和磁性质。我们考虑了替代掺杂和间隙掺杂。不管是单掺杂还是双掺杂,间隙掺杂团簇都是最稳定结构。团簇磁矩主要来自Fe-3d态的贡献,4s 和4p 态也贡献了一小部分磁矩。由于轨道杂化,相邻的Zn和Te原子上也产生少量自旋。最重要的是,我们指出间隙双掺杂团簇是铁磁耦合,在纳米量子器件有潜在的应用价值。     

Fe掺杂ZnTe团簇结构和磁性质

本文采用第一性原理密度泛函理论系统的研究了Fe原子单掺杂和双掺杂（ ZnTe）12团簇的结构和磁性质。我们考虑了替代掺杂和间隙掺杂。不管是单掺杂还是双掺杂,间隙掺杂团簇都是最稳定结构。团簇磁矩主要来自Fe－3d态的贡献,4s和4p态也贡献了一小部分磁矩。由于轨道杂化,相邻的Zn和Te原子上也产生少量自旋。最重要的是,我们指出间隙双掺杂团簇是铁磁耦合,在纳米量子器件有潜在的应用价值。     

Magnetic Texturing of Xenon-Irradiated Iron Films Studied by Magnetic Orientation Mössbauer Spectroscopy

Modifications of magnetic properties upon heavy-ion irradiation have been recently investigated for films of ferromagnetic 3d-elements (Fe, Ni, Co) and alloys (permendur, permalloy), in relation to changes of their microstructure. Here we report on Xe-ion irradiation of a highly textured iron film prepared via pulsed-laser deposition on a MgO(100) single crystal and containing a thin ⁵⁷Fe marker layer for magnetic orientation Mössbauer spectroscopy (MOMS). We compare the results with those obtained for a polycrystalline Fe/Si(100) sample produced by electron evaporation and premagnetized before Xe-irradiation in a 300 Oe external field. Characterization of the samples also included magneto-optical Kerr effect (MOKE), Rutherford backscattering spectroscopy (RBS) and X-ray diffraction (XRD).     

Magnetization reversal mechanism of magnetic tunnel junctions

Using the ion-beam-sputtering technique,we have fabricated Fe/Al2O3/Fe magnetic tunnelling junctions (MTJs).We have observed double-peaked shapes of curves,which have a level summit and a symmetrical feature,showing the magnetoresistance of the junction as a function of applied field.We have measured the tunnel conductance of MTJs which have insulating layers of different thicknesses.We have studied the dependence of the magnetoresistance of MTJs on tunnel conductance.The microstructures of hard-and soft-magnetic layers and interfaces of ferromagnets and insulators were probed.Analysing the influence of MJT microstructures,including those having clusters or/and granules in magnetic and non-magnetic films,a magnetization reversal mechanism(MRM) is proposed,which suggests that the MRM of tunnelling junctions may be explained by using a group-by-group reversal model of magnetic moments of the mesoscopical particles.We discuss the influence of MTJ microstructures,including those with clusters or/and granules in the ferromagnetic and non-magnetic films,on the MRM.     

A theoretical approach to local attenuation measurements of shear waves by MRE. Preliminary experimental results

An essential highlight of the presented method is the employment of Magnetic Resonance Elastography (MRE) for local measurements of the attenuation of elastic shear waves introduced into a biological sample. Such a measurement can be accomplished by combining the MRE method with those methods, in which collective displacement of spins is induced by external physical factors, such as variable electric field, strong magnetic field gradient or longitudinal elastic wave. A theoretical basis of the method involving external factors and results of preliminary experiments have been presented in this paper.     

Viscoelasticity of dynamically self-assembled paramagnetic colloidal clusters

Paramagnetic particles in a liquid above a solid dynamically self-assemble into two-dimensional (2D) viscoelastic clusters in a processing magnetic field if the precession angle exceeds the magic angle. Hexagonal clusters rotate with a frequency proportional to the precession frequency of the magnetic field. The rotation is explained by viscoelastic shear waves excited in the clusters that can be visualized slightly above the magic angle. The cluster rotation and the visualization of viscoelastic modes are independent techniques to probe the rheological properties of the cluster. We find agreement between both techniques when determining the 2D cluster viscosity eta(c) approximately 10(-11) N s/m.