Room Temperature Ferromagnetism in Ga1-xHoxN (x=0.0 and 0.05) Diluted Magnetic Semiconductor Thin Films

Holmium doped GaN diluted magnetic semiconductor thin films have been prepared by thermal evaporation technique and subsequent ammonia annealing. X-ray diffraction mea-surements reveal all peaks belong to the purely hexagonal wurtzite structure. Surface mor-phology and composition analysis were carried out by scanning electron microscopy and energy dispersive spectroscopy respectively. The room temperature ferromagnetic proper-ties of Ga_1-xHo_xN(x=0.0, 0.05) films were analyzed using vibrating sample magnetometer at room temperature. Magnetic measurements showed that the undoped films (i.e. GaN) exhibited diamagnetic behavior, while the Ho-doped (Ga_0.95Ho_0.05N) film exhibited a ferro-magnetic behavior.     

Synthesis and Characterization of Iron Nanowires

The iron nanowires can be fabricated via the process in which sodium borohydride reduces iron salts in external magnetic field. The iron nanowires are found to be covered by passivated layers of iron oxide which prevent the oxidation of iron nanowires. In this process, the boron will include in iron nanowires. The average length and diameter of iron nanowires is around 1.2 micrometers and 60 nanometers, respectively. According to ICP results, the contents of B and Fe are about 1.98 wt% and 87.04 wt%, respectively, in iron nanowires. A wide variety of equipment is used to investigate the morphological, microchemical, and structural characteristics of the newly synthesized iron nanowires ––– e.g., XRD, FE‐SEM, HR‐TEM, VSM and XANES. XANES analysis indicates the boron in iron nanowires exists in the form of B₂O₃. The saturation magnetization and the coercive force of iron nanowires are 157.93 emu/g and 9.74 Oe, respectively. In‐situ images of synthesized iron nanowires during reduction process in magnetic field are observed by NSRRC transmission X‐ray microscope. Thus, this study develop a novel process to produce iron nanowires with large quantitates and can control its length and diameter by various the concentration of precursors for various applications.     

电沉积铁族薄膜的磁性圆二色研究

采用循环伏安法在GaAs(100)单晶表面电沉积了铁族金属单质薄膜. 扫描电子显微镜(SEM)结果显示, Fe族金属薄膜的晶粒较小, 薄膜平整度较高。通过X射线衍射(XRD)谱分析了Fe, Co, Ni在GaAs(100)晶面上的外延生长. 使用磁光克尔效应装置研究了Fe族金属薄膜的宏观磁性, 用同步辐射圆偏振软X射线测量了铁族单质磁性薄膜的吸收谱, 获得了X射线磁性圆二色谱, 并通过加和定则计算了磁性薄膜中Fe族金属原子的轨道磁距和自旋磁矩.     

Building Nanocomposite Magnets by Coating a Hard Magnetic Core with a Soft Magnetic Shell

Controlling exchange coupling between hard magnetic and soft magnetic phases is the key to the fabrication of advanced magnets with tunable magnetism and high energy density. Using FePt as an example, control over the magnetism in exchange‐coupled nanocomposites of hard magnetic face‐centered tetragonal (fct) FePt and soft magnetic Co (or Ni, Fe₂C) is shown. The dispersible hard magnetic fct‐FePt nanoparticles are first prepared with their coercivity (H_c) reaching 33 kOe. Then core/shell fct‐FePt/Co (or Ni, Fe₂C) nanoparticles are synthesized by reductive thermal decomposition of the proper metal precursors in the presence of fct‐FePt nanoparticles. These core/shell nanoparticles are strongly coupled by exchange interactions and their magnetic properties can be rationally tuned by the shell thickness of the soft phase. This work provides an ideal model system for the study of exchange coupling at the nanoscale, which will be essential for building superstrong magnets for various permanent magnet applications in the future.     

A new sample substrate for imaging and correlating organic and trace metal composition in biological cells and tissues

Many disease processes involve alterations in the chemical makeup of tissue. Synchrotron-based infrared (IR) and X-ray fluorescence (XRF) microscopes are becoming increasingly popular tools for imaging the organic and trace metal compositions of biological materials, respectively, without the need for extrinsic labels or stains. Fourier transform infrared microspectroscopy (FTIRM) provides chemical information on the organic components of a material at a diffraction-limited spatial resolution of 2–10 μm in the mid-infrared region. The synchrotron X-ray fluorescence (SXRF) microprobe is a complementary technique used to probe trace element content in the same systems with a similar spatial resolution. However to be most beneficial, it is important to combine the results from both imaging techniques on a single sample, which requires precise overlap of the IR and X-ray images. In this work, we have developed a sample substrate containing a gold grid pattern on its surface, which can be imaged with both the IR and X-ray microscopes. The substrate consists of a low trace element glass slide that has a gold grid patterned on its surface, where the major and minor parts of the grid contain 25 and 12 nm gold, respectively. This grid pattern can be imaged with the IR microscope because the reflectivity of gold differs as a function of thickness. The pattern can also be imaged with the SXRF microprobe because the Au fluorescence intensity changes with gold thickness. The tissue sample is placed on top of the patterned substrate. The grid pattern’s IR reflectivity image and the gold SXRF image are used as fiducial markers for spatially overlapping the IR and SXRF images from the tissue. Results show that IR and X-ray images can be correlated precisely, with a spatial resolution of less than one pixel (i.e., 2–3 microns). The development of this new tool will be presented along with applications to paraffin-embedded metalloprotein crystals, Alzheimer’s disease, and hair composition.     

Chemical Oxidative Synthesis and Characterization of Poly(8-hydroxyquinoline) Particles

The chemical oxidative polymerization (OP) of 8-hydroxyquinoline (HQ) in an organic medium leaded to the formation of the C-2 and C-4 linking poly (8-hydroxyquinoline) (PHQ). The structure of PHQ was confirmed by UV-Vis, FT-IR, and ¹H-NMR. The characterization of polymer was performed by TG-DTA, differential scanning calorimetry, dynamic mechanical analysis, dynamic light scattering, size exclusion chromatography, X-ray diffraction, cyclic voltammetry, atomic force microscope, photoluminescence and solubility tests. The fluorescence spectrum of PHQ exhibited an emission peak at approximately 525 nm in DMSO. Accordingly, it was found PHQ emitted green light whereas HQ emitted yellow light in DMSO solvent. Optical band gaps (E_g) of PHQ was calculated to be 3.31 eV. The electrical conductivities of iodine doped-PHQ and undoped-PHQ were measured with four-point probe technique. Magnetic particles was prepared by chemical precipitation of mixed Fe(II) and Fe(III) salts and modified with HQ by using an in situ chemical oxidation polymerization method in organic medium.     

Structural and magnetic properties of Zn1−xSbxCr2−x/3Se4 (x=0.11, 0.16 and 0.20) single crystals

Single crystals of Zn_1−xSb_xCr_2−x/3Se₄ based on the ZnCr₂Se₄ spinel, which is known to exhibit interesting magnetic and electronic transport properties, have been prepared by solid state reaction from the appropriate selenides. Three compounds of different Sb content (x=0.11, 0.16, and 0.20) were studied by X-ray diffraction, X-ray photoelectron scattering technique and macroscopic magnetic measurements with the aim to determine (i) stability of the cubic symmetry and (ii) influence of the Sb admixture on the magnetic properties. The results show that the Sb³⁺ and Zn²⁺ ions share the tetrahedral sites in the spinel structure, while the Cr³⁺ions carrying magnetic moments, are located in the octahedral sites. The X-ray photoelectron spectroscopy (XPS) data indicate that in this series of compounds the chromium ions have a 3d³ electronic configuration. The three samples studied order antiferromagnetically at low temperatures, with the magnetic characteristics being hardly altered with respect to those reported for the parent ZnCr₂Se₄ compound.     

Nuclear Magnetic Resonance and X-ray Crystallography to Improve Struvite Determination

Ammonium and phosphate removal from industrial streams is important for many chemical processes, especially wastewater and sewerage treatment. Struvite precipitation is a popular choice and has been well characterized in model systems. However, struvite is a member of a family of similar phosphates of various valences and degrees of hydration. This paper shows that the ammonium phosphate precipitation from complex waste of decaying urine is identical to the product in model and other organic systems, i.e., struvite. We have shown that titration assays are possible for struvite, but they are difficult and hence we have also used nuclear magnetic resonance (NMR) and X-ray crystallography. NMR shows the high purity of struvite. Surprisingly, the crystals from this system are large and generate improved structural determination by X-ray crystallography compared to struvite prepared in solution or discovered in other natural systems. These large crystals allow facile separation of struvite, compared to more conventional methods using fluidized bed reactors which generate irregular concretions with difficulty.     

Structure and dynamics of polymeric materials in nano-scale

The nano-palpation technique,i.e.,nanometer-scale elastic and viscoelastic measurements based on atomic force microscope,is introduced.It is demonstrated to be very useful in analyzing nanometer-scale materials properties for the surfaces and interfaces of various types of soft materials.It enables us to obtain not only structural information but also mechanical information about a material at the same place and at the same time.     

3D-Non-destructive Imaging through Heavy-Metal Eosin Salt Contrast Agents

Conventional histology is a destructive technique based on the evaluation of 2D slices of a 3D biopsy. By using 3D X-ray histology these obstacles can be overcome, but their application is still restricted due to the inherently low attenuation properties of soft tissue. In order to solve this problem, the tissue can be stained before X-ray computed tomography imaging (CT) to enhance the soft tissue X-ray contrast. Evaluation of brominated fluorescein salts revealed a mutual influence of the number of bromine atoms and the cations applied on the achieved contrast enhancement. The dibromo fluorescein barium salt turned out to be the ideal X-ray contrast agent, allowing for 3D imaging and subsequent complementing counterstaining applying standard histological techniques.     

Spectral Differences of the Molecule-ion Adducts of β-Cyclodextrin and Lithium Carbonate

A small shielding effect on the hydrogen atoms of chiral carbons of β-cyclodextrin (β-CD) was detected by ¹H nuclear magnetic resonance, but a large environmental change of the chiral carbon atoms at high concentration ratios of lithium carbonate (Li₂CO₃) to β-CD was observed by polarimetry in aqueous solution. These findings urged us to investigate whether different formation conditions of the molecule-ion system between Li₂CO₃ and β-CD in solid state were involved in different spectral performances. To answer the question, we prepared three adducts of Li₂CO₃ to β-CD, i.e., samples 1, 2, and 3, by magnetic stirring, solvothermal and grinding conditions, respectively. Powder X-ray diffraction and Fourier transformation infrared spectroscopy provided the information of formation of the three molecule-ion adducts. Besides, scanning electron microscope images provided different surface information of the three adducts. Further, significant spectral differences in thermal behavior of these adducts were found by thermogravimetry and derivative thermogravimetry.     

Magnetically active Ag–Zn nanoferrites synthesized by solution combustion route: physical chemical studies and density functional theory analysis

Nanoparticles with mixed compositions, particularly spinel ferrites with magnetic activity, have arisen as contrast agents for magnetic resonance imaging, magnetic hyperthermia. For such applications, it is desirable to possess specific particle size and physicochemical properties, i.e., magnetic response, porosity, crystallinity, and so on. It is well known that controlling specific variables in the synthetic process has a dramatic effect on final product properties and behavior. Amid preparation techniques reported in the literature, low-temperature solution combustion method has shown the ability to control and direct synthesis simply and efficiently. We are presenting a study about controlling and tuning the magnetic properties and the effect of particle size modified in Ag–Zn nanoferrites with different amounts of Co and Ni as doping metals. Different combinations of Co and Ni within Ag–Zn (Ag_0.25Zn_0.5-xM_xFe_2.25O₄) nanoferrites have been synthesized using the low-temperature solution combustion technique, and this method proved to be efficient and reliable for developing homogenous, fine structured materials. X-ray diffraction confirmed that the atomic structure of prepared nanoferrites is pure and cubic, whereas electron microscopy confirmed a semispherical and monodisperse morphology with particle diameter around 20 nm. The magnetic behavior of bred materials has been explained by analyzing magnetic factors such as saturation magnetization, coercivity, and retentivity, and all experimental findings are matched with theoretical density functional theory (DFT) studies to understand the effect of each material within A and B sites in ferrite crystal cell. The observed magnetic properties highlight the superparamagnetic behavior and the effect of doping metals which is an asset in developing new materials for diagnostic and therapeutic applications. DFT modeling was achieved in an attempt to understand the effect of metal substitution in cubic ferrite cells.     

Influence of X-ray tube spectral distribution on uncertainty of calculated fluorescent radiation intensity

The relative radiation intensity (R_i) defined as fluorescent radiation intensity of analyte in specimen to fluorescent radiation intensity of pure element or compound, e.g., oxide is used in calculation in both fundamental parameter methods and in theoretical influence coefficient algorithms. Accuracy of calculated R_i is determined by uncertainties of atomic parameters, spectrometer geometry and also by X-ray tube spectral distribution. This paper presents the differences between R_i calculated using experimental and theoretical X-ray tube spectra evaluated by three different algorithms proposed by Pella et al., Ebel, and Finkelshtein–Pavlova. The calculations are performed for the most common targets, i.e., Cr, Mo, Rh and W. In this study, R_i is calculated for V, Cr, Mn, Fe, Co, Ni, Cu and Mo in steels as an example. The differences between R_i calculated using different X-ray tube spectrum algorithms are presented when pure element standard, multielement standard similar to the analyzed material and one pure element standard for all analytes is used in X-ray fluorescence analysis. The differences between R_i for intermediate-thickness samples (and also for thin films) and for X-ray tube, which ran for many hours, are also evaluated.     

Synthesis and characterization of polyaniline nanoparticles in the presence of magnetic field and samarium chloride

A new and economical method of preparing polyaniline (PANI) nanoparticles will be introduced in this article. Compared with conventional methods, this method is much more simple and convenient. Scanning electron microscope (SEM) shows that the diameter of particles are between 30 and 50 nm, which is in good agreement with the results of a transmission electron microscope (TEM). Polyaniline/SmCl₃/Bp, polyaniline/SmCl₃ and polyaniline/HCl were prepared in a solution containing 1.0 mol dm⁻³ aniline, 1.0 mol dm⁻³ HCl with and without 0.5 mol dm⁻³ SmCl₃, in the presence and in the absence of a magnetic field, respectively. Their conductivity, UV-vis spectra, FTIR spectra, X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were investigated. Changes in UV-vis and FTIR spectra indicate a strong interaction between Samarium ions (SmCl₃) and polyaniline chains. The conductivity of PANI depends on magnetization and concentration of Sm³⁺. Polyaniline/SmCl₃/Bp has the higher degree of crystallinity than that of polyaniline/HCl.     

Design of an apparatus for polarization measurement in soft X-ray region

A novel apparatus for polarization measurement in the soft X-ray region has been designed, constructed, and installed in the evaluation beamline for soft X-ray optical elements (BL-11) at the SR Center of Ritsumeikan University, Shiga, Japan. It allows us to perform conventional reflection and transmission measurements including rocking curve measurement as well as polarimetric and ellipsometric measurements based on the rotating-analyzer method by using six independently movable motorized stages. As a preliminary test of the apparatus, the reflection profile of a Mo/SiO₂ multilayer mirror prepared by an ion beam sputtering technique, which is designed as a reflection polarizer for use of 13.9 nm, has been measured by the apparatus. The result is compared with that by an existing reflectometer, and the azimuth angle dependence of the reflection intensity has been demonstrated. Consequently, it is shown that the apparatus has the capability to perform the rotating-analyzer ellipsometry.     

Core-Level Spectroscopy of 2-Thiouracil at the Sulfur L1- and L2,3-Edges Utilizing a SASE Free-Electron Laser

In this paper, we report X-ray absorption and core-level electron spectra of the nucleobase derivative 2-thiouracil at the sulfur L₁- and L_2,3-edges. We used soft X-rays from the free-electron laser FLASH2 for the excitation of isolated molecules and dispersed the outgoing electrons with a magnetic bottle spectrometer. We identified photoelectrons from the 2p core orbital, accompanied by an electron correlation satellite, as well as resonant and non-resonant Coster–Kronig and Auger–Meitner emission at the L₁- and L_2,3-edges, respectively. We used the electron yield to construct X-ray absorption spectra at the two edges. The experimental data obtained are put in the context of the literature currently available on sulfur core-level and 2-thiouracil spectroscopy.     

基于软X射线光谱的锂电池材料的电子结构与演变的研究进展

开发新型高能量密度以及低成本的锂离子电池, 是有效应对能源危机和环境挑战的可行路径之一. 锂离子电池材料的电子结构与电子态的演化决定了材料诸多本征性质以及电池综合性能. 探测并操控电极材料电子态的演化对探求电极反应的物理机理、 促进电池材料发展具有重要意义. 基于同步辐射的软X射线光谱技术可以直接探测费米能级附近的电子态. 本文从阴阳离子氧化还原反应的不同角度对利用软X射线光谱对电子态演变的研究进行了总结, 获得了电极材料电化学循环过程中过渡金属与氧的电子态演化信息, 系统阐述并总结了不同锂离子电池材料中电子态的演化以及氧化还原反应机理的最新研究进展.     

Irradiation-induced reduction and luminescence properties of Sm doped in BaBPO5

Usually, Sm²⁺ ions could be reduced by heating the materials in reducing atmospheres. Exposure to ionizing radiations is also known to cause Sm³⁺→Sm²⁺ conversion. In this work, BaBPO₅ doped with the samarium ion was prepared by high temperature solid-state reaction. Sm²⁺ ions were obtained by two different reduction methods, i.e., heating in H₂ reduced atmosphere and X-ray irradiation. The measurements of X-ray diffraction (XRD), and scanning electron microscope (SEM) were investigated. It is found that the conversion of Sm³⁺→Sm²⁺ is very efficient in BaBPO₅ hosts after X-ray irradiation. Sm²⁺ ions under these two reduction methods exhibit different characteristics that were studied by measurements of luminescence and decay. The results showed that the luminescence properties of Sm²⁺ ions in BaBPO₅ were highly dependent on the sample preparation conditions.     

Ab initio Hartree-Fock calculations of molecular X-ray intensities. Validity of one-center approximations

Ab initio Hartree-Fock calculations of relative X-ray transition probabilities for core hole states of N₂, CO, H₂O and NH₃ have been carried out and compared with the respective high-resolution soft X-ray spectra. The same one-determinental wavefunctions were employed for both initial and final states and the dependence of the X-ray transition moments on the choice of orbitals and of basis set parameters was investigated. In particular, orbitals optimized for a transition state were tested. The use of the one-center intensity model as a guide for the assignment of second row X-ray spectra was justified at bothab initio and semiempirical (CNDO) levels of approximation. The breakdown of the MO-picture for inner-valence electrons is demonstrated in the X-ray spectrum of N₂ and the analogy with the corresponding photoelectron bands is pointed out.     

Development and research for applying innovative magnetic soft mold imprinting techniques in microstructure component manufacturing

The present study employs an innovative technique, which uses PDMS soft mold, blended with magnetic powder as the transmission and imprinting methods, and integrates features from soft micromolding PMMA, an electro‐magnetically controlled, well‐proportioned, pressing technique in order to study how to create microlens arrays through a magnetic soft mold imprinting resist technique. Thus, it renders nanometer imprinting applications, and its technology, more developed and mature. The research findings revealed that, PDMS, blended with magnetic powder, can accurately recast and duplicate nanometer microstructures. Under well‐proportioned magnetic pressing, controlled by an electro‐magnetic disk, it can effectively fill and shape resist microstructures. The composite material of PDMS, with added magnetic iron powder, can effectively improve mechanical strength properties of pure PDMS soft mold, which is easily transformed for imprinting. Meanwhile, owing to the unique features of PDMS soft mold, conformal contact with the base material is possible; therefore, the effective imprinting area and the duplicated representation are significantly improved. In addition, as magnetic PDMS soft mold is easily produced and fast in recasting, the costs can be effectively reduced. In addition, due to features such as low surface free energy and a tendency not to stick to resist in imprinting, the soft mold is evenly controlled by the electro‐magnetic disk for imprinting duplication, highlighting the advantages of microstructure imprinting procedures. Copyright © 2008 John Wiley & Sons, Ltd.