Structure and magnetic properties of vacuum annealed FePt/Ag nano-multilayers

The hard disk driver (HDD) technology has been loping quickly for recent years. An aerial density of 2 has been demonstrated by Fujitsu and Seagate espectively. To further improve the recording density, the ic effect will be a serious problem tropy of a- alloy thin films in the ordered 0 phase exhibit a perpendicular magnetic anisotropy Ku of the order of 106 J/m3 at room tempera-[1,2] and is very attractive for future high density mag- In the FePt (L10) phase, Fe and Pt atomic c axis, w…     

Structure,optical,and magnetic properties of Mn-doped ZnO films prepared by sputtering

<正>The microstructural,optical,and magnetic properties and room-temperature photoluminescence(PL) of Mn-doped ZnO thin films were studied.The chemical compositions were examined by energy dispersive X-ray spectroscopy(EDS) and the charge state of Mn ions in the ZnO:Mn films was characterized by X-ray photoelectronic spectrometry(XPS).From the X-ray diffraction(XRD) data of the samples,it can be found that Mn doping does not change the orientation of ZnO thin films.All the films prepared have a wurtzite structure and grow mainly along the c-axis orientation.The grain size and the residual stress were calculated from the XRD results.The optical transmittance of the film decreases with the increase of manganese content in ZnO.The room-temperature photoluminescence of the films shows that the intensity of near band energy(NBE) emission depends strongly on the Mn content.The hysteresis behavior indicates that the films with the Mn content below 9at%are ferromagnetic at room temperature.     

Synthesis of graphene on a Ni film by radio-frequency plasma-enhanced chemical vapor deposition

Large-area single-or multilayer graphene of high quality is synthesized on Ni films by radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) at a relatively low temperature (650℃).In the deposition process,a trace amount of CH4 gas (2-8 sccm (sccm denotes standard cubic centimeter per minute at STP)) is introduced into the PECVD chamber and only a short deposition time (30-60 s) is used.Single-or multilayer graphene is obtained because carbon atoms from the discharging CH4 diffuse into the Ni film and then segregate out at its surface.The layer number of the obtained graphene increases when the deposition time or CH4 gas flow rate is increased.This investigation shows that PECVD is a simple,low-cost,and effective technique to synthesize large-area single-or multilayer graphene,which has potential for application as electronic devices.     

Preparation and magnetic properties of CoFe2O4/TiO2 composite films

Using （Ti（OC4H9）4） and metal chlorates as starting materials, CoFe2O4/TiO2 composite films were prepared by sol-gel method. The effects of heat treatment temperature and pH of the precursor on microstructure and magnetic properties were studied. The phase structure of the samples was examined by X-ray diffraction. The microstructure was examined by scanning electron microscope, atomic force microscope and polarized microscope. The magnetic property was measured by vibrating sample magnetometer. The results show that the crystals of different phases grow up independently. CoFe2O4 is uniformly embedded into the TiO2 matrix in the prepared composite films, and the growth of composite films is dependent on the heat treatment temperatures and PH of the precursor. The average size of CoFe2O4 crystal is 19 nm in Nanocomposite film prepared when the heat treatment temperature is 800℃ and the pH of the precursor is between 2 and 3. The magnetism of the composite films is enhanced as the heat treatment temperature increases.     

Dripping and evolution behavior of primary slag bearing TiO_2 through the coke packed bed in a blast-furnace hearth

To investigate the flow of primary slag bearing TiO_2 in the cohesive zone of blast furnaces,experiments were carried out based on the laboratory-scale packed bed systems. It is concluded that the initial temperature of slag dripping increases with decreasing Fe O content and increasing TiO_2 content. The slag holdup decreases when the Fe O content is in the range of 5wt%–10wt%,whereas it increases when the Fe O content exceeds 10wt%. Meanwhile,the slag holdup decreases when the TiO_2 content increases from 5wt% to 10wt% but increases when the TiO_2 content exceeds 10wt%. Moreover,slag/coke interface analysis shows that the reaction between Fe O and TiO_2 occurs between the slag and the coke. The slag/coke interface is divided into three layers: slag layer,iron-rich layer,and coke layer. TiO_2 in the slag is reduced by carbon,and the generated Ti diffuses into iron.     

Structure and 57Fe conversion electron Mössbauer spectroscopy study of Mn-Zn ferrite nanocrystal thin films by electroless plating in aqueous solution

Mn1-xZnxFe2O4thin films with various Zn contents and of different thickness were synthesized on glass substrates directly by electroless plating in aqueous solution at 90℃ without heat treatment. The Mn-Zn ferrite films have a single spinel phase structure and well-crystallized columnar grains growing per- pendicularly to the substrates. The results of conversion electron ^57Fe Mossbauer spectroscopy （CEMS） Indicate that the cation distribution of Mn1-xZnxFe204 ferrite nanocrystal thin films fabricated by electroless plating is different from the bulk materials＇ and a great quantity of Fe^3＋ ions are still present on A sites for x〉0.5. When the Zn content of the films increases, Fe^3＋ ions in the films transfer from A sites to B sites and the hyperfine magnetic field reduces, suggesting that Zn2. has strong chemical affinity towards the A sites. On the other side, with the increase of the thickness of the films, Fe3＋ ions, at B sites in the spinel structure, increase and the array of magnetic moments no longer lies in the thin film plane completely. At x = 0.5, Hc and Ms of Mn1-xZnxFe204thin films show a minimum of 3.7 kA/m and a maximum of 419.6 kA/m, respectively.     

Preparation of graphene and TiO2 layer by layer composite with highly photocatalytic efficiency

A process for fabricating graphene and TiO2 layer by layer composite was introduced to improve the photocatalytic activity by controlling the layers, thickness and the mass ratio between graphene and TiO2. The graphene oxide (GO) was synthesized from natural graphite pow der by the modified Hummers met hod. Large-area uniform GO and TiO2 thin films were made by a spin-coating process in turn. After exposure of the TiO2/GO multilayer film to UV light irradiation which allows the reduction of GO to graphene, a novel photocatalyt ic structure as graphene and TiO2 layer by layer composite was synthesized. The cross-sectional SEM image showed that a clear layer by layer microstructure with a single layer thickness of graphene or TiO2 was in the range of about 50 nm. The total thickness of the film was around 5 μm which was varied according to the layer number of spin coating process. Raman spectra revealed th at significant structural changes occurred through UV light irradiation. Photodegrada tion for methylene blue (MB) exhibited that the layer by layer com posite is of higher photocatalytic activity than the pure TiO2 layer.     

Dripping and evolution behavior of primary slag bearing TiO<Subscript>2</Subscript> through the coke packed bed in a blast-furnace hearth

To investigate the flow of primary slag bearing TiO₂ in the cohesive zone of blast furnaces,experiments were carried out based on the laboratory-scale packed bed systems.It is concluded that the initial temperature of slag dripping increases with decreasing FeO content and increasing TiO₂ content.The slag holdup decreases when the FeO content is in the range of 5wt%-10wt%,whereas it increases when the FeO content exceeds 10wt%.Meanwhile,the slag holdup decreases when the TiO₂ content increases from 5wt% to 10wt% but increases when the TiO₂ content exceeds 10wt%.Moreover,slag/coke interface analysis shows that the reaction between FeO and TiO₂ occurs between the slag and the coke.The slag/coke interface is divided into three layers:slag layer,iron-rich layer,and coke layer.TiO₂ in the slag is reduced by carbon,and the generated Ti diffuses into iron.     

Decoration of C60 nanorods with nickel and their magnetic properties

We studied the coating of C60 nanorods with nickel by electroless plating method and investigated their magnetic properties. The morphology and structure of the nickel layer coated on C60 nanorods were characterized by transmission electron microscopy （TEM）, energy-dispersive X-ray spectroscopy （EDX）, X-ray diffraction （XRD） and Raman spectroscopy. The coated nickel is in the form of nano-sized crystals and becomes a continuous layer as reaction time increases. The hysteresis loop shows a super paramagnetic characteristic similar to that of nanometer-sized nickel particle. These results suggest that the average size of nickel particles on C60 rods is below 10 nm. Our study has shown that electroless plating is an efficient and simple method for coating C60 nanorods with nickel.     

Magnetic Films on Self-assembled Nanospheres

1 Results Nanoparticle media using arrays of monodisperse nanoparticles with high magneticanisotropy are assumed to be the ideal future magnetic recording media. However,key requirements like control of the magnetic anisotropy orientation along with magnetic domain isolation have not been achieved so far. Here, we report on a combination of a two-dimensional topographic pattern formed of self-assembled nanoparticles with sizes as small as 20 nm and magnetic multilayer film deposition[1]. The so formed nanostructures on top of a sphere are monodisperse, reveal a uniform magnetic anisotropy and are magnetically exchange isolated(see Fig.1 at page 710). This system is distinct from the classical nanostructure geometries: Neither extrinsic properties nor the intrinsic properties are uniform in space. The film is extended over a wide region of the sphere and thus shows substantial curvature. The film thickness varies and so do the intrinsic magnetic properties most notable the magneto-crystalline anisotropy, which is a key factor affecting the fundamental nature of the reversal process[2]. Co/Pd multilayers containing thin Co layers of 0.3 nm thickness result in an anisotropy direction pointing perpendicular to the particle surface. This has a drastic impact on the switching mechanism which differs remarkably from a Stoner-Wohlfarth behavior. For Co/Pt and Co/Pd multilayer film deposition, the anisotropy direction depends critically on the Co layer thickness, thus, changing the orientation from parallel to perpendicular to the particle surface below a critical thickness of about 0.8 nm. Increasing the Co thickness allows the creation of systems with a spin reorientation transition across the cap. Experimental results will be compared to micromagnetic simulations. Furthermore, the magnetic nanopattern is used to study the size-dependent scaling of exchange bias in nanostructures. [Pd/Co]-CoO and [Pt/Co]-IrMn layers with perpendicular magnetic anisotropy were deposited onto different arrays of monodisperse PS nanospheres with a diameter ranging from 58 to 320 nm[3]. Below the blocking temperature we find for both systems a strong increase of the exchange bias field compared to continuous films. Interestingly, the exchange bias field increases drastically with decreasing particle size and shows a strong dependence on the applied cooling fields accompanied by a strong training effect.     

在MgO(001)基板上生长连续的L10-FePt 纳米薄膜

用磁控溅射法在加热到400℃的MgO(001)基片上沉积了总厚度为25 nm 的[Fe(0.6 nm)/Fe_30.5Pt_69.5(1.9nm)]₁₀ 多层连续薄膜, 并对其在[500, 900]℃的温度范围进行了3h 的真空热处理. 结果表明, 薄膜在沉积过程中发生了层间扩散, 形成A1 相的FePt 合金, 表现为软磁特性; 热处理温度高于700℃时, 薄膜内形成L1₀ 相的(001)织构, 其单轴磁晶各向异性能高于2.5×10⁷ erg cc^-1; 薄膜能在800℃以下保持形貌连续. 借助于半导体载流子扩散和复合模型, 对薄膜在高温下形貌保持连续的机理进行了探讨. 分析认为, 虽然薄膜在沉积过程中发生了层间扩散, 但内部仍然残存微弱的周期性成分起伏, 这可以有效阻碍热处理过程中因相变而引起的Pt 元素析出, 从而抑制了因形成富Pt 晶界而导致的形貌不连续. 这种薄膜可以方便地用于微加工制作磁性阵列和隧道结.     

Influence of post-annealing on the properties of Ta-doped In<Subscript>2</Subscript>O<Subscript>3</Subscript> transparent conductive films

Ta-doped In₂O₃ transparent conductive oxide films were deposited on glass substrates using radio-frequency (RF) sputtering at 300°C. The influence of post-annealing on the structural, morphologic, electrical and optical properties of the films was investigated using X-ray diffraction, field emission scanning electron microscopy, Hall measurements and optical transmission spectroscopy. The obtained films were polycrystalline with a cubic structure and were preferentially oriented in the (222) crystallographic direction. The lowest resistivity, 5.1×10⁻⁴ Ω cm, was obtained in the film annealed at 500°C, which is half of that of the un-annealed film (9.9×10⁻⁴ Ω cm). The average optical transmittance of the films was over 90%. The optical bandgap was found to decrease with increasing annealing temperature.     

Giant magneto-optical faraday effect of nanometer Fe-In<Subscript>2</Subscript>O<Subscript>3</Subscript> granular films

The giant magneto-optical Faraday effect of nanometer ferromagnetic metal-semiconductor matrix Fe-ln2O3 granular films prepared by the radio frequency sputtering are studied. The result shows that the Faraday rotation angle θF value of the granular film samples with Fe volume fraction x = 35% is of the order of 10^5（°）/cm at room temperature. Temperature dependence of the Faraday rotation angle θF of Fe0.35（In2O3）0.65 granular films shows that θF value below 10 K increases rapidly with the decrease of the temperature, and when T= 4.2 K, θF value is 106（°）/cm. Through the study of the dependence of low field susceptibility on temperature and the hysteresis loops at different temperatures, it has been found that when the temperature decreases to a critical point Tp = 10 K, the transformation of state from ferro-agnetic to spin-glass-like occurs in Fe0.35（In2O3）0.65 granular films. The remarkable increase of the Faraday rotation angle θF value of Fe0.35（In2O3）0.65 granular films below 10 K seems to arise from the sp-d exchange interaction of the granular film samples in the spin-glass-like state.     

Near-infrared to visible up-conversion emissions of Er^3＋ doped Al2O3 powders derived from the sol-gel method

The Er3 doped Al2O3 powders were prepared by the sol-gel method using the aluminium isopropoxide [Al(OC3H7)3]-derived Al2O3 sols with addition of the erbium nitrate [Er(NO3)3.5H2O]. The different phase structure, including three crystalline types of (Al,Er)2O3 phases, γ, θ, α, and two Er-Al-O phases, ErAlO3 and Al10Er6O24, was obtained with the 1 mol% Er3 doped Al2O3 powders at the different sintering temperatures of 600―1200℃. The green and red up-conversion emissions centered at about 523, 545 and 660 nm, corresponding respectively to the 2H11/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3 , were detected by a 978 nm semiconductor laser diodes excitation. The phase structure and OH content had evident influence on the up-conversion emissions intensity. The maximum intensities of both the green and red emissions were obtained respectively for the Er3 doped Al2O3 powders sintered at 1200 ℃, which was composed mainly of α-(Al,Er)2O3, less of ErAlO3 and Al10Er6O24 phases, and with the least OH content. The two-photon absorption up-conversion process was involved in the green and red up-conversion emissions of the Er3 doped Al2O3 powders.     

Magnetic properties of perpendicularly orientated L1<Subscript>0</Subscript> FePt nanoparticles

L10 FePt films were deposited on MgO (001) substrates heated to 700°C by magnetron sputtering.Assisted by the misfit of lattice between film and substrate,strong (001) texture was formed.The film at nominal thickness t N=5 nm was composed of nanoparticles with a size of～70 nm,and showed a high coercivity of～105 kOe at 4.2 K.At t N=～50 nm,as the film changed from discontinuous to continuous,the coercivity dropped about one order of magnitude.Micromagnetic simulation implies that the magnetization reversal is...     

The giant magnetocaloric effect in Gd<Subscript>5</Subscript>Si<Subscript>2</Subscript>Ge<Subscript>2</Subscript> with low purity gadolinium

The giant magnetocaloric effect Gd5Si2Ge2 alloy was prepared with 99wt% low purity commercial Gd. Powder XRD and magnetic measurements showed that the Gd5Si2Ge2 alloy annealed at 1200℃ for 1h had a significant magnetic- crystallographic first order phase transition at about 270 K. The maximal magnetic entropy change is 17.55 J· kg^-1· K^-1 under a magnetic field change of 0-5 T. The distinct increase of magnetic entropy change belongs to the first-order phase transition from the orthorhombic Gd5Si4-type to the monoclinic Gd5Si2Ge2-type after high temperature heat-treatment.     

Molecular simulation study of the binding mechanism of [α-PTi<Subscript>2</Subscript>W<Subscript>10</Subscript>O<Subscript>40</Subscript>]<Superscript>7−</Superscript> for its promising broad-spectrum inhibitory activity to FluV-A neuraminidase

Polyoxometalate (POM) has promising antiviral activities. It shows broad-spectrum inhibiting ability, high efficiency, and low tox-icity. Experimental assays show that titanium containing polyoxotungstates have anti-influenza-virus activity. In this paper, the bind-ing mechanisms of five isomers of di-Ti-substituted polyoxotungstate, [α-1,2-PTi₂W₁₀O₄₀]^7– (α-1,2), [α-1,6-PTi₂W₁₀O₄₀]^7– (α-1,6), [α-1,5-PTi₂W₁₀O₄₀]^7– (α-1,5), [α-1,4-PTi₂W₁₀O₄₀]^7– (α-1,4) and [α-1,11-PTi₂W₁₀O₄₀]^7– (α-1,11), to five subtypes of influenza virus A neuraminidase (FluV-A NA) were investigated in the context of aqueous solution by using molecular docking and molecular dynamics studies. The results show that the isomer α-1,2 is superior to other isomers as a potential inhibitor to neuraminidase. The positively charged arginine residues around the active site of NA could be induced by negatively charged POM to adapt themselves and could form salt bridge interactions and hydrogen bond interactions with POM. The binding free energies of POM/NA complexes range from –5.36 to –8.31 kcal mol^–1. The electrostatic interactions are found to be the driving force during the binding process of POM to NA. The conformational analysis shows that POM tends to bind primarily with N1 and N8 at the edge of the active pocket, which causes the conformational change of the pincers structure comprising residue 347 and loop 150. Whereas, the active pockets of N2, N9 and N4 are found to be more spacious, which allows POM to enter into the active pockets directly and anchor there firmly. This study shows that negatively charged ligand as POM could induce the reorganization of the active site of NA and highlights POM as a promising inhibitor to NA despite the ever increasing mutants of NA.     

Decay dynamics of excited CS<Subscript>2</Subscript> and NH<Subscript>3</Subscript> investigated by femtosecond laser

By using the home-made femtosecond laser system and the time-of-flightmass spectrometer, the decay dynamics of excited carbon disulfide (CS2) and ammonia (NH3) are investigated in real time by pump-probe multiphoton ionization detection. The estimated lifetime constant of the NH3 state (514 fs) agreed quite well with the literature report. For the first time, the decay lifetime constants of the NH3 ′1A′1 state (93793 fs), the CS2 state (153 ± 10 fs), and the CS2 Rydberg state[2-3]6sσg(3Ⅱg)(948 ± 23 fs) are obtained.     

Comparative analysis of the dissolution kinetics of galena in binary solutions of HCl/FeCl<Subscript>3</Subscript> and HCl/H<Subscript>2</Subscript>O<Subscript>2</Subscript>

A comparative study of the dissolution kinetics of galena ore in binary solutions of FeCl₃/HCl and H₂O₂/HCl has been undertaken. The dissolution kinetics of the galena was found to depend on leachant concentration, reaction temperature, stirring speed, solid-to-liquid ratio, and particle diameter. The dissolution rate of galena ore increases with the increase of leachant concentration, reaction temperature, and stirring speed, while it decreases with the increase of solid-to-liquid ratio and particle diameter. The activation energy (E _a) of 26.5 kJ/mol was obtained for galena ore dissolution in 0.3 M FeCl₃/8.06 M HCl, and it suggests the surface diffusion model for the leaching reaction, while the E _a value of 40.6 kJ/mol was obtained for its dissolution in 8.06 M H₂O₂/8.06 M HCl, which suggests the surface chemical reaction model for the leaching reaction. Furthermore, the linear relationship between rate constants and the reciprocal of particle radius supports the fact that dissolution is controlled by the surface reaction in the two cases. Finally, the rate of reaction based on the reaction-controlled process has been described by a semiempirical mathematical model. The Arrhenius and reaction constants of 11.023 s⁻¹, 1.25×10⁴ and 3.65×10² s⁻¹, 8.02×10⁶ were calculated for the 0.3 M FeCl₃/8.06 M HCl and 8.06 M H₂O₂/8.06 M HCl binary solutions, respectively.     

Structural and electrical properties of HCl-polyaniline-Ag composites synthesized by polymerization using Ag-coated (NH4)2S2O8 powder

Ag nanoparticles were sputter-deposited on ammonium persulfate ((NH₄)₂S₂O₈) powder to obtain (NH₄)₂S₂O₈-Ag powder, which was used to synthesize the HCl-doped polyaniline-Ag (HCl-PANI-Ag) composite via a polymerization procedure. The Ag nanoparticles were dispersed in the HCl-PANI matrix, and their sizes mainly ranged from 3 to 6 nm. The Ag nanoparticles did not affect the structure of emeraldine salt in the composite, and they increased the ordered crystalline regions in the HCl-PANI matrix. The HCl-PANI-Ag composite had a conductivity of (6.8 ±0.1) S/cm, which is about four times larger than that of the HCl-PANI. The charge transport mechanism in the composite is explained by the three-dimensional Mott variable-range hopping (3D-Mott-VRH).