Dependence of Magnetic Properties and Microstructure of Ni81Fe19 Film on Base Vacuum and Sputtering Pressure

The Ni81Fe19 / Ta films with different NiFe thickness were prepared at different base vacuums and sputtering pressures. The results of magnetic measurement and atomic force microscope (AFM) showed that the films prepared at higher base vacuum and lower sputtering pressure had larger R/R. The reason should be that higher base vacuum and lower sputtering pressure introduce larger grain-size and lower surface roughness, which will weaken the scattering of electrons, reduce the resistance R, and increase R/R.     

Chemical states of the atoms in magnetic multilayers Ta/NiO x /Ni81Fe19/Ta and Co/AlO x /Co

Ta/NiO _x /Ni₈₁Fe₁₉/Ta and Co/AlO _x /Co multilayers were prepared by rf reactive and dc magnetron sputtering. The exchange coupling field (H _ex) and the coercivity (H _c) of NiO _x /Ni₈₁Fe₁₉ as a function of the ratio of Ar to O₂ during the deposition process were studied. The composition and chemical states at the interface region of NiO _x /NiFe were also investigated using the X-ray photoelectron spectroscopy (XPS) and peak decomposition technique. The results show that when the ratio of Ar to O₂ is equal to 7 and the argon sputtering pressure is 0.57 Pa, the x value is approximately 1 and the valence of nickel is +2. At this point, NiO _x is antiferromagnetic NiO and the corresponding H_ex is the largest. As the ratio of Ar/O₂ deviates from 7, the H _ex will decrease due to the presence of magnetic impurities such as Ni⁺³ or metallic Ni at the interface region of NiO _x /NiFe, while the H _c will increase due to the metallic Ni. Al layers in Co/AlO _x /Co multilayers were also studied by angle-resolved XPS. Our finding is that the bottom Co could be completely covered by depositing an Al layer about 1.8 nm. The thickness of AlO _x was 1.2 nm.     

Composition design of superhigh strength maraging stainless steels using a cluster model

The composition characteristics of maraging stainless steels were studied in the present work investigation using a cluster-plus-glue-atom model. The least solubility limit of high-temperature austenite to form martensite in basic Fe–Ni–Cr corresponds to the cluster formula [NiFe12]Cr3,where NiFe12is a cuboctahedron centered by Ni and surrounded by 12 Fe atoms in FCC structure and Cr serves as glue atoms. A cluster formula [NiFe12](Cr2Ni) with surplus Ni was then determined to ensure the second phase(Ni3M) precipitation,based on which new multicomponent alloys [(Ni,Cu)16Fe192](Cr32(Ni,Mo,Ti,Nb,Al,V)16) were designed. These alloys were prepared by copper mould suction casting method,then solid-solution treated at 1273 K for 1 h followed by water-quenching,and finally aged at 783 K for 3 h. The experimental results showed that the multi-element alloying results in Ni3M precipitation on the martensite,which enhances the strengths of alloys sharply after ageing treatment. Among them,the aged [(Cu4Ni12)Fe192](Cr32(Ni8.5Mo2Ti2Nb0.5Al1V1)) alloy(Fe74.91Ni8.82Cr11.62Mo1.34Ti0.67Nb0.32Al0.19V0.36Cu1.78wt%) has higher tensile strengths with YS?1456 MPa and UTS?1494 MPa. It also exhibits good corrosion-resistance in 3.5 wt% NaCl solution.     

A FeNiMnC alloy with strain glass transition

Recent experimental and theoretical investigations suggested that doping sufficient point defects into a normal ferroelastic/martensitic alloy systems could lead to a frozen disordered state of local lattice strains(nanomartensite domains), thereby suppressing the long-range strain-ordering martensitic transition. In this study, we attempt to explore the possibility of developing novel ferrous Elinvar alloys by replacing nickel with carbon and manganese as dopant species. A nominal Fe_(89)Ni_5Mn_(4.6)C_(1.4) alloy was prepared by argon arc melting, and XRD, DSC, DMA and TEM techniques were employed to characterize the strain glass transition signatures, such as invariance in average structure, frequency dispersion in dynamic mechanical properties(storage modulus and internal friction) and the formation of nanosized strain domains. It is indicated that doping of Ni, Mn and C suppresses γ→α long-range strain-ordering martensitic transformation in Fe_(89)Ni_5Mn_(4.6)C_(1.4) alloy, generating randomly distributed nanosized domains by strain glass transition.     

Solvother mal synthesis of Co1-xNixFe2O4 nanoparticles and its application in ammonia vapors detection

Magnetic Co1-xNixFe2O4 nanoparticles (NPs) were successfully synthesized via a solvothermal method using ethylene glycol as solvent.The samples were characterized by X-ray diffraction (XRD),field emiss...     

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.     

Self-assembly of N-3-γ-pyridyl Aza[60]fulleroid on Au(111)

Self-assembled monolayers of novel C₆₀ derivative, N-3-γ-pyridyl Aza[60]fulleroid (C₆₀Py), on Au(111) were studied by a scanning tunneling microscope under ultrahigh vacuum (UHV). C₆₀Py molecules were assembled on Au (111) via pyridyl nitrogen-Au interaction. The sole assembly of C₆₀Py molecules on Au (111) only exhibited randoml aggregation of C₆₀Py even the films were annealed at 50 and 105°C. By co-assembling with benzyl mercaptan (BM), the C₆₀PyBM films showed highly dense aggregation, but C₆₀Py assemblies still had disordered structure. After the co-assembled C₆₀Py-BM films were annealed at 50°C, BM molecules were partially desorbed, but the assembly of C₆₀Py remained without obvious change. After the co-assembled C₆₀Py-BM films were further annealed at 105°C, the C₆₀Py monolayers with ordered structure were obtained, while the BM molecules were nearly thoroughly desorbed from the surface. Here, the BM molecules play a key role as a surfactant in the formation of the ordered C₆₀Py monolayer.     

Magnetoresistance of the ferromagnetic nanocontacts fabricated by electrodeposition

A "T" shaped micro-gap was fabricated by mechanical polishing between two Cu film electrodes on the surface of single-sided bonded copper.A nano-gap was then fabricated in the prepared micro-gap by resistance feedback controlled electroplating.Finally Ni 80 Fe 20 ferromagnetic nanocontacts of several sizes were fabricated in the prepared nano-gap by resistance feedback controlled electroplating.The magnetoresistance of each Ni 80 Fe 20 ferromagnetic nanocontact was not related to its size.Fabrication of the Ni 80 Fe 20 ferromagnetic nanocontacts in the nano-gap can reduce the contribution of magnetostriction to the magnetoresistance.The magnetoresistance values of the Ni 80 Fe 20 ferromagnetic nanocontacts were as high as those of the Ni ferromagnetic nanocontacts.This implies that the contribution of magnetostriction to the ballistic magnetoresistance of the ferromagnetic nanocontacts can be neglected.The ferromagnetic nanocontacts fabricated in this study,and in other cases,have two anisotropic interfaces on the sides of the nanocontacts.However,the magnetic field can alter the contribution of the interaction between the two anisotropic interfaces to the ballistic magnetoresistance of the ferromagnetic nanocontacts,and this effect can not be ruled out yet.     

Bimetallic-organic coordination polymers to prepare N-doped hierarchical porous carbon for high performance supercapacitors

Single metal-organic coordination polymers have limited functions as precursors for porous carbon electrode materials.The construction of bimetallic organic coordination polymers can effectively utilize the advantages of each single metal-organic coordination polymer to improve the performance of the derived carbon materials.Herein,High performance nitrogen-doped porous carbon(BC_(Fe–Ni))have been produced by directly carbonizing bimetallic organic coordination polymers formed by 4,4'-bipyridine(BPD)reaction with Fe Cl_3and NiCl_2.The BC_(Fe–Ni) exhibits high nitrogen content(12.66 at%),large specific surface area(1049.51 m~2g~(-1))and hierarchical porous structure,which contributes to an excellent gravimetric specific gravity of 320.5 Fg~(-1)and 108%of specific capacitance retention after 10000 cycles.The BC_(Fe–Ni)assembled symmetrical supercapacitor shows an energy density of 18.3 Wh kg~(-1)at a power density of 350 W kg~(-1).It is expected that the as-prepared N-doped porous carbon derived from bimetallic-organic coordination polymer is a promising electrode material for high performance energy storage devices.     

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.     

铁镍磷化物电极材料的制备及电催化析氢性能

为了解决电解水析氢过程中所用贵金属材料的高昂成本问题,采用水热-低温磷化法制备了一种低廉、环保、高效的析氢催化剂Fe_xNi_1-x-P。与传统制备方法比较,该方法在水热合成前驱体过程中,利用镍盐和铁盐与无水乙醇发生氧化还原反应,生成的OH^-可以沉淀金属离子,随后前驱体与NaH₂PO₂低温磷化制得Fe_xNi_1-x-P。通过研究发现,Fe_0.5Ni_0.5-P电极材料表现出优异的催化活性。在1.0 mol·L^-1 KOH溶液中,电流密度为10 mA·cm^-2时,电极Fe_0.5Ni_0.5-P需要的过电位仅为113 mV,1 000圈循环伏安测试后,极化曲线无明显衰减。提供了一种制备Fe_xNi_1-x-P的简便方法,为开发清洁能源系统的环境友好型催化剂提供了新思路。     

Antilocalization sensing of interactions between two-dimensional electrons and surface species

We apply antilocalization measurements to experimentally study the interactions and exchange between InAs surface accumulation electrons and local magnetic moments of the rare earth ions Sm3?,Gd3?,Ho3?,and Dy3?,of the transition metal ions Ni2?,Co2?,and Fe3?,and of Fe3O4nanoparticles and Fe3?-phthalocyanine deposited on the surface.The influence of the deposited species on the surface electrons is observed through the changes in the spin–orbit scattering and magnetic spin-flip scattering rates,which carry information about magnetic interactions.Experiments indicate a temperature-dependent magnetic spin-flip scattering for Ho3?,Dy3?,Ni2?,and Co2?.Concerning the spin–orbit scattering rate,we observe an increase,except for the cases of Ni2?,Fe3?,Fe3O4nanoparticles and Fe3?-phthalocyanine.We also observe an increase in SO scattering in another system where we study the interactions of Au nanoparticles and ferromagnetic Co0.6Fe0.4nanopillars and an In0.53Ga0.47As quantum well.Experimental results are analyzed and compared to theoretical models.Our method provides a controlled way to probe the quantum properties of two-dimensional electron systems,either on the surface of InAs or in a quantum well.     

Ni~(2+)含量对纳米晶Ni_xZn_(1-x)Fe_2O_4电磁性能的影响

以丙烯酰胺为聚合单体,N,N′-亚甲基双丙烯酰胺为网络剂,通过高分子凝胶法制备了尖晶石型Ni_xZn_(1-x)Fe_zO_4(x=0,0.2,0.5,0.8和1)纳米晶.采用FT-IR,XRD,TEM和波导法对产物进行表征.结果表明,纳米晶Ni_xZn_(1-x)Fe_2O_4红外吸收峰的晶格常数和电磁性能强烈地依赖于Ni~(2+)含量,随着Ni~(2+)含量增加,红外光谱显示金属一氧离子(M-O)化学键的特征吸收峰出现了蓝移,该峰蓝移60 cm~(-1).通过TEM照片可知Ni_xZn_(1-x)Fe_2O_4的平均粒径随x的变化较小,x分别为0,0.5和1时,粒子的平均粒径分别为12,1...     

Synthesis and application of bilayer-surfactant-enveloped Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles: water-based bilayer-surfactant-enveloped ferrofluids

Superparamagnetic carbon-coated Fe₃O₄ nanoparticles with high magnetization (85 emu·g-1) and high crystallinity were synthesized using polyethylene glycol-4000 (PEG (4000)) as a carbon source. Fe₃O₄ water-based bilayer-surfactant-enveloped ferrofluids were subsequently prepared using sodium oleate and PEG (4000) as dispersants. Analyses using X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy indicate that the Fe₃O₄ nanoparticles with a bilayer surfactant coating retain the inverse spinel-type structure and are successfully coated with sodium oleate and PEG (4000). Transmission electron microscopy, vibrating sample magnetometry, and particle-size analysis results indicate that the coated Fe₃O₄ nanoparticles also retain the good saturation magnetization of Fe₃O₄ (79.6 emu·g-1) and that the particle size of the bilayer-surfactant-enveloped Fe₃O₄ nanoparticles is 42.97 nm, which is substantially smaller than that of the unmodified Fe₃O₄ nanoparticles (486.2 nm). UV–vis and zeta-potential analyses reveal that the ferrofluids does not agglomerate for 120 h at a concentration of 4 g·L-1, which indicates that the ferrofluids are highly stable.     

Molecule modification and mass deposition induced by the implantation of low energy Fe+ ion beams into amino acids

Fe⁺ ion beams with the energy of 110 keV were implanted into films of L(+)-cysteine (HSCH₂CH(NH₂)COOH). One of the single crystals grown in hydrochloric acid solution with the implanted samples through slow evaporation was structurally characterized by the X-ray crystallography. The crystal is monoclinic, space group C2, with a = 1.8534(4) nm, b = 0.5234(1) nm, c = 0.7212(1) nm, β= 103.72°, V = 0.67965(3) nm³, Z = 4, F(000) = 144.0, D{clac} = 1.763 g · cm⁻³, μ(MoK _a = 1.06 mm⁻¹, T = 293(2) K. R = 0.0379, wR = 0.0835 for 660 observed reflections (I > 2σ(I)). The structural formula of the crystal compound is (CH₂CH(NH₂)NO₂)ClFe (M _r = 180.38 u). Products of heavy ion beam irradiation were purified and it was directly confirmed that the implanted Fe⁺ ions had been deposited in the novel molecules. The same doses of Fe⁺ ion beams of the same energy were implanted into films of L(+)-cysteine hydrochloride monohydrate. FTIR spectroscopy of the implanted samples proved that some of the original molecules were seriously damaged and significant modifications were induced.     

Preparation of Fe3O4@Au nano-composites by self-assembly technique for immobilization of glucose oxidase

Superparamagnetism amination nanocrystals Fe₃O₄ with 3-aminopropyltriethyloxy silane (APTES) were prepared by modified co-precipitation method. Next, 4-5 nm gold nanoparticles, prepared by classical Frens procedure, were coated on the surface of the amination Fe₃O₄ by self-assembly technology. The prepared Fe₃O₄@Au nanocomposite particles were investigated by transmission electron microscopy (TEM), UV-vis, infrared spectrum (FT-IR), and vibrating sample magnetometer (VSM) in order to elucidate the morphology, optics and magnetic properties of the nanocomposites. Their uniform distribution of particle size, which is about 15 nm, and good magnetic responsiveness were observed. In view of the fact that Fe₃O₄ owns superparamagnetism and that nano-gold can readily combine with biological molecules, glucose oxidase (GO _x ) was chosen as a model to penetrate the condition of immobilizing enzyme, and enzymatic properties of resultant immobilized enzyme were studied as well. By systematic optimization, we established that at 28°C, and pH (5.5) and when mole ratio of Fe₃O₄:HAuCl₄ was 0.5:1, the immobilization provided the best results. Finally, we are glad to find that the immobilized enzyme exhibits excellent thermostability in addition to its better stability than free enzyme. Thus, herein described immobilized enzyme could be used repeatedly with the assistance of an external magnetic field. Supported by the Science Foundation of Sichuan Province, China (Grant No. 2005A033) and Science Foundation of Sichuan Agricultural University for Distinguished Young Teachers (Grant No. 007202)     

纳米Zn1-xCuxO薄膜的结构及光学性质

采用射频磁控溅射制备了不同Cu掺杂浓度的ZnO薄膜．以X射线衍射、扫描电镜等对薄膜的结构和形貌进行了表征,XRD和SEM测试结果显示Cu掺杂量为5．0at．％时,Zno9,Cu0.05O薄膜呈纳米柱状结构．同时也对薄膜的光致发光（PL）进行了研究．结果表明,406nm的发光峰源于带边自由激子电子的复合,440nm的发光峰则和薄膜中的锌间隙Zni缺陷有关．     

Effect of thickness on structures of ultrathin diamond-like carbon films

Diamond-like carbon (DLC) films with different thickness were deposited by filtered cathode vacuum arc (FCVA). Vis-Raman and spectroscopic ellipsometry were employed to analyze the structure of DLC films. The wavelength of Vis-Raman is 514.5 nm. Experimental results show that structures of DLC films are affected by film thicknesses. When the film thickness increases from 2 to 30 nm, the G-peak position (G-pos) shifts to higher wavelength, the intensity ratio I_D/I_G and the extinction coefficient Ks decrease. It is indicated that the content of sp3 bond increases with film thickness. However, when the film thickness increases from 30 nm to 50 nm, I_D/I_G and Ks increase. The content of sp³ bonds decreases with film thickness.     

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.     

Magnetic properties and giant magnetoresistance effect of nanometer Fe−In2O3 granular films

Nanometer ferromagnetic metal-semiconductor matrix Fe−In₂O₃ granular films are fabricated by the radio frequency sputtering. Magnetic properties and the giant magnetoresistance (GMR) effect of Fe_x(In₂O₃)_1−x granular film samples are studied. The result shows that the magnetoresistance (MR) ratio Δρ/ρ ₀ value of the granular film samples with Fe volume fraction x=35% is 4.5% at room temperature. The temperature dependence (T=1.5–300 K) of the MR ratio Δρ/ρ ₀ value of Fe_0.35(In₂O₃)_0.65 granular films shows that Δρ/ρ ₀ value below 10 K increases rapidly with the decrease of the temperature, and when T=2 K, Δρ/ρ ₀ value is 85%. 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 T _p=10 K, the change of the structure in Fe_0.35)In₂O₃)_0.65 granular films results in the transformation of state from ferromagnetic to spin-glass-like. The remarkable increase of the MR ratio Δρ/ρ ₀ value of Fe_0.35(In₂O₃)_0.65 granular films below 10 K seems to arise from the peculiar conducting mechanism of the granular film samples in the spin-glass-like state.