bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improvement of crystallographic characteristics of CoCrTa thin film using double underlayer
Authors: Kim Y.J. , Kong S.H. , Nakagawa S. , Naoe M. , Kim K.H. 
Published: April 2011

ABSTRACTHigh c-axis oriented CoCr-based thin films are expected for ultra-high density recording media in perpendicular magnetic recording system. In order to improve dispersion angle of c-axis of CoCr-based for perpendicular magnetic recording media, we prepared trilayered film with double underlayer using New Facing Targets Sputtering apparatus. The thickness of magnetic layer CoCrTa and double underlayer, such as interlayer Pt, paramagnetic CoCr, underlayer Ti was fixed 50nm and 20nm respectively. In order to prepare the thin film, we fixed argon gas pressure 1mTorr, substrate temperature 250°C and input current 0.5A. The crystallographic characteristics of CoCrTa layer with varying interlayer thickness (0- 20nm) have been investigated. By the result, the CoCrTa trilayered thin film with interlayer Pt showed good c-axis orientation 3.45° and 3.62° at thickness 5nm and 10nm respectively. However, CoCrTa thin film using interlayer paramagnetic CoCr showed 8.28° and 8.62° at thickness 5nm and 10nm respectively.
In-Situ Characterization Of Ultra-Small Magnetic Junctions Made By Electrochemical Techniques
Authors: Sokolov A. , Jennings J.R. , Yang C-S , Redepenning J. , Doudin B. 
Published: April 2011

ABSTRACTElectrochemical impedance spectroscopy is used to characterize the growth of NiO over Ni electrodes. We find a limited increase of thickness and a significant increase of porosity of the oxide as a function of time and anodization potential. Conductance measurements performed on Ni/NiO/Co junctions of 30 nm diameters indicate the presence of a Coulomb blockade at low temperatures and small bias. Tunneling is observed at higher bias. Small magnetoresistance ratios (1%) are found.
Studies on Crystal Structure and Magnetic Scaling Behavior of Perovskite-Like (La1−xPbx)MnO3 System with x = 0 - 0.5
Authors: Huang Ting-Sheng , Chen Chiung-Hsiung , Tai Ming-Fong 
Published: April 2011

ABSTRACTThe magnetic critical behaviors in the perovskite-like (La1−xPbx)MnO3 series with x = 0.0 ∼ 0.5 are studied by means of dc magnetic measurements. All the samples crystallize in the rhombohedral unit cell with a C R 3 space group (a 0.54 nm and c 1.33 nm). The detailed crystallographic parameters of all the samples are obtained by the refinements of the powder x-ray diffraction data using the Rietveld method. The substitution effect of Pb2+ ions on La3+ sites induces a mixed-valence state of Mn3+/Mn4+ and enhances magnetic transition temperature in the (La1−xPbx)MnO3 system. The transition temperature TC increases with the Pb content from 225 K as x = 0 to 355 K as x = 0.5. The canonical spin-glass behaviors in low fields and the scaling behaviors of magnetic physical quantities are clearly observed in all our samples. The values of the related critical exponents and the scaling functions of magnetic data are close to those of the conventional spin glass systems.
Magnetization reversal and magnetic anisotropy of Fe, Ni and Co nanowires in nanoporous alumina membranes
Authors: Kröll M. , Jongh L. J. de , Luis F. , Paulus P. , Schmid G. 
Published: April 2011

ABSTRACTThe magnetization reversal and magnetic anisotropy of Fe, Ni and Co nanowires is studied at low temperatures. All nanowires show a strong shape anisotropy with the easy axis being parallel to the long axis of the wires. Co nanowires additionally show a temperature dependent magnetocrystalline anisotropy along the hexagonal c-axis, which is directed nearly perpendicular to the long axis of the wires, as is confirmed by X-Ray diffraction measurements [1] and reported by Strijkers et al. who performed NMR measurements on samples prepared in a similar way [2]. Therefore, at low temperatures and for large wire diameters a competition between magnetocrystalline and shape anisotropies can be observed. Co wires with a small diameter, however, do not show a significant magnetocrystalline anisotropy. Fcc-Co, which is only known as a high-temperature Co modification and which does not have a large magnetocrystalline anisotropy constant, becomes the predominant Co modification here [1,3]. Investigations on the size dependence of the switching field for Fe and Ni nanowires provide information about the magnetization reversal process, which takes place via a nucleation of small magnetic domains probably at the end of the wires, and subsequent propagation of the domain wall along the wire.
The Role of Disorder in the Magnetic Properties of Mechanically Milled Nanostructured Alloys
Authors: Leslie-Pelecky Diandra L. , Kirkpatrick Elaine M. , Pekarek Tom , Schalek Richard L. , Shand Paul , Williams Deborah S. , Yue Lanping 
Published: April 2011

ABSTRACTMechanical milling provides a unique means of studying the influence of grain size and disorder on the magnetic properties of nanostructured alloys. This paper compares the role of milling in the nanostructure evolution of two ferromagnets – SmCo5 and GdAl2 – and the subsequent impact of nanostructure on magnetic properties and phase transitions. The ferromagnetic properties of SmCo5 are enhanced by short (< 2 hours) milling times, producing up to an eight-fold increase in coercivity and high remanence ratios. The coercivity increase is attributed to defect formation and strain. Additional milling increases the disorder and produces a mix of ferromagnetic and antiferromagnetic interactions that form a magnetically glassy phase. GdAl2, which changes from ferromagnetic in its crystalline form to spin-glass-like in its amorphous form, is a model system for studying the dependence of magnetically glassy behavior on grain size and disorder. Nanostructured GdAl2 with a mean grain size of 8 nm shows a combination of ferromagnetic and magnetically glassy behavior, in contrast to previous studies of nanostructured GdAl2 with a grain size of 20 nm that show only spin-glass-like behavior.
Nanocomposite with Non-Spherical Granules – Logarithmic Field Dependence of Giant Magnetoresistance
Authors: Meilikhov E. , Raquet B. 
Published: April 2011

ABSTRACTMagnetoresistance of the nanocomposite Fex(SiO2)1−x (x≍0.6) at high enough magnetic field is logarithmic function of the magnetic field. Such a dependence does not fall into the known theory of giant magnetoresistance of ferromagnetic nanocomposites. This paper examines the giant magnetoresistance of such a system in terms of a simple model where the non-ordinary quasi-logarithmic magnetic field dependence of nanocomposite magnetoresistance is related to the non-spherical granules' distribution over their shapes.
Tailoring of Magnetic Properties of Glass coated Microwires
Authors: Zhukov A.P. , González J. , Zhukova V. , Blanco J.M. 
Published: April 2011

ABSTRACTThe magnetic behaviour of the glass-covered metallic microwires with a wide compositional range of composition with soft and hard magnetic character is presented. The effect of conventional furnace and dc current annealing under dc axial magnetic field or without it as well as of a chemical etching on the magnetic properties of Co and Fe-based glass coated microwires has been studied. Such treatments modify the magnetic parameters. In particular, annealing under applied magnetic field (field annealing) can improve significantly such magnetic parameters as permeability. Such phenomenology can be interpreted considering the noticeable magnetic anisotropy induced by the combined effects of the magnetic field and strong internal stresses arising from the coating. Giant magnetoimpedance (GMI) effect was observed in nearly-zero magnetostrictive amorphous microwires. Upon careful heat treatment, FeCuNbSiB amorphous microwires devitrificate into nanocrystalline structure with large variety of magnetic parameters. Hard magnetic materials with coercivity up to 800 Oe were obtained as a result of decomposition of metastable phases in Co-Ni-Cu microwires as well as after crystallization process of FeCuNbSiB amorphous microwires.
X-ray Magnetic Linear Dichroism of Fe-Ni Alloys on Cu(111)
Authors: Johnson T.F. , Chiang S. , Sato Y. , Arena D.A. , Morton S.A. , Hochstrasser M. , Tobin J.G. , Shine J.D. , Giacomo J.A. , Thayer G.E. , Land D.P. , Zhu X.D. 
Published: April 2011

ABSTRACTWe have prepared FexNi1−x multilayers on Cu(111) in order to learn how to control the structure and magnetism of these thin alloy films, which are relevant to the giant magnetoresistance (GMR) effect used in magnetic disk drive heads. Using the Spectromicroscopy Facility (7.0.1.2) on Undulator Beamline 7.0 at the Advanced Light Source, we have measured X-ray magnetic linear dichroism (XMLD) signals from both Fe and Ni 3p lines for fourteen different thin Ni-Fe alloy films on Cu(111), with Fe concentration ranging from 9% to 84% and for a variety of film thicknesses. The Curie temperature for all of these samples was in the range 200K to 500K. For many of these films, the Curie temperature was considerably lower than was previously seen for similar films deposited on Cu(100). For a particular Fe concentration x, the Curie temperature increases with alloy film thickness. For a specific film thickness, the Curie temperature has a maximum near x≍0.4.
Effect of scattering noise on the data fidelity of holograms recorded in photorefractive crystals
Authors: Qin Mingyan , Tao Shiquan , Liu Guoqing , Ding Xiaohong , Wang Dayong 
Published: April 2011

ABSTRACTIn this paper a method is proposed to investigate how the scattering noise of photorefractive crystals influences the quality of an input data page in holographic storage. By illuminating the crystal under investigation with an intense coherent light beam, and measuring the signal-to-noise ratio (SNR) of an image formed through the crystal before and after the exposure, the loss of SNR provides a good assessment for the suitability of the crystal for data storage. A variety of doped lithium niobate crystals were investigated. The results show that the intensity of fanning light increases with increase of the doping concentration, but there is no strict correlation between the fanning strength and the fidelity degradation. Owing to the low noise and high data fidelity, iron-and- zinc co-doped lithium niobate crystal is a potential material for high-density holographic data storage.
Synthesis of Ultrathin Ta-C Films by Twist-Filtered Cathodic Arc Carbon Plasmas
Authors: Anders André , Kulkarni Ashok V. 
Published: April 2011

ABSTRACTThe application of cathodic-arc-deposited films has been very slow due to the infamous macroparticle problem. We report about the application of the open Twist Filter as the key component to an advanced filtered cathodic arc system. Ultrathin tetrahedral amorphous carbon (ta-C) films have been deposited on 6 inch wafers. Film propertieshave been investigated with respect to application in the magnetic data storage industry. Films can be deposited in a reproducible manner where film thickness control relies on arc pulse counting once deposition rates have been calibrated. Films of 3 nm thickness have been deposited that passed acid and Battelle corrosion tests. Monte Carlo Simulation of energetic carbon deposition shows the formation of an intermixed transition layer of about 1 nm. The simulation indicates that because the displacement energy of carbon isnot smaller than of magnetic materials, films thinner than 2 nm are either not high in sp3 content or represent a carbidic phase.
Elastic Constants of Nanometer Thick Diamond-like Carbon Films
Authors: Beghi Marco G. , Bottani Carlo E. , LiBassi Andrea , Pastorelli Rosanna , Tanner Brian K. , Ferrari Andrea C. , Robertson John 
Published: April 2011

ABSTRACTCarbon films of thickness down to 2 nanometers are necessary to achieve a storage density of 100 Gbit/in2 in magnetic hard disks. Reliable methods to measure the properties of these ultrathin films still have to be developed. We show for the first time that combining Surface Brillouin Scattering (SBS) and X-ray reflectivity measurements the elastic constants of such films can be obtained. Tetrahedral amorphous carbon films were deposited on silicon, by an S bend filtered cathodic vacuum arc, which provides a continuous coverage on large areas free of macroparticles. Films of thickness down to 2 nm and density of ∼3 g/cm3 were produced and characterized. The dispersion relations of surface acoustic waves are measured by SBS for films of different thickness and for the bare substrate. Waves can be described by a continuum elastic model. Fitting of the dispersion relations, computed for given film properties, to the measured dispersion relations allows the derivation of the elastic constants. Fora 8 nm thick film we find a Young's modulus E around 400 GPa, with a shear modulus G lying in the 130 – 210 GPa interval. For a 4.5 nm thick film, E is around 240 GPa, with G lying in the 70 – 130 GPa interval. Results for even thinner films become highly sensitive to the precision of the substrate properties, and indicate that the above values are lower bounds. We thus show that we can grow and characterize nanometer size tetrahedral amorphous carbon films, which maintain their density and mechanical properties down to the nm range.
Comparison of CPM, PDS and Optical Transmittance of Amorphous Carbon Nitride Films Made by a Nitrogen Radical Sputter Method
Authors: Katsuno Takashi , Nitta Shoji , Habuchi Hitoe 
Published: April 2011

ABSTRACTAmorphous carbon nitride films a-CNX, deposited in our laboratory by a radical sputter method, show high photosensitivity PS, where PS is the ratio of photoconductivity sP and dark-electrical conductivity sd. A-CNX made a layer-by-layer method, LLa-CNX, has the highest photosensitivity in our various preparation conditions. The photoconductivity in a-CNX and LLa-CNX shows dependence on photon energy in the range 2 eV to 6.2 eV. The constant photocurrent method (CPM), photothermal deflection spectroscopy (PDS) and optical transmittance spectra are used to obtain the information in the optical energy band gap and defect states. A-CNX and LLa-CNX are good photoconductors especially at energy higher than 3 eV. Therefore it is not difficult to obtain CPM spectra in the high photon energy region. CPM spectra are obtained by dc- and ac- measurements. The value of the absorption coefficient a spectra obtained by dc-CPM is larger than that of ac-CPM, which increases with increasing frequency of the measurement. In this paper, CPM data is used to discuss a model of density of states (DOS) of a-CNX by comparison with PDS and optical transmittance spectra.
Nanodevice fabrication on hydrogenated diamond surface using atomic force microscope
Authors: Tachiki Minoru , Fukuda Tohru , Seo Hokuto , Sugata Kenta , Banno Tokishige , Umezawa Hitoshi , Kawarada Hiroshi 
Published: April 2011

ABSTRACTNanofabrication on a hydrogen-terminated diamond surface is performed usingan atomic force microscope (AFM) anodization. Locally insulated areas less than 30 nm aresuccessfully obtained. Side-gated field effect transistors (FETs) are fabricated using the local anodization, and they operate successfully. Single hole transistors composed ofone side-gated FET and two tunneling junctions are also fabricated and operate at liquid nitrogen temperature (77 K).
Designability of Graphitic Cones
Authors: Treacy M. M. J. , Kilian J. 
Published: April 2011

ABSTRACTWe show that, with topologically flexible seeds which are allowed to explore different growth modes, graphitic cones are inherently more “designable” than flat graphitic disks. The designability of a structure is the number of seed topologies encoding that structure.We illustrate designability with a simple model, where graphite grows onto Cn (5≤n≤30) ring seeds. For a wide range of ring sizes, cones are the most likely topological outcome. Results from the model agree well with data from special cone-rich carbon black samples.The concept of designability allows entropy to be incorporated into the “pentagon road” model of the formation of curved graphitic structures.
Nano-Sized [60]Fullerene-Cyclodextrin Molecules
Authors: Park Jeong-Seo , Kang Han-Chang , Geckeler Kurt E. 
Published: April 2011

ABSTRACTAs [60]fullerene is a very hydrophobic macromolecule, there have been a number of attempts to make it more hydrophilic for biomedical applications. By attaching hydrophilic moieties such as poly(oxyethylene)(POE) chains and cyclodextrin molecules to [60]fullerene, novel water-soluble and biocompatible materials have been successfully prepared [1,2].The synthesis of novel macrocyclic fullerene conjugates which are water-soluble is reported. The telechelic fullerene derivatives have been prepared via addition reaction of POE-based arms with covalently bonded β-cyclodextrin (CD) to [60]fullerene. To this end, a mono-tosylated CD derivative has been prepared in pyridine and then reacted with an amino-functional POE in the presence of triethylamine. The subsequent reaction of [60]fullerene with the hydrophilic POE-conjugated CD-derivative yielded the macrofullerene after separation and purification procedures.The macrocyclic [60]fullerene derivatives obtained were soluble in water and characterized by UV-VIS and FT-IR spectroscopy as well as light scattering measurements and thermogravimetric analysis.
Ab Initio Study of Si Doped Carbon Nanotubes: Electronic and Structural Properties
Authors: Fazzio A. , Baierle R. J. , Fagan Solange B. , Mota Ronaldo , da Silva Antônio J. R. 
Published: April 2011

ABSTRACTWe report the electronic and structural properties of silicon doped carbon nanotubes using first principles calculations based on the density-functional theory. In the doped metallic nanotube a resonant state appears about 0.7 eV above the Fermi level and for the semiconductor tube the Si introduces an empty level at approximately 0.6 eV above the top of the valence band.
Surface Patterns by Solvent Evaporation of Colloidal Zeolite Suspension
Authors: Wang Huanting , Wang Zhengbao , Huang Limin , Mitra Anupam , Yan Yushan 
Published: April 2011

ABSTRACTSurface patterns of porous zeolite structures such as knotted-rope web and wrinkled honeycomb were obtained by dynamic self-assembly of zeolite nanoparticles during solvent evaporation of colloidal zeolite suspension. The study shows that extra ethanol in zeolite synthesis solution is crucial for pattern formation. The addition of ethanol helps produce zeolite nanoparticles with a specific range of particle size during the hydrothermal synthesis. It also provides uniform dynamic driving force for pattern formation during its preferential evaporation. In addition, surface patterns vary with suspension compositions. The patterned zeolite structures have a well-defined bimodal pore size distribution (i.e., 0.55 nm and 2.6 nm) with high BET surface area of 680∼750m2&/g.
A Novel Low Temperature Synthesis Method for Semiconductor Nanowires
Authors: Sharma Shashank , Sunkara Mahendra K. , Miranda Raul , Lian Guoda , Dickey Elizabeth C. 
Published: April 2011

ABSTRACTWe present a novel synthesis technique to grow bulk quantities of semiconductor nanowires at temperatures less than 500 °C. Gallium is used as the liquid medium in a mechanism similar to vapor-liquid-solid (VLS). We demonstrated this low temperature technique with silicon and carbon nanowires. Gallium exhibits extremely low solubility for several elemental semiconductors. This property enables nucleation and growth of nanometer scale wires from large sized gallium droplets (>1 μm) eliminating the need for creation of quantum sized metal droplets.
Eu3+-Doped Y2O3-SiO2 Nanocomposite Obtained by a Sol-Gel Method
Authors: Cannas Carla , Casu Mariano , Licheri Roberta , Musinu Anna , Piccaluga Giorgio , Speghini Adolfo , Bettinelli Marco 
Published: April 2011

ABSTRACTA Y2O3-SiO2 nanocomposite doped with Eu3+ was obtained by a sol-gel method and characterized by X-ray diffraction, IR, 29Si NMR and laser-excited luminescence spectroscopy. It was found that small (2-3 nm) yttria nanoparticles are homogeneously dispersed in, and interacting with, the amorphous silica matrix. Luminescence spectroscopy indicates that the Eu3+ ion is preferentially located inside or at the surface of highly disordered Y2O3 nanoparticles. These luminescent nanocomposites form a class of materials which could find applications in the field of phosphors.
Ultrasound-Enhanced Spray Drying of Polymer Micro-emulsions for Nanoparticles Synthesis
Authors: Tsai Shirley C. , Chen C. Y. , Song Y. L. , Tsai C. S. , Tsai H. S. , Chiu W. Y. 
Published: April 2011

ABSTRACTIn this paper we report the experimental results that polymer micro-emulsions (up to 10 wt%) behave like Newtonian liquids in ultrasound-modulated two-fluid (UMTF) atomization. Specifically, the emulsion drops generated are much smaller and more narrowly sized than those generated in conventional ultrasonic atomization (without air). After spray drying, the PMMA emulsion drops yield uniform nanoparticles that were originally dispersed in the micro-emulsion. Contrary to the conventional view that viscoelastic liquids are more difficult to atomize than Newtonian liquids, we found that ultrasound enhanced atomization of viscoelastic liquids such as gel-forming xanthan gum solutions. Under similar aerodynamic conditions using UMTF atomization at 54 kHz, 40-μm-diameter uniform drops were obtained for Xan solutions, but not for Newtonian aqueous glycerol of same viscosity.
Magnetic Properties of Co Nanoparticles in an AlMCM41 Mesoporous Host
Authors: Jung Jin-Seung , Kim Jun-Yong , Chae Weon-Sik , Kim Yong-Rok , Jun Jong-Ho , Malkinski Leszek , Zhou Weilie , Kumbhar Amar , Viciu Marilena L. , Wiley John B. , O'Connor Charles J. 
Published: April 2011

ABSTRACTUltrafine cobalt particles in AlMCM41 silica tubes have been synthesized by ion exchange and the reduction with sodium borohydride. The role of this stable host matrix of AlMCM41 silica is to prevent agglomeration of the magnetic particles attached to the walls of AlMCM41 silica pores. The size of the host pores naturally limits the particle dimensions and thus improves their size distribution. Both magnetic susceptibility measurements and transmission electron microscopy (TEM) show a narrow distribution size of the nanoparticles. Well controlled insertion of the magnetic material to the host channel excludes formation of bulk particles outside the host material grains, which was confirmed by the TEM studies. X-ray diffraction data did not show peaks corresponding to a crystalline cobalt, but this maybe due to small size of particles and their relatively small volume fraction. The content of Co in the AlMCM41 host was measured using both magnetic measurements and elemental analysis.
Applications of ZnS:Mn2+ nanocrystals
Authors: Suyver J. F. , Meijerink A. , Kelly J. J. 
Published: April 2011

ABSTRACTNonstoichiometric precursor-ratios for the synthesis of ZnS:Mn2+ are discussed and the significant influence on the luminescence features and crystal size is explained. From the temperature quenching of the ZnS photoluminescence a luminescence excitation model is proposed. Measurements of the photoelectrochemical properties of nanocrystalline ZnS electrodes doped with Mn2+ are also presented and discussed. The observation of both anodic and cathodic photocurrent is direct evidence for the nanocrystalline nature of the system. In-situ photoluminescence measurements showed stable Mn2+ related photoluminescence over a large potential range.