bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cluster-Assembled Iron-Platinum Nanocomposite Permanent Magnets
Authors: Rui Xiangxin , Sun Zhiguang , Xu Yingfan , Sellmyer David J. , Shield Jeffrey E. 
Published: April 2011

ABSTRACTExchange-spring nanocomposite permanent magnets have received a great deal of attention for their potential for improved the energy products. Predicted results, however, has been elusive. Optimal properties rely on a uniformly fine nanostructure. Particularly, the soft magnetic phase must be below approximately 10 nm to ensure complete exchange coupling. Inert gas condensation (IGC) is an ideal processing route to produce sub-10 nm clusters method. Two distinct nanostructures have been produced. In the first, Fe clusters were embedded in an FePt matrix by alternate deposition from two sources. Fe cluster content ranged from 0 to 30 volume percent. Post-deposition multi-step heat treatments converted the FePt from the A1 to L10 structure. An energy product of approximately 21 MGOe was achieved. Properties deteriorated rapidly at cluster concentrations above 14 volume due to uncoupled soft magnetic regions (from cluster-cluster contacts) and cooperative reversal. The second nanostructure, designed to overcome those disadvantages, involved intra-cluster structuring. Here, Fe-rich Fe-Pt clusters separated by C or SiO2 were fabricated. Phase separation into Fe3Pt and FePt and ordering was induced during post-deposition multi-step heat treatments. By confining the soft and hard phases to individual clusters, full exchange coupling was accomplished and cooperative reversal between clusters was effectively eliminated. An energy product of more than 25 MGOe was achieved, and the volume fraction of the soft phase was increased to greater than 0.5 while maintaining a coercivity of 6.5 kOe. The results provide new insight into developing high energy product nanostructured permanent magnets.
Magnetic Anisotropy and Magnetocaloric Effect (MCE) in NiFe2O4 Nanoparticles
Authors: Gass J. , Frey N. A. , Morales M. B. , Miner M. J. , Srinath S. , Srikanth H. 
Published: April 2011

ABSTRACTMagnetic refrigeration based on the magnetocaloric effect (MCE) has been proposed as an attractive alternative to gas compression technology. Some calculations suggest that MCE can be obtained with higher efficiencies than compressor driven refrigeration. We examine the MCE in a system of nickel ferrite nanoparticles with size range of 6 to 15 nm. A peak in the MCE at 55 K is observed that increases with higher magnetic fields. This gives this system a relatively high peak entropy change compared to other ferrite systems. A sensitive radio-frequency (RF) transverse susceptibility measurement has also been used to study the magnetic anisotropy. We show that the MCE peak is not associated with the blocking temperature and is likely a field-driven surface spin reorientation which also has a signature in the transverse susceptibility. Work supported by NSF-CTS-0408933 and ARO- W911NF-05-1-0354
Synthesis and Magnetic Properties of Co Nanorod Superlattices
Authors: Wetz Fabienne , Soulantica Katerina , Respaud Marc , Falqui Andrea , Chaudret Bruno 
Published: April 2011

ABSTRACTWe present the synthesis and magnetic properties of Co nanorods spontaneously organized in superlattices over a surface of several microns. This material results from the thermal decomposition of a cobalt precursor under hydrogen, in the presence of a long-chain amine and a long-chain acid as shape control agents. These nanorod superlattices are ferromagnetic at room temperature and they are characterized by a strong coercive field as a consequence of their large magnetic anisotropy. This system can be considered as a good candidate for high density magnetic recording.
Interface Morphology of Metallic Multilayers by Means of Deposition Simulation
Authors: Shintani Kazuhito , Kometani Y. , Nakajima T. , Yano Y. 
Published: April 2011

ABSTRACTGrowth of a Co/Cu/Co multilayer is investigated by molecular-dynamics simulation. The interactions between Co and Cu atoms are calculated in terms of the generic-embedded atom method potential. It is confirmed that two-dimensional island growth of Cu atoms on the Co substrate occurs in the simulations. The roughnesses of the surface and the interface are evaluated by means of the standard deviations of the heights of the surface and interface atoms. Intermixing atoms between the layers are also counted. We conclude that there exists an optimum combination of the incident energies of deposited Cu and Co atoms which minimizes both the roughness and intermixing of the interface.
Characterization of Microstructure and Composition of Fe-B Nanobars as Biosensor Platform
Authors: Li Suiqiong , Fu Liling , Wang Chongmin , Lea Scott , Arey Bruce , Engelhard Mark , Cheng Z.-Y. 
Published: April 2011

ABSTRACTIndividual magnetostrictive nanobars and arrays comprised of magnetostrictive nanobars were recently introduced as a high performance biosensor platform. In this paper, we report the fabrication and characterization of magnetostrictive nanobars based on Fe-B alloy. The nanobars were synthesized using a template-based electrochemical deposition method. The composition and microstructure of the Fe-B nanobars are directly related to their performance as a biosensor platform. The Fe-B nanobar arrays and individual nanobar were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), as well as Auger electron spectroscopy (AES). Morphologically, nanobars have a very flat top and a smooth cylindrical surface, which are critical factors for obtaining high performance as sensor platforms. Structurally, electron diffraction reveals that the Fe-B nanobars are amorphous. AES analysis indicates that Fe-B nanobars show no significant compositional variation along the length direction. It is found that the nanobars were covered by an oxidation layer of a typical thickness of ∼ 10 nm. It is believed that this oxidation layer is related to the passivation of nanobars in air. High temperature annealing and subsequent structural analysis indicate that the Fe-B nanobars possess a good thermal stability.
Magnetic and Ferroelectric Properties of YMnO3 Epitaxial Thin Films
Authors: Maeda Kazuhiro , Yshimura Takeshi , Fujimura Norifumi 
Published: April 2011

ABSTRACTYMnO3, which is one of hexagonal RMnO3 compounds, has antiferromagnetic and ferroelectric properties, simultaneously. Recently, it has been reported that cross-correlation in the magnetic dielectric properties on hexagonal YMnO3 single crystals. However, the cross-correlation in the magnetic-ferroelectric properties has not been understood yet. In this study, we investigated the cross correlation between magnetism and ferroelectricity on YMnO3 epitaxial films with excellent crystallinity. YMnO3 epitaxial films were deposited pulsed laser deposition. The YMnO3 epitaxial films show the dielectric anomalies at around Néel point of the films. It was suggested that the ferroelectric domain switching was suppressed by the magnetic ordering. The relationship between the magnetic structure and the ferroelectric properties are discussed in terms of the temperature dependences of magnetization and dielectric permittivity. Moreover, the ablation plume of YMnO3 was investigated by optical emission spectroscopy. The effect of the ablation conditions on the thin film growth and electrical properties was discussed.
Magnetoelectric Properties of Multiferroic Composites with Pseudo 1-3 Type Structure
Authors: Shi Zhan , Nan Ce-Wen , Zhang Jie , Ma Jing , Li JingFeng 
Published: April 2011

ABSTRACTA pseudo 1-3 type multiferroic composite consisting of Pb(Zr,Ti)O3 (PZT) rod array (with base) and Terfenol-D/Epoxy matrix was prepared by the dice-and-fill technique. Simple series and parallel mixture rules well described the measured dielectric and piezoelectric constants. Large magnetoelectric coefficients were observed in the pseudo 1-3 type composite, e.g., over 300 mV/cmi×Oe below 40 kHz and over 4500 mV/ cm×Oe at resonant frequency. The ME response strongly depends on the magnetostrictive behavior of the matrix and the volume fraction of PZT rods, which gives us two convenient way to modify their magnetoelectric response. For this pseudo 1-3 type multiferroic composite, the remarkable magnetoelectric response and well-developed fabrication technique are advantageous for their practical applications in piezoelectric-magnetoelectric multifunctional devices and large bandwidth magnetic sensors.
Theory of Spin-charge-orbital States in the Frustrated System RFe2O4
Authors: Ishihara Sumio , Naka Makoto , Nagano Aya 
Published: April 2011

ABSTRACTElectronic structure in multiferroic compound RFe2O4. is studied theoretically. We suggest that orbital degree of freedom in a Fe2+ ion is active. The effective Hamiltonian for spin, charge and orbital degrees of freedom is derived. Numerical analyses with the multi-canonical Monte-Carlo simulation show that the electric polarization is attributed to the charge order with momentum (1/3, 1/3). A magnitude of the polarization is enhanced around the magnetic ordering temperature due to the coupling between spin and charge. Conventional orbital order is not expected from the numerical calculation. We discuss possible orbital state at low temperatures.
Thermal Stability of Defects in Substrates for Multiferroic Materials
Authors: Jeddy Shehnaz , Zvanut Mary Ellen , Lassiter Brian Einstein , Janowski Gregg M , Brillson Leonard J 
Published: April 2011

ABSTRACTStrontium Titanate (STO) substrates were studied by electron paramagnetic resonance (EPR) spectroscopy to assess possible changes incurred by deposition of multiferroic thin films. To this effect, STO was vacuum annealed at pressures of 10−5 Torr for one hour at temperatures in the range of 200 – 500 °C. EPR spectra, measured before and after each anneal, revealed changes in the amount of three different defects, Cr3+, Fe3+ and an iron-oxygen vacancy complex, Fe3+Vo. The latter was used to monitor the diffusion of oxygen. EPR analysis showed that Fe3+Vo increases from its as-grown value, suggesting that a charged oxygen species is mobile in the substrate under film deposition conditions. Coupled with a subsequent O2 anneal showing minimal change in the Fe3+Vo signal, the data indicate a loss of oxygen from the sample during vacuum annealing. As charged oxygen vacancies may affect the substrate as well as the substrate/ thin film interface, these results are important for understanding the behavior of multiferroic devices built on STO substrates.
Epitaxial Growth of SrTiO3 Thin Films on TiN/Si Substrates Using RF Sputtering
Authors: Wang Chun , Kryder Mark H 
Published: April 2011

ABSTRACTEpitaxial SrTiO3 (001) thin films with a TiN template layer have been deposited on Si(001) single crystal substrates by RF sputtering. The deposited SrTiO3 films show a surface with roughness of 0.66nm. The orientation relationship was determined to be SrTiO3(001)[110]∥TiN(001)[110]∥Si(001)[110]. The microstructure and interface of the multilayer was studied using high resolution transmission electron microscopy (TEM). The electron diffraction pattern confirmed the epitaxial relationship between each layer.
Luminescence and Raman Based Real Time Imaging of Ferroelectric Domain Walls
Authors: Dierolf Volkmar , Capek Pavel , Sandmann Christian 
Published: April 2011

ABSTRACTWe studied ferroelectric domain wall regions in lithium niobate using the photoluminescence of intentionally doped rare earth ions (such as Er3+) as well as Raman spectroscopy and present an overview of the current status of our ongoing investigations. We find that the Er emission is a sensitive tool to observe changes in local electric fields as well as reconfiguration of defect dipoles across the domain wall. The Raman spectra, on the other hand can be used to identify charges that accumulate asymmetrically across a domain wall. We further demonstrate that the imaging methods offer sufficient sensitivity to observe the changes associated with a domain in real time while it is moving.
Magneto-Optical Kerr Effect in Multiferroic Nanostructures
Authors: Corbo Matthew T. , Straub Florian , Zheng Haimei , de la Paz Cruz Maria , Suzuki Yuri 
Published: April 2011

ABSTRACTWe report the study of the magneto-optical properties of composite multiferroic thin films composed of CoFe2O4 nanopillars embedded in a BiFeO3 matrix. The magneto-optical Kerr rotation and Kerr ellipticity in these films have been measured and are in good agreement with magnetization measurements. The Kerr signal has been studied as a function of film composition and nanopillar diameter confirming that the magneto-optical signal is due solely to the CoFe2O4 nanopillars.
Surface Reactions of Metal Catalysts for Carbon Nanotubes on an Oxide Thin Layer/Si Substrates Studied by in-situ Micro X-ray Adsorption Spectroscopy using SPELEEM
Authors: Maeda Fumihiko , Hibino Hiroki , Suzuki Satoru , Guo FangZhun , Watanabe Yoshio 
Published: April 2011

ABSTRACTTo clarify the reaction process of Co and Fe with a oxide layer on Si substrates, the annealing processes were analyzed using spectroscopic photoemission and low-energy electron microscopy for a special surface where oxide areas and clean substrate areas (voids) coexist closely in a micrometer-order view. From analyses of XAS spectra and edge jump ratios obtained from the photoemission electron microscopy image, we clarified that Co atoms in the void area remain because of the formation of silicides, but that those on the oxide layer disappear because metallic Co atoms easily diffuse. In contrast, in the case of Fe, we found the formation of various silicides and their gradual diffusion into Si substrate even in the form of silicides.
Thermodynamics and Kinetics of Oxidation of Pure Indium Solders
Authors: Schoeller Harry , Kim Jongman , Park Seungbae , Cho Junghyun 
Published: April 2011

ABSTRACTMicroElectroMechanical System (MEMS) devices often require low-temperature, fluxless soldering techniques due to their high temperature sensitivity and performance requirements of the components. While seeking the development of a soldering technology using pure indium, the major focus of this study is to assess the thermodynamics and kinetics of indium oxidation at various solder reflow environments that will ultimately provide a processing window for solder reflow and surface oxide cleaning. With a glove box employed to generate reducing environments, oxygen, moisture, and hydrogen contents were varied to examine their effects on oxidation and reduction behavior of indium. We also explored oxidation mechanisms at different regimes of temperature and time. In particular, electron transport from indium to indium oxide is shown to be the rate controlling mechanism under specific oxidizing conditions. For accurate thickness measurements, a spectroscopic ellipsometer was employed. In addition, the effect of indium oxidation on solder joint reliability was observed via wetting angle and interfacial shear strength measurements.
Mechanical Property Measurement of Interconnect Materials by Magnetostrictive Sensors
Authors: Liang Cai , Mathison Leslie , Prorok Barton C. 
Published: April 2011

ABSTRACTThis paper reports on the measurement of elastic modulus for some electronic thin film materials used in electronic interconnects by a magnetostrictive sensor. Thin film materials of Au, Sn, In and Au-rich lead free solder (AuSn) were sputter deposited onto well defined strips of Metglas™. This material possesses magnetostrictive properties whereby it deforms when subjected by a magnetic field and generates a magnetic field when deformed. The MetglasTM strip is driven to resonance via a modulated magnetic field generated by a coil. The elastic modulus of the above materials was determined by measuring the resonant frequency of the sensors before and after film deposition and using the frequency shift, two analytical approaches were employed to extract values. The as sputtered films were examined by X-ray Diffraction (XRD) and Scanning Election Microscope (SEM) to characterize their microstructures. The elastic modulus of Au films was determined by employing two mathematical methodologies that resulted in values of 71.2GPa and 75.9GPa, which exhibit less than 5% divergence. Errors in the different measuring methodologies are discussed. Moreover, elastic modulus values of solder materials of AuSn (80/20 wt%), tin and indium films, which were also measured in their as deposited forms, will be discussed. This method represents a potentially new, non-destructive method to determine critical material properties of as deposited materials.
Evaluation of Void Formation Mechanism in Cu Thin Films; Separation of The Effect of Electron Wind Force and Stress
Authors: Fujii Yousuke , Tsutsumi Masanori , Inoue Junya , Koseki Toshihiko 
Published: April 2011

ABSTRACTElectromigration (EM) and stress-induced voiding (SIV) in Cu and Cu alloys thin films were studied separately. The characterization of EM was evaluated in a modified interconnect structure where the effect of current density can be observed in the absence of stress disturbance. SIV, on the other hand, is examined in detail by applying a uniform stress to Cu films without electric current. Results of EM tests clearly showed that void and hillock formations were concentrated mainly in the region with high current density gradient without stress disturbance. SIV test performed under the high stress of 1GPa showed that voids were observed to form at grain boundaries and grain boundary triple junctions. Under the high stress, SIV is shown to be generated in the absence of stress gradient. Also, the effect of alloying to EM and SIV was investigated in detail.
Well-Aligned In-situ Formed Open-End Carbon Nanotube for Device and Assembly Applications
Authors: Zhu Lingbo , Wong ChingPing 
Published: April 2011

ABSTRACTCarbon nanotubes (CNTs) have been proposed for applications in microelectronic applications, especially for electrical interconnects, thermal management, and nanodevices, due to their excellent electrical, thermal, and mechanical properties. In this paper, we reported a simple process to achieve simultaneous CNT growth and opening of the CNT ends, while keeping alignment of the original CNT films/arrays. The addition of relatively low reactivity oxidizing agents (water) into the reaction furnace enables the feasibility. We proposed using novel CNT transfer technology, enabled by open-ended CNTs, to circumvent the high carbon nanotube (CNT) growth temperature and poor adhesion with the substrates that currently plague CNT implementation. The process is featured with separation of high-temperature CNT growth and low-temperature CNT device assembly. Field emission testing of the as-assembled CNT devices is in a good agreement with the Fowler-Nordheim (FN) equation, with a field enhancement factor of 4540.
A Patch-Type Flexible Physiological Monitor on a Non-Woven Material
Authors: Chang Wen-Yang , Chang Jin-Sheng , Chu Chun-Hsun , Ho Tzong-Che , Lin Yu-Cheng 
Published: April 2011

AbstractThe study reported is about an integrated wireless physiological monitor module of the flexible patch type, used on a non-woven material to package this module by a hot press process. The module can monitor the body temperature and heart rate. Experimental results showed that the specification and accuracy should be 25-40 °C ± 0.5 °C and 50-200 bpm ± 2 bpm. The main advantage of the module is that the postural change can be monitored. At the same time, it has also a good adhesion between substrate and components, without crack of conductor trace line after bending the module repeatedly. Thickness is about 2 mm. The aim of this study is to speed up the physiological technology and to create more efficiency by miniaturization. In addition, the acceptance level of wearing it is increased by the small and ergonomic design.
Tailoring Magnetic Microspheres with Controlled Porosity
Authors: Toprak Muhammet S , McKenna Brandon J , Waite Herb , Stucky Galen D 
Published: April 2011

AbstractThe synthesis of organic and inorganic nano- and microspheres has attracted much interest for a variety of applications ranging from drug delivery to chemical storage and catalysis. We recently demonstrated the assembly of magnetic nanoparticles and polycations into hybrid microspheres in a single-step synthesis via complex coacervation. These microspheres showed viability for bio-applications as indicated by toxicity tests, and are therefore potential targeted drug delivery devices, as they can be directed magnetically. This work reports the recent progress on the potential use of these assemblies in drug release by controlling their porosity. Fluorescein tagged dextran molecules with different MW have been infiltrated into these entities to determine critical pore size by confocal fluorescence microscopy. Different physicochemical characterization results are also presented.
Development of Structure-Property Relationships in Disordered Zirconia Thin Films for High Energy Density Mim Capacitors
Authors: Sethi Guneet , Lanagan Michael T. , Furman Eugene , Horn Mark W. 
Published: April 2011

AbstractAmorphous zirconium oxide thin films were prepared by reactive magnetron sputtering. The dielectric films were characterized by impedance spectroscopy with temperature. The effect of annealing on capacitor performance was studied. Annealing gold electroded thin films at 250°C greatly reduced the losses with little changes in crystallinity. Space charge relaxation started to appear at 190°C. The activation energy for the relaxation was 0.84 eV with a very low relaxation frequency at room temperature (0.23μHz). Electrode effects dominated at very low frequencies at all temperatures. AC conductivity followed the universality behavior for the AC charge transport showing that the films are highly disordered. No DC conductivity regime was observed indicating that DC conductivity is very low. DC conductivity of the films was of the order of 10−13 S/m, which is lesser than the comparable thickness high quality gate oxides.
Studies on Curvature Deformation Control of Bilayer Cantilever Fabricated by Surface Micromachining of SOI Wafer
Authors: Huang Yu-Ming , Sohgawa Masayuki , Noda Minoru , Yamashita Kaoru , Okuyama Masanori , Noma Haruo 
Published: April 2011

AbstractThe Cr/Si bilayer cantilevers for an integrated multi-axis tactile sensor were fabricated by Si surface micromachining process. Among the cantilevers with various shapes, the rectangular and semicircular cantilevers can be deflected upward with good controllability. The maximum deflections are compared with those calculated by finite element method. Calculated deflections of Cr/Si cantilever agree considerably with the measured one. So, it is considered that the analysis by finite element method is useful as optimization of layer thickness and size to obtain the Cr/Si bilayer cantilevers with accurate deflection.
BCB Based Packaging for Low Actuation Voltage RF MEMS Devices
Authors: Peyrou David , PENNEC Fabienne , Achkar Hikmat , PONS Patrick , Coccetti Fabio , Aubert Hervé , Plana Robert 
Published: April 2011

AbstractThis paper outlines the issues related to RF MEMS packaging and low actuation voltage. It is presented an original approach concerning the modeling of the capacitive contact using multi-physics simulation and advanced characterization. A similar approach is used concerning the packaging development where multi-physic simulations are used to optimize the process. A devoted package architecture is proposed featuring very low loss at microwave range.