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Sample records for nanostructured cu4o1624 magnetic

  1. Advanced Magnetic Nanostructures

    CERN Document Server

    Sellmyer, David

    2006-01-01

    Advanced Magnetic Nanostructures is devoted to the fabrication, characterization, experimental investigation, theoretical understanding, and utilization of advanced magnetic nanostructures. Focus is on various types of 'bottom-up' and 'top-down' artificial nanostructures, as contrasted to naturally occurring magnetic nanostructures, such as iron-oxide inclusions in magnetic rocks, and to structures such as perfect thin films. Chapter 1 is an introduction into some basic concepts, such as the definitions of basic magnetic quantities. Chapters 2-4 are devoted to the theory of magnetic nanostructures, Chapter 5 deals with the characterization of the structures, and Chapters 6-10 are devoted to specific systems. Applications of advanced magnetic nanostructures are discussed in Chapters11-15 and, finally, the appendix lists and briefly discusses magnetic properties of typical starting materials. Industrial and academic researchers in magnetism and related areas such as nanotechnology, materials science, and theore...

  2. Manganese Nanostructures and Magnetism

    Science.gov (United States)

    Simov, Kirie Rangelov

    The primary goal of this study is to incorporate adatoms with large magnetic moment, such as Mn, into two technologically significant group IV semiconductor (SC) matrices, e.g. Si and Ge. For the first time in the world, we experimentally demonstrate Mn doping by embedding nanostructured thin layers, i.e. delta-doping. The growth is observed by in-situ scanning tunneling microscopy (STM), which combines topographic and electronic information in a single image. We investigate the initial stages of Mn monolayer growth on a Si(100)(2x1) surface reconstruction, develop methods for classification of nanostructure types for a range of surface defect concentrations (1.0 to 18.2%), and subsequently encapsulate the thin Mn layer in a SC matrix. These experiments are instrumental in generating a surface processing diagram for self-assembly of monoatomic Mn-wires. The role of surface vacancies has also been studied by kinetic Monte Carlo modeling and the experimental observations are compared with the simulation results, leading to the conclusion that Si(100)(2x1) vacancies serve as nucleation centers in the Mn-Si system. Oxide formation, which happens readily in air, is detrimental to ferromagnetism and lessens the magnetic properties of the nanostructures. Therefore, the protective SC cap, composed of either Si or Ge, serves a dual purpose: it is both the embedding matrix for the Mn nanostructured thin film and a protective agent for oxidation. STM observations of partially deposited caps ensure that the nanostructures remain intact during growth. Lastly, the relationship between magnetism and nanostructure types is established by an in-depth study using x-ray magnetic circular dichroism (XMCD). This sensitive method detects signals even at coverages less than one atomic layer of Mn. XMCD is capable of discerning which chemical compounds contribute to the magnetic moment of the system, and provides a ratio between the orbital and spin contributions. Depending on the amount

  3. Magnetism in carbon nanostructures

    CERN Document Server

    Hagelberg, Frank

    2017-01-01

    Magnetism in carbon nanostructures is a rapidly expanding field of current materials science. Its progress is driven by the wide range of applications for magnetic carbon nanosystems, including transmission elements in spintronics, building blocks of cutting-edge nanobiotechnology, and qubits in quantum computing. These systems also provide novel paradigms for basic phenomena of quantum physics, and are thus of great interest for fundamental research. This comprehensive survey emphasizes both the fundamental nature of the field, and its groundbreaking nanotechnological applications, providing a one-stop reference for both the principles and the practice of this emerging area. With equal relevance to physics, chemistry, engineering and materials science, senior undergraduate and graduate students in any of these subjects, as well as all those interested in novel nanomaterials, will gain an in-depth understanding of the field from this concise and self-contained volume.

  4. Noncollinear magnetism in manganese nanostructures

    Czech Academy of Sciences Publication Activity Database

    Zelený, Martin; Šob, Mojmír; Hafner, J.

    2009-01-01

    Roč. 80, č. 14 (2009), 144414/1-144414/19 ISSN 1098-0121 R&D Projects: GA AV ČR IAA100100920; GA MŠk OC09011 Institutional research plan: CEZ:AV0Z20410507 Keywords : magnetism of nanostructures * nanowires * noncollinear magnetism * manganese Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.475, year: 2009

  5. Thermoelectric effects in magnetic nanostructures

    NARCIS (Netherlands)

    Hatami, Moosa; Bauer, Gerrit E.W.; Zhang, Q.F.; Kelly, Paul J.

    2009-01-01

    We model and evaluate the Peltier and Seebeck effects in magnetic multilayer nanostructures by a finite-element theory of thermoelectric properties. We present analytical expressions for the thermopower and the current-induced temperature changes due to Peltier cooling/heating. The thermopower of a

  6. Advanced Nanostructured Magnetic Materials

    National Research Council Canada - National Science Library

    Sellmyer, David J

    2004-01-01

    ... out. Novel physical systems have been synthesized and studied including: hard/soft nanocomposites, magnetic nanowires, thermally processed multilayer films, and nanoparticle-assembled composites...

  7. Physics of magnetic nanostructures

    CERN Document Server

    Owens, Frank J

    2015-01-01

    This book discusses how the important properties of materials such as the cohesive energy, and the electronic and vibrational structures are affected when materials have at least one length in the nanometer range. The author uses relatively simple models of the solid state to explain why these changes in the size and dimension in the nanometer regime occur. The text also reviews the physics of magnetism and experimental methods of measuring magnetic properties necessary to understanding how nanosizing affects magnetism. Various kinds of magnetic structures are presented by the author in order to explain how nanosizing influences their magnetic properties. The book also presents potential and actual applications of nanomaterials in the fields of medicine and computer data storage.

  8. Geometry and magnetism of L10 nanostructures

    International Nuclear Information System (INIS)

    Sorge, K.D.; Skomski, R.; Daniil, M.; Michalski, S.; Gao, L.; Zhou, J.; Yan, M.; Sui, Y.; Kirby, R.D.; Liou, S.H.; Sellmyer, D.J.

    2005-01-01

    The fabrication and magnetism of L1 0 nanostructures with different shapes (such as nanoparticles and nanotubes) is investigated. These nanostructures are produced by hydrogen processing and focused ion beam milling. The structures exhibit interesting reversal modes and are of present or potential interest for sensors and imaging, as well as magnetic recording

  9. Imaging magnetic domains in Ni nanostructures

    International Nuclear Information System (INIS)

    Asenjo, A.; Jaafar, M.; Gonzalez, E.M.; Martin, J.I.; Vazquez, M.; Vicent, J.L.

    2007-01-01

    The study of nanomagnets is the subject of increasing scientific effort. The size, the thickness and the geometric shape of the elements determine the magnetic properties and then the domain configuration. In this work, we fabricated by electron-beam lithography the three different arrays of Ni nanostructures keeping the size, the thickness and also the distance constant between the elements but varying the geometry: square, triangular and circular. The domain structure of the nanomagnets is studied by magnetic force microscopy

  10. Nanostructured electronic and magnetic materials

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    and magnetic materials are provided. Advantages of nanocrystalline magnetic mate- rials in the context of ... 2.2 Phosphors for high definition TV. Better resolution of television screens could be ..... materials and that of preparing nanoparticles. This will remain a challenge for the future if nanomaterials are to be competitive.

  11. Magnetic nanostructures: radioactive probes and recent developments

    International Nuclear Information System (INIS)

    Prandolini, M J

    2006-01-01

    The miniaturization of magnetic sensors and storage devices down to the nano-scale leads to drastic changes in magnetic phenomena compared with the same devices with a larger size. Excited-nuclear-probe (radioactive probe) techniques are ideal for investigating these new magnetic nanostructures. By observing the magnetic hyperfine fields (and in some cases the electric-field-gradients (EFGs)) at the nuclei of radioactive probes, microscopic information about the magnetic environment of the probes is acquired. The magnetic hyperfine field is particularly sensitive to the s-spin polarization of the conduction electrons and to the orbital magnetic moment of the probe atom. Three methods of inserting radioactive probes into magnetic nanostructures are presented; neutron activation, recoil implantation and 'soft-landing', followed by descriptions of their application to selected examples. In some cases, these methods offer the simultaneous creation and observation of new magnetic materials at the atomic scale. This review focuses firstly on the induced magnetism in noble-metal spacer layers between either ferromagnetic (FM) or FM/antiferromagnetic (AFM) layers in a trilayer structure. Using the method of low-temperature nuclear orientation, the s-spin polarization of noble-metal probes was measured and was found to be very sensitive to the magnetic properties at both the FM and AFM interfaces. Secondly, the recoil implantation of radioactive Fe probes into rare-earth hosts and d-band alloys and subsequent measurement using time-differential perturbed angular distribution offer the possibility of controlling the chemical composition and number of nearest-neighbours. This method was used to prepare local 3d-magnetic clusters in a non-magnetic matrix and to observe their magnetic behaviour. Finally, non-magnetic radioactive probes were 'soft-landed' onto Ni surfaces and extremely lattice-expanded ultrathin Ni films. By measuring the magnetic hyperfine fields and EFGs at

  12. Patterning nanostructures to study magnetization processes

    International Nuclear Information System (INIS)

    Atkinson, D

    2005-01-01

    Lithography techniques such as electron-beam lithography and focused-ion-beam milling are widely used to fabricate structures with dimensions well below 1 μm. These techniques have been used to produce planar magnetic structures with sub-micrometer dimensions and well controlled geometry. This has allowed the study of basic magnetic behaviour and the development of structures with potential for applications in magnetic recording and magnetic logic devices. The techniques of electron beam lithography and focused-ion-beam milling for the fabrication of magnetic nanostructures are outlined here. These techniques have been used to fabricate ribbon-like planar nanowires to study the behaviour of the individual magnetic domain walls which mediate the reversal process in such elongated structures. These methods allow the production of structures in which the location of domain wall formation and position can be controlled, allowing separation and study of the domain wall nucleation and propagation processes. Domain wall injection and domain wall propagation behaviour are investigated and shown to be stochastic processes

  13. The investigation of nanostructures of magnetic recording media by TEM

    International Nuclear Information System (INIS)

    Peng Yingguo; Ohkubo, Tadakatsu; Laughlin, David E.

    2003-01-01

    Diverse applications of transmission electron microscopy techniques used in investigating the nanostructures of magnetic recording materials are presented. Specimen preparation methods are discussed for the specific case of magnetic thin film recording media. Investigations of the crystallographic orientation, grain size and distribution, and interfacial nanostructures are presented

  14. Nanostructured silicon ferromagnet collected by a permanent neodymium magnet.

    Science.gov (United States)

    Okuno, Takahisa; Thürmer, Stephan; Kanoh, Hirofumi

    2017-11-30

    Nanostructured silicon (N-Si) was prepared by anodic electroetching of p-type silicon wafers. The obtained magnetic particles were separated by a permanent neodymium magnet as a magnetic nanostructured silicon (mN-Si). The N-Si and mN-Si exhibited different magnetic properties: the N-Si exhibited ferromagnetic-like behaviour, whereas the mN-Si exhibited superparamagnetic-like behaviour.

  15. Hybrid nanostructured materials with tunable magnetic characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Torres-Martínez, Nubia E.; Garza-Navarro, M. A., E-mail: marco.garzanr@uanl.edu.mx; García-Gutiérrez, Domingo; González-González, Virgilio A.; Torres-Castro, Alejandro; Ortiz-Méndez, U. [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica (Mexico)

    2014-12-15

    We report on the development of hybrid nanostructured materials (HNM) based on spinel-metal-oxide nanoparticles (SMON) stabilized in carboxymethyl-cellulose (CMC)/cetyltrimethyl-ammonium-bromide (CTAB) templates, with tunable magnetic characteristics. These HNM were synthesized using a one-pot chemical approach to obtain CMC/CTAB templates with controllable size and morphology, where the SMON could be densely arranged. The synthesized HNM were characterized by transmission electron microscopy and its related techniques, such as bright field (BF) and Z-contrast (HAADF-STEM) imaging, and selected area electron diffraction, as well as static magnetic measuring. Experimental evidence suggests that the morphology and size of the CMC/CTAB templates are highly dependent on the weight ratio of CTAB:SMON, as well as the hydration days of the CMC that is used for the synthesis of the HNM. Controlling these parameters allows modifying the density of the SMON arrangement in the CMC/CTAB templates. Moreover, magnetic features such as remanence, coercivity, and blocking/de-blocking processes of the particles’ magnetic moments are highly dependent on the interactions among the SMON assembled in the templates. Hence, the magnetic characteristics of HNM can be modulated or tuned by controlling the manner the SMON are arranged within the CMC/CTAB templates.

  16. Magnetic properties of nickel nanostructures grown in AAO membrane

    International Nuclear Information System (INIS)

    Oh, S.-L.; Kim, Y.-R.; Malkinski, L.; Vovk, A.; Whittenburg, S.L.; Kim, E.-M.; Jung, J.-S.

    2007-01-01

    One-dimensional nanostructures can be built by performing chemical or electrochemical reactions in the pores of a suitable host or matrix material. We have developed a method of electrodeposition of nickel nanostructures inside cylindrical pores of the anodic aluminum oxide (AAO) membranes, which provides precise control of the nanostructure height. We were able to fabricate hexagonal arrays of particles in the form of spheres, rods and long wires. Magnetization measurements of these nanostructures as function of field and temperature were carried out using a superconducting quantum-interference device magnetometer. The shape of nickel nanostructures has been investigated by field emission scanning electron microscope. The coercivity of the nickel nanostructures measured with the field perpendicular to the membrane was increasing with increasing aspect ratio of the nanostructures. These experimental values of the coercivity, varying from 200 Oe for the spherical nanodots to 730 Oe for the nanowires, are in a fair agreement with our micromagnetic modeling calculations

  17. Magnetic properties of nickel nanostructures grown in AAO membrane

    Energy Technology Data Exchange (ETDEWEB)

    Oh, S -L [Department of Chemistry, Yonsei University, Seoul (Korea, Republic of); Kim, Y -R [Department of Chemistry, Yonsei University, Seoul (Korea, Republic of); Malkinski, L [Advanced Material Research Institute, University of New Orleans, New Orleans, LA 70148 (United States); Vovk, A [Advanced Material Research Institute, University of New Orleans, New Orleans, LA 70148 (United States); Whittenburg, S L [Advanced Material Research Institute, University of New Orleans, New Orleans, LA 70148 (United States); Kim, E -M [Korea Basic Science Institute, Kangnung 210-702 (Korea, Republic of); Jung, J -S [Department of Chemistry, Kangnung National University, Kangnung 210-702 (Korea, Republic of)

    2007-03-15

    One-dimensional nanostructures can be built by performing chemical or electrochemical reactions in the pores of a suitable host or matrix material. We have developed a method of electrodeposition of nickel nanostructures inside cylindrical pores of the anodic aluminum oxide (AAO) membranes, which provides precise control of the nanostructure height. We were able to fabricate hexagonal arrays of particles in the form of spheres, rods and long wires. Magnetization measurements of these nanostructures as function of field and temperature were carried out using a superconducting quantum-interference device magnetometer. The shape of nickel nanostructures has been investigated by field emission scanning electron microscope. The coercivity of the nickel nanostructures measured with the field perpendicular to the membrane was increasing with increasing aspect ratio of the nanostructures. These experimental values of the coercivity, varying from 200 Oe for the spherical nanodots to 730 Oe for the nanowires, are in a fair agreement with our micromagnetic modeling calculations.

  18. Study of magnetization switching in coupled magnetic nanostructured systems

    Science.gov (United States)

    Radu, Cosmin

    A study of magnetization dynamics experiments in nanostructured materials using the rf susceptibility tunnel diode oscillator (TDO) method is presented along with a extensive theoretical analysis. An original, computer controlled experimental setup that measures the change in susceptibility with the variation in external magnetic field and sample temperature was constructed. The TDO-based experiment design and construction is explained in detail, showing all the elements of originality. This experimental technique has proven reliable for characterizing samples with uncoupled magnetic structure and various magnetic anisotropies like: CrO2, FeCo/IrMn and Co/SiO2 thin films. The TDO was subsequently used to explore the magnetization switching in coupled magnetic systems, like synthetic antiferromagnet (SAF) structures. Magnetoresistive random access memory (MRAM) is an important example of devices where the use of SAF structure is essential. To support the understanding of the SAF magnetic behavior, its configuration and application are reviewed and more details are provided in an appendix. Current problems in increasing the scalability and decreasing the error rate of MRAM devices are closely connected to the switching properties of the SAF structures. Several theoretical studies that were devoted to the understanding of the concepts of SAF critical curve are reviewed. As one can notice, there was no experimental determination of SAF critical curve, due to the difficulties in characterizing a magnetic coupled structure. Depending of the coupling strength between the two ferromagnetic layers, on the SAF critical curve one distinguishes several new features, inexistent in the case of uncoupled systems. Knowing the configuration of the SAF critical curve is of great importance in order to control its switching characteristics. For the first time a method of experimentally recording the critical curve for SAF is proposed in this work. In order to overcome technological

  19. Dendrimer-magnetic nanostructure: a Monte Carlo simulation

    Science.gov (United States)

    Jabar, A.; Masrour, R.

    2017-11-01

    In this paper, the magnetic properties of ternary mixed spins (σ,S,q) Ising model on a dendrimer nanostructure are studied using Monte Carlo simulations. The ground state phase diagrams of dendrimer nanostructure with ternary mixed spins σ = 1/2, S = 1 and q = 3/2 Ising model are found. The variation of the thermal total and partial magnetizations with the different exchange interactions, the external magnetic fields and the crystal fields have been also studied. The reduced critical temperatures have been deduced. The magnetic hysteresis cycles have been discussed. In particular, the corresponding magnetic coercive filed values have been deduced. The multiples hysteresis cycles are found. The dendrimer nanostructure has several applications in the medicine.

  20. Hybride magnetic nanostructure based on amino acids functionalized polypyrrole

    Energy Technology Data Exchange (ETDEWEB)

    Nan, Alexandrina, E-mail: alexandrina.nan@itim-cj.ro; Bunge, Alexander; Turcu, Rodica [National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat, 400293 Cluj-Napoca (Romania)

    2015-12-23

    Conducting polypyrrole is especially promising for many commercial applications because of its unique optical, electric, thermal and mechanical properties. We report the synthesis and characterization of novel pyrrole functionalized monomers and core-shell hybrid nanostructures, consisting of a conjugated polymer layer (amino acids functionalized pyrrole copolymers) and a magnetic nanoparticle core. For functionalization of the pyrrole monomer we used several amino acids: tryptophan, leucine, phenylalanine, serine and tyrosine. These amino acids were linked via different types of hydrophobic linkers to the nitrogen atom of the pyrrole monomer. The magnetic core-shell hybrid nanostructures are characterized by various methods such as FTIR spectroscopy, transmission electron microscopy (TEM) and magnetic measurements.

  1. Magnetic properties of nanostructured CuFe2O4

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Goya, G.F.; Rechenberg, H.R.

    1999-01-01

    The structural evolution and magnetic properties of nanostructured copper ferrite, CuFe2O4, have been investigated by X-ray diffraction, Mossbauer spectroscopy, and magnetization measurements. Nanometre-sized CuFe2O4 particles with a partially inverted spinel structure were synthesized by high...

  2. Present and future applications of magnetic nanostructures grown by FEBID

    Energy Technology Data Exchange (ETDEWEB)

    Teresa, J.M. de [CSIC-Universidad de Zaragoza, Departamento de Fisica de la Materia Condensada, Instituto de Ciencia de Materiales de Aragon (ICMA), Saragossa (Spain); Universidad de Zaragoza, Laboratorio de Microscopias Avanzadas (LMA), Instituto de Nanociencia de Aragon (INA), Saragossa (Spain); Fernandez-Pacheco, A. [University of Cambridge, TFM Group, Cavendish Laboratory, Cambridge (United Kingdom)

    2014-12-15

    Currently, magnetic nanostructures are routinely grown by focused electron beam induced deposition (FEBID). In the present article, we review the milestones produced in the topic in the past as well as the future applications of this technology. Regarding past milestones, we highlight the achievement of high-purity cobalt and iron deposits, the high lateral resolution obtained, the growth of 3D magnetic deposits, the exploration of magnetic alloys and the application of magnetic deposits for Hall sensing and in domain-wall conduit and magnetologic devices. With respect to future perspectives of the topic, we emphasize the potential role of magnetic nanostructures grown by FEBID for applications related to highly integrated 2D arrays, 3D nanowires devices, fabrication of advanced scanning-probe systems, basic studies of magnetic structures and their dynamics, small sensors (including biosensors) and new applications brought by magnetic alloys and even exchange biased systems. (orig.)

  3. Magnetic Cluster States in Nanostructured Materials

    International Nuclear Information System (INIS)

    Leslie-Pelecky, Diandra

    2008-01-01

    The goal of this work is to fabricate model nanomaterials with different types of disorder and use atomic-scale characterization and macroscopic magnetization measurements to understand better how specific types of disorder affects macroscopic magnetic behavior. This information can be used to produce magnetic nanomaterials with specific properties for applications such as permanent magnets, soft magnetic material for motors and biomedical applications.

  4. In situ transmission electron microscopy for magnetic nanostructures

    DEFF Research Database (Denmark)

    Ngo, Duc-The; Kuhn, Luise Theil

    2016-01-01

    Nanomagnetism is a subject of great interest because of both application and fundamental aspects in which understanding of the physical and electromagnetic structure of magnetic nanostructures is essential to explore the magnetic properties. Transmission electron microscopy (TEM) is a powerful tool...... that allows understanding of both physical structure and micromagnetic structure of the thin samples at nanoscale. Among TEM techniques, in situ TEM is the state-of-the-art approach for imaging such structures in dynamic experiments, reconstructing a real-time nanoscale picture of the properties......-structure correlation. This paper aims at reviewing and discussing in situ TEM magnetic imaging studies, including Lorentz microscopy and electron holography in TEM, applied to the research of magnetic nanostructures....

  5. Synthesis and magnetic properties of superparamagnetic CoAs nanostructures

    Science.gov (United States)

    Desai, P.; Ashokaan, N.; Masud, J.; Pariti, A.; Nath, M.

    2015-03-01

    This article provides a comprehensive guide on the synthesis and characterization of superparamagnetic CoAs nanoparticles and elongated nanostructures with high blocking temperature, (TB), via hot-injection precipitation and solvothermal methods. Cobalt arsenides constitute an important family of magnetically active solids that find a variety of applications ranging from magnetic semiconductors to biomedical imaging. While the higher temperature hot-injection precipitation technique (300 °C) yields pure CoAs nanostructures, the lower temperature solvothermal method (200 °C) yields a mixture of CoAs nanoparticles along with other Co-based impurity phases. The synthesis in all these cases involved usage of triphenylarsine ((C6H5)3As) as the As precursor which reacts with solid Co2(CO)8 by ligand displacement to yield a single source precursor. The surfactant, hexadecylamine (HDA) further assists in controlling the morphology of the nanostructures. HDA also provides a basic medium and molten flux-like conditions for the redox chemistry to occur between Co and As at elevated temperatures. The influence of the length of reaction time was investigated by studying the evolution of product morphology over time. It was observed that while spontaneous nucleation at higher temperature followed by controlled growth led to the predominant formation of short nanorods, with longer reaction time, the nanorods were further converted to nanoparticles. The size of the nanoparticles obtained, was mostly in the range of 10-15 nm. The key finding of this work is exceptionally high coercivity in CoAs nanostructures for the first time. Coercivity observed was as high as 0.1 T (1000 Oe) at 2 K. These kinds of magnetic nanostructures find multiple applications in spintronics, whereas the superparamagnetic nanoparticles are viable for use in magnetic storage, ferrofluids and as contrast enhancing agents in MRI.

  6. Controlling the flux dynamics in superconductors by nanostructured magnetic arrays

    Science.gov (United States)

    Kapra, Andrey

    In this thesis we investigate theoretically how the critical current jc of nano-engineered mesoscopic superconducting film can be improved and how one can control the dynamics of the magnetic flux, e.g., the transition from flux-pinned to flux-flow regime, using arrays of magnetic nanostructures. In particularly we investigate: (1) Vortex transport phenomena in superconductors with deposited ferromagnetic structures on top, and the influence of the sample geometry on the critical parameters and on the vortex configurations. Changing geometry of the magnetic bars and magnetization of the bars will affect the critical current jc of the superconducting film. Such nanostructured ferromagnets strongly alter the vortex structure in its neighborhood. The influence of geometry, position and magnetization of the ferromagnet (single bar or regular lattice of the bars) on the critical parameters of the superconductor is investigated. (2) Effect of flux confinement in narrow superconducting channels with zigzag-shaped banks: the flux motion is confined in the transverse (perpendicular) direction of a diamond-cell-shape channel. The matching effect for the magnetic flux is found in the system relevantless of boundary condition. We discuss the dynamics of vortices in the samples and vortex pattern formation in the channel. We show how the inclusion of higher-Tc superconductor into the sample can lead to enhanced properties of the system. By adding an external driving force, we study the vortex dynamics. The different dynamic regimes are discussed. They allowed an effective control of magnetic flux in superconductors.

  7. Large magnetoresistance tunnelling through a magnetically modulated nanostructure

    International Nuclear Information System (INIS)

    Lu Maowang; Zhang Lide

    2003-01-01

    Based on a combination of an inhomogeneous magnetic field and a two-dimensional electron gas, we have constructed a giant magnetoresistance nanostructure, which can be realized experimentally by the deposition of two parallel ferromagnetic strips on top of a semiconductor heterostructure. We have theoretically studied the magnetoresistance for electrons tunnelling through this nanostructure. It is shown that there exists a significant transmission difference between the parallel and antiparallel magnetization configurations, which leads to a large magnetoresistance. It is also shown that the magnetoresistance ratio strongly depends not only on incident electronic energy but also on the ferromagnetic strips, and thus a much larger magnetoresistance ratio can be obtained by properly fabricating the ferromagnetic strips in the system

  8. Nanostructured magnetic alginate composites for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Bedê, Pedro Marins; Silva, Marcelo Henrique Prado da; Figueiredo, André Ben-Hur da Silva, E-mail: marceloprado@ime.eb.br [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil); Finotelli, Priscilla Vanessa [Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil). Faculdade de Farmácia

    2017-07-01

    This is a study of the preparation and characterization of polymeric-magnetic nanoparticles. The nanoparticles used were magnetite (Fe{sub 3}O{sub 4} ) and the chosen polymers were alginate and chitosan. Two types of samples were prepared: uncoated magnetic nanoparticles and magnetic nanoparticles encapsulated in polymeric matrix. The samples were analyzed by XRD, light scattering techniques, TEM, and magnetic SQUID. The XRD patterns identified magnetite (Fe{sub 3}O{sub 4} ) as the only crystalline phase. TEM analyses showed particle sizes between 10 and 20nm for magnetite, and 15 and 30nm for the encapsulated magnetite. The values of magnetization ranged from 75 to 100emu/g for magnetite nanoparticles, and 8 to 12emu/g for coated with chitosan, at different temperatures of 20K and 300K. The saturation of both samples was in the range of 49 to 50KOe. Variations of results between the two kinds of samples were attributed to the encapsulation of magnetic nanoparticles by the polymers. (author)

  9. Magnetic properties of nanostructured spinel ferrites and ...

    Indian Academy of Sciences (India)

    exchange interaction strength because of an increase in the magnetic ion concentration in the A-site on milling, ... By using a copper wheel, rotating with the ... Zn ferrite with a small applied field of 4 mT for two different grain sizes. The Néel ... By varying the concentration of the oxidant (KNO3) or ferric ions, we could achieve.

  10. Peculiarities of extra high frequency magnetoimpedance in magnetic nanostructures

    International Nuclear Information System (INIS)

    Tarpov, S.

    2005-01-01

    Full text: The work presents a review of the comprehensive researches of dynamic properties of electron system in low dimensional magnetic nanostructures. Namely we discuss here the results of study of multilayered and granular low dimension magnets, demonstrating the Giant Magnetic Resistance (GMR) and Giant Magnetic Impedance (GMI) phenomena. We applied the Electron Spin Resonance (Ferromagnetic Resonance) technique and the method of non-resonance absorption of wavelength of millimeter waveband. Results obtained by these two methods are compared with study of GMR effect (which is conversed into Tunnel Magnetic Resistance (TMR) effect for granular systems). Special experimental cells have been designed for various specimens and for operation at 20-100 GHz with the aim to carry out static and dynamic experiments in the same experimental cycle. These quasi optical resonators provide the load quality factor between 3 000 and 25 000. The technique and installation designed allowed define the magnetization for various types of Co- and Fe- nanogranular structures [1]. The certain correlation between magneto impedance (magnetoresistance) and the magnetic structure of the specimen has been detected and the physical model was suggested. The shape of magnetic particles, forming the granular nanostructure was defined on the base of the joint FMR/GMI researches. It was shown that majority of the particles have ellipsoidal shape with some definite relation between axes. The main axis of each of these ellipsoids is stretched in the surface of the specimen and demonstrate one-to-one mapping with the magnetic anisotropy field. The numerical statistical simulation of FMR- absorption in multicomponent nanomagnetic structures has been performed. The modified Monte-Carlo technique [2] was applied for description of Fe-Co multilayered system. The magnitude of the packing density for magnetic atoms was estimated. [1] S.Tarapov, T.Bagmut, A.Granovsky, V.Derkach, S.Nedukh, A.Plevako, S

  11. Magnetic Nanostructures Spin Dynamics and Spin Transport

    CERN Document Server

    Farle, Michael

    2013-01-01

    Nanomagnetism and spintronics is a rapidly expanding and increasingly important field of research with many applications already on the market and many more to be expected in the near future. This field started in the mid-1980s with the discovery of the GMR effect, recently awarded with the Nobel prize to Albert Fert and Peter Grünberg. The present volume covers the most important and most timely aspects of magnetic heterostructures, including spin torque effects, spin injection, spin transport, spin fluctuations, proximity effects, and electrical control of spin valves. The chapters are written by internationally recognized experts in their respective fields and provide an overview of the latest status.

  12. Neutron scattering on magnetic nano-structures

    International Nuclear Information System (INIS)

    Ott, F.

    2009-03-01

    The thesis describes measurements of the scrape-off layer (SOL) ion temperature T i with a retarding field analyzer (RFA) in the limiter tokamak Tore Supra. In the first chapter, some well known facts about nuclear fusion, limiter SOL, Langmuir probes, etc. are briefly recalled. Various diagnostics for SOL T i measurements developed in the past are addressed as well. The second chapter is dedicated to the RFA. The principle of the RFA, technical details and operation of the Tore Supra RFA, and the influence of instrumental effects on RFA measurements are addressed. In the third chapter, the experimental results are presented in the form of papers published (or submitted for publication) during the thesis. Some research that was not completed at the time of writing is summarized in the last chapter. Considerable emphasis is placed on study of the instrumental effects of RFAs and their influence on T i measurements. In general, the influence of instrumental effects on T i measurements is found to be relatively small. Selective ion transmission through the RFA slit is found to be responsible for an overestimation of T i by less than 14% even for relatively thick slit plates. The effect of positive space charge inside the analyzer, the influence of the electron repelling grid, the misalignment of the probe head with respect to the magnetic field, and the attenuation of the incident ion current by some of the probe components on T i measurements is negligible. The instrumental study is followed by systematic measurements of T i (as well as other parameters) in the Tore Supra SOL. This includes the scaling of SOL temperatures and electron density with the main plasma parameters (such as the plasma density, toroidal magnetic field, working gas, and the radiated power fraction). Except at very high densities or in detached plasmas, SOL T i is found to be higher than T e by up to a factor of 7. While SOL T i is found to vary by almost two orders of magnitude, following the

  13. Magnetic anisotropies of (Ga,Mn)As films and nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Frank

    2011-02-02

    In this work the magnetic anisotropies of the diluted magnetic semiconductor (Ga,Mn)As were investigated experimentally. (Ga,Mn)As films show a superposition of various magnetic anisotropies which depend sensitively on various parameters such as temperature, carrier concentration or lattice strain. However, the anisotropies of lithographically prepared (Ga,Mn)As elements differ significantly from an unpatterned (Ga,Mn)As film. In stripe-shaped structures this behaviour is caused by anisotropic relaxation of the compressive lattice strain. In order to determine the magnetic anisotropies of individual (Ga,Mn)As nanostructures a combination of ferromagnetic resonance and time-resolved scanning Kerr microscopy was employed in this thesis. In addition, local changes of the magnetic anisotropy in circular and rectangular structures were visualized by making use of spatially resolved measurements. Finally, also the influence of the laterally inhomogeneous magnetic anisotropies on the static magnetic properties, such as coercive fields, was investigated employing spatially resolved static MOKE measurements on individual (Ga,Mn)As elements. (orig.)

  14. Precipitation synthesis and magnetic properties of self-assembled magnetite-chitosan nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Bezdorozhev, Oleksii; Kolodiazhnyi, Taras; Vasylkiv, Oleg, E-mail: oleg.vasylkiv@nims.go.jp

    2017-04-15

    This paper reports the synthesis and magnetic properties of unique magnetite-chitosan nanostructures synthesized by the chemical precipitation of magnetite nanoparticles in the presence of chitosan. The influence of varying synthesis parameters on the morphology of the magnetic composites is determined. Depending on the synthesis parameters, magnetite-chitosan nanostructures of spherical (9–18 nm), rice-seed-like (75–290 nm) and lumpy (75–150 nm) shapes were obtained via self-assembly. Spherical nanostructures encapsulated by a 9–15 nm chitosan layer were assembled as well. The prospective morphology of the nanostructures is combined with their excellent magnetic characteristics. It was found that magnetite-chitosan nanostructures are ferromagnetic and pseudo-single domain. Rice-seed-like nanostructures exhibited a coercivity of 140 Oe and saturation magnetization of 56.7 emu/g at 300 K. However, a drop in the magnetic properties was observed for chitosan-coated spherical nanostructures due to the higher volume fraction of chitosan. - Highlights: • Magnetite-chitosan nanostructures are synthesized via self-assembly. • Different morphology can be obtained by adjusting the synthesis parameters. • An attractive combination of magnetic properties and morphology is obtained. • Magnetite-chitosan nanostructures are ferrimagnetic and pseudo-single domain.

  15. Precipitation synthesis and magnetic properties of self-assembled magnetite-chitosan nanostructures

    International Nuclear Information System (INIS)

    Bezdorozhev, Oleksii; Kolodiazhnyi, Taras; Vasylkiv, Oleg

    2017-01-01

    This paper reports the synthesis and magnetic properties of unique magnetite-chitosan nanostructures synthesized by the chemical precipitation of magnetite nanoparticles in the presence of chitosan. The influence of varying synthesis parameters on the morphology of the magnetic composites is determined. Depending on the synthesis parameters, magnetite-chitosan nanostructures of spherical (9–18 nm), rice-seed-like (75–290 nm) and lumpy (75–150 nm) shapes were obtained via self-assembly. Spherical nanostructures encapsulated by a 9–15 nm chitosan layer were assembled as well. The prospective morphology of the nanostructures is combined with their excellent magnetic characteristics. It was found that magnetite-chitosan nanostructures are ferromagnetic and pseudo-single domain. Rice-seed-like nanostructures exhibited a coercivity of 140 Oe and saturation magnetization of 56.7 emu/g at 300 K. However, a drop in the magnetic properties was observed for chitosan-coated spherical nanostructures due to the higher volume fraction of chitosan. - Highlights: • Magnetite-chitosan nanostructures are synthesized via self-assembly. • Different morphology can be obtained by adjusting the synthesis parameters. • An attractive combination of magnetic properties and morphology is obtained. • Magnetite-chitosan nanostructures are ferrimagnetic and pseudo-single domain.

  16. Characterization of the magnetic micro- and nanostructure in unalloyed steels by magnetic force microscopy

    Science.gov (United States)

    Batista, L.; Rabe, U.; Hirsekorn, S.

    2013-01-01

    The formation of a cementite phase influences significantly the macroscopic mechanical and magnetic properties of steels. Based on a correlation between mechanical and magnetic properties, mechanical properties as well as the morphology and content of the cementite phase can be inspected by electromagnetic non-destructive testing methods. The influence of the carbon content on bulk magnetic properties of unalloyed steels is studied on a macroscopic scale by hysteresis loop and Barkhausen noise measurements. The micro- and nanostructure is investigated by atomic force microscopy and magnetic force microscopy. Surface topography images and magnetic images of globular cementite precipitates embedded in a ferrite matrix are presented. The size, shape, and orientation of the precipitates influence the domain configuration. Applied external magnetic fields cause magnetization processes mainly in the ferrite matrix: Bloch walls move and are pinned by the cementite precipitates. The correlation between the microscopic observations and macroscopic magnetic properties of the material is discussed.

  17. Electrochemical synthesis of magnetic nanostructures using anodic aluminum oxide templates

    Science.gov (United States)

    Gong, Jie

    In this dissertation, template electrodeposition was employed to fabricate high quality magnetic nanostructures suited for the reliable investigation of novel spintronics phenomena such as CIMS, BMR, and CPP-GMR. Several critical aspects/steps relating to the synthesis process were investigated in this work. In order to obtain high quality magnetic nanostructures, free-standing and Si-supported anodic aluminum oxide templates with closely controlled pore diameters, lengths, as well as constriction sizes, were synthesized by anodization, followed by appropriate post-processing. The pore opening size on the barrier layer can be controlled down to 5 nm by ion beam etching. After optimization of the compositional, structural, and magnetic properties of homogeneous FeCoNiCu layers electrodeposited under different conditions, the pulsed deposition process of FeCoNI/Cu multilayers on n-Si was studied. The influence of Cu deposition potential and Fe2+ concentration on microstructure, chemical and electrochemical properties, magnetic properties, and hence magnetotransport properties were assessed. The dissolution of the FM layer during potential transition was minimized in order to control interface sharpness. Combined with the systematic sublayer thickness and FM layer composition optimization, unprecedented GMR sensitivity of 0.11%/Oe at 5-15 Oe was obtained. Growth of multilayer nanowires was performed, and contact to a single wire was attempted using an electrochemical technique. We succeeded in addressing a small number of nanowires and measured a CPP-GMR of 17%. Template electrodeposition thus provides a promising way to repeatably fabricate prototypes for spin dependent transport studies.

  18. The spin structure of magnetic nanoparticles and in magnetic nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Disch, Sabrina

    2011-09-26

    The present thesis provides an extensive and original contribution to the investigation of magnetic nanoparticles regarding synthesis and structural characterization using advanced scattering methods in all length scales between the atomic and mesoscopic size range. Particular emphasis is on determination of the magnetic structure of single nanoparticles as well as preparation and characterization of higher dimensional assemblies thereof. The unique physical properties arising from the finite size of magnetic nanoparticles are pronounced for very small particle sizes. With the aim of preparing magnetic nanoparticles suitable for investigation of such properties, a micellar synthesis route for very small cobalt nanoparticles is explored. Cobalt nanoparticles with diameters of less than 3 nm are prepared and characterized, and routes for variation of the particle size are developed. The needs and limitations of primary characterization and handling of such small and oxidation-sensitive nanoparticles are highlighted and discussed in detail. Comprehensive structural and magnetic characterization is performed on iron oxide nanoparticles of {proportional_to} 10 nm in diameter. Particle size and narrow size distribution are determined with high precision. Investigation of the long range and local atomic structure reveals a particle size dependent magnetite - maghemite structure type with lattice distortions induced at the particle surface. The spatial magnetization distribution within these nanoparticles is determined to be constant in the particle core with a decrease towards the particle surface, thus indicating a magnetic dead layer or spin canting close to the surface. Magnetically induced arrangements of such nanoparticles into higher dimensional assemblies are investigated in solution and by deposition of long range ordered mesocrystals. Both cases reveal a strong dependence of the found structures on the nanoparticle shape (spheres, cubes, and heavily truncated

  19. Magnetic layering transitions in a polyamidoamine (PAMAM) dendrimer nano-structure: Monte Carlo study

    Science.gov (United States)

    Ziti, S.; Aouini, S.; Labrim, H.; Bahmad, L.

    2017-02-01

    We study the magnetic layering transitions in a polyamidoamine (PAMAM) dendrimer nano-structure, under the effect of an external magnetic field. We examine the magnetic properties, of this model of the spin S=1 Ising ferromagnetic in real nanostructure used in several scientific domains. For T=0, we give and discuss the ground state phase diagrams. At non null temperatures, we applied the Monte Carlo simulations giving important results summarized in the form of the phase diagrams. We also analyzed the effect of varying the external magnetic field, and found the layering transitions in the polyamidoamine (PAMAM) dendrimer nano-structure.

  20. Information processing in patterned magnetic nanostructures with edge spin waves.

    Science.gov (United States)

    Lara, Antonio; Robledo Moreno, Javier; Guslienko, Konstantin Y; Aliev, Farkhad G

    2017-07-17

    Low dissipation data processing with spins is one of the promising directions for future information and communication technologies. Despite a significant progress, the available magnonic devices are not broadband yet and have restricted capabilities to redirect spin waves. Here we propose a breakthrough approach to spin wave manipulation in patterned magnetic nanostructures with unmatched characteristics, which exploits a spin wave analogue to edge waves propagating along a water-wall boundary. Using theory, micromagnetic simulations and experiment we investigate spin waves propagating along the edges in magnetic structures, under an in-plane DC magnetic field inclined with respect to the edge. The proposed edge spin waves overcome important challenges faced by previous technologies such as the manipulation of the spin wave propagation direction, and they substantially improve the capability of transmitting information at frequencies exceeding 10 GHz. The concept of the edge spin waves allows to design a broad of logic devices such as splitters, interferometers, or edge spin wave transistors with unprecedented characteristics and a potentially strong impact on information technologies.

  1. Hydroxylation of benzene to phenol over magnetic recyclable nanostructured CuFe mixed-oxide catalyst

    CSIR Research Space (South Africa)

    Makgwane, PR

    2015-03-01

    Full Text Available A highly active and magnetically recyclable nanostructured copper–iron oxide (CuFe) catalyst has been synthesized for hydroxylation of benzene to phenol under mild reaction conditions. The obtained catalytic results were correlated with the catalyst...

  2. Mercury removal from solution by superconducting magnetic separation with nanostructured magnetic adsorbents

    Energy Technology Data Exchange (ETDEWEB)

    Okamoto, T., E-mail: okamoto-takayuki@ed.tmu.ac.jp [Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan); Tachibana, S.; Miura, O. [Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan); Takeuchi, M. [Komazawa Jin Clinic, 1-19-8 Komazawa, Setagayaku, Tokyo 154-0012 (Japan)

    2011-11-15

    Recently, mercury Hg concentration in human blood increases due to expanding the global mercury contamination. Excess mercury bioaccumulation poses a significant health risk. In order to decrease mercury concentration in the environment and human blood, we have developed two different kinds of nanostructured magnetic adsorbents for mercury to apply them to superconducting magnetic separation instead of conventional filtration. One is magnetic beads (MBs) which have nanosize magnetite particles in the core and a lot of SH radicals on the surface to adsorb Hg ions effectively. MBs were developed mainly to remove mercury from human blood. The maximum amount of the adsorption for MBs is 6.3 mg/g in the solution in less than a minute. Dithiothreitol can easily remove mercury adsorbed to MBs, hence MBs can be reusable. The other is nanostructured magnetic activated carbon (MAC) which is activated carbon with mesopores and nanosize magnetite. The maximum amount of the adsorption for MAC is 38.3 mg/g in the solution. By heat-treatment mercury can be easily removed from MAC. We have studied superconducting magnetic separation using each adsorbent for mercury removal from solution.

  3. Mesoporous magnetic secondary nanostructures as versatile adsorbent for efficient scavenging of heavy metals

    Science.gov (United States)

    Bhattacharya, Kakoli; Parasar, Devaborniny; Mondal, Bholanath; Deb, Pritam

    2015-01-01

    Porous magnetic secondary nanostructures exhibit high surface area because of the presence of plentiful interparticle spaces or pores. Mesoporous Fe3O4 secondary nanostructures (MFSNs) have been studied here as versatile adsorbent for heavy metal scavenging. The porosity combined with magnetic functionality of the secondary nanostructures has facilitated efficient heavy metal (As, Cu and Cd) remediation from water solution within a short period of contact time. It is because of the larger surface area of MFSNs due to the porous network in addition to primary nanostructures which provides abundant adsorption sites facilitating high adsorption of the heavy metal ions. The brilliance of adsorption property of MFSNs has been realized through comprehensive adsorption studies and detailed kinetics. Due to their larger dimension, MFSNs help in overcoming the Brownian motion which facilitates easy separation of the metal ion sorbed secondary nanostructures and also do not get drained out during filtration, thus providing pure water. PMID:26602613

  4. Magnetization jumps in nanostructured Nd–Fe–B alloy at low temperatures

    International Nuclear Information System (INIS)

    Neznakhin, D.S.; Bolyachkin, A.S.; Volegov, A.S.; Markin, P.E.; Andreev, S.V.; Kudrevatykh, N.V.

    2015-01-01

    Magnetic properties of the nanostructured isotropic alloy on the base of Nd 2 Fe 14 B type phase were investigated at low temperatures. The evaluated average grain size of this phase was much smaller than its critical single domain diameter. Hence the magnetization and demagnetization processes were expected to be performed by coherent magnetization rotation. For such coercivity type system magnetization jumps were revealed on the demagnetization hysteresis loop branch in the vicinity of the coercive force at temperatures below 4 K. It was shown that magnetization jumps have a stochastic behavior and their number strongly depends on the temperature and the mass of measured samples. High temperature spikes corresponding to magnetization discontinuities were observed. All these results allowed to propose that magnetization jumps in nanostructured magnetics with magnetization rotation reversal processes comply with the local heating model. - Highlights: • Magnetization reversals of the nanostructured Nd–Fe–B-type alloy were obtained below 4 K. • Magnetization jumps were first observed for magnetization rotation coercivity type magnets. • Staircase magnetization reversal was explained within the framework of the local heating model

  5. Manipulation of magnetic vortex parameters in disk-on-disk nanostructures with various geometry

    Directory of Open Access Journals (Sweden)

    Maxim E. Stebliy

    2015-03-01

    Full Text Available Magnetic nanostructures in the form of a sandwich consisting of two permalloy (Py disks with diameters of 600 and 200 nm separated by a nonmagnetic interlayer are studied. Magnetization reversal of the disk-on-disk nanostructures depends on the distance between centers of the small and big disks and on orientation of an external magnetic field applied during measurements. It is found that manipulation of the magnetic vortex chirality and the trajectory of the vortex core in the big disk is only possible in asymmetric nanostructures. Experimentally studied peculiarities of a motion path of the vortex core and vortex parameters by the magneto-optical Kerr effect (MOKE magnetometer are supported by the magnetic force microscopy imaging and micromagnetic simulations.

  6. Phase diagrams and switching of voltage and magnetic field in dilute magnetic semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Escobedo, R. [Departamento de Matematica Aplicada y Ciencias de la Computacion, Universidad de Cantabria, 39005 Santander (Spain); Carretero, M.; Bonilla, L.L. [G. Millan Institute, Fluid Dynamics, Nanoscience and Industrial Maths., Universidad Carlos III de Madrid, 28911 Leganes (Spain); Unidad Asociada al Instituto de Ciencia de Materiales, CSIC, 28049 Cantoblanco, Madrid (Spain); Platero, G. [Instituto de Ciencia de Materiales, CSIC, 28049 Cantoblanco, Madrid (Spain)

    2010-04-15

    The response of an n-doped dc voltage biased II-VI multi-quantum well dilute magnetic semiconductor nanostructure having its first well doped with magnetic (Mn) impurities is analyzed by sweeping wide ranges of both the voltage and the Zeeman level splitting induced by an external magnetic field. The level splitting versus voltage phase diagram shows regions of stable self-sustained current oscillations immersed in a region of stable stationary states. Transitions between stationary states and self-sustained current oscillations are systematically analyzed by both voltage and level splitting abrupt switching. Sudden voltage or/and magnetic field changes may switch on current oscillations from an initial stationary state, and reciprocally, current oscillations may disappear after sudden changes of voltage or/and magnetic field changes into the stable stationary states region. The results show how to design such a device to operate as a spin injector and a spin oscillator by tuning the Zeeman splitting (through the applied external magnetic field), the applied voltage and the sample configuration parameters (doping density, barrier and well widths, etc.) to select the desired stationary or oscillatory behavior. Phase diagram of Zeeman level splitting {delta} vs. dimensionless applied voltage {phi} for N = 10 QWs. White region: stable stationary states; black: stable self-sustained current oscillations. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. A novel rhombohedron-like nickel ferrite nanostructure: Microwave combustion synthesis, structural characterization and magnetic properties

    Directory of Open Access Journals (Sweden)

    G. Suresh Kumar

    2016-09-01

    Full Text Available Research on nickel ferrite nanostructures has drawn a great interest because of its inherent chemical, physical and electronic properties. In this study, we have synthesized rhombohedron – like nickel ferrite nanostructure by a rapid microwave assisted combustion method using ethylenediamminetetraacetic acid as a chelating agent. X-ray diffraction, Fourier transform infrared spectrometer, transmission electron microscope and energy dispersive X-ray microanalyser were used to characterize the prepared sample. The magnetic behaviour was analysed by means of field dependent magnetization measurement which indicates that the prepared sample exhibits a soft ferromagnetic nature with saturation magnetization of 63.034 emu/g. This technique can be a potential method to synthesize novel nickel ferrite nanostructure with improved magnetic properties.

  8. Nanostructure, Composition, and Magnetic Behavior of Mechanically Alloyed Fe-Mo

    Czech Academy of Sciences Publication Activity Database

    Jirásková, Yvonna; Buršík, Jiří; Turek, Ilja

    2013-01-01

    Roč. 26, č. 5 (2013), s. 1717-1721 ISSN 1557-1939. [ICSM 2012 /3./. Istanbul, 29.04.2012-04.05.2012] R&D Projects: GA ČR(CZ) GAP108/11/1350 Keywords : Nanostructured material * Mechanical alloying * Magnetic properties * Grain core * Defects Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.930, year: 2013

  9. Monte Carlo simulations of magnetic and thermodynamic properties for different nanostructure geometries

    Energy Technology Data Exchange (ETDEWEB)

    Konstantinova, Elena, E-mail: elena.konst@ifsudestemg.edu.br; Sales, José Antonio de

    2014-10-01

    Creation of magnetic nanodevices leads, in particular, to a growing interest in theoretical investigation of different types of magnetic nanostructures. The purpose of our work is to consider how the properties of such nanomaterials depend on their geometry and on the crystal structure. We report on the Monte Carlo simulation of magnetic nanostructures of different geometric forms, which are based on simple cubic and body-centered cubic cells. The magnetization of spin, magnetic susceptibility and specific heat are investigated for nano-disks, nano-bars and nano-balls of different magnitudes. The combination of dipole and Heisenberg-model interaction are considered for the ferromagnetic case. It is shown that magnetic and thermodynamic properties of nanostructures strongly depend on their geometry. The structures with a body-centered cubic unit cell manifest stronger dependence on size and geometric form. In this case one can interpret the results as an effective reduction of dimension from 3D to 2D for decreasing size of the compound. - Highlights: • Thermodynamic properties of nano-balls are dependent on their size. • Magnetic properties of nano-bars depend on their thickness. • The hysteresis loop is dependent on the geometry of the nanostructure.

  10. In Vivo Deep Tissue Fluorescence and Magnetic Imaging Employing Hybrid Nanostructures.

    Science.gov (United States)

    Ortgies, Dirk H; de la Cueva, Leonor; Del Rosal, Blanca; Sanz-Rodríguez, Francisco; Fernández, Nuria; Iglesias-de la Cruz, M Carmen; Salas, Gorka; Cabrera, David; Teran, Francisco J; Jaque, Daniel; Martín Rodríguez, Emma

    2016-01-20

    Breakthroughs in nanotechnology have made it possible to integrate different nanoparticles in one single hybrid nanostructure (HNS), constituting multifunctional nanosized sensors, carriers, and probes with great potential in the life sciences. In addition, such nanostructures could also offer therapeutic capabilities to achieve a wider variety of multifunctionalities. In this work, the encapsulation of both magnetic and infrared emitting nanoparticles into a polymeric matrix leads to a magnetic-fluorescent HNS with multimodal magnetic-fluorescent imaging abilities. The magnetic-fluorescent HNS are capable of simultaneous magnetic resonance imaging and deep tissue infrared fluorescence imaging, overcoming the tissue penetration limits of classical visible-light based optical imaging as reported here in living mice. Additionally, their applicability for magnetic heating in potential hyperthermia treatments is assessed.

  11. Magnetic resonance of semiconductors and their nanostructures basic and advanced applications

    CERN Document Server

    Baranov, Pavel G; Jelezko, Fedor; Wrachtrup, Jörg

    2017-01-01

    This book explains different magnetic resonance (MR) techniques and uses different combinations of these techniques to analyze defects in semiconductors and nanostructures. It also introduces novelties such as single defects MR and electron-paramagnetic-resonance-based methods: electron spin echo, electrically detected magnetic resonance, optically detected magnetic resonance and electron-nuclear double resonance – the designated tools for investigating the structural and spin properties of condensed systems, living matter, nanostructures and nanobiotechnology objects. Further, the authors address problems existing in semiconductor and nanotechnology sciences that can be resolved using MR, and discuss past, current and future applications of MR, with a focus on advances in MR methods. The book is intended for researchers in MR studies of semiconductors and nanostructures wanting a comprehensive review of what has been done in their own and related fields of study, as well as future perspectives.

  12. Characterization of magnetization processes in nanostructured rare earth-transition metal films

    International Nuclear Information System (INIS)

    Zheng Guangping; Zhan Yangwen; Liu Peng; Li Mo

    2003-01-01

    We synthesize rare earth-transition metal (RE-TM) amorphous films using the electrodeposition method (RE=Nd, Gd and TM=Co). Nanocrystructured RE-TM films are prepared by thermal treatment of as-synthesized films below the glass-crystal transition temperature. Based on the magnetoelastic effect, the magnetization processes in nanostructured samples are characterized by acoustic internal friction measurements using the vibrating-reed technique. Since internal friction and the Young's modulus are sensitive to grain boundary and magnetic domains movement, this technique seems to characterize the effects of nanostructures on the magnetization processes in RE-TM films well. We find that the magnetoelastic effect in nanostructured RE-TM film increases with an increase in grain size

  13. Fe and Co nanostructures embedded into the Cu(100) surface: Self-Organization and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Kolesnikov, S. V., E-mail: kolesnikov@physics.msu.ru; Klavsyuk, A. L.; Saletsky, A. M. [Moscow State University, Faculty of Physics (Russian Federation)

    2015-10-15

    The self-organization and magnetic properties of small iron and cobalt nanostructures embedded into the first layer of a Cu(100) surface are investigated using the self-learning kinetic Monte Carlo method and density functional theory. The similarities and differences between the Fe/Cu(100) and the Co/Cu(100) are underlined. The time evolution of magnetic properties of a copper monolayer with embedded magnetic atoms at 380 K is discussed.

  14. Acoustically modulated magnetic resonance imaging of gas-filled protein nanostructures

    Science.gov (United States)

    Lu, George J.; Farhadi, Arash; Szablowski, Jerzy O.; Lee-Gosselin, Audrey; Barnes, Samuel R.; Lakshmanan, Anupama; Bourdeau, Raymond W.; Shapiro, Mikhail G.

    2018-05-01

    Non-invasive biological imaging requires materials capable of interacting with deeply penetrant forms of energy such as magnetic fields and sound waves. Here, we show that gas vesicles (GVs), a unique class of gas-filled protein nanostructures with differential magnetic susceptibility relative to water, can produce robust contrast in magnetic resonance imaging (MRI) at sub-nanomolar concentrations, and that this contrast can be inactivated with ultrasound in situ to enable background-free imaging. We demonstrate this capability in vitro, in cells expressing these nanostructures as genetically encoded reporters, and in three model in vivo scenarios. Genetic variants of GVs, differing in their magnetic or mechanical phenotypes, allow multiplexed imaging using parametric MRI and differential acoustic sensitivity. Additionally, clustering-induced changes in MRI contrast enable the design of dynamic molecular sensors. By coupling the complementary physics of MRI and ultrasound, this nanomaterial gives rise to a distinct modality for molecular imaging with unique advantages and capabilities.

  15. Metal complex-based templates and nanostructures for magnetic resonance/optical multimodal imaging agents

    NARCIS (Netherlands)

    Galindo Millan, Jealemy

    2012-01-01

    In this thesis, new approaches directed towards simple and functional imaging agents (IAs) for magnetic resonance (MR) and fluorescence multimodal imaging are proposed. In Chapter 3, hybrid silver nanostructures (hAgNSs), grown using a polyamino carboxylic acid scaffold, namely

  16. Magnetic Properties of Large-Scale Nanostructured Graphene Systems

    DEFF Research Database (Denmark)

    Gregersen, Søren Schou

    The on-going progress in two-dimensional (2D) materials and nanostructure fabrication motivates the study of altered and combined materials. Graphene—the most studied material of the 2D family—displays unique electronic and spintronic properties. Exceptionally high electron mobilities, that surpass...... those in conventional materials such as silicon, make graphene a very interesting material for high-speed electronics. Simultaneously, long spin-diffusion lengths and spin-life times makes graphene an eligible spin-transport channel. In this thesis, we explore fundamental features of nanostructured...... graphene systems using large-scale modeling techniques. Graphene perforations, or antidots, have received substantial interest in the prospect of opening large band gaps in the otherwise gapless graphene. Motivated by recent improvements of fabrication processes, such as forming graphene antidots and layer...

  17. Coupled spin, elastic and charge dynamics in magnetic nanostructures

    NARCIS (Netherlands)

    Kamra, A.

    2015-01-01

    In this Thesis, I address the interaction of magnetic degrees of freedom with charge current and elastic dynamics in hybrid systems composed of magnetic and non-magnetic materials. The objective, invariably, is to control and study spin dynamics using charge and elastic degrees of freedom. In

  18. Electric control of wave vector filtering in a hybrid magnetic-electric-barrier nanostructure

    Science.gov (United States)

    Kong, Yong-Hong; Lu, Ke-Yu; He, Ya-Ping; Liu, Xu-Hui; Fu, Xi; Li, Ai-Hua

    2018-06-01

    We theoretically investigate how to manipulate the wave vector filtering effect by a traverse electric field for electrons across a hybrid magnetic-electric-barrier nanostructure, which can be experimentally realized by depositing a ferromagnetic stripe and a Schottky-metal stripe on top and bottom of a GaAs/Al x Ga1- x As heterostructure, respectively. The wave vector filtering effect is found to be related closely to the applied electric field. Moreover, the wave vector filtering efficiency can be manipulated by changing direction or adjusting strength of the traverse electric field. Therefore, such a nanostructure can be employed as an electrically controllable electron-momentum filter for nanoelectronics applications.

  19. Epitaxial strain-engineered self-assembly of magnetic nanostructures in FeRh thin films

    International Nuclear Information System (INIS)

    Witte, Ralf; Kruk, Robert; Molinari, Alan; Wang, Di; Brand, Richard A; Hahn, Horst; Schlabach, Sabine; Provenzano, Virgil

    2017-01-01

    In this paper we introduce an innovative bottom–up approach for engineering self-assembled magnetic nanostructures using epitaxial strain-induced twinning and phase separation. X-ray diffraction, 57 Fe Mössbauer spectroscopy, scanning tunneling microscopy, and transmission electron microscopy show that epitaxial films of a near-equiatomic FeRh alloy respond to the applied epitaxial strain by laterally splitting into two structural phases on the nanometer length scale. Most importantly, these two structural phases differ with respect to their magnetic properties, one being paramagnetic and the other ferromagnetic, thus leading to the formation of a patterned magnetic nanostructure. It is argued that the phase separation directly results from the different strain-dependence of the total energy of the two competing phases. This straightforward relation directly enables further tailoring and optimization of the nanostructures’ properties. (paper)

  20. Magnetic response of hybrid ferromagnetic and antiferromagnetic core-shell nanostructures.

    Science.gov (United States)

    Khan, U; Li, W J; Adeela, N; Irfan, M; Javed, K; Wan, C H; Riaz, S; Han, X F

    2016-03-21

    The synthesis of FeTiO3-Ni(Ni80Fe20) core-shell nanostructures by a two-step method (sol-gel and DC electrodeposition) has been demonstrated. XRD analysis confirms the rhombohedral crystal structure of FeTiO3(FTO) with space group R3[combining macron]. Transmission electron microscopy clearly depicts better morphology of nanostructures with shell thicknesses of ∼25 nm. Room temperature magnetic measurements showed significant enhancement of magnetic anisotropy for the permalloy (Ni80Fe20)-FTO over Ni-FTO core-shell nanostructures. Low temperature magnetic measurements of permalloy-FeTiO3 core-shell structure indicated a strong exchange bias mechanism with magnetic coercivity below the antiferromagnetic Neel temperature (TN = 59 K). The exchange bias is attributed to the alignment of magnetic moments in the antiferromagnetic material at low temperature. Our scheme opens a path towards optimum automotive systems and wireless communications wherein broader bandwidths and smaller sizes are required.

  1. Hybrid luminescent/magnetic nanostructured porous silicon particles for biomedical applications

    Science.gov (United States)

    Muñoz-Noval, Álvaro; Sánchez-Vaquero, Vanessa; Torres-Costa, Vicente; Gallach, Darío; Ferro-Llanos, Vicente; Javier Serrano, José; Manso-Silván, Miguel; García-Ruiz, Josefa Predestinación; Del Pozo, Francisco; Martín-Palma, Raúl J.

    2011-02-01

    This work describes a novel process for the fabrication of hybrid nanostructured particles showing intense tunable photoluminescence and a simultaneous ferromagnetic behavior. The fabrication process involves the synthesis of nanostructured porous silicon (NPSi) by chemical anodization of crystalline silicon and subsequent in pore growth of Co nanoparticles by electrochemically-assisted infiltration. Final particles are obtained by subsequent sonication of the Co-infiltrated NPSi layers and conjugation with poly(ethylene glycol) aiming at enhancing their hydrophilic character. These particles respond to magnetic fields, emit light in the visible when excited in the UV range, and internalize into human mesenchymal stem cells with no apoptosis induction. Furthermore, cytotoxicity in in-vitro systems confirms their biocompatibility and the viability of the cells after incorporation of the particles. The hybrid nanostructured particles might represent powerful research tools as cellular trackers or in cellular therapy since they allow combining two or more properties into a single particle.

  2. Beam-induced magnetic property modifications: Basics, nanostructure fabrication and potential applications

    International Nuclear Information System (INIS)

    Devolder, T.; Bernas, H.; Ravelosona, D.; Chappert, C.; Pizzini, S.; Vogel, J.; Ferre, J.; Jamet, J.-P.; Chen, Y.; Mathet, V.

    2001-01-01

    We have developed an irradiation technique that allows us to tune the magnetic properties of thin films without affecting their roughness. We discuss the mechanisms involved and the applications. He + ion irradiation of Co/Pt multilayers lowers their magnetic anisotropy in a controlled way, reducing the coercive force and then leading to in-plane magnetization. By X-ray reflectometry, we study how irradiation-induced structural modifications correlate with magnetic properties. We also report the L1 0 chemical ordering of FePt by irradiation at 280 deg. C, and the consequent increase of magnetic anisotropy. Planar magnetic patterning at the sub 50 nm scale can be achieved when the irradiation is performed through a mask. New magnetic behaviors result from the fabrication process. They appear to arise from collateral damage. We model these effects in the case of SiO 2 and W masks. The planarity of irradiation-induced patterning and its ability to independently control nanostructure size and coercivity make it very appealing for magnetic recording on nanostructured media. Finally, possible applications to the granular media used in current hard disk drive storage technology are discussed

  3. Nanostructured magnetic particles with polystyrene and their magnetorheological applications.

    Science.gov (United States)

    Fang, Fei Fei; Choi, Hyoung Jin

    2011-03-01

    Magnetorheological (MR) fluids are known to be colloidal suspensions of magnetic particles in a non-magnetic fluid, and exposure to a magnetic field transforms the fluid into a plastic-like solid in milliseconds. To improve the stability against sedimentation and uniform dispersion, two different MR candidates, soft magnetic carbonyl iron (CI) microspheres and magnetite (Fe3O4) particles were modified with polystyrene to be applied for MR fluids in this study. After modification, their unique morphology, crystalline structure and magnetic properties were examined in addition to MR performance and sedimentation characteristics. It was found that this embedded morphology not only effectively prevents direct contact of the magnetic species thus improving particle dispersion but also leads to obvious change in their density, compared with the traditional polymer coating method with a core-shell structure.

  4. Plasmonics of magnetic and topological graphene-based nanostructures

    Science.gov (United States)

    Kuzmin, Dmitry A.; Bychkov, Igor V.; Shavrov, Vladimir G.; Temnov, Vasily V.

    2018-02-01

    Graphene is a unique material in the study of the fundamental limits of plasmonics. Apart from the ultimate single-layer thickness, its carrier concentration can be tuned by chemical doping or applying an electric field. In this manner, the electrodynamic properties of graphene can be varied from highly conductive to dielectric. Graphene supports strongly confined, propagating surface plasmon polaritons (SPPs) in a broad spectral range from terahertz to mid-infrared frequencies. It also possesses a strong magneto-optical response and thus provides complimentary architectures to conventional magneto-plasmonics based on magneto-optically active metals or dielectrics. Despite a large number of review articles devoted to plasmonic properties and applications of graphene, little is known about graphene magneto-plasmonics and topological effects in graphene-based nanostructures, which represent the main subject of this review. We discuss several strategies to enhance plasmonic effects in topologically distinct closed surface landscapes, i.e. graphene nanotubes, cylindrical nanocavities and toroidal nanostructures. A novel phenomenon of the strongly asymmetric SPP propagation on chiral meta-structures and the fundamental relations between structural and plasmonic topological indices are reviewed.

  5. Magnetic Nanostructures Patterned by Self-Organized Materials

    Science.gov (United States)

    2016-01-05

    Palma , J. Escrig, J. C. Denardin Angular dependence of the coercivity and remanence of ordered arrays of Co nanowires Journal of...J. L. Palma , C. Gallardo, L. Spinu, J. M. Vargas, L. S. Dorneles, J. C. Denardin, J. Escrig, Magnetic properties of Fe20 Ni80 antidots: Pore size and...array disorder, Journal of Magnetism and Magnetic Materials., 344, 2013, 8-13 7. E. Vargas, P. Toro, J.L. Palma , J. Escrig, C. Chaneac,

  6. Magnetic anisotropy and order parameter in nanostructured CoPt particles

    Science.gov (United States)

    Komogortsev, S. V.; Iskhakov, R. S.; Zimin, A. A.; Filatov, E. Yu.; Korenev, S. V.; Shubin, Yu. V.; Chizhik, N. A.; Yurkin, G. Yu.; Eremin, E. V.

    2013-10-01

    The correlation of magnetic anisotropy energy with order parameter in the crystallites of CoPt nanostructured particles prepared by thermal decomposition and further annealing has been studied by investigation of the approach magnetization to saturation curves and x-ray powder diffraction pattern profiles. It is shown that magnetic anisotropy energy value in partially ordered CoPt crystallite could be described as an intermediate case between two extremes, corresponding to either single or several c-domains of L10 phase in crystallite.

  7. 3D magnetic nanostructures grown by focused electron and ion beam induced deposition

    Science.gov (United States)

    Fernandez-Pacheco, Amalio

    Three-dimensional nanomagnetism is an emerging research area, where magnetic nanostructures extend along the whole space, presenting novel functionalities not limited to the substrate plane. The development of this field could have a revolutionary impact in fields such as electronics, the Internet of Things or bio-applications. In this contribution, I will show our recent work on 3D magnetic nanostructures grown by focused electron and ion beam induced deposition. This 3D nano-printing techniques, based on the local chemical vapor deposition of a gas via the interaction with electrons and ions, makes the fabrication of complex 3D magnetic nanostructures possible. First, I will show how by exploiting different growth regimes, suspended Cobalt nanowires with modulated diameter can be patterned, with potential as domain wall devices. Afterwards, I will show recent results where the synthesis of Iron-Gallium alloys can be exploited in the field of artificial multiferroics. Moreover, we are developing novel methodologies combining physical vapor deposition and 3D nano-printing, creating Permalloy 3D nanostrips with controllable widths and lengths up to a few microns. This approach has been extended to more complex geometries by exploiting advanced simulation growth techniques combining Monte Carlo and continuum model methods. Throughout the talk, I will show the methodology we are following to characterize 3D magnetic nanostructures, by combining magneto-optical Kerr effect, scanning probe microscopy and electron and X-R magnetic imaging, and I will highlight some of the challenges and opportunities when studying these structures. I acknowledge funding from EPSRC and the Winton Foundation.

  8. Interaction of Individual Skyrmions in a Nanostructured Cubic Chiral Magnet

    Science.gov (United States)

    Du, Haifeng; Zhao, Xuebing; Rybakov, Filipp N.; Borisov, Aleksandr B.; Wang, Shasha; Tang, Jin; Jin, Chiming; Wang, Chao; Wei, Wensheng; Kiselev, Nikolai S.; Zhang, Yuheng; Che, Renchao; Blügel, Stefan; Tian, Mingliang

    2018-05-01

    We report direct evidence of the field-dependent character of the interaction between individual magnetic skyrmions as well as between skyrmions and edges in B 20 -type FeGe nanostripes observed by means of high-resolution Lorentz transmission electron microscopy. It is shown that above certain critical values of an external magnetic field the character of such long-range skyrmion interactions changes from attraction to repulsion. Experimentally measured equilibrium inter-skyrmion and skyrmion-edge distances as a function of the applied magnetic field shows quantitative agreement with the results of micromagnetic simulations. The important role of demagnetizing fields and the internal symmetry of three-dimensional magnetic skyrmions are discussed in detail.

  9. Inorganic Nanostructured High-Temperature Magnet Wires, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This project will develop a high-temperature tolerant electrically-insulating coating for magnet wires. The Phase I program will result in a flexible, inorganic...

  10. Removal of Heavy Metals from Drinking Water by Magnetic Carbon Nanostructures Prepared from Biomass

    OpenAIRE

    Muneeb Ur Rahman Khattak, Muhammad; Zahoor, Muhammad; Muhammad, Bakhtiar; Khan, Farhat Ali; Ullah, Riaz; AbdEI-Salam, Naser M.

    2017-01-01

    Heavy metals contamination of drinking water has significant adverse effects on human health due to their toxic nature. In this study a new adsorbent, magnetic graphitic nanostructures were prepared from watermelon waste. The adsorbent was characterized by different instrumental techniques (surface area analyzer, FTIR, XRD, EDX, SEM, and TG/DTA) and was used for the removal of heavy metals (As, Cr, Cu, Pb, and Zn) from water. The adsorption parameters were determined for heavy metals adsorpti...

  11. Microwave monolithic filter and phase shifter using magnetic nanostructures

    Science.gov (United States)

    Aslam, Shehreen; Khanna, Manoj; Veenugopal, Veerakumar; Kuanr, Bijoy K.

    2018-05-01

    Monolithic Microwave Integrated Circuit (MMIC) have major impact on the development of microwave communication technology. Transition metal based ferromagnetic nano-wired (FMNWs) substrate are of special interest in order to fabricate these MMIC devices. Their saturation magnetization is comparatively higher than ferrites which makes them suitable for high frequency (>10 ˜ 40 GHz) operation at zero or a small applied magnetic field. The CoFeB nanowires in anodic alumina templates were synthesized using three-electrode electro-deposition system. After electro-deposition, 1μm thick Cu layer was sputtered on the top surface of FMNW substrate and lithography was done to design microstrip lines. These microstrip transmission lines were tested for band-stop filters and phase shifters based on ferromagnetic resonance (FMR) over a wide applied magnetic field (H) range. It was observed that attenuation and frequency increase with the increase of magnetic field (upto 5.3 kOe). For phase shifter, the influence of magnetic material was studied for two frequency regions: (i) below FMR and (ii) above FMR. These two frequency regions were suitable for many practical device applications as the insertion loss was very less in these regions in comparison to resonance frequency regions. In the high frequency region (at 35 GHz), the optimal differential phase shift increased significantly to ˜ 250 deg/cm and around low frequency region (at 24 GHz), the optimal differential phase shift is ˜175 deg/cm at the highest field (H) value.

  12. Microwave monolithic filter and phase shifter using magnetic nanostructures

    Directory of Open Access Journals (Sweden)

    Shehreen Aslam

    2018-05-01

    Full Text Available Monolithic Microwave Integrated Circuit (MMIC have major impact on the development of microwave communication technology. Transition metal based ferromagnetic nano-wired (FMNWs substrate are of special interest in order to fabricate these MMIC devices. Their saturation magnetization is comparatively higher than ferrites which makes them suitable for high frequency (>10 ∼ 40 GHz operation at zero or a small applied magnetic field. The CoFeB nanowires in anodic alumina templates were synthesized using three-electrode electro-deposition system. After electro-deposition, 1μm thick Cu layer was sputtered on the top surface of FMNW substrate and lithography was done to design microstrip lines. These microstrip transmission lines were tested for band-stop filters and phase shifters based on ferromagnetic resonance (FMR over a wide applied magnetic field (H range. It was observed that attenuation and frequency increase with the increase of magnetic field (upto 5.3 kOe. For phase shifter, the influence of magnetic material was studied for two frequency regions: (i below FMR and (ii above FMR. These two frequency regions were suitable for many practical device applications as the insertion loss was very less in these regions in comparison to resonance frequency regions. In the high frequency region (at 35 GHz, the optimal differential phase shift increased significantly to ∼ 250 deg/cm and around low frequency region (at 24 GHz, the optimal differential phase shift is ∼175 deg/cm at the highest field (H value.

  13. Nanostructure and magnetic properties of Ni-substituted finemet ribbons

    International Nuclear Information System (INIS)

    Iturriza, N.; Fernandez, L.; Ipatov, M.; Vara, G.; Pierna, A.R.; Val, J.J. del; Chizhik, A.; Gonzalez, J.

    2007-01-01

    Magnetic anisotropy has been induced during the nanocrystallization process of Ni-rich amorphous ferromagnetic (Finemet) ribbons by means of the application of a constant stress during the annealing process. Magnetization measurements have evidenced the anisotropy of the treated samples. The main goal of this work was the analysis of the treated ribbons using X-ray Diffraction (XRD), Transmission Electronic Microscopy (TEM) and Atomic Force Microscopy (AFM). AFM measurements revealed in all the cases a strong nanocrystallisation of the surface without evidences of amorphous matrix, which contrast with XRD and TEM measurements that have shown a high content of amorphous phase in the bulk of the ribbons. Magneto-optical Kerr effect measurements show much higher coercive field values than in the bulk, indicating a complex magnetic behavior for the surface of the ribbons

  14. Giant magnetoresistance effect in nanostructures consisting of magnetic-electric barriers

    International Nuclear Information System (INIS)

    Tang, Wei-Hua; Li, Chun-Shu; Kong, Yong-Hong; Zhang, Gui-Lian

    2007-01-01

    The GMR effect in magnetic-electric barrier nanostructure, which can be realized experimentally by depositing two parallel metallic ferromagnetic strips with an applied voltage on the top of heterostructure, is investigated theoretically. It is shown that a considerable GMR effect can be achieved in such nanosystems due to the significant transmission difference for electrons tunneling through parallel and antiparallel magnetization configurations. It is also shown that the magnetoresistance ratio is strongly dependent upon the applied voltage to metallic ferromagnetic strips in nanosystems, thus may leading to voltage-tunable GMR devices

  15. Ferromagnetic (Ga,Mn)As layers and nanostructures: control of magnetic anisotropy by strain engineering

    Energy Technology Data Exchange (ETDEWEB)

    Wenisch, Jan

    2008-07-01

    This work studies the fundamental connection between lattice strain and magnetic anisotropy in the ferromagnetic semiconductor (Ga,Mn)As. The first chapters provide a general introduction into the material system and a detailed description of the growth process by molecular beam epitaxy. A finite element simulation formalism is developed to model the strain distribution in (Ga,Mn)As nanostructures is introduced and its predictions verified by high-resolution X-ray diffraction methods. The influence of lattice strain on the magnetic anisotropy is explained by an magnetostatic model. A possible device application is described in the closing chapter. (orig.)

  16. Preparation and properties of novel magnetic composite nanostructures: Arrays of nanowires in porous membranes

    International Nuclear Information System (INIS)

    Vazquez, M.; Hernandez-Velez, M.; Asenjo, A.; Navas, D.; Pirota, K.; Prida, V.; Sanchez, O.; Baldonedo, J.L.

    2006-01-01

    In the present work, we introduce our latest achievements in the development of novel highly ordered composite magnetic nanostructures employing anodized nanoporous membranes as precursor templates where long-range hexagonal symmetry is induced by self-assembling during anodization process. Subsequent processing as electroplating, sputtering or pressing are employed to prepare arrays of metallic, semiconductor or polymeric nanowires embedded in oxide or metallic membranes. Particular attention is paid to recent results on controlling the magnetic anisotropy in arrays of metallic nanowires, particularly Co, and nanohole arrays in Ni membranes

  17. Magnetic structure evolution in mechanically milled nanostructured ZnFe2O4 particles

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Wynn, P.; Mørup, Steen

    1999-01-01

    Nanostructured partially-inverted ZnFe2O4 particles have been prepared from bulk ZnFe2O4 by high-energy ball milling in an open container. The grain size reduction, cation site distributions, and the evolution of magnetic structures have been studied by x-ray diffraction with Rietveld structure...... refinements, transmission electron microscopy, and Mossbauer spectroscopy. It is found that a change of magnetic structure from an antiferromagnetic to a ferrimagnetic (or ferromagnetic) structure occurs in the milled samples. This change is correlated with the redistribution of the cations, Zn and Fe...

  18. Size Induced Structural and Magnetic Properties of Nanostructured ...

    African Journals Online (AJOL)

    Their structural and magnetic properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) measurements. The average crystallite size of CoFe2O4was observed to increase from 23 to 65 nm as the annealing temperature was increased from ...

  19. Study of magnetic properties of graphene nanostructures and graphene nanoribbons

    Directory of Open Access Journals (Sweden)

    F Fazileh

    2012-03-01

    Full Text Available The discovery of graphene and its remarkable electronic and magnetic properties has initiated great research interest in this material. Furthermore, there are many derivatives in these graphene related materials among which graphene nanoribbons and graphene nanofragments are candidates for future carbon-based nanoelectronics and spintronics. Theoretical studies have shown that magnetism can arise in various situations such as point defects, disorder and reduced dimensionality. Using a mean field Hubbard model, we studied the appearance of magnetic textures in zero-dimensional graphene nanofragments and one-dimensional graphene zigzag nanoribbons. Among nanofragments, triangular shape, bowtie and coronene were studied. We explain how the shape of these materials, the imbalance in the number of atoms belonging to the graphene sublattices, the existence of zero-energy states and the total and local magnetic moments were related. At the end, we focused on the effects of a model disorder potential (Anderson-type, and illustrate how density of states of zigzag nanoribbons was affected.

  20. The exchange interaction effects on magnetic properties of the nanostructured CoPt particles

    Energy Technology Data Exchange (ETDEWEB)

    Komogortsev, S.V., E-mail: komogor@iph.krasn.ru [Kirensky Institute of Physics, SB RAS, 660036 Krasnoyarsk (Russian Federation); Iskhakov, R.S. [Kirensky Institute of Physics, SB RAS, 660036 Krasnoyarsk (Russian Federation); Zimin, A.A. [Siberian Federal University, 660041 Krasnoyarsk (Russian Federation); Filatov, E.Yu.; Korenev, S.V.; Shubin, Yu.V. [Nikolaev Institute of Inorganic Chemistry, SB RAS, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation); Chizhik, N.A. [Siberian Federal University, 660041 Krasnoyarsk (Russian Federation); Yurkin, G.Yu.; Eremin, E.V. [Kirensky Institute of Physics, SB RAS, 660036 Krasnoyarsk (Russian Federation)

    2016-03-01

    Various manifestations of the exchange interaction effects in magnetization curves of the CoPt nanostructured particles are demonstrated and discussed. The inter-grain exchange constant A in the sponge-like agglomerates of crystallites is estimated as A=(7±1) pJ/m from the approach magnetization to saturation curves that is in good agreement with A=(6.6±0.5) pJ/m obtained from Bloch T {sup 3/2} law. The fractal dimensionality of the exchange coupled crystallite system in the porous media of the disordered CoPt alloy d=(2.60±0.18) was estimated from the approach magnetization to saturation curve. Coercive force decreases with temperature as H{sub c}~T {sup 3/2} which is assumed to be a consequence of the magnetic anisotropy energy reduction due to the thermal spin wave excitations in the investigated CoPt particles. - Highlights: • Nanostructured CoPt particles were synthesized and then annealed in He atmosphere. • The structure of the material and magnetization curves were studied. • The maximum on reduced coercivity vs grain size dependence was observed. • The dimensionality d of exchange coupled crystallite system was estimated. • Exchange stiffness constant A was estimated.

  1. Magnetic and sensitive magnetoelastic properties of Finemet nanostructured ribbon

    International Nuclear Information System (INIS)

    Pham Duc Thang; Hoang Hai Duong; Nguyen Hoang Nghi

    2009-01-01

    Soft-magnetic Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 (Finemet) ribbon has been fabricated by using melt-spinning techniques. After annealing at suitable temperature the ribbon changes from an amorphous to crystalline state which related to the formation of Fe nanocrystallites. Study on the magnetic and magnetoelastic properties of the ribbon is presented. Furthermore, based on the fabricated ribbon stress sensors are simply constructed. The sensors showed high sensitivity of 3.8 mV/MPa as well as a wide working range up to 17 MPa. These sensors are potential for practical applications such as detecting small stress and movement in civil structures.

  2. Magnetoresistance effect in a both magnetically and electrically modulated nanostructure

    International Nuclear Information System (INIS)

    Lu, Mao-Wang; Yang, Guo-Jian

    2007-01-01

    We propose a magnetoresistance device in a both magnetically and electrically modulated two-dimensional electron gas, which can be realized experimentally by the deposition, on the top and bottom of a semiconductor heterostructure, of two parallel metallic ferromagnetic strips under an applied voltage. It is shown that a considerable magnetoresistance effect can be achieved in such a device due to the significant transmission difference for electrons through parallel and antiparallel magnetization configurations. It is also shown that the magnetoresistance ratio depends strongly on the applied voltage to the stripe in the device. These interesting properties may provide an alternative scheme to realize magnetoresistance effect in hybrid ferromagnetic/semiconductor nanosystems, and this system may be used as a voltage-tunable magnetoresistance device

  3. The exchange interaction effects on magnetic properties of the nanostructured CoPt particles

    Science.gov (United States)

    Komogortsev, S. V.; Iskhakov, R. S.; Zimin, A. A.; Filatov, E. Yu.; Korenev, S. V.; Shubin, Yu. V.; Chizhik, N. A.; Yurkin, G. Yu.; Eremin, E. V.

    2016-03-01

    Various manifestations of the exchange interaction effects in magnetization curves of the CoPt nanostructured particles are demonstrated and discussed. The inter-grain exchange constant A in the sponge-like agglomerates of crystallites is estimated as A=(7±1) pJ/m from the approach magnetization to saturation curves that is in good agreement with A=(6.6±0.5) pJ/m obtained from Bloch T 3/2 law. The fractal dimensionality of the exchange coupled crystallite system in the porous media of the disordered CoPt alloy d=(2.60±0.18) was estimated from the approach magnetization to saturation curve. Coercive force decreases with temperature as Hc T 3/2 which is assumed to be a consequence of the magnetic anisotropy energy reduction due to the thermal spin wave excitations in the investigated CoPt particles.

  4. Highly-Ordered Magnetic Nanostructures on Self-Assembled α-Al2O3 and Diblock Copolymer Templates

    International Nuclear Information System (INIS)

    Erb, Denise

    2015-08-01

    This thesis shows the preparation of nanostructured systems with a high degree of morphological uniformity and regularity employing exclusively selfassembly processes, and documents the investigation of these systems by means of atomic force microscopy (AFM), grazing incidence small angle X-ray scattering (GISAXS), and nuclear resonant scattering of synchrotron radiation (NRS). Whenever possible, the X-ray scattering methods are applied in-situ and simultaneously in order to monitor and correlate the evolution of structural and magnetic properties of the nanostructured systems. The following systems are discussed, where highly-ordered magnetic nanostructures are grown on α-Al 2 O 3 substrates with topographical surface patterning and on diblock copolymer templates with chemical surface patterning: - Nanofaceted surfaces of α-Al 2 O 3 - Magnetic nanostructures on nanofaceted α-Al 2 O 3 substrates - Thin films of microphase separated diblock copolymers - Magnetic nanostructures on diblock copolymer thin film templates The fact that the underlying self-assembly processes can be steered by external factors is utilized to optimize the degree of structural order in the nanostructured systems. The highly-ordered systems are well-suited for investigations with X-ray scattering methods, since due to their uniformity the inherently averaged scattered signal of a sample yields meaningful information on the properties of the contained nanostructures: By means of an in-situ GISAXS experiment at temperatures above 1000 C, details on the facet formation on α-Al 2 O 3 surfaces are determined. A novel method, merging in-situ GISAXS and NRS, shows the evolution of magnetic states in a system with correlated structural and magnetic inhomogeneity with lateral resolution. The temperature-dependence of the shape of Fe nanodots growing on diblock copolymer templates is revealed by in-situ GISAXS during sputter deposition of Fe. Combining in-situ GISAXS and NRS, the magnetization

  5. Giant magnetoresistance and quantum transport in magnetic hybrid nanostructures

    International Nuclear Information System (INIS)

    Sanvito, S.

    2000-01-01

    Technological advances in device micro- and nano-fabrication over the past decade has enabled a variety of novel heterojunction device structures to be made. Among these, magnetic multilayers, superconductor/normal metal junctions and carbon nanotubes exhibit a rich variety of features, with the potential for future generations of electronic devices with improved sensitivity and higher packing density. The modeling of such structures in a flexible and accurate way, with a predictive capability is a formidable theoretical challenge. In this thesis I will present a very general numerical technique to compute transport properties of heterogeneous systems, which can be used together with accurate spd tight-binding Hamiltonians or simpler models. I will then apply this technique to several transport problems in the mesoscopic regime. Firstly I will review the material dependence of CPP GMR in perfect crystalline magnetic multilayers, analyze their conductance oscillations and discuss some preliminary results of magnetic tunneling junctions. In the contest of the conductance oscillations I will introduce a simple Kroenig-Penney model which gives a full understanding of the relevant periods involved in the oscillations. I will then present a simple model, which can be used to study disordered magnetic systems and the cross-over from ballistic to diffusive transport. This model explains recent experiments on CPP GMR, which cannot be understood within the usual Boltzmann transport framework. Then I will present results for superconducting/ normal metal and for superconducting/multilayer junctions. In the case of multilayers I will show that in both the ballistic and diffusive regimes the GMR is expected to vanish if a superconducting contact is added and go on to show why this is not the case in practice. Finally I will present features of ballistic transport in multiwall carbon nanotubes and show how the inter-tube interaction can, not only block some of the scattering

  6. Optical properties of semiconductor nanostructures in magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Grochol, M.

    2007-04-03

    In this work, the near bandgap linear optical properties of semiconductor quantum structures under applied magnetic field are investigated. First, the exciton theory is developed starting with the one-electron Hamiltonian in a crystal, continuing with the Luttinger and Bir-Pikus Hamiltonian, and ending with the exciton Hamiltonian in the envelope function approximation. Further, concentrating on the quantum well and thus assuming strong confinement in the growth direction, the motion parallel and perpendicular to the xy-plane is factorized leading to the well-known single sublevel approximation. A magnetic field perpendicular to the xy-plane is applied, and a general theorem describing the behavior of the energy eigenvalues is derived. The strain calculation within the isotropic elasticity approach is described in detail. The Schroedinger equation is solved numerically for both the full model and the factorization with artificially generated disorder potentials. Furthermore the statistical properties of the disorder in a real quantum well have been analyzed. In particular, temperature dependent photoluminescence spectra and diamagnetic shift statistics, have been compared with the experimental ones and very good agreement has been found. The second part of this thesis deals predominantly with highly symmetrical structures embedded in the quantum well: namely quantum rings and dots. First, adopting an ansatz for the wave function, the Hamiltonian matrix is derived discussing which matrix elements are non-zero according to the symmetry of the potential. Additionally, the expectation values of the current and magnetization operators are evaluated. Then, concentrating on the case of the highest (circular) symmetry, the model of zero width ring is introduced. Within this model the close relation between the oscillatory component of the exciton energy (exciton Aharonov-Bohm effect) and the persistent current is revealed. Examples for different material systems follow

  7. Magnetization states and magnetization processes in nanostructures: from a single layer to multilayers

    Czech Academy of Sciences Publication Activity Database

    Maziewski, A.; Fassbender, J.; Kisielewski, J.; Kisielewski, M.; Kurant, Z.; Mazalski, P.; Stobiecki, F.; Stupakiewicz, A.; Sveklo, I.; Tekielak, M.; Wawro, A.; Zablotskyy, Vitaliy A.

    2014-01-01

    Roč. 211, č. 5 (2014), s. 1005-1018 ISSN 1862-6300 R&D Projects: GA ČR GA13-18993S Institutional support: RVO:68378271 Keywords : light and ions irradiation effects * magnetic anisotropy * magnetic domains * magnetic ordering * magnetic ultrathin films and multilayers Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.616, year: 2014

  8. Building Composite Fe-Mn Oxide Flower-Like Nanostructures: A Detailed Magnetic Study

    KAUST Repository

    Zuddas, Efisio; Lentijo Mozo, Sergio; Casu, Alberto; Deiana, Davide; Falqui, Andrea

    2017-01-01

    Here we show that it’s possible to produce different magnetic core-multiple shells heterostructures from monodispersed iron oxide spherical magnetic seeds by finely controlling the amount of a manganese precursor and using in a smart and simple way a cation exchange synthetic approach. In particular, by increasing the amount of precursor we were able to produce nanostructures ranging from Fe3O4/Mn-ferrite core/single shell nanospheres to larger, flower-like Fe3O4/Mn-ferrite/Mn3O4 core-double shell nanoparticles. We first demonstrate how the formation of the initial thin manganese-ferrite shell determines a dramatic reduction of the superficial disorder in the starting iron oxide, bringing to nanomagnets with lower hardness. Then, the growth of the second and most external manganese oxide shell causes the magnetical hardening of the heterostructures, while its magnetic exchange coupling with the rest of the heterostructure can be antiferromagentic or ferromagnetic, depending on the strength of the applied external magnetic field. This response is similar to that of an iron oxide-manganese oxide core-shell system but differs from what observed in multiple-shell heterostructures. Finally, we report as the most external shell becomes magnetically irrelevant above the ferrimagnetic-paramagnetic transition of the manganese oxide and the resulting magnetic behavior of the flower-like structures is then studied in-depth.

  9. Building Composite Fe-Mn Oxide Flower-Like Nanostructures: A Detailed Magnetic Study

    KAUST Repository

    Zuddas, Efisio

    2017-07-21

    Here we show that it’s possible to produce different magnetic core-multiple shells heterostructures from monodispersed iron oxide spherical magnetic seeds by finely controlling the amount of a manganese precursor and using in a smart and simple way a cation exchange synthetic approach. In particular, by increasing the amount of precursor we were able to produce nanostructures ranging from Fe3O4/Mn-ferrite core/single shell nanospheres to larger, flower-like Fe3O4/Mn-ferrite/Mn3O4 core-double shell nanoparticles. We first demonstrate how the formation of the initial thin manganese-ferrite shell determines a dramatic reduction of the superficial disorder in the starting iron oxide, bringing to nanomagnets with lower hardness. Then, the growth of the second and most external manganese oxide shell causes the magnetical hardening of the heterostructures, while its magnetic exchange coupling with the rest of the heterostructure can be antiferromagentic or ferromagnetic, depending on the strength of the applied external magnetic field. This response is similar to that of an iron oxide-manganese oxide core-shell system but differs from what observed in multiple-shell heterostructures. Finally, we report as the most external shell becomes magnetically irrelevant above the ferrimagnetic-paramagnetic transition of the manganese oxide and the resulting magnetic behavior of the flower-like structures is then studied in-depth.

  10. Preparation and characterisation of magnetic nanostructured samples for inelastic neutron scattering experiments

    Energy Technology Data Exchange (ETDEWEB)

    Kreuzpaintner, Wolfgang

    2010-06-22

    Recent advances in thin-film structuring techniques have generated significant interest in the dynamics of spin waves in magnetic nanostructures and the possible use of inelastic neutron scattering (INS) for their investigation. This thesis describes the design and implementation, at GKSS Research Centre, of equipment for preparation of large and laterally submicron and nanometre structured magnetic samples for such future INS experiments. After a brief resume on spin waves in nanostructures, the development work on new purpose-designed equipment, including high vacuum (HV) argon ion beam milling and ultra high vacuum (UHV) e-beam evaporation setups, is described. Ni nanodot as well as Ni and novel Gd nanowire samples were prepared using combinations of sputter deposition, laser interference lithography, argon ion beam milling, e-beam evaporation and self organisation techniques. With reference to sample preparation, epitaxial growth studies for Ni on Si(100) substrate were performed, resulting in the development of a new deposition process, which by thermal tuning allows for the direct epitaxial growth of Ni on Si with unprecedented crystalline quality. The results of various characterisation experiments on the prepared nanostructured samples, including Scanning Electron Microscopy (SEM), microprobe analysis, Atomic and Magnetic Force Microscopy (AFM/MFM), Vibrating Sample Magnetometry (VSM), X-ray Diffraction (XRD) and Reflectivity (XRR), unpolarised and Polarised Neutron Scattering (PNR) and off-specular scattering by X-rays and neutrons using rocking scans and Time-Of-Flight Grazing Incidence Small Angle Neutron Scattering (TOF-GISANS), together with various analysis procedures such as Distorted-Wave Born Approximation (DWBA), are reported. The analysis of a Gd nanowire sample by TOF-GISANS led to a novel evaluation technique which in comparison with single wavelength methods allows portions of reciprocal space to be scanned without changing the angle of

  11. Preparation and characterisation of magnetic nanostructured samples for inelastic neutron scattering experiments

    International Nuclear Information System (INIS)

    Kreuzpaintner, Wolfgang

    2010-01-01

    Recent advances in thin-film structuring techniques have generated significant interest in the dynamics of spin waves in magnetic nanostructures and the possible use of inelastic neutron scattering (INS) for their investigation. This thesis describes the design and implementation, at GKSS Research Centre, of equipment for preparation of large and laterally submicron and nanometre structured magnetic samples for such future INS experiments. After a brief resume on spin waves in nanostructures, the development work on new purpose-designed equipment, including high vacuum (HV) argon ion beam milling and ultra high vacuum (UHV) e-beam evaporation setups, is described. Ni nanodot as well as Ni and novel Gd nanowire samples were prepared using combinations of sputter deposition, laser interference lithography, argon ion beam milling, e-beam evaporation and self organisation techniques. With reference to sample preparation, epitaxial growth studies for Ni on Si(100) substrate were performed, resulting in the development of a new deposition process, which by thermal tuning allows for the direct epitaxial growth of Ni on Si with unprecedented crystalline quality. The results of various characterisation experiments on the prepared nanostructured samples, including Scanning Electron Microscopy (SEM), microprobe analysis, Atomic and Magnetic Force Microscopy (AFM/MFM), Vibrating Sample Magnetometry (VSM), X-ray Diffraction (XRD) and Reflectivity (XRR), unpolarised and Polarised Neutron Scattering (PNR) and off-specular scattering by X-rays and neutrons using rocking scans and Time-Of-Flight Grazing Incidence Small Angle Neutron Scattering (TOF-GISANS), together with various analysis procedures such as Distorted-Wave Born Approximation (DWBA), are reported. The analysis of a Gd nanowire sample by TOF-GISANS led to a novel evaluation technique which in comparison with single wavelength methods allows portions of reciprocal space to be scanned without changing the angle of

  12. Microstructural and magnetic behavior of nanostructured soft alloys prepared by mechanical grinding and gas atomization

    International Nuclear Information System (INIS)

    Marin, P.; Lopez, M.; Garcia-Escorial, A.; Lieblich, M.

    2007-01-01

    Nanocrystalline powder of Fe-Si-B-Cu-Nb has been obtained by means of mechanical milling of the corresponding nanocrystalline ribbons. Gas atomization technique has been used to minimize the magnetic hardening due to stress effects observed in ball-milled samples. Fe-Si-B-Cu-Nb and Fe-Si nanocrystalline samples have been prepared by gas atomization. The aim of our work is to analyse the particle size dependence of coercivity in this nanostructured alloys and to show the analogies and differences between ball-milled and gas atomized samples

  13. Magnetic field-assisted synthesis of wire-like Co3O4 nanostructures: Electrochemical and photocatalytic studies

    International Nuclear Information System (INIS)

    Zhao, Xiubin; Pang, Zhanwen; Wu, Mingzai; Liu, Xiansong; Zhang, Hui; Ma, Yongqing; Sun, Zhaoqi; Zhang, Lide; Chen, Xiaoshuang

    2013-01-01

    Graphical abstract: Schematic illustration for the magnetic field-assisted growth of wire-like Co 3 O 4 nanostructure. Display Omitted Highlights: ► Co 3 O 4 nanowires are prepared by magnetic field hydrothermal reduction and annealing. ► These Co 3 O 4 nanowires possess enhanced capacitance. ► The Co 3 O 4 nanowires have a good photocatalytic activity for methyl orange. -- Abstract: Wire-like Co 3 O 4 nanostructures were prepared by the combination of magnetic field-assisted hydrothermal reduction of cobalt ions and the subsequent ambient annealing at 500 °C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the structure and morphological evolution of the products. The results show that the wire-like nanostructures possess diameters about 250 nm and lengths over 10 μm. The possible formation mechanism of the wire-like Co 3 O 4 nanostructures is also proposed based on the SEM results. Galvanostatic methods were used to characterize the electrochemical properties. The measurements indicate that the wire-like Co 3 O 4 nanostructures show larger discharge and charge capacities than that of spherical Co 3 O 4 nanoparticles prepared in the absence of magnetic field. In addition, the photocatalytic activity of the products was investigated by measuring the photodegradation of methyl orange solution under ultraviolet radiation, which shows that both the wire-like and spherical products have a good photocatalytic activity.

  14. Advances on the nanostructuration of magnetic molecules on surfaces: the case of single-molecule magnets (SMM).

    Science.gov (United States)

    Gómez-Segura, Jordi; Veciana, Jaume; Ruiz-Molina, Daniel

    2007-09-28

    SMMs exhibit slow magnetization relaxation rates characteristic of nanodomain particles whose origin is however on individual molecules. For this reason, they have attracted much interest due to their potential applications in high-density information storage devices and quantum computing applications, where for instance, each molecule can be used as a magnetic bit of information. However, for this to become a reality, several basic studies such as their deposition on surfaces are still highly required. Here we will revise all the experimental approximations that have been so far reported for their addressing, nanostructuration and study on surfaces, from the use of stamps as templates to their anchorage to gold surface through the use of thiol-based ligands. It is also important to emphasize that the results and methodologies described along this review are applicable not only to SMMs but to any molecular material.

  15. Nanostructure and magnetization reversal process in TbFeCo/Yx(FeCo)1-x spring-magnet type multilayers

    International Nuclear Information System (INIS)

    Duc, N.H.; Huong Giang, D.T.; Chau, N.

    2004-01-01

    Studies of the naturally formed nanostructure and magnetization reversal process were performed for the sputtered Tb(Fe 0.55 Co 0.45 ) 1.5 /Y x (Fe 0.7 Co 0.3 ) 1-x multilayers (0≤x≤0.2) with a TbFeCo layer thickness t TbFeCo =12 nm and YFeCo layer thickness t YFeCo =10 nm. The structural investigations showed that nanocrystals are naturally formed and coexist within the amorphous matrix in Y 0.1 (FeCo) 0.9 layers. In this state, low magnetic coercivity and large parallel magnetostrictive susceptibility are observed. The results are discussed in terms of the crystalline discontinuity of the soft YFeCo layers

  16. Low-angle polarized neutron and X-ray scattering from magnetic nanolayers and nanostructures

    CERN Document Server

    Paul, Amitesh

    2017-01-01

    This research monograph presents the latest results related to the characterization of low dimensional systems. Low-angle polarized neutron scattering and X-ray scattering at grazing incidence are used as the two main techniques to explore various physical phenomena of these systems. Special focus is put on systems like thin film transition metal and rare-earth layers, oxide heterostructures, hybrid systems, self-assembled nanostructures and self-diffusion.  Readers will gain in-depth knowledge about the usage of specular scattering and off-specular scattering techniques. Investigation of in-plane and out-of-plane structures and magnetism with vector magnetometric information is illustrated comprehensively. The book caters to a wide audience working in the field of nano-dimensional magnetic systems and the neutron and X-ray reflectometry community in particular.

  17. Physical property control in core/shell inorganic nanostructures for fluorescence and magnetic targeting applications

    Science.gov (United States)

    Roberts, Stephen K.

    Nanomaterials show immense promise for the future in numerous areas of application. Properties that are unique from the bulk material and are tunable allow for innovation in material design. This thesis will focus on controlling the physical properties of core/shell nanostructures to enhance the utility of the materials. The first focus is on the impact of different solvent mixtures during the shell growth phase of SILAR based core/shell quantum dot synthesis is studied. Gaining insight into the mechanism for SILAR growth of core/shell nanoparticles allows improved synthetic yields and precursor binding, providing enhanced control to synthesis of core/shell nanoparticles. The second focus of this thesis is exploring the use of magnetic nanoparticles for magnetic drug targeting for cardiovascular conditions. Magnetic targeting for drug delivery enables increased local drug concentration, while minimizing non-specific interactions. In order to be effective for magnetic targeting, it must be shown that low magnetic strength is sufficient to capture flowing nanoparticles. By demonstrating the binding of a therapeutic agent to the surface at medicinal levels, the viability for use as a nanoparticle drug delivery system is improved.

  18. Highly ordered FEPT and FePd magnetic nano-structures: Correlated structural and magnetic studies

    International Nuclear Information System (INIS)

    Lukaszew, Rosa Alejandra; Cebollada, Alfonso; Clavero, Cesar; Garcia-Martin, Jose Miguel

    2006-01-01

    The micro-structure of epitaxial FePt and FePd films grown on MgO (0 0 1) substrates is correlated to their magnetic behavior. The FePd films exhibit high chemical ordering and perpendicular magnetic anisotropy. On the other hand FePt films exhibit low chemical ordering, with nano-grains oriented in two orthogonal directions, forcing the magnetization to remain in the plane of the films

  19. Growth, structure and magnetic properties of FePt nanostructures on NaCl(001) and MgO(001)

    International Nuclear Information System (INIS)

    Liscio, F; Maret, M; Doisneau-Cottignies, B; Makarov, D; Albrecht, M; Roussel, H

    2010-01-01

    A comparison of the structural and magnetic properties of FePt nanostructures grown at different temperatures on NaCl(001) and MgO(001) substrates is presented. A strong influence of the deposition temperature on the epitaxial growth as well as on the size distribution of FePt nanostructures grown on NaCl substrates is observed. In spite of a large lattice mismatch between FePt and NaCl, a 'cube-over-cube' growth of nanostructures with a narrow size distribution was achieved at 520 K. Moreover, the growth of FePt nanostructures on NaCl(001) is not preceded by the formation of a wetting layer as observed on MgO(001). The higher degree of L1 0 chemical ordering in FePt nanostructures grown on MgO(001) accompanied by the absence of L1 0 variants with an in-plane tetragonal c-axis indicates that the tensile epitaxial stress induced by the MgO substrate is a key factor in the formation of the L1 0 phase with an out-of-plane c-axis. Superparamagnetic behavior is revealed for the FePt nanostructures grown on NaCl(001) due to their small size and relatively poor chemical order.

  20. Copper, gold, and silver decorated magnetic core-polymeric shell nanostructures for destruction of pathogenic bacteria

    Science.gov (United States)

    Padervand, Mohsen; Karanji, Ahmad Kiani; Elahifard, Mohammad Reza

    2017-05-01

    Fe3O4 magnetic nanoparticles (MNPs) were prepared by co-precipitation method. The nanoparticles were silica coated using TEOS, and then modified by the polymeric layers of polypropylene glycol (PPG) and polyethylene glycol (PEG). Finally, the core-shell samples were decorated with Ag, Au, and Cu nanoparticles. The products were characterized by vibrating sample magnetometry (VSM), TGA, SEM, XRD, and FTIR methods. The antibacterial activity of the prepared samples was evaluated in inactivation of E. coli and S. aureus microorganisms, representing the Gram-negative and Gram-positive species, respectively. The effect of solid dosage, bacteria concentration and type of polymeric modifier on the antibacterial activity was investigated. TEM images of the bacteria were recorded after the treatment time and according to the observed changes in the cell wall, the mechanism of antibacterial action was discussed. The prepared nanostructures showed high antibacterial activity against both Gram-negative and Gram-positive bacteria. This was due to the leaching of metal ions which subsequently led to the lysis of bacteria. A theoretical investigation was also done by studying the interaction of loaded metals with the nucleotide components of the microorganism DNA, and the obtained results were used to explain the experimental data. Finally, based on the observed inactivation curves, we explain the antibacterial behavior of the prepared nanostructures mathematically.

  1. Controlling the Optical and Magnetic Properties of Nanostructured Cuprous Oxide Synthesized from Waste Electric Cables

    Science.gov (United States)

    Abdelbasir, S. M.; El-Sheikh, S. M.; Rashad, M. M.; Rayan, D. A.

    2018-03-01

    Cuprous oxide Cu2O nanopowders were purposefully synthesised from waste electric cables (WECs) via a simple precipitation route at room temperature using lactose as a reducing agent. In this regard, dimethyl sulfoxide (DMSO) was first applied as an organic solvent for the dissolution of the cable insulating materials. Several parameters were investigated during dissolution of WECs such as dissolution temperature, time and solid/liquid ratio to determine the dissolution percentage of the insulating materials in DMSO. The morphology and the optical properties of the formed Cu2O particles were investigated using X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy and UV-visible-near IR spectrophotometer. XRD data confirmed the presence of single crystalline phase of Cu2O nanoparticles. FE-SEM and TEM images revealed spherical, cubic and octahedral shapes with the various particle sizes ranged from 16 to 57 nm depending on the synthesis conditions. A possible mechanism explaining the Cu2O nanostructures formation was proposed. The band gap energies of the Cu2O nanostructures were estimated and the values were located between 1.5 and 2.08 eV. Photoluminescence spectroscopy analysis clearly showed a noticeably blue-shifted emission for the synthesized samples compared to spectrum of the bulk. Eventually, magnetic properties of the synthesized nanoparticles have been measured by vibrating sample magnetometer and the attained results implied that the synthesized particles are weakly ferromagnetic in nature at normal temperature.

  2. Scalable high-affinity stabilization of magnetic iron oxide nanostructures by a biocompatible antifouling homopolymer

    KAUST Repository

    Luongo, Giovanni

    2017-10-12

    Iron oxide nanostructures have been widely developed for biomedical applications, due to their magnetic properties and biocompatibility. In clinical application, the stabilization of these nanostructures against aggregation and non-specific interactions is typically achieved using weakly anchored polysaccharides, with better-defined and more strongly anchored synthetic polymers not commercially adopted due to complexity of synthesis and use. Here, we show for the first time stabilization and biocompatibilization of iron oxide nanoparticles by a synthetic homopolymer with strong surface anchoring and a history of clinical use in other applications, poly(2-methacryloyloxyethy phosphorylcholine) (poly(MPC)). For the commercially important case of spherical particles, binding of poly(MPC) to iron oxide surfaces and highly effective individualization of magnetite nanoparticles (20 nm) are demonstrated. Next-generation high-aspect ratio nanowires (both magnetite/maghemite and core-shell iron/iron oxide) are furthermore stabilized by poly(MPC)-coating, with nanowire cytotoxicity at large concentrations significantly reduced. The synthesis approach is exploited to incorporate functionality into the poly(MPC) chain is demonstrated by random copolymerization with an alkyne-containing monomer for click-chemistry. Taking these results together, poly(MPC) homopolymers and random copolymers offer a significant improvement over current iron oxide nanoformulations, combining straightforward synthesis, strong surface-anchoring and well-defined molecular weight.

  3. Scalable high-affinity stabilization of magnetic iron oxide nanostructures by a biocompatible antifouling homopolymer

    KAUST Repository

    Luongo, Giovanni; Campagnolo, Paola; Perez, Jose E.; Kosel, Jü rgen; Georgiou, Theoni K.; Regoutz, Anna; Payne, David J; Stevens, Molly M.; Ryan, Mary P.; Porter, Alexandra E; Dunlop, Iain E

    2017-01-01

    Iron oxide nanostructures have been widely developed for biomedical applications, due to their magnetic properties and biocompatibility. In clinical application, the stabilization of these nanostructures against aggregation and non-specific interactions is typically achieved using weakly anchored polysaccharides, with better-defined and more strongly anchored synthetic polymers not commercially adopted due to complexity of synthesis and use. Here, we show for the first time stabilization and biocompatibilization of iron oxide nanoparticles by a synthetic homopolymer with strong surface anchoring and a history of clinical use in other applications, poly(2-methacryloyloxyethy phosphorylcholine) (poly(MPC)). For the commercially important case of spherical particles, binding of poly(MPC) to iron oxide surfaces and highly effective individualization of magnetite nanoparticles (20 nm) are demonstrated. Next-generation high-aspect ratio nanowires (both magnetite/maghemite and core-shell iron/iron oxide) are furthermore stabilized by poly(MPC)-coating, with nanowire cytotoxicity at large concentrations significantly reduced. The synthesis approach is exploited to incorporate functionality into the poly(MPC) chain is demonstrated by random copolymerization with an alkyne-containing monomer for click-chemistry. Taking these results together, poly(MPC) homopolymers and random copolymers offer a significant improvement over current iron oxide nanoformulations, combining straightforward synthesis, strong surface-anchoring and well-defined molecular weight.

  4. Numerical evaluation of energy barriers and magnetic relaxation in interacting nanostructured magnetic systems

    International Nuclear Information System (INIS)

    Chubykalo-Fesenko, Oksana A.; Chantrell, Roy W.

    2004-01-01

    We discuss a model to quantify long-time thermally induced magnetization reversal in magnetic systems with distributed properties. Two algorithms, based on kinetic and Metropolis Monte Carlo are introduced. While the former requires the constant recalculation of all energy barriers and is useful when the interactions are weak, the latter uses the Metropolis Monte Carlo to estimate the magnetization trajectory and, consequently, only the most probable transition rates are evaluated. The ridge optimization method is used to evaluate the energy barriers in a multidimensional energy landscape. The algorithms are applied to a granular system modeled by means of Voronoi polyhedra and having random in-plane anisotropy

  5. Neutron scattering—The key characterization tool for nanostructured magnetic materials

    Energy Technology Data Exchange (ETDEWEB)

    Fitzsimmons, M.R., E-mail: fitz@lanl.gov [Los Alamos National Laboratory (United States); Schuller, Ivan K. [University of California, San Diego (United States)

    2014-01-15

    The novel properties of materials produced using nanoscale manufacturing processes often arise from interactions across interfaces between dissimilar materials. Thus, to characterize the structure and magnetism of nanoscale materials demands tools with interface specificity. Neutron scattering has long been known to provide unique and quantitative information about nuclear and magnetic structures of bulk materials. Moreover, the specialty techniques of polarized neutron reflectometry and small angle neutron scattering (SANS) with polarized neutron beams and polarization analysis, are ideally and often uniquely suited to studies of nanostructured magnetic materials. Since neutron scattering is a weakly interacting probe, it gives quantifiable and easily-interpreted information on properties of statistically representative quantities of bulk, thin film and interfacial materials. In addition, neutron scattering can provide information to complement that obtained with bulk probes (magnetization, Kerr effect) or surface measurements obtained with scanning probe microscopy or resonant soft x-ray scattering. The straightforward interpretation and the simultaneous availability of structural information, make neutron scattering the technique of choice for the structural and physical characterization of many novel materials, especially those with buried interfaces, ones allowing for isotopic substitutions to decorate buried interfaces, or cases where the magnetic response to an external stimulus can be measured. We describe recent applications of neutron scattering to important thin film materials systems and future opportunities. Unquestionably, neutron scattering has played a decisive role in the development and study of new emergent phenomena. We argue with the advent of new techniques in neutron scattering and sample environment, neutron scattering's role in such studies will become even more dominant. In particular, neutron scattering will clarify and distinguish

  6. Investigation of magnetic and magneto-transport properties of ferromagnetic-charge ordered core-shell nanostructures

    Science.gov (United States)

    Das, Kalipada

    2017-10-01

    In our present study, we address in detail the magnetic and magneto-transport properties of ferromagnetic-charge ordered core-shell nanostructures. In these core-shell nanostructures, well-known half metallic La0.67Sr0.33MnO3 nanoparticles (average particle size, ˜20 nm) are wrapped by the charge ordered antiferromagnetic Pr0.67Ca0.33MnO3 (PCMO) matrix. The intrinsic properties of PCMO markedly modify it into such a core-shell form. The robustness of the PCMO matrix becomes fragile and melts at an external magnetic field (H) of ˜20 kOe. The analysis of magneto-transport data indicates the systematic reduction of the electron-electron and electron-magnon interactions in the presence of an external magnetic field in these nanostructures. The pronounced training effect appears in this phase separated compound, which was analyzed by considering the second order tunneling through the grain boundaries of the nanostructures. Additionally, the analysis of low field magnetoconductance data supports the second order tunneling and shows the close value of the universal limit (˜1.33).

  7. Systematic Investigation of Controlled Nanostructuring of Mn 12 Single-Molecule Magnets Templated by Metal–Organic Frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Aulakh, Darpandeep [Department of Chemistry; amp, Biomolecular Science, Clarkson University, Potsdam, New York 13699, United States; Xie, Haomiao [Department of Chemistry, Texas A& amp,M University, College Station, Texas 77845, United States; Shen, Zhe [Department of Chemistry, Texas A& amp,M University, College Station, Texas 77845, United States; Harley, Alexander [Department of Chemistry; amp, Biomolecular Science, Clarkson University, Potsdam, New York 13699, United States; Zhang, Xuan [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States; Yakovenko, Andrey A. [X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States; Dunbar, Kim R. [Department of Chemistry, Texas A& amp,M University, College Station, Texas 77845, United States; Wriedt, Mario [Department of Chemistry; amp, Biomolecular Science, Clarkson University, Potsdam, New York 13699, United States

    2017-05-25

    This is the first systematic study exploring metal–organic frameworks (MOFs) as platforms for the controlled nanostructuring of molecular magnets. We report the incorporation of seven single-molecule magnets (SMMs) of general composition [Mn12O12(O2CR)16(OH2)4], with R = CF3 (1), (CH3)CCH2 (2), CH2Cl (3), CH2Br (4), CHCl2 (5), CH2But (6), and C6H5 (7), into the hexagonal channel pores of a mesoporous MOF host. The resulting nanostructured composites combine the key SMM properties with the functional properties of the MOF. Synchrotron-based powder diffraction with difference envelope density analysis, physisorption analysis (surface area and pore size distribution), and thermal analyses reveal that the well-ordered hexagonal structure of the host framework is preserved, and magnetic measurements indicate that slow relaxation of the magnetization, characteristic of the corresponding Mn12 derivative guests, occurs inside the MOF pores. Structural host–guest correlations including the bulkiness and polarity of peripheral SMM ligands are discussed as fundamental parameters influencing the global SMM@MOF loading capacities. These results demonstrate that employing MOFs as platforms for the nanostructuration of SMMs is not limited to a particular host–guest system but potentially applicable to a multitude of other molecular magnets. Such fundamental findings will assist in paving the way for the development of novel advanced spintronic devices.

  8. Self-assembled magnetic nanostructures: Epitaxial Ni nanodots on TiN/Si (001) surface

    International Nuclear Information System (INIS)

    Zhou, H.; Narayan, J.

    2006-01-01

    Systems containing single domain magnetic particles are of great interest in view of their possible applications in ultrahigh-density data storage and magnetoelectronic devices. The focus of this work is plan-view STEM Z-contrast imaging study of the self-assembly growth of magnetic nickel nanostructures by domain matching epitaxy under Volmer-Weber (V-W) mode. The growth was carried out using pulsed laser deposition (PLD) technique with epitaxial titanium nitride film as the template, which was in turn grown on silicon (001) substrate via domain matching epitaxy. Our results show that the base of nickel islands is rectangular with the two principal edges parallel to two orthogonal directions, which is [110] and [1-bar 1 0] for [001] oriented growth. The size distribution of the islands is relatively narrow, comparable to that obtained from self-assembled islands grown under Stranski-Krastanow (S-K) mode. A certain degree of self-organization was also found in the lateral distribution of islands: island chains were observed along the directions close to , which are also the edge directions. The interaction between neighboring islands through the island edge-induced strain field is believed to be responsible for the size uniformity and the lateral ordering

  9. Raman spectra, photoluminescence, magnetism and magnetoelectric coupling in pure and Fe doped BaTiO{sub 3} nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Verma, Kuldeep Chand, E-mail: kuldeep0309@yahoo.co.in [Akal School of Physics, Eternal University, Baru Sahib, Sirmour, Himachal Pradesh 173 101 (India); Gupta, Vinay [Department of Physics and Astrophysics, University of Delhi, Delhi 110 007 (India); Kaur, Jaspreet [Akal School of Physics, Eternal University, Baru Sahib, Sirmour, Himachal Pradesh 173 101 (India); Kotnala, R.K. [National Physical Laboratory, New Delhi 110 012 (India)

    2013-11-25

    Highlights: •Multiferroic nanostructures by surfactant free hydrothermal method. •Stoichiometric effect on nanostructures. •Raman spectroscopy and Photoluminescence. •Transmission electron microscopy. •Magnetoelectric coupling. -- Abstract: Structural, microstructural, Raman spectroscopy, photoluminescence, saturation magnetization and magnetoelectric (ME) measurement of BaTiO{sub 3} (BFT0) and BaFe{sub 0.01}Ti{sub 0.99}O{sub 3} (BFT1) nanostructures have been studied. BFT0 and BFT1 were prepared by a hydrothermal method of processing temperature 180 °C/48 h. The X-ray diffraction pattern shows the coexistence of cubic/tetragonal and hexagonal phases for BFT0 and cubic/tetragonal for BFT1. The Raman spectra confirm the coexistence of tetragonal and hexagonal phases in BFT0 and cubic in BFT1. Transmission electron microscopy images show nanorods of hexagonal shaped faces for BFT0 and cubic shaped nanowires for BFT1. The resulting mechanism of the formation of these nanostructures is discussed. The experimental and theoretical results by photoluminescence are related to the degree of disorder existing in both BFT0 and BFT1 and suggest the presence of localized states existing inside of the band gap which are directly affected for degree of order–disorder. A strong ferromagnetism in BFT1 and diamagnetism in BFT0 is observed by magnetic hysteresis. As BFT1 is ferromagnetic, the value of linear coefficient, α called Magnetoelectric (ME) coefficient is calculated as ∼16 mV/Oe cm at a fixed frequency of 850 Hz. This ME coefficient α corresponds to induction of polarization by a magnetic field or of magnetization by an electric field. The observed optimum dc bias field at which the maximum ME coupling occurs is ∼750 Oe.

  10. Raman spectra, photoluminescence, magnetism and magnetoelectric coupling in pure and Fe doped BaTiO3 nanostructures

    International Nuclear Information System (INIS)

    Verma, Kuldeep Chand; Gupta, Vinay; Kaur, Jaspreet; Kotnala, R.K.

    2013-01-01

    Highlights: •Multiferroic nanostructures by surfactant free hydrothermal method. •Stoichiometric effect on nanostructures. •Raman spectroscopy and Photoluminescence. •Transmission electron microscopy. •Magnetoelectric coupling. -- Abstract: Structural, microstructural, Raman spectroscopy, photoluminescence, saturation magnetization and magnetoelectric (ME) measurement of BaTiO 3 (BFT0) and BaFe 0.01 Ti 0.99 O 3 (BFT1) nanostructures have been studied. BFT0 and BFT1 were prepared by a hydrothermal method of processing temperature 180 °C/48 h. The X-ray diffraction pattern shows the coexistence of cubic/tetragonal and hexagonal phases for BFT0 and cubic/tetragonal for BFT1. The Raman spectra confirm the coexistence of tetragonal and hexagonal phases in BFT0 and cubic in BFT1. Transmission electron microscopy images show nanorods of hexagonal shaped faces for BFT0 and cubic shaped nanowires for BFT1. The resulting mechanism of the formation of these nanostructures is discussed. The experimental and theoretical results by photoluminescence are related to the degree of disorder existing in both BFT0 and BFT1 and suggest the presence of localized states existing inside of the band gap which are directly affected for degree of order–disorder. A strong ferromagnetism in BFT1 and diamagnetism in BFT0 is observed by magnetic hysteresis. As BFT1 is ferromagnetic, the value of linear coefficient, α called Magnetoelectric (ME) coefficient is calculated as ∼16 mV/Oe cm at a fixed frequency of 850 Hz. This ME coefficient α corresponds to induction of polarization by a magnetic field or of magnetization by an electric field. The observed optimum dc bias field at which the maximum ME coupling occurs is ∼750 Oe

  11. Tuning magnetic properties of magnetoelectric BiFeO 3-NiFe 2O 4 nanostructures

    Science.gov (United States)

    Crane, S. P.; Bihler, C.; Brandt, M. S.; Goennenwein, S. T. B.; Gajek, M.; Ramesh, R.

    2009-02-01

    Multifunctional thin film nanostructures containing soft magnetic materials such as nickel ferrite are interesting for potential applications in microwave signal processing because of the possibility to shrink the size of device architecture and limit device power consumption. An essential prerequisite to future applications of such a system is a firm understanding of its magnetic properties. We show that nanostructures composed of ferrimagnetic NiFe 2O 4 pillars in a multiferroic BiFeO 3 matrix can be tuned magnetically by altering the aspect ratio of the pillars by depositing films of varying thickness. Magnetic anisotropy is studied using ferromagnetic resonance, which shows that the uniaxial magnetic anisotropy in the growth direction changes sign upon increasing the film thickness. The magnitude of this anisotropy contribution can be explained via a combination of shape and magnetostatic effects, using the object-oriented micromagnetic framework (OOMMF). The key factors determining the magnetic properties of the films are shown to be the aspect ratio of individual pillars and magnetostatic interactions between neighboring pillars.

  12. Tuning magnetic properties of magnetoelectric BiFeO3-NiFe2O4 nanostructures

    International Nuclear Information System (INIS)

    Crane, S.P.; Bihler, C.; Brandt, M.S.; Goennenwein, S.T.B.; Gajek, M.; Ramesh, R.

    2009-01-01

    Multifunctional thin film nanostructures containing soft magnetic materials such as nickel ferrite are interesting for potential applications in microwave signal processing because of the possibility to shrink the size of device architecture and limit device power consumption. An essential prerequisite to future applications of such a system is a firm understanding of its magnetic properties. We show that nanostructures composed of ferrimagnetic NiFe 2 O 4 pillars in a multiferroic BiFeO 3 matrix can be tuned magnetically by altering the aspect ratio of the pillars by depositing films of varying thickness. Magnetic anisotropy is studied using ferromagnetic resonance, which shows that the uniaxial magnetic anisotropy in the growth direction changes sign upon increasing the film thickness. The magnitude of this anisotropy contribution can be explained via a combination of shape and magnetostatic effects, using the object-oriented micromagnetic framework (OOMMF). The key factors determining the magnetic properties of the films are shown to be the aspect ratio of individual pillars and magnetostatic interactions between neighboring pillars

  13. Shape-Controlled Synthesis of Magnetic Iron Oxide@SiO₂-Au@C Particles with Core-Shell Nanostructures.

    Science.gov (United States)

    Li, Mo; Li, Xiangcun; Qi, Xinhong; Luo, Fan; He, Gaohong

    2015-05-12

    The preparation of nonspherical magnetic core-shell nanostructures with uniform sizes still remains a challenge. In this study, magnetic iron oxide@SiO2-Au@C particles with different shapes, such as pseduocube, ellipsoid, and peanut, were synthesized using hematite as templates and precursors of magnetic iron oxide. The as-obtained magnetic particles demonstrated uniform sizes, shapes, and well-designed core-shell nanostructures. Transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) analysis showed that the Au nanoparticles (AuNPs) of ∼6 nm were uniformly distributed between the silica and carbon layers. The embedding of the metal nanocrystals into the two different layers prevented the aggregation and reduced the loss of the metal nanocrystals during recycling. Catalytic performance of the peanut-like particles kept almost unchanged without a noticeable decrease in the reduction of 4-nitrophenol (4-NP) in 8 min even after 7 cycles, indicating excellent reusability of the particles. Moreover, the catalyst could be readily recycled magnetically after each reduction by an external magnetic field.

  14. Structural and magnetic properties of cobalt nanostructures on SiO{sub 2}/Si(1 1 1) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Bounour-Bouzamouche, W. [LSPM (CNRS-UPR 3407), Université Paris 13, PRES Sorbonne-Paris-Cité, 99 avenue Jean-Baptiste Clément, 93430 Villetaneuse (France); LEREC, Université d’Annaba, BP12 – 23000 (Algeria); Chérif, S.M., E-mail: cherif@univ-paris13.fr [LSPM (CNRS-UPR 3407), Université Paris 13, PRES Sorbonne-Paris-Cité, 99 avenue Jean-Baptiste Clément, 93430 Villetaneuse (France); Farhat, S.; Roussigné, Y.; Tallaire, A.; Gicquel, A. [LSPM (CNRS-UPR 3407), Université Paris 13, PRES Sorbonne-Paris-Cité, 99 avenue Jean-Baptiste Clément, 93430 Villetaneuse (France); Lungu, C.P. [NILPR, 409, Magurele, JudIlfov, 077125 Bucharest (Romania); Guerioune, M. [LEREC, Université d’Annaba, BP12 – 23000 (Algeria)

    2014-11-30

    Highlights: • Heat and plasma treatments of ultrathin cobalt films deposited on SiO{sub 2}/Si(1 1 1) create highly auto-organized structures. • Direct correlation between the film thickness and the size of the nanoparticles formed after thermal annealing. • Modification of the surface morphology strongly influences the magnetic response of the investigated films. • Formation of Co islands in triangular shapes is found to play a key role in the enhancement of the coercive field. - Abstract: 2D architectures of cobalt onto silicon (1 1 1) surfaces were elaborated by patterning of magnetic cobalt in the nanometer scale. A continuous cobalt layer of 1, 3 and 10 nm thickness, respectively, was first deposited by means of thermoionic vacuum arc technique and then, thermally annealed in vacuum at temperatures ranging from 450 to 800 °C. Surface structure was analyzed by atomic force and field emission-scanning electron microscopies. Above 750 °C, regular triangular shape cobalt nanostructures are formed with pattern dimensions varying between 10 and 200 nm. Good control of shape and packing density could be achieved by adjusting the initial thickness and the thermal and hydrogen plasma treatments. Magnetic properties were investigated using vibrating sample magnetometer technique. The evolution of the coercive field versus packing density and dimensions of the nanostructures was studied and compared to micromagnetic calculations. The observed nanostructures have been modeled by a series of shapes tending to a fractal curve.

  15. Nanostructured Materials for Magnetoelectronics

    CERN Document Server

    Mikailzade, Faik

    2013-01-01

    This book provides an up-to-date review of nanometer-scale magnetism and focuses on the investigation of the basic properties of magnetic nanostructures. It describes a wide range of physical aspects together with theoretical and experimental methods. A broad overview of the latest developments in this emerging and fascinating field of nanostructured materials is given with emphasis on the practical understanding and operation of submicron devices based on nanostructured magnetic materials.

  16. Magnetic Properties of Gadolinium-Doped ZnO Films and Nanostructures

    KAUST Repository

    Roqan, Iman S.

    2016-08-29

    The magnetic properties of Gd-doped ZnO films and nanostructures are important to the development of next-generation spintronic devices. Here, we elucidate the significant role played by Gd-oxygen-deficiency defects in mediating/inducing ferromagnetic coupling in in situ Gd-doped ZnO thin films deposited at low oxygen pressure by pulsed laser deposition (PLD). Samples deposited at higher oxygen pressures exhibited diamagnetic responses. Vacuum annealing was used on these diamagnetic samples (grown at a relatively high oxygen pressures) to create oxygen- deficiency defects with the aim of demonstrating reproducibility of room-temperature ferromagnetism (RTFM). Samples annealed at oxygen environment exhibited super‐ paramagnetism and blocking-temperature effects. The samples possessed secondary phases; Gd segregation led to superparamagnetism. Theoretical studies showed a shift of the 4f level of Gd to the conduction band minimum (CBM) in Gd-doped ZnO nanowires, which led to an overlap with the Fermi level, resulting in strong exchange coupling and consequently RTFM.

  17. Removal of Heavy Metals from Drinking Water by Magnetic Carbon Nanostructures Prepared from Biomass

    Directory of Open Access Journals (Sweden)

    Muhammad Muneeb Ur Rahman Khattak

    2017-01-01

    Full Text Available Heavy metals contamination of drinking water has significant adverse effects on human health due to their toxic nature. In this study a new adsorbent, magnetic graphitic nanostructures were prepared from watermelon waste. The adsorbent was characterized by different instrumental techniques (surface area analyzer, FTIR, XRD, EDX, SEM, and TG/DTA and was used for the removal of heavy metals (As, Cr, Cu, Pb, and Zn from water. The adsorption parameters were determined for heavy metals adsorption using Freundlich and Langmuir isotherms. The adsorption kinetics and effect of time, pH, and temperature on heavy metal ions were also determined. The best fits were obtained for Freundlich isotherm. The percent adsorption showed a decline at high pH. Best fit was obtained with second-order kinetics model for the kinetics experiments. The values of ΔH° and ΔG° were negative while that of ΔS° was positive. The prepared adsorbent has high adsorption capacities and can be efficiently used for the removal of heavy metals from water.

  18. Magnetic and microstructural properties of thin NdFeB based films and nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Bommer, Lars; Goll, Dagmar [Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany)

    2010-07-01

    The magnetic and microstructural properties of NdFeB and NdFeB/Fe thin films and nanostructures are presented. Samples with Cr buffer and protection layer (minimum thickness: d=50 nm) have been produced by ion beam sputtering at elevated temperatures (T{sub s}=700 C) using Al{sub 2}O{sub 3} and MgO(001) single crystal substrates. Films deposited on Al{sub 2}O{sub 3} substrates show c-axis growth in out-of-plane direction down to thicknesses of the NdFeB film of d=10 nm with coercivities up to {mu}{sub 0}H{sub c}=1 T. The texture of films deposited on MgO(001) substrates is less pronounced and films below d=20 nm show no hard magnetic behavior. For comparison, films were deposited at room temperature on Al{sub 2}O{sub 3} and MgO(001) followed by post-annealing in Ar atmosphere (T{sub pa}=525-650 C) leading to coercivities as high as {mu}{sub 0}H{sub c}=1.2 T but with isotropic behavior. By TEM images the grain structure of the NdFeB samples is studied. Bilayers of NdFeB (d=50 nm) and Fe (d=0-20 nm) show fully exchange coupled behavior. From the temperature dependence of the coercivity the microstructural parameters of all samples have been determined. Furthermore NdFeB periodical patterns were produced by means of electron beam lithography with dot sizes of 1000 nm and 500 nm, respectively.

  19. Comparison of microstructure and magnetic properties of 3% Si-steel, amorphous and nanostructure Finemet

    Energy Technology Data Exchange (ETDEWEB)

    Yousefi, M., E-mail: masoud_yousefi@hotmail.com; Rahmani, Kh.; Amiri Kerahroodi, M.S.

    2016-12-15

    This paper presents a comparison of microstructure and magnetic properties of polycrystalline 3%Si-steel, amorphous and nano-crystalline alloy Fe{sub 73.5}Cu{sub 1}Nb{sub 3}Si{sub 13.5}B{sub 9} (known as Finemet). Si-steels are industrially produced by casting, hot and cold rolling, annealing and coating. Samples of thin amorphous ribbons were prepared by the planar flow casting (PFC) method. Nano-crystalline samples are obtained after annealing in vacuum furnace at 560 °C for 1 h. The structure of specimens was investigated by XRD, SEM and FE-SEM. Also, magnetic properties were measured using vibrating sample magnetometer (VSM). The results showed that, hysteresis losses in as-quenched and nano-crystalline ribbons were by 94.75% and 96.06% less than 3%Si-steel, respectively. After the heat treatment of amorphous specimens, hysteresis area was decreased by 25% in comparison with heat treated specimen. This decreasing is occurred due to the formation of Fe{sub 3}Si nanostructure with size of 10–17 nm and removing segregation after heat treatment. - Highlights: • The structure of specimens was investigated by XRD, SEM and FE-SEM. • Hysteresis losses of amorphous ribbon, was 94.75% less than 3% Si-steel. • After heat treatment, hysteresis losses was less than the 3% Si-steel by 96.06%. • Formation of Fe3Si nano structure with size of 10-17 nm. • Removing segregation after heat treatment.

  20. Magnetic and structural studies on nanostructured Gd/Cr multilayer films

    International Nuclear Information System (INIS)

    Gadioli, G.Z.; Rouxinol, F.P.; Gelamo, R.V.; Cardoso, L.P.; Gama, S.; Bica de Moraes, M.A.

    2013-01-01

    Investigations of magnetic phases, transition temperatures and coercivity were performed in multilayered Gd/Cr films as a function of the crystalline state and morphology of the Gd layers. The films were deposited by dc magnetron sputtering at three substrate temperatures, T s , (room temperature, 300 and 500 °C). The Gd and Cr thicknesses were of 10 and 30 nm, respectively. Two series of three films were prepared. In one of the series, the films had a single Gd/Cr bilayer; in the other, 15 bilayers. The discontinuous or granular nature of the Gd layers was revealed by scanning electron microscopy Grazing incidence angle x-ray diffraction was used to investigate the crystalline state of the Gd and Cr layers. These techniques revealed that grain average size and crystalline order increase with increasing T s . From dc magnetic measurements, the co-existence of ferromagnetic and superferromagnetic phases in the Gd layers was observed, and Curie transition temperatures, T C , were determined. High coercive fields at low temperature (2 K) were measured in hysteresis cycles. Field-cooled and zero field-cooled magnetizations as functions of temperature curves exhibited, for some of the samples, a low temperature peak suggesting a freezing transition to a cluster glass state. This was confirmed by complementary ac-susceptibility measurements carried out as a function of temperature, for various frequencies of the ac field. Some results of this work – the decline in T C for decreasing Gd grain size, the high coercive field and its dependence on particle size, and the behavior of the magnetization at low temperatures for the sample deposited at room temperature – are discussed in terms of finite size and surface effects in nanosized particles. - Highlights: • Sputter-deposited Gd/Cr multilayer films with nanostructured Gd layers • Ferromagnetic and superferromagnetic phases are observed. • Ferromagnetic phase dependent of the deposition temperature • Improved

  1. Magnetic field induced changes in linear and nonlinear optical properties of Ti incorporated Cr2O3 nanostructured thin film

    Science.gov (United States)

    Baraskar, Priyanka; Chouhan, Romita; Agrawal, Arpana; Choudhary, R. J.; Sen, Pranay K.; Sen, Pratima

    2018-03-01

    We report the magnetic field effect on the linear and nonlinear optical properties of pulse laser ablated Ti-incorporated Cr2O3 nanostructured thin film. Optical properties have been experimentally analyzed under Voigt geometry by performing ultraviolet-visible spectroscopy and closed aperture Z-scan technique using a continuous wave He-Ne laser source. Nonlinear optical response reveals a single peak-valley feature in the far field diffraction pattern in absence of magnetic field (B = 0) confirming self-defocussing effect. This feature switches to a valley-peak configuration for B = 5000G, suggesting self-focusing effect. For B ≤ 750G, oscillations were observed revealing the occurrence of higher order nonlinearity. Origin of nonlinearity is attributed to the near resonant d-d transitions observed from the broad peak occurring around 2 eV. These transitions are of magnetic origin and get modified under the application of external magnetic field. Our results suggest that magnetic field can be used as an effective tool to monitor the sign of optical nonlinearity and hence the thermal expansion in Ti-incorporated Cr2O3 nanostructured thin film.

  2. Influence of Fe substitution on structural and magnetic features of BiMn2O5 nanostructures

    Science.gov (United States)

    Gaikwad, Vishwajit M.; Goyal, Saveena; Yanda, Premakumar; Sundaresan, A.; Chakraverty, Suvankar; Ganguli, Ashok K.

    2018-04-01

    Nanostructures of complex oxides [BiFexMn2-xO5 (x = 0, 1, 2)] have been designed to study their structural, optical and magnetic behaviour. X-ray diffraction data (XRD) revealed orthorhombic phase with Pbam space group. Noticeable expansion in unit cell parameters has been found from BiMn2O5 (x = 0) to BiFe2O4.5 (x = 2). The observed structural changes via tuning of B-site (x = 0-2) played an important role in overall magnetic properties. Transmission electron microscopic images confirm that the average particle size of all the materials are in nano domain range with different morphologies. From optical studies, it has been found that the observed energy band gap values are strongly related to 3d electron numbers. These values appear to be larger than that reported for bulk. Isothermal magnetization plots (at 5 K) show increase in coercivity (Hc) from x = 0 to x = 2. Temperature dependent magnetization studies implied anti-ferromagnetic interactions for BiMn2O5, frustrated magnet for BiFeMnO5 and ferromagnetic behaviour for BiFe2O4.5. Ferromagnetic state of nanostructured BiFe2O4.5 is in contrast with its bulk counterparts.

  3. Optical and magnetic properties of Co-doped CuO flower/plates/particles-like nanostructures.

    Science.gov (United States)

    Basith, N Mohamed; Vijaya, J Judith; Kennedy, L John; Bououdina, M; Hussain, Shamima

    2014-03-01

    In this study, pure and Co-doped CuO nanostructures (0.5, 1.0, 1.5, and 2.0 at wt% of Co) were synthesized by microwave combustion method. The prepared samples were characterized by X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and vibrating sample magnetometry (VSM). Powder X-ray diffraction patterns refined by the Rietveld method indicated the formation of single-phase monoclinic structure. The surface morphology and elemental analysis of Co-doped CuO nanostructures were studied by using HR-SEM and EDX. Interestingly, the morphology was found to change considerably from nanoflowers to nanoplates then to nanoparticles with the variation of Co concentration. The optical band gap calculated using DRS was found to be 2.1 eV for pure CuO and increases up to 3.4 eV with increasing cobalt content. Photoluminescence measurements also confirm these results. The magnetic measurements indicated that the obtained nanostructures were ferromagnetic at room temperature with an optimum value of saturation magnetization at 1.0 wt.% of Co-doped CuO, i.e., 970 micro emu/g.

  4. Synthesis of adenine mediated superparamagnetic colloidal β-FeOOH nanostructure(s): study of their morphological changes and magnetic behavior

    International Nuclear Information System (INIS)

    Kumar, Anil; Gupta, Sudhir Kumar

    2013-01-01

    This paper describes the synthesis of adenine-mediated superparamagnetic β-FeOOH nanostructures in aqueous medium. Capping by adenine provides a synthetic control to manipulate their size, morphology, optical and magnetization properties. β-FeOOH binds to adenine mainly through –NH 2 , N(3); N(9)H and N(7) of the pyridine and imidazole rings, respectively. At low [adenine], it produces nanorods, but at higher [adenine] (>1 × 10 −2 mol dm −3 ), increasing numbers of spherical nanoparticles encapsulating β-FeOOH with an average diameter of 2.5 nm in the core and adenine molecules in the shell are obtained, causing an increase in the specific surface area by about twofold. Dynamic light scattering technique also depicts a regular decrease in their hydrodynamic size with increasing [adenine] and exhibits the highest stability with a zeta potential of ∼67 mV for the sample containing 2 × 10 −2 mol dm −3 adenine (SP5). An increasing [adenine] from 1 × 10 −3 to 2 × 10 −2 mol dm −3 in these samples enhanced the value of saturation magnetization (M S ), due to β-FeOOH, gradually from 2.0 to 6.9 emu g −1 at 300 K, but at S at 300 K having potential for environmental and biological applications.

  5. Giant magnetic anisotropy of heavy p-elements on high-symmetry substrates: a new paradigm for supported nanostructures

    Science.gov (United States)

    Pang, Rui; Deng, Bei; Shi, Xingqiang; Zheng, Xiaohong

    2018-04-01

    Nanostructures with giant magnetic anisotropy energies (MAEs) are desired in designing miniaturized magnetic storage and quantum computing devices. Previous works focused mainly on materials or elements with d electrons. Here, by taking Bi–X(X = In, Tl, Ge, Sn, Pb) adsorbed on nitrogenized divacancy of graphene and Bi atoms adsorbed on MgO(100) as examples, through ab initio and model calculations, we propose that special p-element dimers and single-adatoms on symmetry-matched substrates possess giant atomic MAEs of 72–200 meV, and has room temperature structural stability. The huge MAEs originate from the p-orbital degeneracy around the Fermi level in a symmetry-matched surface ligand field and the lifting of this degeneracy when spin–orbit interaction (SOI) is taken into account. Especially, we developed a simplified quantum mechanical model for the design principles of giant MAEs of supported magnetic adatoms and dimers. Thus, our discoveries and mechanisms provide a new paradigm to design giant atomic MAE of p electrons in supported nanostructures.

  6. Probing of O2 vacancy defects and correlated magnetic, electrical and photoresponse properties in indium-tin oxide nanostructures by spectroscopic techniques

    Science.gov (United States)

    Ghosh, Shyamsundar; Dev, Bhupendra Nath

    2018-05-01

    Indium-tin oxide (ITO) 1D nanostructures with tunable morphologies i.e. nanorods, nanocombs and nanowires are grown on c-axis (0 0 0 1) sapphire (Al2O3) substrate in oxygen deficient atmosphere through pulsed laser deposition (PLD) technique and the effect of oxygen vacancies on optical, electrical, magnetic and photoresponse properties is investigated using spectroscopic methods. ITO nanostructures are found to be enriched with significant oxygen vacancy defects as evident from X-ray photoelectron and Raman spectroscopic analysis. Photoluminescence spectra exhibited intense mid-band blue emission at wavelength of region of 400-450 nm due to the electronic transition from conduction band maxima (CBM) to the singly ionized oxygen-vacancy (VO+) defect level within the band-gap. Interestingly, ITO nanostructures exhibited significant room-temperature ferromagnetism (RTFM) and the magnetic moment found proportional to concentration of VO+ defects which indicates VO+ defects are mainly responsible for the observed RTFM in nanostructures. ITO nanowires being enriched with more VO+ defects exhibited strongest RTFM as compared to other morphologies. Current voltage (I-V) characteristics of ITO nanostructures showed an enhancement of current under UV light as compared to dark which indicates such 1D nanostructure can be used as photovoltaic material. Hence, the study shows that there is ample opportunity to tailor the properties of ITOs through proper defect engineering's and such photosensitive ferromagnetic semiconductors might be promising for spintronic and photovoltaic applications.

  7. Fabrication, Light Emission, and Magnetism of Silica Nanoparticles Hybridized with AIE Luminogens and Inorganic Nanostructures

    Science.gov (United States)

    Faisal, Mahtab

    Much research efforts have been devoted in developing new synthetic approaches for fluorescent silica nanoparticles (FSNPs) due to their potential high-technological applications. However, light emissions from most of the FSNPs prepared so far have been rather weak. This is due to the emission quenching caused by the aggregation of fluorophores in the solid state. We have observed a novel phenomenon of aggregation-induced emission (AIE): a series of propeller-shaped molecules such as tetraphenylethene (TPE) and silole are induced to emit efficiently by aggregate formation. Thus, they are ideal fluorophors for the construction of FSNPs and my thesis work focuses on the synthesis of silica nanoparticles containing these luminogens and magnetic nanostructures. Highly emissive FSNPs with core-shell structures are fabricated by surfactant-free sol-gel reactions of tetraphenylethene- (TPE) and silole-functionalized siloxanes followed by the reactions with tetraethoxysilane. The FSNPs are uniformly sized, surface-charged and colloidally stable. The diameters of the FSNPs are tunable in the range of 45--295 nm by changing the reaction conditions. Whereas their TPE and silole precursors are non-emissive, the FSNPs emit strong visible lights, thanks to the novel aggregation-induced emission characteristics of the TPE and silole aggregates in the hybrid nanoparticles. The FSNPs pose no toxicity to living cells and can be utilized to selectively image cytoplasm of HeLa cells. Applying the same tool in the presence of citrate-coated magnetite nanoparticles, uniform magnetic fluorescent silica nanoparticles (MFSNPs) with smooth surfaces are fabricated. These particles exhibit appreciable surface charges and hence good colloidal stability. They are superparamagnetic, exhibiting no hysteresis at room temperature. UV irradiation of a suspension of MFSNPs in ethanol gives strong blue and green emissions. The MFSNPs can selectively stain the cytoplasmic regions of the living cells

  8. A full-field transmission x-ray microscope for time-resolved imaging of magnetic nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Ewald, J.; Nisius, T.; Abbati, G.; Baumbach, S.; Overbuschmann, J.; Wilhein, T. [Institute for X-Optics (IXO), Hochschule Koblenz, Joseph-Rovan-Allee 2, 53424 Remagen (Germany); Wessels, P.; Wieland, M.; Drescher, M. [The Hamburg Centre for Ultrafast Imaging (CUI), University of Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); Institut für Experimentalphysik, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); Vogel, A. [Institut für Angewandte Physik, University of Hamburg, Jungiusstraße 11, 20355 Hamburg (Germany); Viefhaus, J. [Deutsches Elektronen-Synchrotron (DESY), Notkestraße 85, 22607 Hamburg (Germany); Meier, G. [The Hamburg Centre for Ultrafast Imaging (CUI), University of Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg (Germany)

    2016-01-28

    Sub-nanosecond magnetization dynamics of small permalloy (Ni{sub 80}Fe{sub 20}) elements has been investigated with a new full-field transmission microscope at the soft X-ray beamline P04 of the high brilliance synchrotron radiation source PETRA III. The soft X-ray microscope generates a flat-top illumination field of 20 μm diameter using a grating condenser. A tilted nanostructured magnetic sample can be excited by a picosecond electric current pulse via a coplanar waveguide. The transmitted light of the sample plane is directly imaged by a micro zone plate with < 65 nm resolution onto a 2D gateable X-ray detector to select one particular bunch in the storage ring that probes the time evolution of the dynamic information successively via XMCD spectromicroscopy in a pump-probe scheme. In the experiments it was possible to generate a homogeneously magnetized state in patterned magnetic layers by a strong magnetic Oersted field pulse of 200 ps duration and directly observe the recovery to the initial flux-closure vortex patterns.

  9. Effect of magnetic field on energy spectrum and localization of electron in CdS/HgS/CdS/HgS/CdS multilayered spherical nanostructure

    Energy Technology Data Exchange (ETDEWEB)

    Holovatsky, V.A., E-mail: ktf@chnu.edu.ua; Bernik, I.B.; Yakhnevych, M. Ya.

    2017-03-01

    The theoretical investigation of magnetic field effect on energy spectrum and localization of the electron and oscillator strengths of intraband quantum transitions in the nanostructure CdS/HgS/CdS/HgS/CdS is performed. The calculations are made in the framework of effective mass approximation and rectangular potential barriers model using the method of the expansion of quasi-particle wave functions over the complete basis of functions obtained as the exact solutions of the Schrodinger equation for the electron in the nanostructure without the magnetic field. It is shown that the magnetic field violates the spherical symmetry of the system and takes off the degeneration of energy spectrum with respect to the magnetic quantum number. The energy of the electron in the states with m≥0 increases when magnetic field enhances; for the states with m<0 these dependences are non-monotonous (decreasing at first and then increasing). Moreover, the ground state of electron is formed alternately by the states with m=0, −1, −2, …. Magnetic field influences on the distribution of quasi-particle density. It is shown that the electron significantly changes its localization in the nanostructure with two potential wells tunneling through the potential barrier under the effect of magnetic field, changing the oscillator strengths of intraband quantum transitions.

  10. A new approach for crystallization of copper(ii) oxide hollow nanostructures with superior catalytic and magnetic response

    Science.gov (United States)

    Singh, Inderjeet; Landfester, Katharina; Chandra, Amreesh; Muñoz-Espí, Rafael

    2015-11-01

    We report the synthesis of copper(ii) oxide hollow nanostructures at ambient pressure and close to room temperature by applying the soft templating effect provided by the confinement of droplets in miniemulsion systems. Particle growth can be explained by considering a mechanism that involves both diffusion and reaction control. The catalytic reduction of p-nitrophenol in aqueous media is used as a model reaction to prove the catalytic activity of the materials: the synthesized hollow structures show nearly 100 times higher rate constants than solid CuO microspheres. The kinetic behavior and the order of the reduction reaction change due to the increase of the surface area of the hollow structures. The synthesis also leads to modification of physical properties such as magnetism.We report the synthesis of copper(ii) oxide hollow nanostructures at ambient pressure and close to room temperature by applying the soft templating effect provided by the confinement of droplets in miniemulsion systems. Particle growth can be explained by considering a mechanism that involves both diffusion and reaction control. The catalytic reduction of p-nitrophenol in aqueous media is used as a model reaction to prove the catalytic activity of the materials: the synthesized hollow structures show nearly 100 times higher rate constants than solid CuO microspheres. The kinetic behavior and the order of the reduction reaction change due to the increase of the surface area of the hollow structures. The synthesis also leads to modification of physical properties such as magnetism. Electronic supplementary information (ESI) available: Associated structural and morphological analysis, XPS characterization, BET surface area, catalytic measurements, recycle tests of the catalyst, and magnetic characterizations. See DOI: 10.1039/c5nr05579b

  11. The magnetic-resonance properties study of nanostructures for spintronics by FMR

    International Nuclear Information System (INIS)

    Kupriyanova, G; Zyubin, A; Astashonok, A; Orlova, A; Prokhorenko, E

    2011-01-01

    In this work we report the study of the magnetic-resonance properties such as magnetic anisotropy, magnetic damping, and interlayer exchange coupling between ferromagnetic layers separated by a nonmagnetic spacer by FMR to assess their applicability in a functional magnetic tunnel junction.

  12. Discontinuous spring magnet-type magnetostrictive Terfecohan/YFeCo multilayers: A novel nanostructured material principle for excellent magnetic softness

    International Nuclear Information System (INIS)

    Duc, N.H.; Huong Giang, D.T.

    2007-01-01

    Novel physics and reversal mechanisms of the whole system switching (WS) and individual switching (IS) type are reported for hard/soft TbFeCo/YFeCo exchange-spring multilayers. The WS type usually occurs in multilayered systems, in which the magnetic anisotropy of hard TbFeCo layers is neglectable. For such a system, the ferrimagnetically coupled hard/soft multilayered state is recovered after removing applied fields from the magnetized state. At low negative fields, the magnetization switching occurs collectively for all magnetic moments in the whole system. In this case, the low-coercivity mechanism is discussed on the basis of a hard/soft interfacial point contact. This configuration is realized for TbFeCo/YFeCo discontinuous exchange-spring multilayers, in which the magnetic (Fe,Co) nanograins coexist with non-magnetic amorphous phase in the soft layers. In this state, a magnetic coercivity as small as 0.4 mT is achieved. It is considered as an excellent magnetic softness of rare-earth-based systems. Enhancing the magnetic anisotropy in the hard TbFeCo layers, the magnetization switching follows the IS type at low temperatures. Starting to decrease the applied magnetic field from the high-field state, one observes the first reversal of the magnetic moments in the soft high-magnetization YFeCo-layers in positive magnetic fields. This is the reason for the observation of the negative coercivity as well as negative-biasing phenomena

  13. Microemulsion based approach for nanospheres assembly into anisotropic nanostructures of NiMnO3 and their magnetic properties

    Science.gov (United States)

    Jha, Menaka; Kumar, Sandeep; Garg, Neha; Ramanujachary, Kandalam V.; Lofland, Samuel E.; Ganguli, Ashok K.

    2018-02-01

    The present study focuses on synthesis of anisotropic nanostructures of nickel manganese oxide (NiMnO3) obtained by thermal decomposition of nanocrystalline nickel manganese oxalate precursor, Ni0.5Mn0.5(C2O4)·2H2O which crystallized as nanorods. The synthesis of the oxalate precursor has been carried out via microemulsion-mediated process with cationic and non-ionic surfactants. The microemulsion led to reverse micelles, and the film flexibility of the micelle in presence of non-ionic surfactant (Tergitol) was reduced by increasing the chain length of the co-surfactant (1-butanol, 1-hexanol and 1-octanol) which led to the increase in reaction rate and hence increase in the aspect ratio of the nickel manganese oxalate by up to four times. However, in the presence of cationic surfactant, highly uniform nickel manganese oxalate nanorods were obtained. Further, the decomposition of the oxalate precursor was optimized to maintain the anisotropy of the rods of ternary metal oxide (NiMnO3). An electron microscopy study showed that the rods were made up of an assembly of ultrafine nanospheres. The NiMnO3 nanostructures were all ferrimagnetic with Curie temperature ranging between 437 and 467 K showing increasing saturation magnetization with increase in aspect ratio of the nanorods.

  14. Ultrathin Carbon with Interspersed Graphene/Fullerene-like Nanostructures: A Durable Protective Overcoat for High Density Magnetic Storage.

    Science.gov (United States)

    Dwivedi, Neeraj; Satyanarayana, Nalam; Yeo, Reuben J; Xu, Hai; Ping Loh, Kian; Tripathy, Sudhiranjan; Bhatia, Charanjit S

    2015-06-25

    One of the key issues for future hard disk drive technology is to design and develop ultrathin (Forming carbon overcoats (COCs) having interspersed nanostructures by the filtered cathodic vacuum arc (FCVA) process can be an effective approach to achieve the desired target. In this work, by employing a novel bi-level surface modification approach using FCVA, the formation of a high sp(3) bonded ultrathin (~1.7 nm) amorphous carbon overcoat with interspersed graphene/fullerene-like nanostructures, grown on magnetic hard disk media, is reported. The in-depth spectroscopic and microscopic analyses by high resolution transmission electron microscopy, scanning tunneling microscopy, time-of-flight secondary ion mass spectrometry, and Raman spectroscopy support the observed findings. Despite a reduction of ~37% in COC thickness, the FCVA-processed thinner COC (~1.7 nm) shows promising functional performance in terms of lower coefficient of friction (~0.25), higher wear resistance, lower surface energy, excellent hydrophobicity and similar/better oxidation corrosion resistance than current commercial COCs of thickness ~2.7 nm. The surface and tribological properties of FCVA-deposited COC was further improved after deposition of lubricant layer.

  15. Observations of the Kondo effect and its coexistence with ferromagnetism in a magnetically undoped metal oxide nanostructure

    Science.gov (United States)

    Sapkota, Keshab R.; Maloney, F. Scott; Wang, Wenyong

    2018-04-01

    In this work, we report unusual observations of Kondo effect and coexistence of Kondo effect and ferromagnetism in indium tin oxide (ITO) nanowires that were synthesized without incorporating any magnetic impurities. The temperature-dependent resistivity (ρ -T ) data exhibited an upturn below 80 K and then tended to saturate below 10 K. The ρ -T and magnetoresistance data were analyzed using the n -channel Kondo model, and from the obtained values of S =1 and n ˜1 , the nanowires were expected to be an underscreened Kondo system. A model was also proposed to explain the formation of localized S =1 spin centers in the ITO nanowires. This work could provide insights into the understanding of spin-related novel phenomena in metal oxide nanostructures.

  16. The Use of Gadolinium-Carbon Nanostructures to Magnetically Enhance Stem Cell Retention for Cellular Cardiomyoplasty

    Science.gov (United States)

    Tran, Lesa A.; Hernández-Rivera, Mayra; Berlin, Ari N.; Zheng, Yi; Sampaio, Luiz; Bové, Christina; Cabreira-Hansen, Maria da Graça; Willerson, James T.; Perin, Emerson C.; Wilson, Lon J.

    2014-01-01

    In this work, the effectiveness of using Gadonanotubes (GNTs) with an external magnetic field to improve retention of transplanted adult mesenchymal stem cells (MSCs) during cellular cardiomyoplasty was evaluated. As a high-performance T1-weighted magnetic resonance imaging (MRI) cell tracking label, the GNTs are gadolinium-loaded carbon nanotube capsules that render MSCs magnetic when internalized. MSCs were internally labeled with either superparamagnetic GNTs or colloidal diamagnetic lutetium (Lu). In vitro cell rolling assays and ex vivo cardiac perfusion experiments qualitatively demonstrated increased magnetic-assisted retention of GNT-labeled MSCs. Subsequent in vivo epicardial cell injections were performed around a 1.3 T NdFeB ring magnet sutured onto the left ventricle of female juvenile pigs (n = 21). Cell dosage, magnet exposure time, and endpoints were varied to evaluate the safety and efficacy of the proposed therapy. Quantification of retained cells in collected tissues by elemental analysis (Gd or Lu) showed that the external magnet helped retain nearly three times more GNT-labeled MSCs than Lu-labeled cells. The sutured magnet was tolerated for up to 168 hours; however, an inflammatory response to the magnet was noted after 48 hours. These proof-of-concept studies support the feasibility and value of using GNTs as a magnetic nanoparticle facilitator to improve cell retention during cellular cardiomyoplasty. PMID:24148239

  17. The use of gadolinium-carbon nanostructures to magnetically enhance stem cell retention for cellular cardiomyoplasty.

    Science.gov (United States)

    Tran, Lesa A; Hernández-Rivera, Mayra; Berlin, Ari N; Zheng, Yi; Sampaio, Luiz; Bové, Christina; Cabreira-Hansen, Maria da Graça; Willerson, James T; Perin, Emerson C; Wilson, Lon J

    2014-01-01

    In this work, the effectiveness of using Gadonanotubes (GNTs) with an external magnetic field to improve retention of transplanted adult mesenchymal stem cells (MSCs) during cellular cardiomyoplasty was evaluated. As a high-performance T1-weighted magnetic resonance imaging (MRI) cell tracking label, the GNTs are gadolinium-loaded carbon nanotube capsules that render MSCs magnetic when internalized. MSCs were internally labeled with either superparamagnetic GNTs or colloidal diamagnetic lutetium (Lu). In vitro cell rolling assays and ex vivo cardiac perfusion experiments qualitatively demonstrated increased magnetic-assisted retention of GNT-labeled MSCs. Subsequent in vivo epicardial cell injections were performed around a 1.3 T NdFeB ring magnet sutured onto the left ventricle of female juvenile pigs (n = 21). Cell dosage, magnet exposure time, and endpoints were varied to evaluate the safety and efficacy of the proposed therapy. Quantification of retained cells in collected tissues by elemental analysis (Gd or Lu) showed that the external magnet helped retain nearly three times more GNT-labeled MSCs than Lu-labeled cells. The sutured magnet was tolerated for up to 168 h; however, an inflammatory response to the magnet was noted after 48 h. These proof-of-concept studies support the feasibility and value of using GNTs as a magnetic nanoparticle facilitator to improve cell retention during cellular cardiomyoplasty. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Collective magnetic behaviors of Fe-Ag nanostructured thin films above the percolation limit

    International Nuclear Information System (INIS)

    Alonso, J.; Fdez-Gubieda, M. L.; Barandiaran, J. M.; Svalov, A.; Sarmiento, G.; Fernandez Barquin, L.; Pedro, I. de; Orue, I.

    2009-01-01

    The magnetic behavior of sputtered and pulsed laser deposited (PLD) Fe x Ag 100-x thin films with 27≤x≤55 has been studied by means of ac and dc magnetic measurements. Sputtered samples present a continuous decrease in the magnetization, down to 310 K for x=30, where a magnetic transition into a superparamagnetic state with the presence of dipolar interactions is observed. The ac susceptibility measurements indicate that this transition resembles that of three dimensional glassy systems. Sputtered samples with higher concentration of Fe present a similar but slower thermal evolution of magnetization. PLD samples with x≥50 show a Curie-Weiss-type transition above ∼200 K triggered by direct exchange interactions. As the temperature decreases, the system behaves like a ferromagnet and below ∼75 K, a transition into a cluster-glass state appears. As the composition decreases, these phenomena vanish

  19. Highly ordered mesoporous cobalt oxide nanostructures: synthesis, characterisation, magnetic properties, and applications for electrochemical energy devices.

    Science.gov (United States)

    Wang, Guoxiu; Liu, Hao; Horvat, Josip; Wang, Bei; Qiao, Shizhang; Park, Jinsoo; Ahn, Hyojun

    2010-09-24

    Highly ordered mesoporous Co(3)O(4) nanostructures were prepared using KIT-6 and SBA-15 silica as hard templates. The structures were confirmed by small angle X-ray diffraction, high resolution transmission electron microscopy, and N(2) adsorption-desorption isotherm analysis. Both KIT-6 cubic and SBA-15 hexagonal mesoporous Co(3)O(4) samples exhibited a low Néel temperature and bulk antiferromagnetic coupling due to geometric confinement of antiferromagnetic order within the nanoparticles. Mesoporous Co(3)O(4) electrode materials have demonstrated the high lithium storage capacity of more than 1200 mAh g(-1) with an excellent cycle life. They also exhibited a high specific capacitance of 370 F g(-1) as electrodes in supercapacitors.

  20. Mn-Rich Nanostructures in Ge1-xMnx: Fabrication, Microstructure, and Magnetic Properties

    Directory of Open Access Journals (Sweden)

    Ying Jiang

    2012-01-01

    Full Text Available Magnetic semiconductors have attracted extensive attention due to their novel physical properties as well as the potential applications in future spintronics devices. Over the past decade, tremendous efforts have been made in the diluted magnetic semiconductors (DMS system, with many controversies disentangled but many puzzles unsolved as well. Here in this paper, we summarize recent experimental results in the growth, microstructure and magnetic properties of Ge-based DMSs (mainly Ge1-xMnx, which have been comprehensively researched owing to their compatibility with Si microelectronics. Growth conditions of high-quality, defect-free, and magnetic Ge1-xMnx bulks, thin films, ordered arrays, quantum dots, and nanowires are discussed in detail.

  1. Thickness-modulated tungsten-carbon superconducting nanostructures grown by focused ion beam induced deposition for vortex pinning up to high magnetic fields.

    Science.gov (United States)

    Serrano, Ismael García; Sesé, Javier; Guillamón, Isabel; Suderow, Hermann; Vieira, Sebastián; Ibarra, Manuel Ricardo; De Teresa, José María

    2016-01-01

    We report efficient vortex pinning in thickness-modulated tungsten-carbon-based (W-C) nanostructures grown by focused ion beam induced deposition (FIBID). By using FIBID, W-C superconducting films have been created with thickness modulation properties exhibiting periodicity from 60 to 140 nm, leading to a strong pinning potential for the vortex lattice. This produces local minima in the resistivity up to high magnetic fields (2.2 T) in a broad temperature range due to commensurability effects between the pinning potential and the vortex lattice. The results show that the combination of single-step FIBID fabrication of superconducting nanostructures with built-in artificial pinning landscapes and the small intrinsic random pinning potential of this material produces strong periodic pinning potentials, maximizing the opportunities for the investigation of fundamental aspects in vortex science under changing external stimuli (e.g., temperature, magnetic field, electrical current).

  2. Application and development of advanced Lorentz microscopy techniques for the study of magnetic nanostructures

    Science.gov (United States)

    Beacham, Robert J.

    This PhD project presents an investigation into the development of magnetic imaging methods in the TEM and their application in imaging narrow domain walls in multilayer magnetic structures. Lorentz microscopy techniques are limited in quantitative magnetic imaging as this generally requires using scanning imaging modes which limits the capability of imaging dynamic processes. The first imaging method developed in this study is a phase gradient technique with the aim of producing quantitative magnetic contrast proportional to the magnetic induction of the sample whilst maintaining a live imaging mode. This method uses a specifically engineered, semi-electron-transparent graded wedge aperture to controllably perturb intensity in the back focal plane. The results of this study found that this method could produce magnetic contrast proportional to the sample induction, however the required gradient of the wedge aperture made this contrast close to the noise level with large associated errors. In the second part of this study we investigated the development of a technique aimed at gaining sub-microsecond temporal resolution within TEMs based on streak imaging. We are using ramped pulsed magnetic fields, applied across nanowire samples to both induce magnetic behaviour and detect the electron beam across the detector with respect to time. We are coupling this with a novel pixelated detector on the TEM in the form of a Medipix/Timepix chip capable of microsecond exposure times without adding noise. Running this detector in integral mode and allowing for practical limitations such as experiment time and aperture stability, the resultant streak images were taken in Fresnel, Foucault and low angle diffraction imaging modes. We found that while this method is theoretically viable, the limiting factor was the contrast of the magnetic signal in the streak and therefore the total image counts. Domain walls (DWs) in synthetic antiferromagnetically (SAF) coupled films patterned

  3. Tuning magnetic properties of magnetoelectric BiFeO{sub 3}-NiFe{sub 2}O{sub 4} nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Crane, S.P. [Department of Materials Science and Engineering, University of California, Berkeley, CA 94720 (United States)], E-mail: scrane@berkeley.edu; Bihler, C.; Brandt, M.S. [Walter Schottky Institut, Technische Universitaet Muenchen, D-85748 Garching (Germany); Goennenwein, S.T.B. [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching (Germany); Gajek, M. [Department of Physics, University of California, Berkeley, CA 94720 (United States); Ramesh, R. [Department of Materials Science and Engineering, University of California, Berkeley, CA 94720 (United States); Department of Physics, University of California, Berkeley, CA 94720 (United States)

    2009-02-15

    Multifunctional thin film nanostructures containing soft magnetic materials such as nickel ferrite are interesting for potential applications in microwave signal processing because of the possibility to shrink the size of device architecture and limit device power consumption. An essential prerequisite to future applications of such a system is a firm understanding of its magnetic properties. We show that nanostructures composed of ferrimagnetic NiFe{sub 2}O{sub 4} pillars in a multiferroic BiFeO{sub 3} matrix can be tuned magnetically by altering the aspect ratio of the pillars by depositing films of varying thickness. Magnetic anisotropy is studied using ferromagnetic resonance, which shows that the uniaxial magnetic anisotropy in the growth direction changes sign upon increasing the film thickness. The magnitude of this anisotropy contribution can be explained via a combination of shape and magnetostatic effects, using the object-oriented micromagnetic framework (OOMMF). The key factors determining the magnetic properties of the films are shown to be the aspect ratio of individual pillars and magnetostatic interactions between neighboring pillars.

  4. Magnetic interaction reversal in watermelon nanostructured Cr-doped Fe nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Maninder; Dai, Qilin; Bowden, Mark; Engelhard, Mark; Wu, Yaqiao; Tang, Jinke; Qiang, You

    2013-01-01

    Cr-doped core-shell Fe/Fe-oxide nanoclusters (NCs) were synthesized at varied atomic percentages of Cr from 0 at. % to 8 at. %. The low concentrations of Cr (<10 at. %) were selected in order to inhibit the complete conversion of the Fe-oxide shell to Cr2O3 and the Fe core to FeCr alloy. The magnetic interaction in Fe/Fe-oxide NCs (rv25 nm) can be controlled by antiferromagnetic Cr-dopant. We report the origin of r-FeCr phase at very low Cr concentration (2 at. %) unlike in previous studies, and the interaction reversal from dipolar to exchange interaction in watermelon-like Cr-doped core-shell NCs. The giant magnetoresistance (GMR) effect,1,2 where an antiferromagnetic (AFM) exchange coupling exists between two ferromagnetic (FM) layers separated by a certain type of magnetic or non-magnetic spacer,3 has significant potential for application in the magnetic recording industry. Soon after the discovery of the GMR, the magnetic properties of multilayer systems (FeCr) became a subject of intensive study. The application of bulk iron-chromium (Fe-Cr) alloys has been of great interest, as these alloys exhibit favorable prop- erties including corrosion resistance, high strength, hardness, low oxidation rate, and strength retention at elevated temper- ature. However, the structural and magnetic properties of Cr-doped Fe nanoclusters (NCs) have not been investigated in-depth. Of all NCs, Fe-based clusters have unique magnetic properties as well as favorable catalytic characteristics in reactivity, selectivity, and durability.4 The incorporation of dopant of varied type and concentration in Fe can modify its chemical ordering, thereby optimizing its electrical, optical, and magnetic properties and opening up many new applications. The substitution of an Fe atom (1.24 A°) by a Cr atom (1.25 A° ) can easily modify the magnetic properties, since (i) the curie temperature (Tc ) of Fe is 1043 K, while Cr is an itinerant AFM with a bulk Neel temperature TN =311 K, and (ii) Fe

  5. Calcium-assisted reduction of cobalt ferrite nanoparticles for nanostructured iron cobalt with enhanced magnetic performance

    International Nuclear Information System (INIS)

    Qi, B.; Andrew, J. S.; Arnold, D. P.

    2017-01-01

    This paper demonstrates the potential of a calcium-assisted reduction process for synthesizing fine-grain (~100 nm) metal alloys from metal oxide nanoparticles. To demonstrate the process, an iron cobalt alloy (Fe_6_6Co_3_4) is obtained by hydrogen annealing 7-nm cobalt ferrite (CoFe_2O_4) nanoparticles in the presence of calcium granules. The calcium serves as a strong reducing agent, promoting the phase transition from cobalt ferrite to a metallic iron cobalt alloy, while maintaining high crystallinity. Magnetic measurements demonstrate the annealing temperature is the dominant factor of tuning the grain size and magnetic properties. Annealing at 700 °C for 1 h maximizes the magnetic saturation, up to 2.4 T (235 emu/g), which matches that of bulk iron cobalt.

  6. Calcium-assisted reduction of cobalt ferrite nanoparticles for nanostructured iron cobalt with enhanced magnetic performance

    Energy Technology Data Exchange (ETDEWEB)

    Qi, B. [University of Florida, Interdisciplinary Microsystems Group, Department of Electrical and Computer Engineering (United States); Andrew, J. S. [University of Florida, Department of Materials Science and Engineering (United States); Arnold, D. P., E-mail: darnold@ufl.edu [University of Florida, Interdisciplinary Microsystems Group, Department of Electrical and Computer Engineering (United States)

    2017-03-15

    This paper demonstrates the potential of a calcium-assisted reduction process for synthesizing fine-grain (~100 nm) metal alloys from metal oxide nanoparticles. To demonstrate the process, an iron cobalt alloy (Fe{sub 66}Co{sub 34}) is obtained by hydrogen annealing 7-nm cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles in the presence of calcium granules. The calcium serves as a strong reducing agent, promoting the phase transition from cobalt ferrite to a metallic iron cobalt alloy, while maintaining high crystallinity. Magnetic measurements demonstrate the annealing temperature is the dominant factor of tuning the grain size and magnetic properties. Annealing at 700 °C for 1 h maximizes the magnetic saturation, up to 2.4 T (235 emu/g), which matches that of bulk iron cobalt.

  7. Plateau on temperature dependence of magnetization of nanostructured rare earth titanates

    Science.gov (United States)

    Rinkevich, A. B.; Korolev, A. V.; Samoylovich, M. I.; Demokritov, S. O.; Perov, D. V.

    2018-05-01

    Magnetic properties of nanocomposite materials containing particles of rare earth titanates of R2Ti2O7 type, where R is a rare earth ion, including "spin ice" materials are investigated. The descending branches of hysteresis loop have been studied in detail in temperature range from 2 to 50 K. It has been shown that nanocomposites with Yb2Ti2O7, Dy2Ti2O7 and Er2Ti2O7 particles have one intersection point of the descending branches in some temperature range unlike many other nanocomposites. It is shown that magnetization has only weak temperature dependence near this point. It has been obtained that nanocomposites with Pr2Ti2O7 and Nd2Ti2O7 particles have no hysteresis loop. All above findings point out to unusual magnetic structures of the studied samples.

  8. Organization dependent collective magnetic properties of secondary nanostructures with differential spatial ordering and magnetic easy axis orientation

    Energy Technology Data Exchange (ETDEWEB)

    Saikia, K. [Department of Physics, Tezpur University (Central University), Tezpur 784028 (India); Sarma, D.D. [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012 (India); Deb, P., E-mail: pdeb@tezu.ernet.in [Department of Physics, Tezpur University (Central University), Tezpur 784028 (India)

    2016-06-15

    Achieving control on the formation of different organization states of magnetic nanoparticles is crucial to harness their organization dependent physical properties in desired ways. In this study, three organization states of iron oxide nanoparticles (γ-Fe{sub 2}O{sub 3}), defining as (i) assembly (ii) network aggregate and (iii) cluster, have been developed by simply changing the solvent evaporation conditions. All three systems have retained the same phase and polydispersity of primary particles. Magnetic measurements show that the partial alignment of the easy axes of the particles in the network system due to the stacking aggregation morphology can result in significant enhancement of the coercivity and remanence values, while the opposite is obtained for the cluster system due to the random orientation of easy axes. Partial alignment in the aggregate system also results in noticeable non-monotonic field dependence of ZFC peak temperature (T{sub peak}). The lowest value of the blocking temperature (T{sub B}) for the cluster system is related to the lowering of the effective anisotropy due to the strongest demagnetizing effect. FC (Field cooled) memory effect was observed to be decreasing with the increasing strength of dipolar interaction of organization states. Therefore, the stacking aggregation and the cluster formation are two interesting ways of magnetic nanoparticles organization for modulating collective magnetic properties significantly, which can have renewed application potentials from recording devices to biomedicine. - Highlights: • Three organization states of magnetic nanoparticles were developed. • Aggregation enhances the H{sub c} and M{sub r}/M{sub s,} while spherical clustering shows opposite. • Organization morphology hardly effects on FC memory effect. • Developed secondary systems can have renewed application potentials in wide spectrum.

  9. Commensurate vortex configurations in thin superconducting films nanostructured by square lattice of magnetic dots

    Energy Technology Data Exchange (ETDEWEB)

    Milosevic, M.V.; Peeters, F.M

    2004-05-01

    Within the phenomenological Ginzburg-Landau (GL) theory, we investigate the vortex structure of a thin superconducting film (SC) with a regular matrix of ferromagnetic dots (FD) deposited on top of it. The vortex pinning properties of such a magnetic lattice are studied, and the field polarity dependent votex pinning is observed. The exact vortex configuration depends on the size of the magnetic dots, their polarity, periodicity of the FD-rooster and the properties of the SC expressed through the effective Ginzburg-Landau parameter {kappa}*.

  10. Commensurate vortex configurations in thin superconducting films nanostructured by square lattice of magnetic dots

    International Nuclear Information System (INIS)

    Milosevic, M.V.; Peeters, F.M.

    2004-01-01

    Within the phenomenological Ginzburg-Landau (GL) theory, we investigate the vortex structure of a thin superconducting film (SC) with a regular matrix of ferromagnetic dots (FD) deposited on top of it. The vortex pinning properties of such a magnetic lattice are studied, and the field polarity dependent votex pinning is observed. The exact vortex configuration depends on the size of the magnetic dots, their polarity, periodicity of the FD-rooster and the properties of the SC expressed through the effective Ginzburg-Landau parameter κ*

  11. Magnetic anisotropy of two-dimensional nanostructures: Transition-metal triangular stripes

    International Nuclear Information System (INIS)

    Dorantes-Davila, J.; Villasenor-Gonzalez, P.; Pastor, G.M.

    2005-01-01

    The magnetic anisotropy energy (MAE) of one-dimensional stripes having infinite length and triangular lateral structure are investigated in the framework of a self-consistent tight-binding method. One observes discontinuous changes in the easy magnetization direction along the crossover from one to two dimensions. The MAE oscillates as a function of stripe width and depends strongly on the considered transition metal (TM). The MAE of the two-leg ladder is strongly reduced as compared to that of the monoatomic chain and the convergence to the two-dimensional limit is rather slow

  12. NATO Advanced Study Institute on Magnetic Nanostructures for Micro-Electromechanical Systems and Spintronic Applications

    CERN Document Server

    Azzerboni, Bruno; Pareti, Luigi; Ghidini, Massimo

    2007-01-01

    Proposes a synergic junction between the characteristic expertise of the engineering and the knowledge of the basic scienceThe main effect should be a cross-cultural fertilization favoring an interdisciplinary enrichment for the readers and their research perspectivesCovers the most advanced fields of modern magnetic nano-technologiesA unique source of up to date information for the young physicist, chemist or engineer as well as a crucial reference for the expert scientist and the teacher of advanced university coursesDeals with the most important topics in the field of modern magnetism in fu

  13. Growth mechanism and interface magnetic properties of Co nanostructures on graphite

    NARCIS (Netherlands)

    Wong, P.K.J.; de Jong, Machiel Pieter; Leonardus, L.; Siekman, Martin Herman; van der Wiel, Wilfred Gerard

    2011-01-01

    We investigated structural, electronic, and magnetic properties of Co adsorbed on highly oriented pyrolytic graphite (HOPG). Distribution and atomic sites of 3d transition-metal Co nanoislands and adatoms on HOPG were experimentally investigated by scanning tunneling microscopy with atomic

  14. FeNi-based flat magnetoimpedance nanostructures with open magnetic flux: New topological approaches

    Energy Technology Data Exchange (ETDEWEB)

    Kurlyandskaya, G.V., E-mail: galina@we.lc.ehu.es [Universidad del País Vasco, UPV/EHU, Dpto. de Electricidad y Electrónica, P.O. Box 644, Bilbao 48080 (Spain); Ural Federal University, Department of Magnetism and Magnetic Nanomaterials, Mira 19, 620002 Ekaterinburg (Russian Federation); Chlenova, A.A. [Ural Federal University, Department of Magnetism and Magnetic Nanomaterials, Mira 19, 620002 Ekaterinburg (Russian Federation); Fernández, E. [Universidad del País Vasco, UPV/EHU, Dpto. de Electricidad y Electrónica, P.O. Box 644, Bilbao 48080 (Spain); Lodewijk, K.J. [Universidad del País Vasco, UPV/EHU, Dpto. de Electricidad y Electrónica, P.O. Box 644, Bilbao 48080 (Spain); Department of Material Sciences, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands)

    2015-06-01

    Classic flat MI multilayers consist of top and bottom ferromagnetic parts of equal thickness separated by a conductive lead. In previous studies symmetric MI structures were considered because they provide the highest sensitivity with respect to uniform external magnetic fields. There are a number of applications where non-uniform magnetic fields of complex configurations must be detected. Non-symmetric MI structures can be advantageous in this particular case. We describe our experience in design, fabrication and characterization of symmetric and non-symmetric MI multilayers with open magnetic flux. Non-symmetry of the structures was obtained by the deposition of top and bottom ferromagnetic parts of MI element of different thickness. MI responses of the structures with even or odd configurations of the FeNi layers were also considered. - Highlights: • Classic flat MI multilayer consists of ferromagnetic parts of equal thickness separated by a conductive lead. • In previous studies symmetric MI structures were considered. • Non-symmetric MI structures can be advantageous for applications where non-uniform magnetic fields are detected. • MI responses of the structures with even or odd configuration can be very different.

  15. FeNi-based flat magnetoimpedance nanostructures with open magnetic flux: New topological approaches

    International Nuclear Information System (INIS)

    Kurlyandskaya, G.V.; Chlenova, A.A.; Fernández, E.; Lodewijk, K.J.

    2015-01-01

    Classic flat MI multilayers consist of top and bottom ferromagnetic parts of equal thickness separated by a conductive lead. In previous studies symmetric MI structures were considered because they provide the highest sensitivity with respect to uniform external magnetic fields. There are a number of applications where non-uniform magnetic fields of complex configurations must be detected. Non-symmetric MI structures can be advantageous in this particular case. We describe our experience in design, fabrication and characterization of symmetric and non-symmetric MI multilayers with open magnetic flux. Non-symmetry of the structures was obtained by the deposition of top and bottom ferromagnetic parts of MI element of different thickness. MI responses of the structures with even or odd configurations of the FeNi layers were also considered. - Highlights: • Classic flat MI multilayer consists of ferromagnetic parts of equal thickness separated by a conductive lead. • In previous studies symmetric MI structures were considered. • Non-symmetric MI structures can be advantageous for applications where non-uniform magnetic fields are detected. • MI responses of the structures with even or odd configuration can be very different

  16. Magnetic characteristics and nanostructures of FePt granular films with GeO2 segregant

    Science.gov (United States)

    Ono, Takuya; Moriya, Tomohiro; Hatayama, Masatoshi; Tsumura, Kaoru; Kikuchi, Nobuaki; Okamoto, Satoshi; Kitakami, Osamu; Shimatsu, Takehito

    2017-01-01

    To realize a granular film composed of L10-FePt grains with high uniaxial magnetic anisotropy energy, Ku, and segregants for energy-assisted magnetic recording, a FePt-GeO2/FePt-C stacked film was investigated in the engineering process. The FePt-GeO2/FePt-C stacked film fabricated at a substrate temperature of 450 °C realized uniaxial magnetic anisotropy, Kugrain , of about 2.5 × 107 erg/cm3, which is normalized by the volume fraction of FePt grains, and a granular structure with an averaged grain size of 7.7 nm. As the thickness of the FePt-GeO2 upper layer was increased to 9 nm, the Ku values were almost constant. That result differs absolutely from the thickness dependences of the other oxide segregant materials such as SiO2 and TiO2. Such differences on the oxide segregant are attributed to their chemical bond. The strong covalent bond of GeO2 is expected to result in high Ku of the FePt-GeO2/FePt-C stacked films.

  17. Impacts of Coulomb Interactions on the Magnetic Responses of Excitonic Complexes in Single Semiconductor Nanostructures

    Directory of Open Access Journals (Sweden)

    Fu Ying-Jhe

    2010-01-01

    Full Text Available Abstract We report on the diamagnetic responses of different exciton complexes in single InAs/GaAs self-assembled quantum dots (QDs and quantum rings (QRs. For QDs, the imbalanced magnetic responses of inter-particle Coulomb interactions play a crucial role in the diamagnetic shifts of excitons (X, biexcitons (XX, and positive trions (X−. For negative trions (X− in QDs, anomalous magnetic responses are observed, which cannot be described by the conventional quadratic energy shift with the magnetic field. The anomalous behavior is attributed to the apparent change in the electron wave function extent after photon emission due to the strong Coulomb attraction by the hole in its initial state. In QRs, the diamagnetic responses of X and XX also show different behaviors. Unlike QDs, the diamagnetic shift of XX in QRs is considerably larger than that of X. The inherent structural asymmetry combined with the inter-particle Coulomb interactions makes the wave function distribution of XX very different from that of X in QRs. Our results suggest that the phase coherence of XX in QRs may survive from the wave function localization due to the structural asymmetry or imperfections.

  18. Structural, magnetic and optical properties of ZnO nanostructures converted from ZnS nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Prayas Chandra; Ghosh, Surajit; Srivastava, P.C., E-mail: pcsrivastava50@gmail.com

    2016-09-15

    Graphical abstract: The phase conversion of ZnS to highly crystalline hexagonal ZnO was done by heat treatment. - Highlights: • Phase change of cubic ZnS to hexagonal ZnO via heat treatment. • Band gap was found to decrease with increasing calcinations temperature. • ZnO samples have higher magnetic moment than ZnS. • Blocking Temperature of the samples is well above room temperature. • Maximum negative%MR with saturation value ∼38% was found for sample calcined at 600° C. - Abstract: The present work concentrates on the synthesis of cubic ZnS and hexagonal ZnO semiconducting nanoparticle from same precursor via co-precipitation method. The phase conversion of ZnS to highly crystalline hexagonal ZnO was done by heat treatment. From the analysis of influence of calcination temperature on the structural, optical and vibrational properties of the samples, an optimum temperature was found for the total conversion of ZnS nanoparticles to ZnO. Role of quantum confinement due to finite size is evident from the blue shift of the fundamental absorption in UV–vis spectra only in the ZnS nanoparticles. The semiconducting nature of the prepared samples is confirmed from the UV–vis, PL study and transport study. From the magnetic and transport studies, pure ZnO phase was found to be more prone to magnetic field.

  19. Synthesis of Ni core NiO shell nanostructure and magnetic investigation for shell thickness determination

    International Nuclear Information System (INIS)

    Arabi, H.; Bruck, E.; Tichelaar, F.D.

    2007-01-01

    Full text: Nickel oxide has received a considerable amount of attention in recent years for its catalytic, electronic and magnetic properties. Ni nanoparticles with an average size of 8 nm were prepared by dc - arc discharge in argon atmosphere. A current of 130 A and 300 milli bar pressure of argon have been applied. The produced Ni nanoparticles were annealed for oxidizing in air at 350 for six hours to produce antiferromagnetic NiO particles. The structure of Ni and NiO nanoparticles and size estimation of them studied by means of X-ray diffraction. The size and morphology of the particles were also characterized by high resolution transmission microscopy (TEM). The Ni core NiO shell structure, resulting from the oxidation process, were studied by magnetic properties measurements. A quantum design squid magnetometer, model MPMS5S was used for measuring saturation magnetization of both nanoparticles of Ni with and without NiO layer. By knowing the density of Ni and NiO, we were able to deduce the thickness of the Ni core and NiO outer layer. They are around 3 and 5 nanometers respectively. (authors)

  20. Nanostructure and magnetic properties of CoNi-alloy-based nanoparticles dispersed in a silica matrix

    International Nuclear Information System (INIS)

    De Julian, C.; Sangregorio, C.; Mattei, G.; Battaglin, G.; Cattaruzza, E.; Gonella, F.; Lo Russo, S.; D'Orazio, F.; Lucari, F.; De, G.; Gatteschi, D.; Mazzoldi, P.

    2001-01-01

    A comparative study of the magnetic behavior of FCC alloy CoNi (1:1) nanoparticles, embedded in a silica matrix and prepared by the ion implantation and sol-gel techniques, is presented. The blocking temperature is related to the size distribution, and, at least for the ion-implanted samples, only an enhanced effective anisotropy explains the experimental results. The hysteretic behavior is explained in terms of the temperature dependence of the anisotropy and of the particle volume fraction that determines the dipolar interactions

  1. Nanostructure and magnetic properties of CoNi-alloy-based nanoparticles dispersed in a silica matrix

    Energy Technology Data Exchange (ETDEWEB)

    De Julian, C. E-mail: dejulian@padova.infm.it; Sangregorio, C.; Mattei, G.; Battaglin, G.; Cattaruzza, E.; Gonella, F.; Lo Russo, S.; D' Orazio, F.; Lucari, F.; De, G.; Gatteschi, D.; Mazzoldi, P

    2001-05-01

    A comparative study of the magnetic behavior of FCC alloy CoNi (1:1) nanoparticles, embedded in a silica matrix and prepared by the ion implantation and sol-gel techniques, is presented. The blocking temperature is related to the size distribution, and, at least for the ion-implanted samples, only an enhanced effective anisotropy explains the experimental results. The hysteretic behavior is explained in terms of the temperature dependence of the anisotropy and of the particle volume fraction that determines the dipolar interactions.

  2. Biodistribution of doxorubicin and nanostructured ferrocarbon carrier particles in organism during magnetically controlled drug delivery

    Energy Technology Data Exchange (ETDEWEB)

    Kuznetsov, Anatoly A.; Filippov, Victor I.; Nikolskaya, Tatiana A. [Institute of Biochemical Physics, Russian Academy of Sciences, Kosygin St. 4, Moscow 119991 (Russian Federation); Budko, Andrei P. [Oncological Center, Russian Academy of Medical Sciences, Moscow (Russian Federation); Kovarskii, Alexander L. [Institute of Biochemical Physics, Russian Academy of Sciences, Kosygin St. 4, Moscow 119991 (Russian Federation); Zontov, Sergei V. [Oncological Center, Russian Academy of Medical Sciences, Moscow (Russian Federation); Kogan, Boris Ya. [Institute of Biochemical Physics, Russian Academy of Sciences, Kosygin St. 4, Moscow 119991 (Russian Federation); Kuznetsov, Oleg A. [Institute of Biochemical Physics, Russian Academy of Sciences, Kosygin St. 4, Moscow 119991 (Russian Federation)], E-mail: kuznetsov_oa@yahoo.com

    2009-05-15

    Biodistribution of doxorubicin and ferrocarbon carrier particles in organism during and after magnetically controlled anti-tumor drug delivery and deposition was studied. Animal tests show high concentration of the cytostatic drug in the target zone, while its concentration is three orders of magnitude lower in bloodstream and other organs. A significant depot of the drug remains on the deposited particles days after the procedure. Macrophages actively phagocytose the ferrocarbon (FeC) particles and remain viable long enough to carry them to the lymph nodes.

  3. Biodistribution of doxorubicin and nanostructured ferrocarbon carrier particles in organism during magnetically controlled drug delivery

    International Nuclear Information System (INIS)

    Kuznetsov, Anatoly A.; Filippov, Victor I.; Nikolskaya, Tatiana A.; Budko, Andrei P.; Kovarskii, Alexander L.; Zontov, Sergei V.; Kogan, Boris Ya.; Kuznetsov, Oleg A.

    2009-01-01

    Biodistribution of doxorubicin and ferrocarbon carrier particles in organism during and after magnetically controlled anti-tumor drug delivery and deposition was studied. Animal tests show high concentration of the cytostatic drug in the target zone, while its concentration is three orders of magnitude lower in bloodstream and other organs. A significant depot of the drug remains on the deposited particles days after the procedure. Macrophages actively phagocytose the ferrocarbon (FeC) particles and remain viable long enough to carry them to the lymph nodes.

  4. Strong Interlayer Magnon-Magnon Coupling in Magnetic Metal-Insulator Hybrid Nanostructures

    Science.gov (United States)

    Chen, Jilei; Liu, Chuanpu; Liu, Tao; Xiao, Yang; Xia, Ke; Bauer, Gerrit E. W.; Wu, Mingzhong; Yu, Haiming

    2018-05-01

    We observe strong interlayer magnon-magnon coupling in an on-chip nanomagnonic device at room temperature. Ferromagnetic nanowire arrays are integrated on a 20-nm-thick yttrium iron garnet (YIG) thin film strip. Large anticrossing gaps up to 1.58 GHz are observed between the ferromagnetic resonance of the nanowires and the in-plane standing spin waves of the YIG film. Control experiments and simulations reveal that both the interlayer exchange coupling and the dynamical dipolar coupling contribute to the observed anticrossings. The coupling strength is tunable by the magnetic configuration, allowing the coherent control of magnonic devices.

  5. Magnetic interaction reversal in watermelon nanostructured Cr-doped Fe nanoclusters

    International Nuclear Information System (INIS)

    Kaur, Maninder; Qiang, You; Dai, Qilin; Tang, Jinke; Bowden, Mark; Engelhard, Mark; Wu, Yaqiao

    2013-01-01

    Cr-doped core-shell Fe/Fe-oxide nanoclusters (NCs) were synthesized at varied atomic percentages of Cr from 0 at. % to 8 at. %. The low concentrations of Cr ( 2 O 3 and the Fe core to FeCr alloy. The magnetic interaction in Fe/Fe-oxide NCs (∼25 nm) can be controlled by antiferromagnetic Cr-dopant. We report the origin of σ-FeCr phase at very low Cr concentration (2 at. %) unlike in previous studies, and the interaction reversal from dipolar to exchange interaction in watermelon-like Cr-doped core-shell NCs

  6. Magnetic interaction reversal in watermelon nanostructured Cr-doped Fe nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Maninder; Qiang, You, E-mail: youqiang@uidaho.edu [Department of Physics, University of Idaho, Moscow, Idaho 83844 (United States); Dai, Qilin; Tang, Jinke [Department of Physics and Astronomy, University of Wyoming, Laramie, Wyoming 82071 (United States); Bowden, Mark; Engelhard, Mark [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Wu, Yaqiao [Department of Materials Science and Engineering, Boise State University, Boise, Idaho 83725 (United States); Center for Advanced Energy Studies, Idaho Falls, Idaho 83401 (United States)

    2013-11-11

    Cr-doped core-shell Fe/Fe-oxide nanoclusters (NCs) were synthesized at varied atomic percentages of Cr from 0 at. % to 8 at. %. The low concentrations of Cr (<10 at. %) were selected in order to inhibit the complete conversion of the Fe-oxide shell to Cr{sub 2}O{sub 3} and the Fe core to FeCr alloy. The magnetic interaction in Fe/Fe-oxide NCs (∼25 nm) can be controlled by antiferromagnetic Cr-dopant. We report the origin of σ-FeCr phase at very low Cr concentration (2 at. %) unlike in previous studies, and the interaction reversal from dipolar to exchange interaction in watermelon-like Cr-doped core-shell NCs.

  7. Microscopic theory of spin-filtering in non-magnetic semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Kubis, T.; Vogl, P. [Walter Schottky Institute, Technische Universitaet Muenchen, Am Coulombwall 3, 85748 Garching (Germany)

    2008-07-01

    In this paper, we investigate the intrinsic spin-Hall effect in mesoscopic systems, i.e. spin-orbit induced spin-polarizations with and without external magnetic fields in confined two-dimensional systems at low temperatures. We employ a non-equilibrium Green's function approach that takes into account the coupling of non-equilibrium spin occupancies and spin-resolved electronic scattering states in open nanometer quantum systems. Importantly, our calculations go beyond the widely used continuum approximation of the spin-orbit interaction in the envelope function approximation and are based on a microscopic relativistic tight-binding approach that ensures the spin-orbit effects to be properly taken into account for any degree of charge confinement and localization and to all orders in the electron wave vector. We show that the qualitative trends and results in spin polarizations, their dependency on charge density, spin-orbit interaction strength, and confinement, as obtained within the envelope function approximation, agree with the results of atomistic calculations. The quantitative results, on the other hand, can differ significantly. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Hysteretic features of Ising-type segmented nanostructure with alternating magnetic wires

    International Nuclear Information System (INIS)

    Kantar, Ersin

    2016-01-01

    In the present study, a theoretical approach to investigate the hysteresis behaviors in segmented nanowires is described and applied to spin-1/2 and spin-1 hexagonal nanowire. The hysteresis loop, coercive field and remanent magnetization of a segmented Ising nanowire (SIN) are obtained by using the effective-field theory with correlations. The effects of the temperature, crystal field and geometrical parameters of nanowires on the hysteresis behaviors of the system are investigated. A number of characteristic behaviors are found, such as the occurrence of single and triple hysteresis loops for appropriate values of the crystal field. The hysteresis behaviors are also strongly dependent on geometrical parameters. Comparisons between the obtained theoretical results and some experimental works of segmented nanowire arrays with hysteresis behaviors are made and a very good agreement is obtained. - Highlights: • The hysteresis behaviors of a segmented Ising nanowire are obtained. • The effective-field theory with correlations are used to calculations. • The effects of the temperature and crystal field on the system are investigated. • The geometrical parameters have a significant effect on the system are observed. • The single and triple loops for appropriate values of the crystal field are obtained.

  9. Shape induced (spherical, sheets and rods) optical and magnetic properties of CdS nanostructures with enhanced photocatalytic activity for photodegradation of methylene blue dye under ultra-violet irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Bilal; Kumar, Sachin; Kumar, Sumeet; Ojha, Animesh K., E-mail: animesh@mnnit.ac.in

    2016-09-15

    CdS nanostructures of different shapes such as, nanoparticles (NPs), nanosheets (NS) and nanorods (NRs) have been synthesized by one step chemical solvothermal method. The synthesized samples were characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy, UV–visible (UV-VIS) spectroscopy, Raman spectroscopy (RS) and vibrating sample magnetometer (VSM) techniques. The effect of shape on optical and magnetic properties of CdS nanostructures was studied. The optical band gap and emission spectra are found to be shape dependent. CdS NRs were found to have high saturation (Ms) magnetization than that of CdS NPs and NS. The role of shape on photocatalytic performance of CdS NPs, NS and NRs was investigated by monitoring the photodegradation of methylene blue (MB) dye under the UV irradiation of wavelength 365 nm. The lower recombination rate of electron-hole pairs and larger surface area as reactive facets for adsorption of MB dye molecules in CdS NS are mainly lead to the better photocatalytic performance of CdS NS compared to NPs and NRs. - Highlights: • Synthesis of CdS nanostructures with different shapes (spherical, rod and sheet) by easy and low cost solvothermal method. • Shape induced optical and magnetic properties of CdS nanostructures have been investigated. • The shapes of nanostructures play an important role for photocatalytic performance of CdS nanostructures.

  10. Study of morphology effects on magnetic interactions and band gap variations for 3d late transition metal bi-doped ZnO nanostructures by hybrid DFT calculations

    Energy Technology Data Exchange (ETDEWEB)

    Datta, Soumendu, E-mail: soumendu@bose.res.in; Baral, Sayan; Mookerjee, Abhijit [Department of Condensed Matter Physics and Material Sciences, S.N. Bose National Centre for Basic Sciences, JD Block, Sector-III, Salt Lake City, Kolkata 700 098 (India); Kaphle, Gopi Chandra [Central Department of Physics, Tribhuvan University, Kathmandu (Nepal)

    2015-08-28

    Using density functional theory (DFT) based electronic structure calculations, the effects of morphology of semiconducting nanostructures on the magnetic interaction between two magnetic dopant atoms as well as a possibility of tuning band gaps have been studied in the case of the bi-doped (ZnO){sub 24} nanostructures with the impurity dopant atoms of the 3d late transition metals—Mn, Fe, Co, Ni, and Cu. To explore the morphology effect, three different structures of the host (ZnO){sub 24} nano-system, having different degrees of spatial confinement, have been considered: a two dimensional nanosheet, a one dimensional nanotube, and a finite cage-shaped nanocluster. The present study employs hybrid density functional theory to accurately describe the electronic structure of all the systems. It is shown here that the magnetic coupling between the two dopant atoms remains mostly anti-ferromagnetic in the course of changing the morphology from the sheet geometry to the cage-shaped geometry of the host systems, except for the case of energetically most stable bi-Mn doping, which shows a transition from ferromagnetic to anti-ferromagnetic coupling with decreasing aspect ratio of the host system. The effect of the shape change, however, has a significant effect on the overall band gap variations of both the pristine as well as all the bi-doped systems, irrespective of the nature of the dopant atoms and provides a means for easy tunability of their optoelectronic properties.

  11. Curie temperature and magnetic phase transition of nanostructured ultrathin Fe/GaAs (001). Size dependence and relevance of dipolar coupling

    Energy Technology Data Exchange (ETDEWEB)

    Meier, Roland

    2009-07-01

    In the present work the impact of lateral patterning of ultrathin ferromagnetic films down to the nanometer range on the magnetic phase transition has been investigated. In this respect on the one hand a size effect on the Curie temperature and, referring to that, the relevance of dipolar coupling were a matter of particular interest. On the other hand the characteristics of the critical behavior itself, becoming apparent by the accurate evaluation of the curvature shape of the magnetization as a function of temperature at T{sub c}, were analyzed with regard to potential and expected size effects. The investigation of similar nanostructures with respect to an effect on Curie temperature respectively phase transition may draw up a correlation. Therefore more than hundred samples were fabricated for this work extensively by means of MBE (Molecular Beam Epitaxy) and ESL (Electron Beam Epitaxy) methods, measured by MOKE (Magneto-Optical Kerr Effect) technique and systematically evaluated. (orig.)

  12. Magnetic and structural investigations on La0.6Sr0.4MnO3 nanostructured manganite: Evidence of a ferrimagnetic shell

    International Nuclear Information System (INIS)

    Andrade, V.M.; Caraballo-Vivas, R.J.; Costas-Soares, T.; Pedro, S.S.; Rocco, D.L.; Reis, M.S.; Campos, A.P.C.; Coelho, A.A.

    2014-01-01

    This paper presents the structural and magnetic properties of La 0.6 Sr 0.4 MnO 3 nanoparticles with sizes from 21 to 106 nm, which have been prepared using the sol–gel method. The reduction of the nanoparticles' size tends to broaden the paramagnetic to ferromagnetic transition, as well as to promote magnetic hysteresis and a remarkable change on the magnetic saturation. In order to better understand the magnetic behavior of those nanoparticles, a simple model based on a ferromagnetic core and a ferrimagnetic shell was considered, where the magnetization was described in terms of the standard mean-field Brillouin function. This model matches the experimental data, leading to conclusion the nanoparticles with size <40nm are single magnetic domain. In addition, the output fitting parameters give information on the Landé factor of the core and shell. - Graphical abstract: Core–shell model: The core has a ferromagnetic character, while the shell is ferrimagnetic. Each one has two sub-lattices (Mn 3+ and Mn 4+ ) that interact through a mean-field (see Eq. (6)). Interactions strength and signals are also represented in this figure. In this figure the arrows (or vectors) represent the magnetic moment of ions Mn 3+ (s=2) and Mn 4+ (s=3/2). βλ's describe the ferromagnetic interaction between Mn 4+ ions into the core (βλ co ) and into the shell (βλ sh ), while αλ's represent ferromagnetic interaction between Mn 3+ ions into the core (αλ co ) and into the shell (αλ sh ). The −λ sh and +λ co co are associated to the mean field parameter of interaction between Mn 3+ and Mn 4+ sub-lattices in the shell (ferrimagnetic, negative sign) and core (ferromagnetic, positive sign), respectively. - Highlights: • Evidences of ferromagnetic shell in La 0.6 Sr 0.4 MnO 3 ferromagnetic nanoparticles. • Core(ferromagnetic)–shell(ferromagnetic) model for nanostructured manganite. • Sol–gel method was successfully used to obtain nanostructured

  13. Nanostructure investigation of magnetic nanomaterial Ni0.5Zn0.3Cu0.2Fe2O4 synthesized by sol-gel method

    International Nuclear Information System (INIS)

    Pransisco, Prengki; Shafie, Afza; Guan, Beh Hoe

    2015-01-01

    Magnetic nanomaterial Ni 0.5 Zn 0.3 Cu 0.2 Fe 2 O 4 was successfully prepared by using sol-gel method. Heat treatment on material is always giving defect on properties of material. This paper investigates the effect of heat treatment on nanostructure of magnetic nanomaterial Ni 0.5 Zn 0.3 Cu 0.2 Fe 2 O 4 . According to thermo gravimetric analysis (TGA) that after 600°C there is no more weight loss detected and it was decided as minimum calcination temperature. Intensity, crystallite size, structure, lattice parameter and d-spacing of the material were investigated by using X-ray diffraction (XRD). High resolution transmission electron microscope (HRTEM) was used to examine nanostructure, nanosize, shape and distribution particle of magnetic material Ni 0.5 Zn 0.3 Cu 0.2 Fe 2 O 4 and variable pressure field emission scanning electron microscope (VP-FESEM) was used to investigate the surface morphology and topography of the material. The XRD result shows single-phase cubic spinel structure with average crystallite size in the range of 25.6-95.9 nm, the value of the intensity of the material was increased with increasing temperature, and followed by lattice parameter was increased with increasing calcination temperature, value of d-spacing was relatively decreased with accompanied increasing temperature. From HRTEM result the distribution of particles was tend to be agglomerates with particle size of 7.8-17.68 nm. VP-FESEM result shows that grain size of the material increases with increasing calcination temperature and the surface morphology shows that the material is in hexagonal shape and it was also proved by mapping result which showing the presence each of constituents inside the compound

  14. A simple aloe vera plant-extracted microwave and conventional combustion synthesis: Morphological, optical, magnetic and catalytic properties of CoFe2O4 nanostructures

    Science.gov (United States)

    Manikandan, A.; Sridhar, R.; Arul Antony, S.; Ramakrishna, Seeram

    2014-11-01

    Nanocrystalline magnetic spinel CoFe2O4 was synthesized by a simple microwave combustion method (MCM) using ferric nitrate, cobalt nitrate and Aloe vera plant extracted solution. For the comparative study, it was also prepared by a conventional combustion method (CCM). Powder X-ray diffraction, energy dispersive X-ray and selected-area electron diffraction results indicate that the as-synthesized samples have only single-phase spinel structure with high crystallinity and without the presence of other phase impurities. The crystal structure and morphology of the powders were revealed by high resolution scanning electron microscopy and transmission electron microscopy, show that the MCM products of CoFe2O4 samples contain sphere-like nanoparticles (SNPs), whereas the CCM method of samples consist of flake-like nanoplatelets (FNPs). The band gap of the samples was determined by UV-Visible diffuse reflectance and photoluminescence spectroscopy. The magnetization (Ms) results showed a ferromagnetic behavior of the CoFe2O4 nanostructures. The Ms value of CoFe2O4-SNPs is higher i.e. 77.62 emu/g than CoFe2O4-FNPs (25.46 emu/g). The higher Ms value of the sample suggest that the MCM technique is suitable for preparing high quality nanostructures for magnetic applications. Both the samples were successfully tested as catalysts for the conversion of benzyl alcohol. The resulting spinel ferrites were highly selective for the oxidation of benzyl alcohol and exhibit important difference among their activities. It was found that CoFe2O4-SNPs catalyst show the best performance, whereby 99.5% selectivity of benzaldehyde was achieved at close to 93.2% conversion.

  15. Effect of Rashba and Dresselhaus Spin-Orbit Couplings on Electron Spin Polarization in a Hybrid Magnetic-Electric Barrier Nanostructure

    Science.gov (United States)

    Yang, Shi-Peng; Lu, Mao-Wang; Huang, Xin-Hong; Tang, Qiang; Zhou, Yong-Long

    2017-04-01

    A theoretical study has been carried out on the spin-dependent electron transport in a hybrid magnetic-electric barrier nanostructure with both Rashba and Dresselhaus spin-orbit couplings, which can be experimentally realized by depositing a ferromagnetic strip and a Schottky metal strip on top of a semiconductor heterostructure. The spin-orbit coupling-dependent transmission coefficient, conductance, and spin polarization are calculated by solving the Schrödinger equation exactly with the help of the transfer-matrix method. We find that both the magnitude and sign of the electron spin polarization vary strongly with the spin-orbit coupling strength. Thus, the degree of electron spin polarization can be manipulated by properly adjusting the spin-orbit coupling strength, and such a nanosystem can be employed as a controllable spin filter for spintronics applications.

  16. Bi-Component Nanostructured Arrays of Co Dots Embedded in Ni80Fe20 Antidot Matrix: Synthesis by Self-Assembling of Polystyrene Nanospheres and Magnetic Properties.

    Science.gov (United States)

    Coïsson, Marco; Celegato, Federica; Barrera, Gabriele; Conta, Gianluca; Magni, Alessandro; Tiberto, Paola

    2017-08-23

    A bi-component nanostructured system composed by a Co dot array embedded in a Ni 80 Fe 20 antidot matrix has been prepared by means of the self-assembling polystyrene nanospheres lithography technique. Reference samples constituted by the sole Co dots or Ni 80 Fe 20 antidots have also been prepared, in order to compare their properties with those of the bi-component material. The coupling between the two ferromagnetic elements has been studied by means of magnetic and magneto-transport measurements. The Ni 80 Fe 20 matrix turned out to affect the vortex nucleation field of the Co dots, which in turn modifies the magneto-resistance behaviour of the system and its spinwave properties.

  17. Calculations of spin-polarized Goos-Hänchen displacement in magnetically confined GaAs/Al x Ga1-x As nanostructure modulated by spin-orbit couplings

    Science.gov (United States)

    Lu, Mao-Wang; Chen, Sai-Yan; Zhang, Gui-Lian; Huang, Xin-Hong

    2018-04-01

    We theoretically investigate Goos-Hänchen (GH) displacement by modelling the spin transport in an archetypal device structure—a magnetically confined GaAs/Al x Ga1-x As nanostructure modulated by spin-orbit coupling (SOC). Both Rashba and Dresselhaus SOCs are taken into account. The degree of spin-polarized GH displacement can be tuned by Rashba or Dresselhaus SOC, i.e. interfacial confining electric field or strain engineering. Based on such a semiconductor nanostructure, a controllable spatial spin splitter can be proposed for spintronics applications.

  18. Calculations of spin-polarized Goos-Hänchen displacement in magnetically confined GaAs/Al x Ga1-x As nanostructure modulated by spin-orbit couplings.

    Science.gov (United States)

    Lu, Mao-Wang; Chen, Sai-Yan; Zhang, Gui-Lian; Huang, Xin-Hong

    2018-04-11

    We theoretically investigate Goos-Hänchen (GH) displacement by modelling the spin transport in an archetypal device structure-a magnetically confined GaAs/Al x Ga 1-x As nanostructure modulated by spin-orbit coupling (SOC). Both Rashba and Dresselhaus SOCs are taken into account. The degree of spin-polarized GH displacement can be tuned by Rashba or Dresselhaus SOC, i.e. interfacial confining electric field or strain engineering. Based on such a semiconductor nanostructure, a controllable spatial spin splitter can be proposed for spintronics applications.

  19. The effect of Mn and B on the magnetic and structural properties of nanostructured Fe60Al40 alloys produced by mechanical alloying.

    Science.gov (United States)

    Rico, M M; Alcázar, G A Pérez; Zamora, L E; González, C; Greneche, J M

    2008-06-01

    The effect of Mn and B on the magnetic and structural properties of nanostructured samples of the Fe60Al40 system, prepared by mechanical alloying, was studied by 57Fe Mössbauer spectrometry, X-ray diffraction and magnetic measurements. In the case of the Fe(60-x)Mn(x)Al40 system, 24 h milling time is required to achieve the BCC ternary phase. Different magnetic structures are observed according to the temperature and the Mn content for alloys milled during 48 h: ferromagnetic, antiferromagnetic, spin-glass, reentrant spin-glass and superparamagnetic behavior. They result from the bond randomness behaviour induced by the atomic disorder introduced by the MA process and from the competitive interactions of the Fe-Fe ferromagnetic interactions and the Mn-Mn and Fe-Mn antiferromagnetic interactions and finally the presence of Al atoms acting as dilutors. When B is added in the Fe60Al40 alloy and milled for 12 and 24 hours, two crystalline phases were found: a prevailing FeAl BCC phase and a Fe2B phase type. In addition, one observes an additional contribution attributed to grain boundaries which increases when both milling time and boron composition increase. Finally Mn and B were added to samples of the Fe60Al40 system prepared by mechanical alloying during 12 and 24 hours. Mn content was fixed to 10 at.% and B content varied between 0 and 20 at.%, substituting Al. X-ray patterns show two crystalline phases, the ternary FeMnAl BCC phase, and a (Fe,Mn)2B phase type. The relative proportion of the last phase increases when the B content increases, in addition to changes of the grain size and the lattice parameter. Such behavior was observed for both milling periods. On the other hand, the magnetic hyperfine field distributions show that both phases exhibit chemical disorder, and that the contribution attributed to the grain boundaries is less important when the B content increases. Coercive field values of about 10(2) Oe slightly increase with boron content

  20. Tailoring of Perpendicular Magnetic Anisotropy in Dy13Fe87 Thin Films with Hexagonal Antidot Lattice Nanostructure

    Directory of Open Access Journals (Sweden)

    Mohamed Salaheldeen

    2018-04-01

    Full Text Available In this article, the magnetic properties of hexagonally ordered antidot arrays made of Dy13Fe87 alloy are studied and compared with corresponding ones of continuous thin films with the same compositions and thicknesses, varying between 20 nm and 50 nm. Both samples, the continuous thin films and antidot arrays, were prepared by high vacuum e-beam evaporation of the alloy on the top-surface of glass and hexagonally self-ordered nanoporous alumina templates, which serve as substrates, respectively. By using a highly sensitive magneto-optical Kerr effect (MOKE and vibrating sample magnetometer (VSM measurements an interesting phenomenon has been observed, consisting in the easy magnetization axis transfer from a purely in-plane (INP magnetic anisotropy to out-of-plane (OOP magnetization. For the 30 nm film thickness we have measured the volume hysteresis loops by VSM with the easy magnetization axis lying along the OOP direction. Using magnetic force microscopy measurements (MFM, there is strong evidence to suggest that the formation of magnetic domains with OOP magnetization occurs in this sample. This phenomenon can be of high interest for the development of novel magnetic and magneto-optic perpendicular recording patterned media based on template-assisted deposition techniques.

  1. Role of field-induced nanostructures, zippering and size polydispersity on effective thermal transport in magnetic fluids without significant viscosity enhancement

    Science.gov (United States)

    Vinod, Sithara; Philip, John

    2017-12-01

    Magnetic nanofluids or ferrofluids exhibit extraordinary field dependant tunable thermal conductivity (k), which make them potential candidates for microelectronic cooling applications. However, the associated viscosity enhancement under an external stimulus is undesirable for practical applications. Further, the exact mechanism of heat transport and the role of field induced nanostructures on thermal transport is not clearly understood. In this paper, through systematic thermal, rheological and microscopic studies in 'model ferrofluids', we demonstrate for the first time, the conditions to achieve very high thermal conductivity to viscosity ratio. Highly stable ferrofluids with similar crystallite size, base fluid, capping agent and magnetic properties, but with slightly different size distributions, are synthesized and characterized by X-ray diffraction, small angle X-ray scattering, transmission electron microscopy, dynamic light scattering, vibrating sample magnetometer, Fourier transform infrared spectroscopy and thermo-gravimetry. The average hydrodynamic diameters of the particles were 11.7 and 10.1 nm and the polydispersity indices (σ), were 0.226 and 0.151, respectively. We observe that the system with smaller polydispersity (σ = 0.151) gives larger k enhancement (130% for 150 G) as compared to the one with σ = 0.226 (73% for 80 G). Further, our results show that dispersions without larger aggregates and with high density interfacial capping (with surfactant) can provide very high enhancement in thermal conductivity, with insignificant viscosity enhancement, due to minimal interfacial losses. We also provide experimental evidence for the effective heat conduction (parallel mode) through a large number of space filling linear aggregates with high aspect ratio. Microscopic studies reveal that the larger particles act as nucleating sites and facilitate lateral aggregation (zippering) of linear chains that considerably reduces the number density of space

  2. Development of nanostructured magnetic materials based on high-purity rare-earth metals and study of their fundamental characteristics

    Czech Academy of Sciences Publication Activity Database

    Pelevin, I.A.; Tereshina, I. S.; Burkhanov, G.S.; Dobatkin, S.V.; Kaminskaya, T.; Karpenkov, D.; Zaleski, A.; Tereshina, Evgeniya

    2014-01-01

    Roč. 56, č. 9 (2014), s. 1778-1784 ISSN 1063-7834 Institutional support: RVO:68378271 Keywords : permanent-magnets * compound * Fe * ND Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 0.821, year: 2014

  3. Luminescence and magnetic behaviour of almond like (Na0.5La0.5)MoO4:RE3+ (RE = Eu, Tb, Dy) nanostructures

    International Nuclear Information System (INIS)

    Krishnan, Rajagopalan; Thirumalai, Jagannathan; Thomas, Sabu; Gowri, Mahasampath

    2014-01-01

    Graphical abstract: Monodispersed almond-like (Na 0.5 La 0.5 )MoO 4 :RE 3+ nanostructures synthesized by employing ethylene-diamine tetra acetic acid (EDTA) using hydrothermal route at 200 °C for 24 h. These nanoparticles were found to be novel bi-functional candidates suitable for high-quality luminescence and magnetic applications. - Highlights: • Almond like structures of (Na 0.5 La 0.5 )MoO 4 :RE 3+ were synthesized by hydrothermal method. • Time dependent self-assembly could be the dominant process for the formation of 3D networks. • Luminescence properties of nanosamples were studied in comparison with bulk sample. • Room temperature magnetic properties of bulk and nanophosphors were investigated. - Abstract: Tetragonal phase (Na 0.5 La 0.5 )MoO 4 :RE 3+ (RE = Eu, Tb, Dy) with almond like hierarchical structures assembled from nanosheets building blocks were successfully synthesized by employing disodium ethylenediaminetetraacetic acid (Na 2 EDTA) using hydrothermal route at 200 °C for 24 h. Field emission scanning electron microscope, transmission electron microscope, and X-ray diffraction patterns were used to characterize the morphology, size, and crystal structure with good resolution. The sequestering agent EDTA acts as quadridentate ligand coordinated with metal ions [Na + , La 3+ /RE 3+ ] facilitating the formation of self-organized 3D networks. The growth mechanism for the formation of almond like nanostructures is explicated in four paths: dissolution, adsorption, in situ transformation in acidic and basic media and the effective collision. Photoluminescence excitation and emission spectra reveals a spectral blue shift which was observed in the nanosamples towards shorter wavelengths compared with the bulk sample. Upon UV irradiation, both bulk and nanostructure show strong luminescence in the red region due to the 5 D 0 → 7 F 2 transition in Eu 3+ . Also, Tb 3+ and Dy 3+ doped (Na 0.5 La 0.5 )MoO 4 phosphor exhibit green and yellow

  4. First-principles calculation of monitoring spin states of small magnetic nanostructures with IR spectrum of CO

    International Nuclear Information System (INIS)

    Li, C; Lefkidis, G; Huebner, W

    2010-01-01

    A fully ab initio controlled ultrafast magnetooptical switching mechanism in small magnetic clusters is achieved through exploiting spin-orbit-coupling enabled Λ processes. The idea is that in the magnetic molecules a fast transition between two almost degenerate states with different spins can be triggered by a laser pulse, which leads to an electron excitation from one of the degenerate states to a highly spin-mixed state and a deexcitation to the state of opposite spin. In this paper a CO molecule is attached to one magnetic center of the clusters, which serves as an experimental marker to map the laser-induced spin manipulation to the IR spectrum of CO. The predicted spin-state-dependent CO frequencies can facilitate experimental monitoring of the processes. We show that spin flip in magnetic atoms can be achieved in structurally optimized magnetic clusters in a subpicosecond regime with linearly polarized light.

  5. Annealing dependence of magnetic properties in nanostructured Sm0.5Y0.5Co5

    International Nuclear Information System (INIS)

    Elizalde-Galindo, J.T.; Hidalgo, J.L.; Botez, C.E.; Matutes-Aquino, J.A.

    2008-01-01

    Nanocrystalline Sm 0.5 Y 0.5 Co 5 powders with high coercivity H C and enhanced remanence M r were prepared by mechanical milling and subsequent annealing. Annealing temperatures T ranging from 973 to 1173 K, and times t ranging from 1 to 5 min were used. X-ray diffraction (XRD) and DC-magnetization measurements were carried out to study the microstructure and magnetic properties of these samples. XRD patterns demonstrate that the average grain size of the nanocrystalline powders depends on the annealing temperature T and time t: ranges from 11 nm (for T=973 K and t=1 min) to 93 nm (for T=1173 K and t=5 min). Magnetic measurements performed at room temperature indicate high coercivity values (H C >955 kA/m), and enhanced remanence (M r /M max >0.5) for all samples. A strong annealing-induced grain size dependence of these magnetic properties was found

  6. Preparation and characterization of magnetic nanostructures based on FeCo / IrMn deposited by cathode sputtering

    International Nuclear Information System (INIS)

    Pereira, Saulo Milani

    2011-01-01

    Spintronic devices based in the transport of spin polarized current, spin's torque and other related phenomena represent big promises in the scenery of the technological miniaturization of current electronic devices. Magnetic materials of great technological relevance for different areas deal with, despite some exceptions, films and multilayered structures with high complexity. Advances on these fields require the control of those structures in atomic scale, in order to be able to tailor their physical properties. The purpose of this work is the preparation of multilayered structures by sputtering, as well the study of magnetic phenomena involved in this structures. The aim is to produce a spin valve. This is a multilayer structure composed of two ferromagnetic layers, separated by a non magnetic spacer. The magnetisation of one of the ferromagnetic layers is free to rotate under the effect of small external fields, whilst the magnetisation of the other ferromagnetic layer remains fixed by means exchange coupling to a antiferromagnetic layer. The structure is tailored to allow the small applied magnetic fields to switch the magnetisation of the ferromagnetic layers from antiparallel state to a parallel state resulting in the variation of the electrical resistivity of the structure (GMR effect). Optimization of deposition conditions was required to obtain structures with exchange bias coupling, and antiferromagnetic coupling through a non magnetic spacer. The correlation between the deposition conditions and the magnetic properties of the films was studied. The work presented in this dissertation has contributed to the characterisation of both magnetic thin films, which can be used on the production of magnetic sensors, and the new sputtering system assembled in the Applied Physics Laboratory of CDTN. (author)

  7. Designed Synthesis of Nanostructured Magnetic Hydroxyapatite Based Drug Nanocarrier for Anti-Cancer Drug Delivery toward the Treatment of Human Epidermoid Carcinoma

    Directory of Open Access Journals (Sweden)

    Bharath Govindan

    2017-06-01

    Full Text Available Superparamagnetic Fe3O4 nanoparticles on hydroxyapatite nanorod based nanostructures (Fe3O4/HAp were synthesized using hydrothermal techniques at 180 °C for 12 h and were used as drug delivery nanocarriers for cancer cell therapeutic applications. The synthesized Fe3O4/HAp nanocomposites were characterized by X-ray diffraction analysis (XRD, Field emission scanning electron microscopy (FESEM, Fourier transform infrared spectroscopy (FTIR, Brunauer-Emmett-Teller (BET-analysis, and vibrating sample magnetometry (VSM. The morphologies of the Fe3O4/HAp nanocomposites show 15 nm Fe3O4 nanoparticles dispersed in the form of rods. The BET result shows that the synthesized samples have a high specific surface area of 80 m2 g−1 with mesoporous structures. Magnetic measurements revealed that the sample has high saturation magnetization of 18 emu/g with low coercivity. The Fe3O4/HAp nanocomposites had a large specific surface area (SSA, high mesoporous volume, and good magnetic property, which made it a suitable nanocarrier for targeted drug delivery systems. The chemotherapeutic agent, andrographolide, was used to investigate the drug delivery behavior of the Fe3O4/HAp nanocomposites. The human epidermoid skin cancer cells (A431 were used as the model targeting cell lines by treating with andrographolide loaded Fe3O4/HAp nanosystems and were further evaluated for their antiproliferative activities and the induction of apoptosis. Also, the present nanocomposite shows better biocompatibility, therefore it can be used as suitable drug vehicle for cancer therapy applications.

  8. Magneto-optical and cyclotron resonance studies of semiconductors and their nanostructures in pulsed high magnetic fields

    International Nuclear Information System (INIS)

    Miura, N.

    1999-01-01

    Full text: We present a review on the recent advances in physics of magneto-optical spectroscopy in the visible range and of infrared cyclotron resonance in pulsed high magnetic fields, which are produced by electromagnetic flux compression up to 500T, by the single-turn coil technique up to 200T or by conventional non-destructive long pulse magnets up to 50T. We discuss the recent results on the spectroscopy of low dimensional excitons in quantum wells and short period superlattices. In very high fields up to 500T, we observed anomalous field dependence of the exciton absorption lines and the 2D - 3D cross-over effects in GaAs/AlAs quantum wells. In GaP/AlP short period superlattices, it was found that the exciton photoluminescence intensity shows a dramatic decrease and the diamagnetic shift was negative when high magnetic fields were applied parallel to the growth direction. We observed also remarkable effects of uniaxial stress, which are ascribed to the cross-over effect between the two inequivalent valleys at the X points. Cyclotron resonance was measured by using various molecular gas lasers as radiation sources in the range 5 - 119 m . We present the results of cyclotron resonance in GaAs/AlGaAs quantum wells with tilted magnetic fields from the growth direction. It was found that the resonant field and the peak intensity show many different features depending on the extent of the Landau level-subband coupling and on the relation between the photon energy and the barrier height. A large hysteresis was observed between the rising and the falling sweeps of the magnetic field, when the cyclotron resonance energy became comparable with the subband spacing. In a diluted magnetic semiconductor CdFeS, we observed anomalous temperature dependence of the effective mass, suggestive of the magnetic polaron effect

  9. One-pot, template- and surfactant-free solvothermal synthesis of high-crystalline Fe{sub 3}O{sub 4} nanostructures with adjustable morphologies and high magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Zong, Yan; Xin, Hongna; Zhang, Jiarui [School of Physics, Northwest University, Xi’an 710000 (China); Li, Xinghua, E-mail: lixinghua04@gmail.com [School of Physics, Northwest University, Xi’an 710000 (China); Feng, Juan [School of Physics, Northwest University, Xi’an 710000 (China); Deng, Xia [School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Sun, Yong [School of Physics, Northwest University, Xi’an 710000 (China); Zheng, Xinliang, E-mail: zhengxl@nwu.edu.cn [School of Physics, Northwest University, Xi’an 710000 (China)

    2017-02-01

    In the present study, high-crystalline and well-defined Fe{sub 3}O{sub 4} nanostructures with tunable morphologies were fabricated through a facile one-pot solvothermal approach. The morphology, crystal structure and chemical compositions of the products were characterized at the nanoscale. X-ray diffraction and selected area electron diffraction patterns indicate that the products have a pure spinel phase without the presence of any other impurity. Based on the transmission electron microscope technology, shape evolution of the products were investigated. Several morphologies including irregular particles, clusters, hollow sphere and octahedrons can be obtained by only adjusting the amount of NaOH without using any surfactant. Magnetism investigations show that all the products perform ferromagnetic behavior with high saturation magnetization at room temperature, which mainly originates from their high crystalline nature and template-free fabrication process. - Highlights: • Fe{sub 3}O{sub 4} were prepared by a template- and surfactant-free solvothermal route. • The shapes of Fe{sub 3}O{sub 4} nanostructures can be controlled by changing the amount of NaOH. • All the Fe{sub 3}O{sub 4} nanostructures with different shapes have high magnetization values.

  10. Structure and magnetic properties of nanostructured MnNi alloys fabricated by mechanical alloying and annealing treatments

    Science.gov (United States)

    Jalal, T.; Hossein Nedjad, S.; Khalili Molan, S.

    2013-05-01

    A nearly equiatomic MnNi alloy was fabricated from the elemental powders by means of mechanical alloying in a planetary ball milling apparatus. X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and measurements of magnetization were conducted to identify the structural states and properties of the prepared alloys. After ball milling for 20 h, a disordered face-centered cubic (f.c.c.) solid solution was formed which increased in lattice parameter by further milling up to 50 h. An exothermic reaction took place at around 300-400°C during continuous heating of the disordered f.c.c. solid solution. This reaction is attributed to a structural ordering leading to the formation of a face-centered tetragonal (f.c.t.) phase with L10 type ordering. Examination of the magnetic properties indicated that the structural ordering increases remnant magnetization and decreases coerecivity.

  11. Spin-related tunneling through a nanostructured electric-magnetic barrier on the surface of a topological insulator.

    Science.gov (United States)

    Wu, Zhenhua; Li, Jun

    2012-01-27

    We investigate quantum tunneling through a single electric and/or magnetic barrier on the surface of a three-dimensional topological insulator. We found that (1) the propagating behavior of electrons in such system exhibits a strong dependence on the direction of the incident electron wavevector and incident energy, giving the possibility to construct a wave vector and/or energy filter; (2) the spin orientation can be tuned by changing the magnetic barrier structure as well as the incident angles and energies.PACS numbers: 72.25.Dc; 73.20.-r; 73.23.-b; 75.70.-i.

  12. Large magnetic anisotropy and tunneling anisotropic magnetoresistance in bi-metallic layered nanostructures: Case study of Mn/W(001)

    Czech Academy of Sciences Publication Activity Database

    Shick, Alexander; Máca, František; Ondráček, Martin; Mryasov, O. N.; Jungwirth, Tomáš

    2008-01-01

    Roč. 78, č. 5 (2008), 054413/1-054413/5 ISSN 1098-0121 R&D Projects: GA ČR GA202/07/0456; GA MŠk LC510; GA ČR GEFON/06/E002; GA ČR GA202/07/0644 EU Projects: European Commission(XE) 015728 - NANOSPIN Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z10100521 Keywords : magnetic anisotropy energy * surface * mangan * tungsten * calculations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.322, year: 2008

  13. Synthesis, nanostructure and magnetic properties of FeCo-reduced graphene oxide composite films by one-step electrodeposition

    International Nuclear Information System (INIS)

    Cao, Derang; Li, Hao; Wang, Zhenkun; Wei, Jinwu; Wang, Jianbo; Liu, Qingfang

    2015-01-01

    FeCo-reduced graphene oxide (FeCo-RGO) composite film was fabricated on indium tin oxide substrate using one-step electrodeposition method. Raman spectroscopy and field emission scanning electron microscope results show that the reduced graphene oxide is coprecipitated with the FeCo film. The energy-dispersive spectrometer results demonstrate that the atomic ratio of Fe/Co in FeCo-RGO composite film is larger than that of the FeCo film under the same fabrication condition. As a result, the FeCo-RGO composite film exhibits good soft magnetic properties and high-frequency properties as well as the FeCo film. The magnetic anisotropy field and saturation magnetization of FeCo-RGO composite film are increased when compared with FeCo film. Furthermore, the ferromagnetic resonance frequency is improved from 2.15 GHz for the FeCo film to 3.9 GHz for the FeCo-RGO composite film. - Highlights: • FeCo-reduced graphene oxide composite film was fabricated on indium tin oxide substrate. • One step electrodeposition method was used. • Good soft magnetic properties were exhibited by the composite films. • Increase of resonance frequency from 2.15 GHz for FeCo film to 3.9 GHz for composite film

  14. Vortices and nanostructured superconductors

    CERN Document Server

    2017-01-01

    This book provides expert coverage of modern and novel aspects of the study of vortex matter, dynamics, and pinning in nanostructured and multi-component superconductors. Vortex matter in superconducting materials is a field of enormous beauty and intellectual challenge, which began with the theoretical prediction of vortices by A. Abrikosov (Nobel Laureate). Vortices, vortex dynamics, and pinning are key features in many of today’s human endeavors: from the huge superconducting accelerating magnets and detectors at the Large Hadron Collider at CERN, which opened new windows of knowledge on the universe, to the tiny superconducting transceivers using Rapid Single Flux Quanta, which have opened a revolutionary means of communication. In recent years, two new features have added to the intrinsic beauty and complexity of the subject: nanostructured/nanoengineered superconductors, and the discovery of a range of new materials showing multi-component (multi-gap) superconductivity. In this book, leading researche...

  15. Modified fractal iron oxide magnetic nanostructure: A novel and high performance platform for redox protein immobilization, direct electrochemistry and bioelectrocatalysis application.

    Science.gov (United States)

    Bagheri, Hasan; Ranjbari, Elias; Amiri-Aref, Mohaddeseh; Hajian, Ali; Ardakani, Yalda Hosseinzadeh; Amidi, Salimeh

    2016-11-15

    A novel biosensing platform based on fractal-pattern of iron oxides magnetic nanostructures (FIOMNs) and mixed hemi/ad-micelle of sodium dodecyl sulfate (SDS) was designed for the magnetic immobilization of hemoglobin (Hb) at a screen printed carbon electrode (SPCE). The FIOMNs was successfully synthesized through hydrothermal approach and characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). In order to provide guidelines for the mixed hemi/ad-micelle formation, zeta-potential isotherms were investigated. The construction steps of the biosensor were evaluated by electrochemical impedance spectroscopy, cyclic voltammetry and Fourier transform infrared spectroscopy. Direct electron transfer of Hb incorporated into the biocomposite film was realized with a pair of quasi-reversible redox peak at the formal potential of -0.355V vs. Ag/AgCl attributing to heme Fe(III)/Fe(II) redox couple. The results suggested that synergistic functions regarding to the hyper-branched and multidirectional structure of FIOMNs and the dual interaction ability of mixed hemi/ad-micelle array of SDS molecules not only induce an effective electron transfer between the Hb and the underlying electrode (high heterogeneous electron transfer rate constant of 2.08s(-1)) but also provide powerful and special microenvironment for the adsorption of the redox proteins. Furthermore, the biosensor displayed an excellent performance to the electrocatalytic reduction of H2O2 with a detection limit of 0.48µM and Michaelis-Menten constant (Km) value of 44.2µM. The fabricated biosensor represented the features of sensitivity, disposable design, low sample volume, rapid and simple preparation step, and acceptable anti-interferences, which offer great perspectives for the screen-determination of H2O2 in real samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Structural and magnetic properties of γ-Fe{sub 2}O{sub 3} nanostructured compacts processed by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Saravanan, P., E-mail: psdrdo@gmail.com [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China); Defence Metallurgical Research Laboratory, Hyderabad 500058 (India); Hsu, Jen-Hwa, E-mail: jhhsu@phys.ntu.edu.tw [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China); Sivaprahasam, D. [International Advanced Research Centre for Powder Metallurgy and New Materials, Chennai 600113 (India); Kamat, S.V. [Defence Metallurgical Research Laboratory, Hyderabad 500058 (India)

    2013-11-15

    Gram quantities of γ-Fe{sub 2}O{sub 3} nanopowders having mean particle size of 20±4 nm were synthesized using a hydrothermal method and then consolidated into dense nanostructured compacts by spark plasma sintering (SPS) at relatively low temperatures: 300–350 °C. The cubic spinel structure of the as-synthesized γ-Fe{sub 2}O{sub 3} nanoparticles (NPs) did not get altered by the SPS process; nevertheless, a moderate increase in their grain sizes was evident in the SPSed compacts (80–125 nm). The physical properties such as density (ρ), coercivity (H{sub c}) and magnetization (M{sub s}) values of γ-Fe{sub 2}O{sub 3} NPs were affected by the SPS temperature. Significantly, higher values of ρ (4.45 g/cm{sup 3}), H{sub c} (274 Oe) and M{sub s} (67.2 emu/g) were achieved for the bulk compact SPSed at 350 °C. This work highlights the merits of sintering γ-Fe{sub 2}O{sub 3} NPs by SPS –as a new method of compaction with useful magnetic properties; which cannot be realized with the conventional sintering techniques. Highlights: • γ-Fe{sub 2}O{sub 3} nanoparticles with mean size of 20±4 nm were hydrothermally synthesized. • Spark plasma sintering of γ-Fe{sub 2}O{sub 3} was performed below phase transition temperature. • Sintered compacts were investigated with respect to SPS temperature: 300–350 °C. • Cubic spinel structure of γ-Fe{sub 2}O{sub 3} nanoparticles was retained in sintered compacts. • Maximum values: ρ (4.45 g/cm{sup 3}), H{sub c} (274 Oe) and M{sub s} (67.2 emu/g) obtained at 350 °C.

  17. Analytic device including nanostructures

    KAUST Repository

    Di Fabrizio, Enzo M.; Fratalocchi, Andrea; Totero Gongora, Juan Sebastian; Coluccio, Maria Laura; Candeloro, Patrizio; Cuda, Gianni

    2015-01-01

    A device for detecting an analyte in a sample comprising: an array including a plurality of pixels, each pixel including a nanochain comprising: a first nanostructure, a second nanostructure, and a third nanostructure, wherein size of the first nanostructure is larger than that of the second nanostructure, and size of the second nanostructure is larger than that of the third nanostructure, and wherein the first nanostructure, the second nanostructure, and the third nanostructure are positioned on a substrate such that when the nanochain is excited by an energy, an optical field between the second nanostructure and the third nanostructure is stronger than an optical field between the first nanostructure and the second nanostructure, wherein the array is configured to receive a sample; and a detector arranged to collect spectral data from a plurality of pixels of the array.

  18. Magnetic Fe{sub 3}O{sub 4}-Au core-shell nanostructures for surface enhanced Raman scattering

    Energy Technology Data Exchange (ETDEWEB)

    Wheeler, D.A.; Adams, S.A.; Zhang, J.Z. [Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, CA 95064 (United States); Lopez-Luke, T. [Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, CA 95064 (United States); Cento de Investigaciones en Optica, A.P. 1-948 Leon, Gto. 37150 (Mexico); Torres-Castro, A. [Universidad Autonoma de Nuevo Leon, A.P. 126-F, Monterrey, NL, 66450 (Mexico)

    2012-11-15

    The synthesis, structural and optical characterization, and application of superparamagnetic and water-dispersed Fe{sub 3}O{sub 4}-Au core-shell nanoparticles for surface enhanced Raman scattering (SERS) is reported. The structure of the nanoparticles was determined by scanning transmission electron microscopy (STEM) and high-resolution transmission electron microscopy (HRTEM). STEM images of the Fe{sub 3}O{sub 4}-Au core-shell nanoparticles reveal an average diameter of 120 nm and a high degree of surface roughness. The nanoparticles, which display superparamagnetic properties due to the core Fe{sub 3}O{sub 4} material, exhibit a visible surface plasmon resonance (SPR) peaked at 580 nm due to the outer gold shell. The nanoparticles are used as a substrate for surface enhanced Raman scattering (SERS) with rhodamine 6G (R6G) as a Raman reporter molecule. The SERS enhancement factor is estimated to be on the order of 10{sup 6}, which is {proportional_to} 2 times larger than that of conventional gold nanoparticles (AuNPs) under similar conditions. Significantly, magnetically-induced aggregation of the Fe{sub 3}O{sub 4}-Au core-shell nanoparticles substantially enhanced SERS activity compared to non-magnetically-aggregated Fe{sub 3}O{sub 4}-Au nanoparticles. This is attributed to both increased scattering from the aggregates as well as ''hot spots'' due to more junction sites in the magnetically-induced aggregates. The magnetic properties of the Fe{sub 3}O{sub 4} core, coupled with the optical properties of the Au shell, make the Fe{sub 3}O{sub 4}-Au nanoparticles unique for various potential applications including biological sensing and therapy. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Effects of coexisting spin disorder and antiferromagnetism on the magnetic behavior of nanostructured (Fe{sub 79}Mn{sub 21}){sub 1−x}Cu{sub x} alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mizrahi, M., E-mail: mizrahi@fisica.unlp.edu.ar, E-mail: cabrera@fisica.unlp.edu.ar [INIFTA-CCT- La Plata-CONICET and Departamento de Física, Facultad de Ciencias Exactas, C. C. 67, Universidad Nacional de La Plata, 1900 La Plata (Argentina); Cabrera, A. F., E-mail: mizrahi@fisica.unlp.edu.ar, E-mail: cabrera@fisica.unlp.edu.ar; Desimoni, J. [IFLP-CCT-La Plata-CONICET and Departamento de Física, Facultad de Ciencias Exactas C.C. 67, Universidad Nacional de La Plata, 1900 La Plata (Argentina); Stewart, S. J. [IFLP-CCT-La Plata-CONICET and Departamento de Física, Facultad de Ciencias Exactas C.C. 67, Universidad Nacional de La Plata, 1900 La Plata (Argentina); Instituto Ciencias de la Salud, Universidad Nacional Arturo Jauretche, Av. Calchaquí No. 6200, Florencio Varela (Argentina)

    2014-06-07

    We report a magnetic study on nanostructured (Fe{sub 79}Mn{sub 21}){sub 1−x}Cu{sub x} (0.00 ≤ x ≤ 0.30) alloys using static magnetic measurements. The alloys are mainly composed by an antiferromagnetic fcc phase and a disordered region that displays a spin-glass-like behavior. The interplay between the antiferromagnetic and magnetically disordered phases establishes an exchange anisotropy that gives rise to a loop shift at temperatures below the freezing temperature of moments belonging to the disordered region. The loop shift is more noticeable as the Cu content increases, which also enhances the spin-glass-like features. Further, in the x = 0.30 alloy the alignment imposed by applied magnetic fields higher than 4 kOe prevail over the configuration determined by the frustration mechanism that characterizes the spin glass-like phase.

  20. Fe_3O_4@B-MCM-41: A new magnetically recoverable nanostructured catalyst for the synthesis of polyhydroquinolines

    International Nuclear Information System (INIS)

    Abdollahi-Alibeik, Mohammad; Rezaeipoor-Anari, Ali

    2016-01-01

    Boron modified MCM-41 with magnetite core (Fe_3O_4@B-MCM-41) as a new magnetically recoverable heterogeneous catalyst was prepared and characterized by SEM, TEM, BET, XRD, VSM and FT-IR techniques. The catalytic activity of Fe_3O_4@B-MCM-41 was investigated in the four-component reaction of aldehyde, dimedone, active methylene compounds and ammonium acetate for the synthesis of polyhydroquinolines. According to optimization and characterization results the catalyst with Si:B:Fe_3O_4 mole composition of 40:4:1 has the best activity. The catalyst could be recovered easily by external magnet and has excellent reusability many times without significant decrease of activity. - Highlights: • Core–shell Fe_3O_4@MCM-41 nanoparticles modified by boron (Fe_3O_4@B-MCM-41). • Fe_3O_4@B-MCM-41 as reusable catalyst for the synthesis of polyhydroquinolines. • Characterization of Fe_3O_4@B-MCM-41 using SEM, TEM, BET, XRD and FT-IR techniques.

  1. Structural and magnetic Properties of TbZn-substituted calcium barium M-type nano-structured hexa-ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Hasan M. [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Department of Electronics, University of York, York YO10 5DD (United Kingdom); Islam, M.U., E-mail: dr.misbahulislam@bzu.edu.pk [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Xu, Yongbing [Department of Electronics, University of York, York YO10 5DD (United Kingdom); Nanjing–York International Centre of Spintronics and Nano-Engineering, Nanjing University, Nanjing 210093 (China); Asif Iqbal, M. [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); National University of Science and Technology, College of E and ME, Islamabad (Pakistan); Ali, Irshad [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan)

    2014-03-15

    Highlights: • Tb–Zn substituted Ca{sub 0.5}Ba{sub 0.5}Fe{sub 12}O{sub 19} samples exhibit single magnetoplumbite phase. • Lattice parameters a and c have increasing values. • Coercivity can be tuned at lower substitution level • Crystallites size was found in the range 18–25 nm by TEM and by Scherrer formula. • These hexa-ferrites are suitable for microwave devices and magnetic recording media. -- Abstract: Effect of TbZn substitution on the structural and magnetic properties of Ca{sub 0.5}Ba{sub 0.5−x}Tb{sub x}Zn{sub y}Fe{sub 12−y}O{sub 19}, (x = 0.00–0.10; y = 0.00–1.00) ferrites prepared by sol–gel auto combustion is reported. The synthesized samples were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Vibrating Sample magnetometery. The X-ray diffraction analysis confirmed single phase M-type hexa-ferrite structure. The lattice parameters were found to increase as TbZn contents increases, which is attributed to the ionic sizes of the implicated cations. The TbZn seems to be completely soluble in the lattice. The results of scanning electron microscopy and transmission electron microscopy shows that the grain size decreases with increase of TbZn substitution. The coercivity values (1277–2025 Oe) of all samples lies in the range of M-type hexa-ferrite and indicate that an increase of anisotropy was achieved by substitution of TbZn, while the size of nanoparticles was drastically reduced between 18 and 25 nm. The increased anisotropy and fine particle size are useful for many applications, such as improving signal noise ratio of recording devices.

  2. Pressure effects on nanostructured manganites

    International Nuclear Information System (INIS)

    Acha, C.; Garbarino, G.; Leyva, A.G.

    2007-01-01

    We have measured the pressure sensitivity of magnetic properties on La 5/8-y Pr y Ca 3/8 MnO 3 (y=0.3) nanostructured powders. Samples were synthesized following a microwave assisted denitration process and a final heat treatment at different temperatures to control the grain size of the samples. A span in grain diameters from 40 nm to ∼1000 nm was obtained. Magnetization curves as a function of temperature were measured following different thermomagnetic histories. AC susceptibility as a function of temperature was also measured at different hydrostatic pressures (up to 10 kbar) and for different frequencies. Our results indicate that the nanostructuration plays a role of an internal pressure, producing a structural deformation with similar effects to those obtained under an external hydrostatic pressure

  3. The role of silicon on the microstructure and magnetic behaviour of nanostructured (Fe{sub 0.7}Co{sub 0.3}){sub 100−x}Si{sub x} powders

    Energy Technology Data Exchange (ETDEWEB)

    Hocine, M. [Département de Génie Mécanique, Faculté de Technologies, Université de M' sila, B.P 166 Ichbelia, M' sila (Algeria); UR-MPE, M' hamed Bougara University, Boumerdes, 35000 Algeria (Algeria); Guittoum, A., E-mail: aguittoum@gmail.com [Nuclear Research Centre of Algiers, 02Bd Frantz Fanon, BP 399, Alger-Gare, Algiers (Algeria); Hemmous, M. [Nuclear Research Centre of Algiers, 02Bd Frantz Fanon, BP 399, Alger-Gare, Algiers (Algeria); Martínez-Blanco, D. [SCTs, University of Oviedo, EPM, Mieres, 33600 Spain (Spain); Gorria, P. [Department of Physics, EPI, University of Oviedo, Gijón, 33203 Spain (Spain); Rahal, B. [Nuclear Research Centre of Algiers, 02Bd Frantz Fanon, BP 399, Alger-Gare, Algiers (Algeria); Blanco, J.A. [Department of Physics, University of Oviedo, CalvoSotelo St., Oviedo, 330 07 Spain (Spain); Sunol, J.J. [Departament de Fisica, Universitat de Girona, Campus de Montillivi, Girona, 17071 Spain (Spain); Laggoun, A. [UR-MPE, M' hamed Bougara University, Boumerdes, 35000 Algeria (Algeria)

    2017-01-15

    Single-phase(Fe{sub 0.7}Co{sub 0.3}){sub 100−x}Si{sub x} nanostructured powders (x=0,5, 10, 15 and 20) have been elaborated by mechanical alloying in order to investigate the effect of silicon on the microstructure and magnetic properties of these alloys. A disordered Fe(Co, Si) solid solution with body centred cubic (bcc) crystal structure is formed after 72 h of milling for all the compositions. The addition of Si gives rise to a progressive decrease of the lattice parameter, from about 2.865 Å for the binary Fe{sub 70}Co{sub 30} compound down to 2.841 Å for the powder with x=20. The sample with the uppermost Si content exhibits the lowest value for the mean grain size (≈10 nm) as well as the largest microstrain (above 1.1%). All the samples are ferromagnetic at room temperature, although the saturation magnetization value reduces almost linearly by adding Si to the composition. A similar trend is observed for the hyperfine magnetic field obtained from the analysis of the room temperature Mössbauer spectra. The hyperfine field distributions show a broad double-peak shape for x>0, which can be ascribed to multiple local environments for the Fe atoms inside a disordered solid solution. - Highlights: • Single-phase (Fe{sub 0.7}Co{sub 0.3}){sub 100−x}Si{sub x} nanostructured powders (x=0, 5, 10, 15 and 20) have been elaborated by mechanical alloying. • The sample with the uppermost Si content exhibits the lowest value for the mean grain size. • The magnetic and hyperfine parameters of (Fe{sub 0.7}Co{sub 0.3}){sub 100−x}Si{sub x} depended intimately on Si content.

  4. Thermoelectric effects in magnetic nanostructures

    NARCIS (Netherlands)

    Bakker, Frank Lennart

    2012-01-01

    Elektronentransport is een belangrijk natuurkundig verschijnsel dat vaak wordt gebruikt in de hedendaagse technologie. Alle elektrische apparaten, variërend van stofzuigers tot computerchips, zijn in principe gebaseerd op dit type transport. Ondanks dat elektronen meerdere eigenschappen hebben,

  5. Thermogravimetric and Magnetic Studies of the Oxidation and Reduction Reaction of SmCoO3 to Nanostructured Sm2O3 and Co

    Science.gov (United States)

    Kelly, Brian; Cichocki, Ronald; Poirier, Gerald; Unruh, Karl

    The SmCoO3 to nanostructured Sm2O3 and Co oxidation and reduction reaction has been studied by thermogravimetric analysis (TGA) measurements in forming gas (FG) and inert N2 atmospheres, x-ray diffraction (XRD) and vibrating sample magnetometry (VSM). The TGA measurements showed two clearly resolvable reduction processes when heating in FG, from the initial SmCoO3 phase through an intermediate nanostructured mixture of Sm2O3 and CoO when heated to 330°C for several minutes, and then the conversion of CoO to metallic Co when heated above 500°C. These phases were confirmed by XRD and VSM. Similar measurements in N2 yielded little mass change below 900°C and coupled reduction processes at higher temperatures. Isoconversional measurements of the CoO to Co reduction reaction in FG yielded activation energies above 2eV/atom in the nanostructured system. This value is several times larger than those reported in the literature or obtained by similar measurements of bulk mixtures of Sm2O3 and CoO, suggesting the nanostructuring was the source of the large increase in activation energy.

  6. Magnetic and structural investigations on La{sub 0.6}Sr{sub 0.4}MnO{sub 3} nanostructured manganite: Evidence of a ferrimagnetic shell

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, V.M.; Caraballo-Vivas, R.J. [Instituto de Física, Universidade Federal Fluminense, 24210-340 Niterói, RJ (Brazil); Costas-Soares, T. [Instituto de Física, Universidade Federal Fluminense, 24210-340 Niterói, RJ (Brazil); IF Sudeste MG, Campus Juiz de Fora - Núcleo de Física, 36080-001 Juiz de Fora, MG (Brazil); Pedro, S.S. [Instituto de Física, Universidade Federal Fluminense, 24210-340 Niterói, RJ (Brazil); Rocco, D.L., E-mail: rocco@if.uff.br [Instituto de Física, Universidade Federal Fluminense, 24210-340 Niterói, RJ (Brazil); Reis, M.S. [Instituto de Física, Universidade Federal Fluminense, 24210-340 Niterói, RJ (Brazil); Campos, A.P.C. [Divisão de Metrologia de Materiais, Instituto Nacional de Metrologia, Qualidade e Tecnologia, 25250-020 Duque de Caxias, RJ (Brazil); Coelho, A.A. [Instituto de Física “Gleb Wataghin”, Universidade Estadual de Campinas, Caixa Postal 6165, 13083-859 Campinas, SP (Brazil)

    2014-11-15

    This paper presents the structural and magnetic properties of La{sub 0.6}Sr{sub 0.4}MnO{sub 3} nanoparticles with sizes from 21 to 106 nm, which have been prepared using the sol–gel method. The reduction of the nanoparticles' size tends to broaden the paramagnetic to ferromagnetic transition, as well as to promote magnetic hysteresis and a remarkable change on the magnetic saturation. In order to better understand the magnetic behavior of those nanoparticles, a simple model based on a ferromagnetic core and a ferrimagnetic shell was considered, where the magnetization was described in terms of the standard mean-field Brillouin function. This model matches the experimental data, leading to conclusion the nanoparticles with size <40nm are single magnetic domain. In addition, the output fitting parameters give information on the Landé factor of the core and shell. - Graphical abstract: Core–shell model: The core has a ferromagnetic character, while the shell is ferrimagnetic. Each one has two sub-lattices (Mn{sup 3+} and Mn{sup 4+}) that interact through a mean-field (see Eq. (6)). Interactions strength and signals are also represented in this figure. In this figure the arrows (or vectors) represent the magnetic moment of ions Mn{sup 3+} (s=2) and Mn{sup 4+} (s=3/2). βλ's describe the ferromagnetic interaction between Mn{sup 4+} ions into the core (βλ{sub co}) and into the shell (βλ{sub sh}), while αλ's represent ferromagnetic interaction between Mn{sup 3+} ions into the core (αλ{sub co}) and into the shell (αλ{sub sh}). The −λ{sub sh} and +λ{sub co}co are associated to the mean field parameter of interaction between Mn{sup 3+} and Mn{sup 4+} sub-lattices in the shell (ferrimagnetic, negative sign) and core (ferromagnetic, positive sign), respectively. - Highlights: • Evidences of ferromagnetic shell in La{sub 0.6}Sr{sub 0.4}MnO{sub 3} ferromagnetic nanoparticles. • Core(ferromagnetic)–shell(ferromagnetic) model for

  7. Nanostructure investigation of magnetic nanomaterial Ni{sub 0.5}Zn{sub 0.3}Cu{sub 0.2}Fe{sub 2}O{sub 4} synthesized by sol-gel method

    Energy Technology Data Exchange (ETDEWEB)

    Pransisco, Prengki, E-mail: prengkipransisco@gmail.com [Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Badan Lingkungan Hidup Derah Kabupaten Empat Lawang South of Sumatera (Indonesia); Shafie, Afza, E-mail: afza@petronas.com.my; Guan, Beh Hoe, E-mail: beh.hoeguan@petronas.com.my [Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

    2015-07-22

    Magnetic nanomaterial Ni{sub 0.5}Zn{sub 0.3}Cu{sub 0.2}Fe{sub 2}O{sub 4} was successfully prepared by using sol-gel method. Heat treatment on material is always giving defect on properties of material. This paper investigates the effect of heat treatment on nanostructure of magnetic nanomaterial Ni{sub 0.5}Zn{sub 0.3}Cu{sub 0.2}Fe{sub 2}O{sub 4}. According to thermo gravimetric analysis (TGA) that after 600°C there is no more weight loss detected and it was decided as minimum calcination temperature. Intensity, crystallite size, structure, lattice parameter and d-spacing of the material were investigated by using X-ray diffraction (XRD). High resolution transmission electron microscope (HRTEM) was used to examine nanostructure, nanosize, shape and distribution particle of magnetic material Ni{sub 0.5}Zn{sub 0.3}Cu{sub 0.2}Fe{sub 2}O{sub 4} and variable pressure field emission scanning electron microscope (VP-FESEM) was used to investigate the surface morphology and topography of the material. The XRD result shows single-phase cubic spinel structure with average crystallite size in the range of 25.6-95.9 nm, the value of the intensity of the material was increased with increasing temperature, and followed by lattice parameter was increased with increasing calcination temperature, value of d-spacing was relatively decreased with accompanied increasing temperature. From HRTEM result the distribution of particles was tend to be agglomerates with particle size of 7.8-17.68 nm. VP-FESEM result shows that grain size of the material increases with increasing calcination temperature and the surface morphology shows that the material is in hexagonal shape and it was also proved by mapping result which showing the presence each of constituents inside the compound.

  8. PREFACE: Self-organized nanostructures

    Science.gov (United States)

    Rousset, Sylvie; Ortega, Enrique

    2006-04-01

    In order to fabricate ordered arrays of nanostructures, two different strategies might be considered. The `top-down' approach consists of pushing the limit of lithography techniques down to the nanometre scale. However, beyond 10 nm lithography techniques will inevitably face major intrinsic limitations. An alternative method for elaborating ultimate-size nanostructures is based on the reverse `bottom-up' approach, i.e. building up nanostructures (and eventually assemble them to form functional circuits) from individual atoms or molecules. Scanning probe microscopies, including scanning tunnelling microscopy (STM) invented in 1982, have made it possible to create (and visualize) individual structures atom by atom. However, such individual atomic manipulation is not suitable for industrial applications. Self-assembly or self-organization of nanostructures on solid surfaces is a bottom-up approach that allows one to fabricate and assemble nanostructure arrays in a one-step process. For applications, such as high density magnetic storage, self-assembly appears to be the simplest alternative to lithography for massive, parallel fabrication of nanostructure arrays with regular sizes and spacings. These are also necessary for investigating the physical properties of individual nanostructures by means of averaging techniques, i.e. all those using light or particle beams. The state-of-the-art and the current developments in the field of self-organization and physical properties of assembled nanostructures are reviewed in this issue of Journal of Physics: Condensed Matter. The papers have been selected from among the invited and oral presentations of the recent summer workshop held in Cargese (Corsica, France, 17-23 July 2005). All authors are world-renowned in the field. The workshop has been funded by the Marie Curie Actions: Marie Curie Conferences and Training Courses series named `NanosciencesTech' supported by the VI Framework Programme of the European Community, by

  9. Fabrication of shape controlled Fe3O4 nanostructure

    International Nuclear Information System (INIS)

    Zheng, Y.Y.; Wang, X.B.; Shang, L.; Li, C.R.; Cui, C.; Dong, W.J.; Tang, W.H.; Chen, B.Y.

    2010-01-01

    Shape-controlled Fe 3 O 4 nanostructure has been successfully prepared using polyethylene glycol as template in a water system at room temperature. Different morphologies of Fe 3 O 4 nanostructures, including spherical, cubic, rod-like, and dendritic nanostructure, were obtained by carefully controlling the concentration of the Fe 3+ , Fe 2+ , and the molecular weight of the polyethylene glycol. Transmission Electron Microscope images, X-ray powder diffraction patterns and magnetic properties were used to characterize the final product. This easy procedure for Fe 3 O 4 nanostructure fabrication offers the possibility of a generalized approach to the production of single and complex nanocrystalline oxide with tunable morphology.

  10. Influence of silicon and atomic order on the magnetic properties of (Fe{sub 80}Al{sub 20}){sub 100}-{sub x}Si{sub x} nanostructured system

    Energy Technology Data Exchange (ETDEWEB)

    Velez, G. Y., E-mail: gyovelca@univalle.edu.co; Perez Alcazar, G. A.; Zamora, Ligia E. [Universidad del Valle, Departamento de Fisica (Colombia); Romero, J. J.; Martinez, A. [Instituto de Magnetismo Aplicado IMA (Spain)

    2010-01-15

    Mechanically alloyed (Fe{sub 80}Al{sub 20}){sub 100-x}Si{sub x} alloys (with x = 0, 10, 15 and 20) were prepared by using a high energy planetary ball mill, with milling times of 12, 24 and 36 h. The structural and magnetic study was conducted by X-rays diffraction and Moessbauer spectrometry. The system is nanostructured and presents only the BCC disordered phase, whose lattice parameter remains constant with milling time, and decreases when the Si content increases. We found that lattice contraction is influenced 39% by the iron substitution and 61% by the aluminum substitution, by silicon atoms. The Moessbauer spectra and their respective hyperfine magnetic field distributions show that for every milling time used here, the ferromagnetism decreases when x increases. For samples with x {>=} 15 a paramagnetic component appears. From the shape of the magnetic field distributions we stated that the larger ferromagnetic phase observed in the samples alloyed during 24 and 36 h is a consequence of the structural disorder induced by mechanical alloying.

  11. Nuclear spins in nanostructures

    International Nuclear Information System (INIS)

    Coish, W.A.; Baugh, J.

    2009-01-01

    We review recent theoretical and experimental advances toward understanding the effects of nuclear spins in confined nanostructures. These systems, which include quantum dots, defect centers, and molecular magnets, are particularly interesting for their importance in quantum information processing devices, which aim to coherently manipulate single electron spins with high precision. On one hand, interactions between confined electron spins and a nuclear-spin environment provide a decoherence source for the electron, and on the other, a strong effective magnetic field that can be used to execute local coherent rotations. A great deal of effort has been directed toward understanding the details of the relevant decoherence processes and to find new methods to manipulate the coupled electron-nuclear system. A sequence of spectacular new results have provided understanding of spin-bath decoherence, nuclear spin diffusion, and preparation of the nuclear state through dynamic polarization and more general manipulation of the nuclear-spin density matrix through ''state narrowing.'' These results demonstrate the richness of this physical system and promise many new mysteries for the future. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  12. Magnets

    International Nuclear Information System (INIS)

    Young, I.R.

    1984-01-01

    A magnet pole piece for an NMR imaging magnet is made of a plurality of magnetic wires with one end of each wire held in a non-magnetic spacer, the other ends of the wires being brought to a pinch, and connected to a magnetic core. The wires may be embedded in a synthetic resin and the magnetisation and uniformity thereof can be varied by adjusting the density of the wires at the spacer which forms the pole piece. (author)

  13. Luminescence and magnetic behaviour of almond like (Na{sub 0.5}La{sub 0.5})MoO{sub 4}:RE{sup 3+} (RE = Eu, Tb, Dy) nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, Rajagopalan [Department of Physics, B.S. Abdur Rahman University, Vandalur, Chennai, Tamil Nadu (India); Thirumalai, Jagannathan, E-mail: jthirumalai@bsauniv.ac.in [Department of Physics, B.S. Abdur Rahman University, Vandalur, Chennai, Tamil Nadu (India); Thomas, Sabu [Polymer Science and Technology, Center for Nanoscience and Nanotechnology, School of Chemical Sciences, Mahatma Gandhi University, Kottayam 686 560, Kerala (India); Gowri, Mahasampath [Department of Chemistry, B.S. Abdur Rahman University, Vandalur, Chennai, Tamil Nadu (India)

    2014-08-01

    Graphical abstract: Monodispersed almond-like (Na{sub 0.5}La{sub 0.5})MoO{sub 4}:RE{sup 3+} nanostructures synthesized by employing ethylene-diamine tetra acetic acid (EDTA) using hydrothermal route at 200 °C for 24 h. These nanoparticles were found to be novel bi-functional candidates suitable for high-quality luminescence and magnetic applications. - Highlights: • Almond like structures of (Na{sub 0.5}La{sub 0.5})MoO{sub 4}:RE{sup 3+} were synthesized by hydrothermal method. • Time dependent self-assembly could be the dominant process for the formation of 3D networks. • Luminescence properties of nanosamples were studied in comparison with bulk sample. • Room temperature magnetic properties of bulk and nanophosphors were investigated. - Abstract: Tetragonal phase (Na{sub 0.5}La{sub 0.5})MoO{sub 4}:RE{sup 3+} (RE = Eu, Tb, Dy) with almond like hierarchical structures assembled from nanosheets building blocks were successfully synthesized by employing disodium ethylenediaminetetraacetic acid (Na{sub 2}EDTA) using hydrothermal route at 200 °C for 24 h. Field emission scanning electron microscope, transmission electron microscope, and X-ray diffraction patterns were used to characterize the morphology, size, and crystal structure with good resolution. The sequestering agent EDTA acts as quadridentate ligand coordinated with metal ions [Na{sup +}, La{sup 3+}/RE{sup 3+}] facilitating the formation of self-organized 3D networks. The growth mechanism for the formation of almond like nanostructures is explicated in four paths: dissolution, adsorption, in situ transformation in acidic and basic media and the effective collision. Photoluminescence excitation and emission spectra reveals a spectral blue shift which was observed in the nanosamples towards shorter wavelengths compared with the bulk sample. Upon UV irradiation, both bulk and nanostructure show strong luminescence in the red region due to the {sup 5}D{sub 0} → {sup 7}F{sub 2} transition in Eu{sup 3

  14. Nanocoatings size effect in nanostructured films

    CERN Document Server

    Aliofkhazraei, Mahmood

    2014-01-01

    Size effect in structures has been taken into consideration over the last years. In comparison with coatings with micrometer-ranged thickness, nanostructured coatings usually enjoy better and appropriate properties, such as strength and resistance. These coatings enjoy unique magnetic properties and are used with the aim of producing surfaces resistant against erosion, lubricant system, cutting tools, manufacturing hardened sporadic alloys, being resistant against oxidation and corrosion. This book reviews researches on fabrication and classification of nanostructured coatings with focus on size effect in nanometric scale. Size effect on electrochemical, mechanical and physical properties of nanocoatings are presented.

  15. Nanostructured composite reinforced material

    Science.gov (United States)

    Seals, Roland D [Oak Ridge, TN; Ripley, Edward B [Knoxville, TN; Ludtka, Gerard M [Oak Ridge, TN

    2012-07-31

    A family of materials wherein nanostructures and/or nanotubes are incorporated into a multi-component material arrangement, such as a metallic or ceramic alloy or composite/aggregate, producing a new material or metallic/ceramic alloy. The new material has significantly increased strength, up to several thousands of times normal and perhaps substantially more, as well as significantly decreased weight. The new materials may be manufactured into a component where the nanostructure or nanostructure reinforcement is incorporated into the bulk and/or matrix material, or as a coating where the nanostructure or nanostructure reinforcement is incorporated into the coating or surface of a "normal" substrate material. The nanostructures are incorporated into the material structure either randomly or aligned, within grains, or along or across grain boundaries.

  16. Development of novel FePt/nanodiamond hybrid nanostructures: L1{sub 0} phase size-growth suppression and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Douvalis, A. P., E-mail: adouval@uoi.gr; Bourlinos, A. B. [University of Ioannina, Physics Department (Greece); Tucek, J.; Čépe, K. [Palacký University Olomouc, Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science (Czech Republic); Bakas, T. [University of Ioannina, Physics Department (Greece); Zboril, R. [Palacký University Olomouc, Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science (Czech Republic)

    2016-05-15

    A new type of hybrid nanomaterial composed of magnetic FePt nanoparticles grown on the surface of nanodiamond nanotemplate assemblies is described for the first time. Post annealing in vacuum of the as-made nanomaterial bearing cubic A1 soft magnetic FePt nanoparticles leads to the development of FePt nanoparticles with tetragonal L1{sub 0} hard, magnetic-phase characteristics, leaving untouched the nanodiamond nanotemplate assemblies. X-ray diffraction, high-resolution transmission electron microscopy including chemical mapping (HRTEM/HAADF), magnetization measurements, and {sup 57}Fe Mössbauer spectroscopy data show that the magnetic FePt nanoparticles, with average sizes of 3 and 8 nm in the as-made and annealed hybrids, respectively, are homogenously distributed within the nanodiamond template in both nanomaterials. As a consequence, their structural, morphological, and magnetic properties differ significantly from the corresponding properties of the nonsupported (free) as-made and annealed FePt nanoparticles with average sizes of 6 and 32 nm, respectively, developed by the same methods. This spatial isolation suppresses the size-growth of the FePt nanoparticles during the post-annealing procedure, triggering superparamagnetic relaxation phenomena, which are exposed as a combination of hard and soft magnetic-phase characteristics.

  17. Injection moulding antireflective nanostructures

    DEFF Research Database (Denmark)

    Christiansen, Alexander Bruun; Clausen, Jeppe Sandvik; Mortensen, N. Asger

    2014-01-01

    We present a method for injection moulding antireflective nanostructures on large areas, for high volume production. Nanostructured black silicon masters were fabricated by mask-less reactive ion etching, and electroplated with nickel. The nickel shim was antistiction coated and used in an inject......We present a method for injection moulding antireflective nanostructures on large areas, for high volume production. Nanostructured black silicon masters were fabricated by mask-less reactive ion etching, and electroplated with nickel. The nickel shim was antistiction coated and used...

  18. Injection moulding antireflective nanostructures

    DEFF Research Database (Denmark)

    Christiansen, Alexander Bruun; Clausen, Jeppe Sandvik; Mortensen, N. Asger

    We present a method for injection moulding antireflective nanostructures on large areas, for high volume production. Nanostructured black silicon masters were fabricated by mask-less reactive ion etching, and electroplated with nickel. The nickel shim was antistiction coated and used in an inject......We present a method for injection moulding antireflective nanostructures on large areas, for high volume production. Nanostructured black silicon masters were fabricated by mask-less reactive ion etching, and electroplated with nickel. The nickel shim was antistiction coated and used...

  19. Nanostructured layers of thermoelectric materials

    Energy Technology Data Exchange (ETDEWEB)

    Urban, Jeffrey J.; Lynch, Jared; Coates, Nelson; Forster, Jason; Sahu, Ayaskanta; Chabinyc, Michael; Russ, Boris

    2018-01-30

    This disclosure provides systems, methods, and apparatus related to thermoelectric materials. In one aspect, a method includes providing a plurality of nanostructures. The plurality of nanostructures comprise a thermoelectric material, with each nanostructure of the plurality of nanostructures having first ligands disposed on a surface of the nanostructure. The plurality of nanostructures is mixed with a solution containing second ligands and a ligand exchange process occurs in which the first ligands disposed on the plurality of nanostructures are replaced with the second ligands. The plurality of nanostructures is deposited on a substrate to form a layer. The layer is thermally annealed.

  20. Nanostructural and magnetic studies of virtually monodispersed NiFe2O4 nanocrystals synthesized by a liquid–solid-solution assisted hydrothermal route

    International Nuclear Information System (INIS)

    Li Xinghua; Tan Guoguo; Chen Wei; Zhou Baofan; Xue Desheng; Peng Yong; Li, Fashen; Mellors, Nigel J.

    2012-01-01

    This study presents a comprehensively and systematically structural, chemical and magnetic characterization of ∼9.5 nm virtually monodispersed nickel ferrite (NiFe 2 O 4 ) nanoparticles prepared using a modified liquid–solid-solution (LSS) assisted hydrothermal method. Lattice-resolution scanning transmission electron microscope (STEM) and converged beam electron diffraction pattern (CBED) techniques are adapted to characterize the detailed spatial morphology and crystal structure of individual NiFe 2 O 4 particles at nano scale for the first time. It is found that each NiFe 2 O 4 nanoparticle is single crystal with an fcc structure. The morphology investigation reveals that the prepared NiFe 2 O 4 nanoparticles of which the surfaces are decorated by oleic acid are dispersed individually in hexane. The chemical composition of nickel ferrite nanoparticles is measured to be 1:2 atomic ratio of Ni:Fe, indicating a pure NiFe 2 O 4 composition. Magnetic measurements reveal that the as-synthesized nanocrystals displayed superparamagnetic behavior at room temperature and were ferromagnetic at 10 K. The nanoscale characterization and magnetic investigation of monodispersed NiFe 2 O 4 nanoparticles should be significant for its potential applications in the field of biomedicine and magnetic fluid using them as magnetic materials.

  1. The effect of structural changes during sintering on the electric and magnetic traits of the Ni96.7Mo3.3 alloy nanostructured powder

    Directory of Open Access Journals (Sweden)

    Ribić-Zelenović L.

    2009-01-01

    Full Text Available Ni96.7Mo3.3 powder was electrochemically obtained. An X-ray diffraction analysis determined that the powder consisted of a 20% amorphous and 80% crystalline phase. The crystalline phase consisted of a nanocrystalline solid nickel and molybdenum solution with a face-centred cubic (FCC lattice with a high density of chaotically distributed dislocations and high microstrain value. The scanning electronic microscopy (SEM showed that two particle structures were formed: larger cauliflower-like particles and smaller dendriteshaped ones. The thermal stability of the alloy was examined by differential scanning calorimetry (DSC and by measuring the temperature dependence of the electrical resistivity and magnetic permeability. Structural powder relaxation was carried out in the temperature range of 450 K to 560 K causing considerable changes in the electrical resistivity and magnetic permeability. Upon structural relaxation, the magnetic permeability of the cooled alloy was about 80% higher than the magnetic permeability of the fresh powder. The crystallisation of the amorphous portion of the powder and crystalline grain increase occurred in the 630 K to 900 K temperature interval. Upon crystallisation of the amorphous phase and crystalline grain increase, the powder had about 50% lower magnetic permeability than the fresh powder and 3.6 times lower permeability than the powder where only structural relaxation took place.

  2. In situ generated gas bubble-assisted modulation of the morphologies, photocatalytic, and magnetic properties of ferric oxide nanostructures synthesized by thermal decomposition of iron nitrate

    International Nuclear Information System (INIS)

    Tong Guoxiu; Guan Jianguo; Xiao Zhidong; Huang Xing; Guan Yao

    2010-01-01

    Ferric oxide (Fe 2 O 3 ) complex nanoarchitectures with high BET specific surface area, superior photocatalytic activity and modulated magnetic properties are facilely synthesized via controlled thermal decomposition of iron(III) nitrate nonahydrate. The products are characterized by X-ray diffraction, Fourier-transforming infrared spectra, field-emission scanning electron microscope, field-emission high-resolution transmission electron microscope, and nitrogen physisorption and micrometrics analyzer. The corresponding photocatalytic activity and static magnetic properties are also evaluated by measuring the photocatalytic degradation of Rhodamine B aqueous solution under visible light illumination and vibrating sample magnetometer, respectively. Simply tuning the decomposition temperature can conveniently modulate the adsorbing/desorbing behaviors of the in situ generated gases on the nucleus surfaces, and consequently the crystalline structures and morphologies of the Fe 2 O 3 complex nanoarchitectures. The as-prepared Fe 2 O 3 complex nanoarchitectures show strong crystal structure and/or morphology-dependent photocatalytic and magnetic performances. The Fe 2 O 3 complex nanoarchitectures with high specific surface area and favorable crystallization are found to be beneficial for improving the photocatalytic activity. This work not only reports a convenient and low-cost decomposition procedure and a novel formation mechanism of complex nanoarchitectures but also provides an efficient route to enhance catalytic and magnetic properties of Fe 2 O 3 .

  3. Probing buried solid-solid interfaces in magnetic multilayer structures and other nanostructures using spectroscopy excited by soft x-ray standing waves

    International Nuclear Information System (INIS)

    Yang, S.-H.; Mun, B.S.; Mannella, N.; Sell, B.; Ritchey, S.B.; Fadley, C.S.; Pham, L.; Nambu, A.; Watanabe, M.

    2004-01-01

    Full text: Buried solid-solid interfaces are becoming increasingly more important in all aspects of nanoscience, and we here dis- cuss the st applications of a new method for selectively studying them with the vuv/soft x-ray spectroscopies. As specific examples, magnetic multilayer structures represent key elements of current developments in spintronics, including giant magnetoresistance, exchange bias, and magnetic tunnel resistance. The buried interfaces in such structures are of key importance to their performance, but have up to now been difficult to study selectively with these spectroscopies. This novel method involves excitation of photoelectrons or fluorescent x-rays with soft x-ray standing waves created by Bragg reflection from a multilayer mirror substrate on which the sample is grown. We will discuss core and valence photoemission, as well soft x-ray emission, results from applying this method to multilayer structures relevant to both giant magnetoresistance (Fe/Cr-[2]) and magnetic tunnel junctions (Al 2 O 3 /FeCo) , including magnetic dichroism measurements. Work supported by the Director, Of e of Science, Of e of Basic Energy Sciences, Materials Science and Engineering Division, U.S. Department of Energy, Contract No. DE-AC03-76SF000

  4. Preparation and characterization of a carbon-based magnetic nanostructure via co-precipitation method: Peroxidase-like activity assay with 3,3ʹ,5,5ʹ-tetramethylbenzidine

    Directory of Open Access Journals (Sweden)

    Navvabeh Salarizadeh

    2017-09-01

    Full Text Available Objective(S: Natural and artificial enzymes have shown important roles in biotechnological processes. Recently, design and synthesis of artificial enzymes especially peroxidase mimics has been interested by many researchers. Due to disadvantages of natural peroxidases, there is a desirable reason of current research interest in artificial peroxidase mimics. Methods: In this study, magnetic multiwall carbon nanotubes with a structure of Fe3O4/MWCNTs as enzyme mimetic were fabricated using in situ co-precipitation method. The structure, composition, and morphology of Fe3O4/MWCNTs nanocomposite were characterized using X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR, and transmission electron microscopy (TEM. The magnetic properties were investigated by the vibrating sample magnetometer (VSM. Peroxidase-like catalytic activity of nanocomposite was investigated using colorimetric and electrochemical tests with 3,3ʹ,5,5ʹ-tetramethylbenzidine (TMB substrate. Results: The obtained data proved the synthesis of Fe3O4/MWCNTs nanocomposite. The average crystallite size of nanostructures was estimated about 12 nm by Debye–Scherer equation. It was found that Fe3O4/MWCNTs nanocomposite exhibit peroxidase-like activity. Colorimetric and electrochemical data demonstrated that prepared nanocomplex has higher catalytic activity toward H2O2 than pure MWCNT nanocatalyst. From electrochemical tests concluded that the Fe3O4/MWCNTs electrode exhibited the better redox response to H2O2, which is ~ 2 times larger than that of the MWCNTs. Conclusions: The synthesis of Fe3O4nanoparticles on MWCNTs was successfully performed by in situ co-precipitation process. Fe3O4/MWCNTs nanocatalyst exhibited a good peroxidase-like activity. These biomimetic catalysts have some advantages such as simplicity, stability and cost effectiveness that can be used in the design of enzyme-based devices for various applied fields.

  5. MAGNET

    CERN Multimedia

    by B. Curé

    2011-01-01

    The magnet operation was very satisfactory till the technical stop at the end of the year 2010. The field was ramped down on 5th December 2010, following the successful regeneration test of the turbine filters at full field on 3rd December 2010. This will limit in the future the quantity of magnet cycles, as it is no longer necessary to ramp down the magnet for this type of intervention. This is made possible by the use of the spare liquid Helium volume to cool the magnet while turbines 1 and 2 are stopped, leaving only the third turbine in operation. This obviously requires full availability of the operators to supervise the operation, as it is not automated. The cryogenics was stopped on 6th December 2010 and the magnet was left without cooling until 18th January 2011, when the cryoplant operation resumed. The magnet temperature reached 93 K. The maintenance of the vacuum pumping was done immediately after the magnet stop, when the magnet was still at very low temperature. Only the vacuum pumping of the ma...

  6. Skyrmion states in thin confined polygonal nanostructures

    Science.gov (United States)

    Pepper, Ryan Alexander; Beg, Marijan; Cortés-Ortuño, David; Kluyver, Thomas; Bisotti, Marc-Antonio; Carey, Rebecca; Vousden, Mark; Albert, Maximilian; Wang, Weiwei; Hovorka, Ondrej; Fangohr, Hans

    2018-03-01

    Recent studies have demonstrated that skyrmionic states can be the ground state in thin-film FeGe disk nanostructures in the absence of a stabilising applied magnetic field. In this work, we advance this understanding by investigating to what extent this stabilisation of skyrmionic structures through confinement exists in geometries that do not match the cylindrical symmetry of the skyrmion—such as squares and triangles. Using simulation, we show that skyrmionic states can form the ground state for a range of system sizes in both triangular and square-shaped FeGe nanostructures of 10 nm thickness in the absence of an applied field. We further provide data to assist in the experimental verification of our prediction; to imitate an experiment where the system is saturated with a strong applied field before the field is removed, we compute the time evolution and show the final equilibrium configuration of magnetization fields, starting from a uniform alignment.

  7. Structural and magnetic evolution of nanostructured Co{sub 40}Fe{sub 10}Zr{sub 10}B{sub 40} prepared by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Raanaei, Hossein, E-mail: hraanaei@yahoo.com [Department of Physics, Persian Gulf University, Bushehr 75169 (Iran, Islamic Republic of); Abbasi, Sadeq [Department of Physics, Persian Gulf University, Bushehr 75169 (Iran, Islamic Republic of); Behaein, Saeed [Department of Physics, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of)

    2015-06-15

    The structural and magnetic properties of nanocrystalline alloy powder Co{sub 40}Fe{sub 10}Zr{sub 10}B{sub 40} prepared by mechanical alloying have been characterized by using X-ray diffraction (XRD), scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and differential scanning calorimeter (DSC). It is shown that the crystallite size has been decreased significantly to about 15 nm after 8 h milling time. On continuing the milling time mechanical crystallization and subsequently the alloying process were noticed up to 190 h. Saturation magnetization decreased during the whole process while coercivity achieved the highest value at the crystallization stage. Post treatment of milled powder at 190 h revealed crystalline constituent elements. - Highlights: • This article focuses on mechanical alloying of Co{sub 40}Fe{sub 10}Zr{sub 10}B{sub 40} system. • Mechanical crystallization is observed. • Structural and magnetic properties were investigated. • The heat treatment revealed the crystalline phases of constituent elements.

  8. Self-assembled nanostructures

    CERN Document Server

    Zhang, Jin Z; Liu, Jun; Chen, Shaowei; Liu, Gang-yu

    2003-01-01

    Nanostructures refer to materials that have relevant dimensions on the nanometer length scales and reside in the mesoscopic regime between isolated atoms and molecules in bulk matter. These materials have unique physical properties that are distinctly different from bulk materials. Self-Assembled Nanostructures provides systematic coverage of basic nanomaterials science including materials assembly and synthesis, characterization, and application. Suitable for both beginners and experts, it balances the chemistry aspects of nanomaterials with physical principles. It also highlights nanomaterial-based architectures including assembled or self-assembled systems. Filled with in-depth discussion of important applications of nano-architectures as well as potential applications ranging from physical to chemical and biological systems, Self-Assembled Nanostructures is the essential reference or text for scientists involved with nanostructures.

  9. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    Operation of the magnet has gone quite smoothly during the first half of this year. The magnet has been at 4.5K for the full period since January. There was an unplanned short stop due to the CERN-wide power outage on May 28th, which caused a slow dump of the magnet. Since this occurred just before a planned technical stop of the LHC, during which access in the experimental cavern was authorized, it was decided to leave the magnet OFF until 2nd June, when magnet was ramped up again to 3.8T. The magnet system experienced a fault also resulting in a slow dump on April 14th. This was triggered by a thermostat on a filter choke in the 20kA DC power converter. The threshold of this thermostat is 65°C. However, no variation in the water-cooling flow rate or temperature was observed. Vibration may have been the root cause of the fault. All the thermostats have been checked, together with the cables, connectors and the read out card. The tightening of the inductance fixations has also been checked. More tem...

  10. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      The magnet was energised at the beginning of March 2012 at a low current to check all the MSS safety chains. Then the magnet was ramped up to 3.8 T on 6 March 2012. Unfortunately two days later an unintentional switch OFF of the power converter caused a slow dump. This was due to a misunderstanding of the CCC (CERN Control Centre) concerning the procedure to apply for the CMS converter control according to the beam-mode status at that time. Following this event, the third one since 2009, a discussion was initiated to define possible improvement, not only on software and procedures in the CCC, but also to evaluate the possibility to upgrade the CMS hardware to prevent such discharge from occurring because of incorrect procedure implementations. The magnet operation itself was smooth, and no power cuts took place. As a result, the number of magnetic cycles was reduced to the minimum, with only two full magnetic cycles from 0 T to 3.8 T. Nevertheless the magnet suffered four stops of the cryogeni...

  11. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      Following the unexpected magnet stops last August due to sequences of unfortunate events on the services and cryogenics [see CMS internal report], a few more events and initiatives again disrupted the magnet operation. All the magnet parameters stayed at their nominal values during this period without any fault or alarm on the magnet control and safety systems. The magnet was stopped for the September technical stop to allow interventions in the experimental cavern on the detector services. On 1 October, to prepare the transfer of the liquid nitrogen tank on its new location, several control cables had to be removed. One cable was cut mistakenly, causing a digital input card to switch off, resulting in a cold-box (CB) stop. This tank is used for the pre-cooling of the magnet from room temperature down to 80 K, and for this reason it is controlled through the cryogenics control system. Since the connection of the CB was only allowed for a field below 2 T to avoid the risk of triggering a fast d...

  12. Quantitatively analyzing the mechanism of giant circular dichroism in extrinsic plasmonic chiral nanostructures by tracking the interplay of electric and magnetic dipoles.

    Science.gov (United States)

    Hu, Li; Tian, Xiaorui; Huang, Yingzhou; Fang, Liang; Fang, Yurui

    2016-02-14

    Plasmonic chirality has drawn much attention because of tunable circular dichroism (CD) and the enhancement for chiral molecule signals. Although various mechanisms have been proposed to explain the plasmonic CD, a quantitative explanation like the ab initio mechanism for chiral molecules, is still unavailable. In this study, a mechanism similar to the mechanisms associated with chiral molecules was analyzed. The giant extrinsic circular dichroism of a plasmonic splitting rectangle ring was quantitatively investigated from a theoretical standpoint. The interplay of the electric and magnetic modes of the meta-structure is proposed to explain the giant CD. We analyzed the interplay using both an analytical coupled electric-magnetic dipole model and a finite element method model. The surface charge distributions showed that the circular current yielded by the splitting rectangle ring causes the ring to behave like a magneton at some resonant modes, which then interact with the electric modes, resulting in a mixing of the two types of modes. The strong interplay of the two mode types is primarily responsible for the giant CD. The analysis of the chiral near-field of the structure shows potential applications for chiral molecule sensing.

  13. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      The magnet and its sub-systems were stopped at the beginning of the winter shutdown on 8th December 2011. The magnet was left without cooling during the cryogenics maintenance until 17th January 2012, when the cryoplant operation resumed. The magnet temperature reached 93 K. The vacuum pumping was maintained during this period. During this shutdown, the yearly maintenance was performed on the cryogenics, the vacuum pumps, the magnet control and safety systems, and the power converter and discharge lines. Several preventive actions led to the replacement of the electrovalve command coils, and the 20A DC power supplies of the magnet control system. The filters were cleaned on the demineralised water circuits. The oil of the diffusion pumps was changed. On the cryogenics, warm nitrogen at 343 K was circulated in the cold box to regenerate the filters and the heat exchangers. The coalescing filters have been replaced at the inlet of both the turbines and the lubricant trapping unit. The active cha...

  14. MAGNET

    CERN Multimedia

    B. Curé

    2013-01-01

      The magnet was operated without any problem until the end of the LHC run in February 2013, apart from a CERN-wide power glitch on 10 January 2013 that affected the CMS refrigerator, causing a ramp down to 2 T in order to reconnect the coldbox. Another CERN-wide power glitch on 15 January 2013 didn’t affect the magnet subsystems, the cryoplant or the power converter. At the end of the magnet run, the reconnection of the coldbox at 2.5 T was tested. The process will be updated, in particular the parameters of some PID valve controllers. The helium flow of the current leads was reduced but only for a few seconds. The exercise will be repeated with the revised parameters to validate the automatic reconnection process of the coldbox. During LS1, the water-cooling services will be reduced and many interventions are planned on the electrical services. Therefore, the magnet cryogenics and subsystems will be stopped for several months, and the magnet cannot be kept cold. In order to avoid unc...

  15. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    The magnet was successfully operated at the end of the year 2009 despite some technical problems on the cryogenics. The magnet was ramped up to 3.8 T at the end of November until December 16th when the shutdown started. The magnet operation met a few unexpected stops. The field was reduced to 3.5 T for about 5 hours on December 3rd due to a faulty pressure sensor on the helium compressor. The following day the CERN CCC stopped unintentionally the power converters of the LHC and the experiments, triggering a ramp down that was stopped at 2.7 T. The magnet was back at 3.8 T about 6 hours after CCC sent the CERN-wide command. Three days later, a slow dump was triggered due to a stop of the pump feeding the power converter water-cooling circuit, during an intervention on the water-cooling plant done after several disturbances on the electrical distribution network. The magnet was back at 3.8 T in the evening the same day. On December 10th a break occurred in one turbine of the cold box producing the liquid ...

  16. MAGNET

    CERN Multimedia

    B. Curé

    2011-01-01

    The CMS magnet has been running steadily and smoothly since the summer, with no detected flaw. The magnet instrumentation is entirely operational and all the parameters are at their nominal values. Three power cuts on the electrical network affected the magnet run in the past five months, with no impact on the data-taking as the accelerator was also affected at the same time. On 22nd June, a thunderstorm caused a power glitch on the service electrical network. The primary water cooling at Point 5 was stopped. Despite a quick restart of the water cooling, the inlet temperature of the demineralised water on the busbar cooling circuit increased by 5 °C, up to 23.3 °C. It was kept below the threshold of 27 °C by switching off other cooling circuits to avoid the trigger of a slow dump of the magnet. The cold box of the cryogenics also stopped. Part of the spare liquid helium volume was used to maintain the cooling of the magnet at 4.5 K. The operators of the cryogenics quickly restarted ...

  17. Hydrothermal synthetic strategies of inorganic semiconducting nanostructures.

    Science.gov (United States)

    Shi, Weidong; Song, Shuyan; Zhang, Hongjie

    2013-07-07

    Because of their unique chemical and physical properties, inorganic semiconducting nanostructures have gradually played a pivotal role in a variety of research fields, including electronics, chemical reactivity, energy conversion, and optics. A major feature of these nanostructures is the quantum confinement effect, which strongly depends on their size, shape, crystal structure and polydispersity. Among all developed synthetic methods, the hydrothermal method based on a water system has attracted more and more attention because of its outstanding advantages, such as high yield, simple manipulation, easy control, uniform products, lower air pollution, low energy consumption and so on. Precise control over the hydrothermal synthetic conditions is a key to the success of the preparation of high-quality inorganic semiconducting nanostructures. In this review, only the representative hydrothermal synthetic strategies of inorganic semiconducting nanostructures are selected and discussed. We will introduce the four types of strategies based on exterior reaction system adjustment, namely organic additive- and template-free hydrothermal synthesis, organic additive-assisted hydrothermal synthesis, template-assisted hydrothermal synthesis and substrate-assisted hydrothermal synthesis. In addition, the two strategies based on exterior reaction environment adjustment, including microwave-assisted and magnetic field-assisted hydrothermal synthesis, will be also described. Finally, we conclude and give the future prospects of this research area.

  18. Electronic transport properties of nanostructured MnSi-films

    Science.gov (United States)

    Schroeter, D.; Steinki, N.; Scarioni, A. Fernández; Schumacher, H. W.; Süllow, S.; Menzel, D.

    2018-05-01

    MnSi, which crystallizes in the cubic B20 structure, shows intriguing magnetic properties involving the existence of skyrmions in the magnetic phase diagram. Bulk MnSi has been intensively investigated and thoroughly characterized, in contrast to MnSi thin film, which exhibits widely varying properties in particular with respect to electronic transport. In this situation, we have set out to reinvestigate the transport properties in MnSi thin films by means of studying nanostructure samples. In particular, Hall geometry nanostructures were produced to determine the intrinsic transport properties.

  19. Carbon and oxide nanostructures. Synthesis, characterisation and applications

    Energy Technology Data Exchange (ETDEWEB)

    Yahya, Noorhana [Universiti Teknologi PETRONAS, Tronoh, Perak (Malaysia). Dept. of Fundamental and Applied Sciences

    2010-07-01

    This volume covers all aspects of carbon and oxide based nanostructured materials. The topics include synthesis, characterization and application of carbon-based namely carbon nanotubes, carbon nanofibres, fullerenes, carbon filled composites etc. In addition, metal oxides namely, ZnO, TiO2, Fe2O3, ferrites, garnets etc., for various applications like sensors, solar cells, transformers, antennas, catalysts, batteries, lubricants, are presented. The book also includes the modeling of oxide and carbon based nanomaterials. The book covers the topics: - Synthesis, characterization and application of carbon nanotubes, carbon nanofibres, fullerenes - Synthesis, characterization and application of oxide based nanomaterials. - Nanostructured magnetic and electric materials and their applications. - Nanostructured materials for petro-chemical industry. - Oxide and carbon based thin films for electronics and sustainable energy. - Theory, calculations and modeling of nanostructured materials. (orig.)

  20. MAGNET

    CERN Multimedia

    B. Curé

    2011-01-01

    The magnet ran smoothly in the last few months until a fast dump occurred on 9th May 2011. Fortunately, this occurred in the afternoon of the first day of the technical stop. The fast dump was due to a valve position controller that caused the sudden closure of a valve. This valve is used to regulate the helium flow on one of the two current leads, which electrically connects the coil at 4.5 K to the busbars at room temperature. With no helium flow on the lead, the voltage drop and the temperatures across the leads increase up to the defined thresholds, triggering a fast dump through the Magnet Safety System (MSS). The automatic reaction triggered by the MSS worked properly. The helium release was limited as the pressure rise was just at the limit of the safety valve opening pressure. The average temperature of the magnet reached 72 K. It took four days to recover the temperature and refill the helium volumes. The faulty valve controller was replaced by a spare one before the magnet ramp-up resumed....

  1. Magnetic nanowires and hyperthermia: How geometry and material affect heat production efficiency

    KAUST Repository

    Contreras, Maria F.; Zaher, A.; Perez, Jose E.; Ravasi, Timothy; Kosel, Jü rgen

    2015-01-01

    Magnetic hyperthermia, which refers to the production of heat by magnetic nanostructures under an alternating magnetic field (AMF), has been previously investigated with superparamagnetic nanobeads as a cancer therapy method. Magnetic nanowires (NWs

  2. Magnetic field orientation dependence of flux pinning in (Gd,Y)Ba2Cu3O7-x coated conductor with tilted lattice and nanostructures

    International Nuclear Information System (INIS)

    Zhang, Y.; Specht, E.D.; Cantoni, C.; Christen, D.K.; Thompson, J.R.; Sinclair, J.W.; Goyal, A.; Zuev, Y.L.; Aytug, T.; Paranthaman, M.P.; Chen, Y.; Selvamanickam, V.

    2009-01-01

    The dependence of the critical current density (J c ) on the orientation of an applied magnetic field was studied for a prototype (Gd,Y)Ba 2 Cu 3 O 7-x (GdYBCO) coated conductor fabricated by MOCVD on an IBAD-MgO template. Additional rare-earth cations (Y and Gd) and Zr were incorporated into the superconducting film to form (Y,Gd) 2 O 3 and BaZrO 3 nanoparticles extended nearly parallel to the a-b planes and to the c-axis, respectively, to enhance the flux pinning. In-field measurement of J c was carried out with electrical current flowing either along or perpendicular to the longitudinal axis of the tape, while a maximum Lorentz force configuration was always maintained. Details in the angular dependence of J c were related to the unique structure of the film, specifically the tilt in the GdYBCO lattice and the tilts in the extended (Y,Gd) 2 O 3 and BaZrO3 nanoparticles. XRD and TEM were used to study the structure of the coated conductor. The effect of the misalignment between the external field H and the internal field B on the angular dependence of J c is discussed.

  3. Magnetic field orientation dependence of flux pinning in (Gd,Y)Ba2Cu3O7-x coated conductor with tilted lattice and nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yifei [ORNL; Specht, Eliot D [ORNL; Cantoni, Claudia [ORNL; Christen, David K [ORNL; Zuev, Yuri L [ORNL; Goyal, Amit [ORNL; Sinclair, J. [University of Tennessee, Knoxville (UTK); Thompson, James R [ORNL; Aytug, Tolga [ORNL; Paranthaman, Mariappan Parans [ORNL; Chen, Y [SuperPower Incorporated, Schenectady, New York; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York

    2009-01-01

    The dependence of the critical current density (J{sub c}) on the orientation of an applied magnetic field was studied for a prototype (Gd,Y)Ba{sub 2}Cu{sub 3}O{sub 7?x} (GdYBCO) coated conductor fabricated by MOCVD on an IBAD-MgO template. Additional rare-earth cations (Y and Gd) and Zr were incorporated into the superconducting film to form (Y,Gd){sub 2}O{sub 3} and BaZrO{sub 3} nanoparticles extended nearly parallel to the a-b planes and to the c-axis, respectively, to enhance the flux pinning. In-field measurement of J{sub c} was carried out with electrical current flowing either along or perpendicular to the longitudinal axis of the tape, while a maximum Lorentz force configuration was always maintained. Details in the angular dependence of J{sub c} were related to the unique structure of the film, specifically the tilt in the GdYBCO lattice and the tilts in the extended (Y,Gd){sub 2}O{sub 3} and BaZrO{sub 3} nanoparticles. XRD and TEM were used to study the structure of the coated conductor. The effect of the misalignment between the external field H and the internal field B on the angular dependence of J{sub c} is discussed.

  4. Study of the magnetic and structural properties of nanostructured powders of Nd{sub 2}Fe{sub 14}B mechanically alloyed

    Energy Technology Data Exchange (ETDEWEB)

    Zamora, L.E.; Perez Alcazar, G.A. [Department of Physics, University of Valle, A.A. 25360, Cali (Colombia); Rojas, Y.A.; Bustos, H. [Department of Physics, University of Tolima, A.A. 546, Ibague (Colombia); Greneche, J.M. [Laboratoire de Physique de l' Etat Condense, UMR CNRS6087, 72085 Le Mans Cedex 9 (France); Oyola Lozano, D.

    2007-07-01

    In this work we report the magnetic and structural properties obtained by Moessbauer spectrometry, Vibrating Sample Magnetometry and X-ray diffraction, of powder of Nd{sub 2}Fe{sub 14}B prepared by mechanical alloying. The mixtures were ball milled during 48 hours and submitted to heat treatments between 500 and 900 C under an argon atmosphere. Structural parameters were derived from high statistics X-ray patterns. The Moessbauer spectra registered at 300 K for samples without heat treatment were fitted by means of a sextet and a hyperfine field distribution, associated to a residual pure iron phase ({alpha}-Fe) and a disordered iron-based phase, respectively. From the spectra at 300 K the formation of the Fe{sub 3}C phase is observed for samples heat treated at 900 C. A quenching above 900 C accelerates the formation of the Fe{sub 3}C phase. The hysteresis loops allow to conclude that these samples behave as soft ferromagnets. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Highly c-axis oriented ZnO:Ni thin film nanostructure by RF magnetron sputtering: Structural, morphological and magnetic studies

    International Nuclear Information System (INIS)

    Siddheswaran, R.; Savková, Jarmila; Medlín, Rostislav; Očenášek, Jan; Životský, Ondřej; Novák, Petr; Šutta, Pavol

    2014-01-01

    Highlights: • Highly preferred oriented columnar ZnO:Ni thin films were prepared by magnetron sputtering. • XRD and azimuthal studies explain the characteristics of orientation in [0 0 1] direction. • Surface morphology and grains distribution were explained by FE-SEM. • XTEM specimen prepared by ion slicing used for TEM microstructure analyses. • Tendency of ferromagnetism by influence of Ni content was studied by VSM. - Abstract: Nickel doped zinc oxide (ZnO:Ni) thin films with different Ni concentrations were deposited on silicon substrates at 400 °C by reactive magnetron sputtering using a mixture of Ar and O 2 gases. The X-ray diffraction and azimuthal patterns of the ZnO:Ni were carried out, and the quality of the strong preferred orientation of crystalline columns in the direction [0 0 1] perpendicular to the substrate surface were analysed. The grain size, distribution, and homogeneity of the thin film surfaces were studied by FE-SEM. The EDX and mapping confirmed that the Ni is incorporated into ZnO uniformly. The microstructure of the textured columns was analysed by TEM and HRTEM analyses. The average thickness and length of the columns were found to be about 50 nm and 600 nm, respectively. The rise of ferromagnetism by the influence of Ni content was studied by VSM magnetic studies at room temperature

  6. Engineering Nano-Structured Multiferroic Thin Films

    Science.gov (United States)

    Cheung, Pui Lam

    Multiferroics exhibit remarkable tunabilities in their ferromagnetic, ferroelectric and magnetoelectric properties that provide the potential in enabling the control of magnetizations by electric field for the next generation non-volatile memories, antennas and motors. In recent research and developments in integrating single-phase ferroelectric and ferromagnetic materials, multiferroic composite demonstrated a promising magnetoelectric (ME) coupling for future applications. Atomic layer deposition (ALD) technique, on the other hand, allows fabrications of complex multiferroic nanostructures to investigate interfacial coupling between the two materials. In this work, radical-enhanced ALD of cobalt ferrite (CFO) and thermal ALD of lead zirconate titanate (PZT) were combined in fabricating complex multiferroic architectures in investigating the effect of nanostructuring and magnetic shape anisotropy on improving ME coupling. In particular, 1D CFO nanotubes and nanowires; 0D-3D CFO/PZT mesoporous composite; and 1D-1D CFO/PZT core-shell nanowire composite were studied. The potential implementation of nanostructured multiferroic composites into functioning devices was assessed by quantifying the converse ME coupling coefficient. The synthesis of 1D CFO nanostructures was realized by ALD of CFO in anodic aluminum oxide (AAO) membranes. This work provided a simple and inexpensive route to create parallel and high aspect ratio ( 55) magnetic nanostructures. The change in magnetic easy axis of (partially filled) CFO nanotubes from perpendicular to parallel in (fully-filled) nanowires indicated the significance of the geometric factor in controlling magnetizations and ME coupling. The 0D-3D CFO/PZT mesoporous composite demonstrated the optimizations of the strain transfer could be achieved by precise thickness control. 100 nm of mesoporous PZT was synthesized on Pt/TiOx/SiO2/Si using amphiphilic diblock copolymers as a porous ferroelectric template (10 nm pore diameter) for

  7. Nanostructured materials for hydrogen storage

    Science.gov (United States)

    Williamson, Andrew J.; Reboredo, Fernando A.

    2007-12-04

    A system for hydrogen storage comprising a porous nano-structured material with hydrogen absorbed on the surfaces of the porous nano-structured material. The system of hydrogen storage comprises absorbing hydrogen on the surfaces of a porous nano-structured semiconductor material.

  8. Nanostructures from nanoparticles

    International Nuclear Information System (INIS)

    Mendes, Paula M; Chen Yu; Palmer, Richard E; Nikitin, Kirill; Fitzmaurice, Donald; Preece, Jon A

    2003-01-01

    This paper reviews recent experimental approaches to the development of surface nanostructures from nanoparticles. The formation of nanowires by electron beam writing in films of gold nanoparticles passivated with a specially designed class of ligand molecules (dialkyl sulfides) is presented, together with illustrations of practical nanostructures. Potential applications of this methodology are discussed. Another alternative to the controlled fabrication of arrays of nanoparticles, based on nanocrystals which contain molecular recognition elements in the ligand shell, is also surveyed. These particles aggregate in the presence of specifically designed molecular dications which act as a molecular binder. Finally, recent work on the formation of nanoscale surface architectures using x-ray patterning of self-assembled monolayers is introduced. Current and potential future applications of these surface nanostructures are discussed

  9. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    The magnet worked very well at 3.8 T as expected, despite a technical issue that manifested twice in the cryogenics since June. All the other magnet sub-systems worked without flaw. The issue in the cryogenics was with the cold box: it could be observed that the cold box was getting progressively blocked, due to some residual humidity and air accumulating in the first thermal exchanger and in the adsorber at 65 K. This was later confirmed by the analysis during the regeneration phases. An increase in the temperature difference between the helium inlet and outlet across the heat exchanger and a pressure drop increase on the filter of the adsorber were observed. The consequence was a reduction of the helium flow, first compensated by the automatic opening of the regulation valves. But once they were fully opened, the flow and refrigeration power reduced as a consequence. In such a situation, the liquid helium level in the helium Dewar decreased, eventually causing a ramp down of the magnet current and a field...

  10. MAGNET

    CERN Multimedia

    B. Curé

    MAGNET During the winter shutdown, the magnet subsystems went through a full maintenance. The magnet was successfully warmed up to room temperature beginning of December 2008. The vacuum was broken later on by injecting nitrogen at a pressure just above one atmosphere inside the vacuum tank. This was necessary both to prevent any accidental humidity ingress, and to allow for a modification of the vacuum gauges on the vacuum tank and maintenance of the diffusion pumps. The vacuum gauges had to be changed, because of erratic variations on the measurements, causing spurious alarms. The new type of vacuum gauges has been used in similar conditions on the other LHC experiments and without problems. They are shielded against the stray field. The lubricants of the primary and diffusion pumps have been changed. Several minor modifications were also carried out on the equipment in the service cavern, with the aim to ease the maintenance and to allow possible intervention during operation. Spare sensors have been bough...

  11. MAGNET

    CERN Multimedia

    Benoit Curé.

    The magnet operation restarted end of June this year. Quick routine checks of the magnet sub-systems were performed at low current before starting the ramps up to higher field. It appeared clearly that the end of the field ramp down to zero was too long to be compatible with the detector commissioning and operations plans. It was decided to perform an upgrade to keep the ramp down from 3.8T to zero within 4 hours. On July 10th, when a field of 1.5T was reached, small movements were observed in the forward region support table and it was decided to fix this problem before going to higher field. At the end of July the ramps could be resumed. On July 28th, the field was at 3.8T and the summer CRAFT exercise could start. This run in August went smoothly until a general CERN wide power cut took place on August 3rd, due to an insulation fault on the high voltage network outside point 5. It affected the magnet powering electrical circuit, as it caused the opening of the main circuit breakers, resulting in a fast du...

  12. MAGNET

    CERN Multimedia

    B. Curé

    2013-01-01

    The magnet is fully stopped and at room temperature. The maintenance works and consolidation activities on the magnet sub-systems are progressing. To consolidate the cryogenic installation, two redundant helium compressors will be installed as ‘hot spares’, to avoid the risk of a magnet downtime in case of a major failure of a compressor unit during operation. The screw compressors, their motors, the mechanical couplings and the concrete blocks are already available and stored at P5. The metallic structure used to access the existing compressors in SH5 will be modified to allow the installation of the two redundant ones. The plan is to finish the installation and commissioning of the hot spare compressors before the summer 2014. In the meantime, a bypass on the high-pressure helium piping will be installed for the connection of a helium drier unit later during the Long Shutdown 1, keeping this installation out of the schedule critical path. A proposal is now being prepared for the con...

  13. Pbte Nanostructures for Spin Filtering and Detecting

    Science.gov (United States)

    Grabecki, G.

    2005-08-01

    An uniqueness of lead telluride PbTe relies on combination of excellent semiconducting properties, like high electron mobility and tunable carrier concentration, with paraelectric behavior leading to huge dielectric constant at low temperatures. The present article is a review of our experimental works performed on PbTe nanostructures. The main result is observation of one-dimensional quantization of the electron motion at much impure conditions than in any other system studied so far. We explain this in terms of dielectric screening of Coulomb potentials produced by charged defects. Furthermore, in an external magnetic field, the conductance quantization steps show very pronounced spin splitting, already visible at several kilogauss. This indicates that PbTe nanostructures have a potential as local spin filtering devices.

  14. Nanostructured piezoelectric energy harvesters

    CERN Document Server

    Briscoe, Joe

    2014-01-01

    This book covers a range of devices that use piezoelectricity to convert mechanical deformation into electrical energy and relates their output capabilities to a range of potential applications. Starting with a description of the fundamental principles and properties of piezo- and ferroelectric materials, where applications of bulk materials are well established, the book shows how nanostructures of these materials are being developed for energy harvesting applications. The authors show how a nanostructured device can be produced, and put in context some of the approaches that are being invest

  15. Spin currents in metallic nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Czeschka, Franz Dominik

    2011-09-05

    A pure spin current, i.e., a flow of angular momentum without accompanying net charge current, is a key ingredient in the field of spintronics. In this thesis, we experimentally investigated two different concepts for pure spin current sources suggested by theory. The first is based on a time-dependent magnetization precession which ''pumps'' a pure spin current into an adjacent non-magnetic conductor. Our experiments quantitatively corroborated important predictions expected theoretically for this approach, including the dependence of the spin current on the sample geometry and the microwave power. Even more important, we could show for the first time that the spin pumping concept is viable in a large variety of ferromagnetic materials and that it only depends on the magnetization damping. Therefore, our experiments established spin pumping as generic phenomenon and demonstrated that it is a powerful way to generate pure spin currents. The second theoretical concept is based on the conversion of charge currents into spin currents in non-magnetic nanostructures via the spin Hall effect. We experimentally investigated this approach in H-shaped, metallic nanodevices, and found that the predictions are linked to requirements not realizable with the present experimental techniques, neither in sample fabrication nor in measurement technique. Indeed, our experimental data could be consistently understood by a spin-independent transport model describing the transition from diffusive to ballistic transport. In addition, the implementation of advanced fabrication and measurement techniques allowed to discover a new non-local phenomenon, the non-local anisotropic magnetoresistance. Finally, we also studied spin-polarized supercurrents carried by spin-triplet Cooper pairs. We found that low resistance interfaces are a key requirement for further experiments in this direction. (orig.)

  16. Epitaxial growth of hybrid nanostructures

    Science.gov (United States)

    Tan, Chaoliang; Chen, Junze; Wu, Xue-Jun; Zhang, Hua

    2018-02-01

    Hybrid nanostructures are a class of materials that are typically composed of two or more different components, in which each component has at least one dimension on the nanoscale. The rational design and controlled synthesis of hybrid nanostructures are of great importance in enabling the fine tuning of their properties and functions. Epitaxial growth is a promising approach to the controlled synthesis of hybrid nanostructures with desired structures, crystal phases, exposed facets and/or interfaces. This Review provides a critical summary of the state of the art in the field of epitaxial growth of hybrid nanostructures. We discuss the historical development, architectures and compositions, epitaxy methods, characterization techniques and advantages of epitaxial hybrid nanostructures. Finally, we provide insight into future research directions in this area, which include the epitaxial growth of hybrid nanostructures from a wider range of materials, the study of the underlying mechanism and determining the role of epitaxial growth in influencing the properties and application performance of hybrid nanostructures.

  17. Handbook of Advanced Magnetic Materials

    CERN Document Server

    Liu, Yi; Shindo, Daisuke

    2006-01-01

    From high-capacity, inexpensive hard drives to mag-lev trains, recent achievements in magnetic materials research have made the dreams of a few decades ago reality. The objective of Handbook of Advanced Magnetic Materials is to provide a timely, comprehensive review of recent progress in magnetic materials research. This broad yet detailed reference consists of four volumes: 1.) Nanostructured advanced magnetic materials, 2.) Characterization and simulation of advanced magnetic materials, 3.) Processing of advanced magnetic materials, and 4.) Properties and applications of advanced magnetic materials The first volume documents and explains recent development of nanostructured magnetic materials, emphasizing size effects. The second volume provides a comprehensive review of both experimental methods and simulation techniques for the characterization of magnetic materials. The third volume comprehensively reviews recent developments in the processing and manufacturing of advanced magnetic materials. With the co...

  18. MAGNET

    CERN Multimedia

    Benoit Curé

    The magnet subsystems resumed operation early this spring. The vacuum pumping was restarted mid March, and the cryogenic power plant was restarted on March 30th. Three and a half weeks later, the magnet was at 4.5 K. The vacuum pumping system is performing well. One of the newly installed vacuum gauges had to be replaced at the end of the cool-down phase, as the values indicated were not coherent with the other pressure measurements. The correction had to be implemented quickly to be sure no helium leak could be at the origin of this anomaly. The pressure measurements have been stable and coherent since the change. The cryogenics worked well, and the cool-down went quite smoothly, without any particular difficulty. The automated start of the turbines had to be fine-tuned to get a smooth transition, as it was observed that the cooling power delivered by the turbines was slightly higher than needed, causing the cold box to stop automatically. This had no consequence as the cold box safety system acts to keep ...

  19. MAGNET

    CERN Multimedia

    B. Curé

    During the winter shutdown, the magnet subsystems went through a full maintenance. The magnet was successfully warmed up to room temperature beginning of December 2008. The vacuum was broken later on by injecting nitrogen at a pressure just above one atmosphere inside the vacuum tank. This was necessary both to prevent any accidental humidity ingress, and to allow for a modification of the vacuum gauges on the vacuum tank and maintenance of the diffusion pumps. The vacuum gauges had to be changed, because of erratic variations on the measurements, causing spurious alarms. The new type of vacuum gauges has been used in similar conditions on the other LHC experiments and without problems. They are shielded against the stray field. The lubricants of the primary and diffusion pumps have been changed. Several minor modifications were also carried out on the equipment in the service cavern, with the aim to ease the maintenance and to allow possible intervention during operation. Spare sensors have been bought. Th...

  20. Nanostructures-History

    Indian Academy of Sciences (India)

    First page Back Continue Last page Graphics. Nanostructures-History. Inspiration to Nanotechnology-. The Japanese scientist Norio Taniguchi of the Tokyo University of Science was used the term "nano-technology" in a 1974 conference, to describe semiconductor processes such as thin film His definition was, ...

  1. Synthesis engineering of iron oxide raspberry-shaped nanostructures.

    Science.gov (United States)

    Gerber, O; Pichon, B P; Ihiawakrim, D; Florea, I; Moldovan, S; Ersen, O; Begin, D; Grenèche, J-M; Lemonnier, S; Barraud, E; Begin-Colin, S

    2017-01-07

    Magnetic porous nanostructures consisting of oriented aggregates of iron oxide nanocrystals display very interesting properties such as a lower oxidation state of magnetite, and enhanced saturation magnetization in comparison with individual nanoparticles of similar sizes and porosity. However, the formation mechanism of these promising nanostructures is not well understood, which hampers the fine tuning of their magnetic properties, for instance by doping them with other elements. Therefore the formation mechanism of porous raspberry shaped nanostructures (RSNs) synthesized by a one-pot polyol solvothermal method has been investigated in detail from the early stages by using a wide panel of characterization techniques, and especially by performing original in situ HR-TEM studies in temperature. A time-resolved study showed the intermediate formation of an amorphous iron alkoxide phase with a plate-like lamellar structure (PLS). Then, the fine investigation of PLS transformation upon heating up to 500 °C confirmed that the synthesis of RSNs involves two iron precursors: the starting one (hydrated iron chlorides) and the in situ formed iron alkoxide precursor which decomposes with time and heating and contributes to the growth step of nanostructures. Such an understanding of the formation mechanism of RSNs is necessary to envision efficient and rational enhancement of their magnetic properties.

  2. Highly coercive thin-film nanostructures

    International Nuclear Information System (INIS)

    Zhou, J.; Skomski, R.; Kashyap, A.; Sorge, K.D.; Sui, Y.; Daniil, M.; Gao, L.; Yan, M.L.; Liou, S.-H.; Kirby, R.D.; Sellmyer, D.J.

    2005-01-01

    The processing, structure, and magnetism of highly coercive Sm-Co and FePt thin-film nanostructures are investigated. The structures include 1:5 based Sm-Co-Cu-Ti magnets, particulate FePt:C thin films, and FePt nanotubes. As in other systems, the coercivity depends on texture and imperfections, but there are some additional features. A specific coercivity mechanism in particulate media is a discrete pinning mode intermediate between Stoner-Wohlfarth rotation and ordinary domain-wall pinning. This mechanism yields a coercivity maximum for intermediate intergranular exchange and explains the occurrence of coercivities of 5 T in particulate Sm-Co-Cu-Ti magnets

  3. Quantum spin transport in semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Schindler, Christoph

    2012-05-15

    In this work, we study and quantitatively predict the quantum spin Hall effect, the spin-orbit interaction induced intrinsic spin-Hall effect, spin-orbit induced magnetizations, and spin-polarized electric currents in nanostructured two-dimensional electron or hole gases with and without the presence of magnetic fields. We propose concrete device geometries for the generation, detection, and manipulation of spin polarization and spin-polarized currents. To this end a novel multi-band quantum transport theory, that we termed the multi-scattering Buettiker probe model, is developed. The method treats quantum interference and coherence in open quantum devices on the same footing as incoherent scattering and incorporates inhomogeneous magnetic fields in a gauge-invariant and nonperturbative manner. The spin-orbit interaction parameters that control effects such as band energy spin splittings, g-factors, and spin relaxations are calculated microscopically in terms of an atomistic relativistic tight-binding model. We calculate the transverse electron focusing in external magnetic and electric fields. We have performed detailed studies of the intrinsic spin-Hall effect and its inverse effect in various material systems and geometries. We find a geometry dependent threshold value for the spin-orbit interaction for the inverse intrinsic spin-Hall effect that cannot be met by n-type GaAs structures. We propose geometries that spin polarize electric current in zero magnetic field and analyze the out-of-plane spin polarization by all electrical means. We predict unexpectedly large spin-orbit induced spin-polarization effects in zero magnetic fields that are caused by resonant enhancements of the spin-orbit interaction in specially band engineered and geometrically designed p-type nanostructures. We propose a concrete realization of a spin transistor in HgTe quantum wells, that employs the helical edge channel in the quantum spin Hall effect.

  4. Quantum spin transport in semiconductor nanostructures

    International Nuclear Information System (INIS)

    Schindler, Christoph

    2012-01-01

    In this work, we study and quantitatively predict the quantum spin Hall effect, the spin-orbit interaction induced intrinsic spin-Hall effect, spin-orbit induced magnetizations, and spin-polarized electric currents in nanostructured two-dimensional electron or hole gases with and without the presence of magnetic fields. We propose concrete device geometries for the generation, detection, and manipulation of spin polarization and spin-polarized currents. To this end a novel multi-band quantum transport theory, that we termed the multi-scattering Buettiker probe model, is developed. The method treats quantum interference and coherence in open quantum devices on the same footing as incoherent scattering and incorporates inhomogeneous magnetic fields in a gauge-invariant and nonperturbative manner. The spin-orbit interaction parameters that control effects such as band energy spin splittings, g-factors, and spin relaxations are calculated microscopically in terms of an atomistic relativistic tight-binding model. We calculate the transverse electron focusing in external magnetic and electric fields. We have performed detailed studies of the intrinsic spin-Hall effect and its inverse effect in various material systems and geometries. We find a geometry dependent threshold value for the spin-orbit interaction for the inverse intrinsic spin-Hall effect that cannot be met by n-type GaAs structures. We propose geometries that spin polarize electric current in zero magnetic field and analyze the out-of-plane spin polarization by all electrical means. We predict unexpectedly large spin-orbit induced spin-polarization effects in zero magnetic fields that are caused by resonant enhancements of the spin-orbit interaction in specially band engineered and geometrically designed p-type nanostructures. We propose a concrete realization of a spin transistor in HgTe quantum wells, that employs the helical edge channel in the quantum spin Hall effect.

  5. Antibacterial Au nanostructured surfaces

    Science.gov (United States)

    Wu, Songmei; Zuber, Flavia; Brugger, Juergen; Maniura-Weber, Katharina; Ren, Qun

    2016-01-01

    We present here a technological platform for engineering Au nanotopographies by templated electrodeposition on antibacterial surfaces. Three different types of nanostructures were fabricated: nanopillars, nanorings and nanonuggets. The nanopillars are the basic structures and are 50 nm in diameter and 100 nm in height. Particular arrangement of the nanopillars in various geometries formed nanorings and nanonuggets. Flat surfaces, rough substrate surfaces, and various nanostructured surfaces were compared for their abilities to attach and kill bacterial cells. Methicillin-resistant Staphylococcus aureus, a Gram-positive bacterial strain responsible for many infections in health care system, was used as the model bacterial strain. It was found that all the Au nanostructures, regardless their shapes, exhibited similar excellent antibacterial properties. A comparison of live cells attached to nanotopographic surfaces showed that the number of live S. aureus cells was flat and rough reference surfaces. Our micro/nanofabrication process is a scalable approach based on cost-efficient self-organization and provides potential for further developing functional surfaces to study the behavior of microbes on nanoscale topographies.We present here a technological platform for engineering Au nanotopographies by templated electrodeposition on antibacterial surfaces. Three different types of nanostructures were fabricated: nanopillars, nanorings and nanonuggets. The nanopillars are the basic structures and are 50 nm in diameter and 100 nm in height. Particular arrangement of the nanopillars in various geometries formed nanorings and nanonuggets. Flat surfaces, rough substrate surfaces, and various nanostructured surfaces were compared for their abilities to attach and kill bacterial cells. Methicillin-resistant Staphylococcus aureus, a Gram-positive bacterial strain responsible for many infections in health care system, was used as the model bacterial strain. It was found that all

  6. Magnetic

    Science.gov (United States)

    Aboud, Essam; El-Masry, Nabil; Qaddah, Atef; Alqahtani, Faisal; Moufti, Mohammed R. H.

    2015-06-01

    The Rahat volcanic field represents one of the widely distributed Cenozoic volcanic fields across the western regions of the Arabian Peninsula. Its human significance stems from the fact that its northern fringes, where the historical eruption of 1256 A.D. took place, are very close to the holy city of Al-Madinah Al-Monawarah. In the present work, we analyzed aeromagnetic data from the northern part of Rahat volcanic field as well as carried out a ground gravity survey. A joint interpretation and inversion of gravity and magnetic data were used to estimate the thickness of the lava flows, delineate the subsurface structures of the study area, and estimate the depth to basement using various geophysical methods, such as Tilt Derivative, Euler Deconvolution and 2D modeling inversion. Results indicated that the thickness of the lava flows in the study area ranges between 100 m (above Sea Level) at the eastern and western boundaries of Rahat Volcanic field and getting deeper at the middle as 300-500 m. It also showed that, major structural trend is in the NW direction (Red Sea trend) with some minor trends in EW direction.

  7. MAGNET

    CERN Multimedia

    Benoit Curé

    The cooling down to the nominal temperature of 4.5 K was achieved at the beginning of August, in conjunction with the completion of the installation work of the connection between the power lines and the coil current leads. The temperature gradient on the first exchanger of the cold box is now kept within the nominal range. A leak of lubricant on a gasket of the helium compressor station installed at the surface was observed and several corrective actions were necessary to bring the situation back to normal. The compressor had to be refilled with lubricant and a regeneration of the filters and adsorbers was necessary. The coil cool down was resumed successfully, and the cryogenics is running since then with all parameters being nominal. Preliminary tests of the 20kA coil power supply were done earlier at full current through the discharge lines into the dump resistors, and with the powering busbars from USC5 to UXC5 without the magnet connected. On Monday evening August 25th, at 8pm, the final commissionin...

  8. MAGNET

    CERN Document Server

    B. Curé

    The first phase of the commissioning ended in August by a triggered fast dump at 3T. All parameters were nominal, and the temperature recovery down to 4.5K was carried out in two days by the cryogenics. In September, series of ramps were achieved up to 3 and finally 3.8T, while checking thoroughly the detectors in the forward region, measuring any movement of and around the HF. After the incident of the LHC accelerator on September 19th, corrective actions could be undertaken in the forward region. When all these displacements were fully characterized and repetitive, with no sign of increments in displacement at each field ramp, it was possible to start the CRAFT, Cosmic Run at Four Tesla (which was in fact at 3.8T). The magnet was ramped up to 18.16kA and the 3 week run went smoothly, with only 4 interruptions: due to the VIP visits on 21st October during the LHC inauguration day; a water leak on the cooling demineralized water circuit, about 1 l/min, that triggered a stop of the cooling pumps, and resulte...

  9. MAGNET

    CERN Multimedia

    Benoit Curé

    2013-01-01

    Maintenance work and consolidation activities on the magnet cryogenics and its power distribution are progressing according to the schedules. The manufacturing of the two new helium compressor frame units has started. The frame units support the valves, all the sensors and the compressors with their motors. This activity is subcontracted. The final installation and the commissioning at CERN are scheduled for March–April 2014. The overhauls of existing cryogenics equipment (compressors, motors) are in progress. The reassembly of the components shall start in early 2014. The helium drier, to be installed on the high-pressure helium piping, has been ordered and will be delivered in the first trimester of 2014. The power distribution for the helium compressors in SH5 on the 3.3kV network is progressing. The 3.3kV switches, between each compressor and its hot spare compressor, are being installed, together with the power cables for the new compressors. The 3.3kV electrical switchboards in SE5 will ...

  10. Synthesis of ferroelectric nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Roervik, Per Martin

    2008-12-15

    The increasing miniaturization of electric and mechanical components makes the synthesis and assembly of nanoscale structures an important step in modern technology. Functional materials, such as the ferroelectric perovskites, are vital to the integration and utility value of nanotechnology in the future. In the present work, chemical methods to synthesize one-dimensional (1D) nanostructures of ferroelectric perovskites have been studied. To successfully and controllably make 1D nanostructures by chemical methods it is very important to understand the growth mechanism of these nanostructures, in order to design the structures for use in various applications. For the integration of 1D nanostructures into devices it is also very important to be able to make arrays and large-area designed structures from the building blocks that single nanostructures constitute. As functional materials, it is of course also vital to study the properties of the nanostructures. The characterization of properties of single nanostructures is challenging, but essential to the use of such structures. The aim of this work has been to synthesize high quality single-crystalline 1D nanostructures of ferroelectric perovskites with emphasis on PbTiO3 , to make arrays or hierarchical nanostructures of 1D nanostructures on substrates, to understand the growth mechanisms of the 1D nanostructures, and to investigate the ferroelectric and piezoelectric properties of the 1D nanostructures. In Paper I, a molten salt synthesis route, previously reported to yield BaTiO3 , PbTiO3 and Na2Ti6O13 nanorods, was re-examined in order to elucidate the role of volatile chlorides. A precursor mixture containing barium (or lead) and titanium was annealed in the presence of NaCl at 760 degrees Celsius or 820 degrees Celsius. The main products were respectively isometric nanocrystalline BaTiO3 and PbTiO3. Nanorods were also detected, but electron diffraction revealed that the composition of the nanorods was

  11. Nanostructures based on alumina hydroxides inhibit tumor growth

    Science.gov (United States)

    Fomenko, A. N.; Korovin, M. S.

    2017-09-01

    Nanoparticles and nanostructured materials are one of the most promising developments for cancer therapy. Gold nanoparticles, magnetic nanoparticles based on iron and its oxides and other metal oxides have been widely used in diagnosis and treatment of cancer. Much less research attention has been payed to nanoparticles and nanostructures based on aluminum oxides and hydroxides as materials for cancer diagnosis and treatment. However recent investigations have shown promising results regarding these objects. Here, we review the antitumor results obtained with AlOOH nanoparticles.

  12. Ductility of Nanostructured Bainite

    Directory of Open Access Journals (Sweden)

    Lucia Morales-Rivas

    2016-12-01

    Full Text Available Nanostructured bainite is a novel ultra-high-strength steel-concept under intensive current research, in which the optimization of its mechanical properties can only come from a clear understanding of the parameters that control its ductility. This work reviews first the nature of this composite-like material as a product of heat treatment conditions. Subsequently, the premises of ductility behavior are presented, taking as a reference related microstructures: conventional bainitic steels, and TRIP-aided steels. The ductility of nanostructured bainite is then discussed in terms of work-hardening and fracture mechanisms, leading to an analysis of the three-fold correlation between ductility, mechanically-induced martensitic transformation, and mechanical partitioning between the phases. Results suggest that a highly stable/hard retained austenite, with mechanical properties close to the matrix of bainitic ferrite, is advantageous in order to enhance ductility.

  13. Hybrid phonons in nanostructures

    CERN Document Server

    Ridley, Brian K

    2017-01-01

    Crystalline semiconductor nanostructures have special properties associated with electrons and lattice vibrations and their interaction, and this is the topic of the book. The result of spatial confinement of electrons is indicated in the nomenclature of nonostructures: quantum wells, quantum wires, and quantum dots. Confinement also has a profound effect on lattice vibrations and an account of this is the prime focus. The documentation of the confinement of acoustic modes goes back to Lord Rayleigh’s work in the late nineteenth century, but no such documentation exists for optical modes. Indeed, it is only comparatively recently that any theory of the elastic properties of optical modes exists, and the account given in the book is comprehensive. A model of the lattice dynamics of the diamond lattice is given that reveals the quantitative distinction between acoustic and optical modes and the difference of connection rules that must apply at an interface. The presence of interfaces in nanostructures forces ...

  14. Nanostructured sulfur cathodes

    KAUST Repository

    Yang, Yuan

    2013-01-01

    Rechargeable Li/S batteries have attracted significant attention lately due to their high specific energy and low cost. They are promising candidates for applications, including portable electronics, electric vehicles and grid-level energy storage. However, poor cycle life and low power capability are major technical obstacles. Various nanostructured sulfur cathodes have been developed to address these issues, as they provide greater resistance to pulverization, faster reaction kinetics and better trapping of soluble polysulfides. In this review, recent developments on nanostructured sulfur cathodes and mechanisms behind their operation are presented and discussed. Moreover, progress on novel characterization of sulfur cathodes is also summarized, as it has deepened the understanding of sulfur cathodes and will guide further rational design of sulfur electrodes. © 2013 The Royal Society of Chemistry.

  15. Canted antiferromagnetic and optical properties of nanostructures of Mn2O3 prepared by hydrothermal synthesis

    International Nuclear Information System (INIS)

    Javed, Qurat-ul-ain; Feng-Ping Wang; Rafique, M. Yasir; Toufiq, Arbab Mohammad; Iqbal, M. Zubair

    2012-01-01

    We have reported new magnetic and optical properties of Mn 2 O 3 nanostructures. The nanostructures have been synthesized by the hydrothermal method combined with the adjustment of pH values in the reaction system. The particular characteristics of the nanostructures have been analyzed by employing X-Ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS), UV—visible spectroscopy, and the vibrating sample magnetometer (VSM). Structural investigation manifests that the synthesized Mn 2 O 3 nanostructures are orthorhombic crystal. Magnetic investigation indicates that the Mn 2 O 3 nanostructures are antiferromagnetic and the antiferromagnetic transition temperature is at T N = 83 K. Furthermore, the Mn 2 O 3 nanostructures possess canted antiferromagnetic order below the Neel temperature due to spin frustration, resulting in hysteresis with large coercivity (1580 Oe) and remnant magnetization (1.52 emu/g). The UV—visible spectrophotometry was used to determine the transmittance behaviour of Mn 2 O 3 nanostructures. A direct optical band gap of 1.2 eV was acquired by using the Davis—Mott model. The UV—visible spectrum indicates that the absorption is prominent in the visible region, and transparency is more than 80% in the UV region

  16. Antibacterial Au nanostructured surfaces.

    Science.gov (United States)

    Wu, Songmei; Zuber, Flavia; Brugger, Juergen; Maniura-Weber, Katharina; Ren, Qun

    2016-02-07

    We present here a technological platform for engineering Au nanotopographies by templated electrodeposition on antibacterial surfaces. Three different types of nanostructures were fabricated: nanopillars, nanorings and nanonuggets. The nanopillars are the basic structures and are 50 nm in diameter and 100 nm in height. Particular arrangement of the nanopillars in various geometries formed nanorings and nanonuggets. Flat surfaces, rough substrate surfaces, and various nanostructured surfaces were compared for their abilities to attach and kill bacterial cells. Methicillin-resistant Staphylococcus aureus, a Gram-positive bacterial strain responsible for many infections in health care system, was used as the model bacterial strain. It was found that all the Au nanostructures, regardless their shapes, exhibited similar excellent antibacterial properties. A comparison of live cells attached to nanotopographic surfaces showed that the number of live S. aureus cells was flat and rough reference surfaces. Our micro/nanofabrication process is a scalable approach based on cost-efficient self-organization and provides potential for further developing functional surfaces to study the behavior of microbes on nanoscale topographies.

  17. PREFACE: Nanostructured surfaces

    Science.gov (United States)

    Palmer, Richard E.

    2003-10-01

    We can define nanostructured surfaces as well-defined surfaces which contain lateral features of size 1-100 nm. This length range lies well below the micron regime but equally above the Ångstrom regime, which corresponds to the interatomic distances on single-crystal surfaces. This special issue of Journal of Physics: Condensed Matter presents a collection of twelve papers which together address the fabrication, characterization, properties and applications of such nanostructured surfaces. Taken together they represent, in effect, a status report on the rapid progress taking place in this burgeoning area. The first four papers in this special issue have been contributed by members of the European Research Training Network ‘NanoCluster’, which is concerned with the deposition, growth and characterization of nanometre-scale clusters on solid surfaces—prototypical examples of nanoscale surface features. The paper by Vandamme is concerned with the fundamentals of the cluster-surface interaction; the papers by Gonzalo and Moisala address, respectively, the optical and catalytic properties of deposited clusters; and the paper by van Tendeloo reports the application of transmission electron microscopy (TEM) to elucidate the surface structure of spherical particles in a catalyst support. The fifth paper, by Mendes, is also the fruit of a European Research Training Network (‘Micro-Nano’) and is jointly contributed by three research groups; it reviews the creation of nanostructured surface architectures from chemically-synthesized nanoparticles. The next five papers in this special issue are all concerned with the characterization of nanostructured surfaces with scanning tunnelling microscopy (STM) and atomic force microscopy (AFM). The papers by Bolotov, Hamilton and Dunstan demonstrate that the STM can be employed for local electrical measurements as well as imaging, as illustrated by the examples of deposited clusters, model semiconductor structures and real

  18. Wave propagation in nanostructures nonlocal continuum mechanics formulations

    CERN Document Server

    Gopalakrishnan, Srinivasan

    2013-01-01

    Wave Propagation in Nanostructures describes the fundamental and advanced concepts of waves propagating in structures that have dimensions of the order of nanometers. The book is fundamentally based on non-local elasticity theory, which includes scale effects in the continuum model. The book predominantly addresses wave behavior in carbon nanotubes and graphene structures, although the methods of analysis provided in this text are equally applicable to other nanostructures. The book takes the reader from the fundamentals of wave propagation in nanotubes to more advanced topics such as rotating nanotubes, coupled nanotubes, and nanotubes with magnetic field and surface effects. The first few chapters cover the basics of wave propagation, different modeling schemes for nanostructures and introduce non-local elasticity theories, which form the building blocks for understanding the material provided in later chapters. A number of interesting examples are provided to illustrate the important features of wave behav...

  19. Preparation of Iron-nickel Alloy Nanostructures via Two Cationic Pyridinium Derivatives as Soft Templates

    Directory of Open Access Journals (Sweden)

    Jingxin Zhou

    2015-09-01

    Full Text Available In this paper, crystalline iron-nickel alloy nanostructures were successfully prepared from two cationic pyridinium derivatives as soft templates in solution. The crystal structure and micrograph of FeNi alloy nanostructures were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy, and the content was confirmed by energy-dispersive spectrometry. The results indicated that the as-prepared nanostructures showed slightly different diameter ranges with the change of cationic pyridinium derivatives on the surface. The experimental data indicated that the adsorption of cationic pyridinium compounds on the surface of particles reduces the surface charge, leading to an isotropic distribution of the residual surface charges. The magnetic behaviours of as-prepared FeNi alloy nanostructures exhibited disparate behaviours, which could be attributed to their grain sizes and distinctive structures. The present work may give some insight into the synthesis and character of new alloy nanomaterials with special nanostructures using new soft templates.

  20. Optical switching systems using nanostructures

    DEFF Research Database (Denmark)

    Stubkjær, Kristian

    2004-01-01

    High capacity multiservice optical networks require compact and efficient switches. The potential benefits of optical switch elements based on nanostructured material are reviewed considering various material systems.......High capacity multiservice optical networks require compact and efficient switches. The potential benefits of optical switch elements based on nanostructured material are reviewed considering various material systems....

  1. Patterned FePt nanostructures using ultrathin self-organized templates

    Science.gov (United States)

    Deng, Chen Hua; Zhang, Min; Wang, Fang; Xu, Xiao Hong

    2018-02-01

    Patterned magnetic thin films are both scientifically interesting and technologically useful. Ultrathin self-organized anodic aluminum oxide (AAO) template can be used to fabricate large area nanodot and antidot arrays. The magnetic properties of these nanostructures may be tuned by the morphology of the AAO template, which in turn can be controlled by synthetic parameters. In this work, ultrathin AAO templates were used as etching masks for the fabrication of both FePt nanodot and antidot arrays with high areal density. The perpendicular magnetic anisotropy of L10 FePt thin films are preserved in the nanostructures.

  2. Semiconductors and semimetals nanostructured systems

    CERN Document Server

    Willardson, Robert K; Beer, Albert C; Reed, Mark A

    1992-01-01

    This is the first available volume to consolidate prominent topics in the emerging field of nanostructured systems. Recent technological advancements have led to a new era of nanostructure physics, allowing for the fabrication of nanostructures whose behavior is dominated by quantum interference effects. This new capability has enthused the experimentalist and theorist alike. Innumerable possibilities have now opened up for physical exploration and device technology on the nanoscale. This book, with contributions from five pioneering researchers, will allow the expert and novice alike to explore a fascinating new field.Provides a state-of-the-art review of quantum-scale artificially nanostructured electronic systemsIncludes contributions by world-known experts in the fieldOpens the field to the non-expert with a concise introductionFeatures discussions of:Low-dimensional condensed matter physicsProperties of nanostructured, ultrasmall electronic systemsMesoscopic physics and quantum transportPhysics of 2D ele...

  3. Peroxidases in nanostructures

    Directory of Open Access Journals (Sweden)

    Ana Maria eCarmona-Ribeiro

    2015-09-01

    Full Text Available Peroxidases are enzymes catalyzing redox reactions that cleave peroxides. Their active redox centers have heme, cysteine thiols, selenium, manganese and other chemical moieties. Peroxidases and their mimetic systems have several technological and biomedical applications such as environment protection, energy production, bioremediation, sensors and immunoassays design and drug delivery devices. The combination of peroxidases or systems with peroxidase-like activity with nanostructures such as nanoparticles, nanotubes, thin films, liposomes, micelles, nanoflowers, nanorods and others is often an efficient strategy to improve catalytic activity, targeting and reusability.

  4. Chiral silicon nanostructures

    International Nuclear Information System (INIS)

    Schubert, E.; Fahlteich, J.; Hoeche, Th.; Wagner, G.; Rauschenbach, B.

    2006-01-01

    Glancing angle ion beam assisted deposition is used for the growth of amorphous silicon nanospirals onto [0 0 1] silicon substrates in a temperature range from room temperature to 475 deg. C. The nanostructures are post-growth annealed in an argon atmosphere at various temperatures ranging from 400 deg. C to 800 deg. C. Recrystallization of silicon within the persisting nanospiral configuration is demonstrated for annealing temperatures above 800 deg. C. Transmission electron microscopy and Raman spectroscopy are used to characterize the silicon samples prior and after temperature treatment

  5. Ab initio density functional calculations of ferromagnetism in low-dimensional nanostructures: From nanowires to nanorods

    Czech Academy of Sciences Publication Activity Database

    Zelený, Martin; Šob, Mojmír; Hafner, J.

    2009-01-01

    Roč. 79, č. 13 (2009), 134421/1-134421/10 ISSN 1098-0121 R&D Projects: GA AV ČR IAA100100920; GA MŠk OC 147 Institutional research plan: CEZ:AV0Z20410507 Keywords : magnetism of nanostructures * nanowires * iron * nickel Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.475, year: 2009

  6. Application of nanodimensional particles and aluminum hydroxide nanostructures for cancer diagnosis and therapy

    Science.gov (United States)

    Korovin, M. S.; Fomenko, A. N.

    2017-09-01

    Nanoparticles and nanostructured materials are one of the most promising developments for cancer therapy. Gold nanoparticles, magnetic nanoparticles based on iron and its oxides and other metal oxides have been widely used in diagnosis and treatment of cancer. Much less researchers' attention has been paid to nanoparticles and nanostructures based on aluminum oxides and hydroxides as materials for cancer diagnosis and treatment. However, recent investigations have shown promising results regarding these objects. Here, we review the antitumor results obtained with different aluminum oxide/hydroxide nanoparticles and nanostructures.

  7. Nanostructures of Boron, Carbon and Magnesium Diboride for High Temperature Superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Pfefferle, Lisa [Yale Univ., New Haven, CT (United States); Fang, Fang [Yale Univ., New Haven, CT (United States); Iyyamperumal, Eswarmoorthi [Yale Univ., New Haven, CT (United States); Keskar, Gayatri [Yale Univ., New Haven, CT (United States)

    2013-12-23

    Direct fabrication of MgxBy nanostructures is achieved by employing metal (Ni,Mg) incorporated MCM-41 in the Hybrid Physical-Chemical Vapor Deposition (HPCVD) reaction. Different reaction conditions are tested to optimize the fabrication process. TEM analysis shows the fabrication of MgxBy nanostructures starting at the reaction temperature of 600oC, with the yield of the nanostructures increasing with increasing reaction temperature. The as-synthesized MgxBy nanostructures have the diameters in the range of 3-5nm, which do not increase with the reaction temperature consistent with templated synthesis. EELS analysis of the template removed nanostructures confirms the existence of B and Mg with possible contamination of Si and O. NEXAFS and Raman spectroscopy analysis suggested a concentric layer-by-layer MgxBy nanowire/nanotube growth model for our as-synthesized nanostructures. Ni k-edge XAS indicates that the formation of MgNi alloy particles is important for the Vapor-Liquid-Solid (VLS) growth of MgxBy nanostructures with fine diameters, and the presence of Mg vapor not just Mg in the catalyst is crucial for the formation of Ni-Mg clusters. Physical templating by the MCM-41 pores was shown to confine the diameter of the nanostructures. DC magnetization measurements indicate possible superconductive behaviors in the as-synthesized samples.

  8. Creation of Principally New Generation of Switching Technique Elements (Reed Switches) with Nanostructured Contact Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Karabanov S M; Zeltser I A; Maizels R M; Moos E N; Arushanov K A, E-mail: zeltseria@rmcip.ru [Russia, Ryazan, 390027, Novaya Str., 51B, Ryazan Metal Ceramics Instrumentation Plant JSC (Russian Federation)

    2011-04-01

    The cycle of activities of the creation of principally new generation of reed switches with nanostructured contact surfaces was implemented. Experimental justification of the opportunity of reed switches creation with modified contact surface was given (instead of precious metals-based galvanic coating). Principally new technological process of modification of magnetically operated contacts contacting surfaces was developed, based on the usage of the ion-plasma methods of nanolayers and nanostructures forming having specified contact features.

  9. Irradiation-Induced Nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Birtcher, R.C.; Ewing, R.C.; Matzke, Hj.; Meldrum, A.; Newcomer, P.P.; Wang, L.M.; Wang, S.X.; Weber, W.J.

    1999-08-09

    This paper summarizes the results of the studies of the irradiation-induced formation of nanostructures, where the injected interstitials from the source of irradiation are not major components of the nanophase. This phenomena has been observed by in situ transmission electron microscopy (TEM) in a number of intermetallic compounds and ceramics during high-energy electron or ion irradiations when the ions completely penetrate through the specimen. Beginning with single crystals, electron or ion irradiation in a certain temperature range may result in nanostructures composed of amorphous domains and nanocrystals with either the original composition and crystal structure or new nanophases formed by decomposition of the target material. The phenomenon has also been observed in natural materials which have suffered irradiation from the decay of constituent radioactive elements and in nuclear reactor fuels which have been irradiated by fission neutrons and other fission products. The mechanisms involved in the process of this nanophase formation are discussed in terms of the evolution of displacement cascades, radiation-induced defect accumulation, radiation-induced segregation and phase decomposition, as well as the competition between irradiation-induced amorphization and recrystallization.

  10. Nanostructures by ion beams

    Science.gov (United States)

    Schmidt, B.

    Ion beam techniques, including conventional broad beam ion implantation, ion beam synthesis and ion irradiation of thin layers, as well as local ion implantation with fine-focused ion beams have been applied in different fields of micro- and nanotechnology. The ion beam synthesis of nanoparticles in high-dose ion-implanted solids is explained as phase separation of nanostructures from a super-saturated solid state through precipitation and Ostwald ripening during subsequent thermal treatment of the ion-implanted samples. A special topic will be addressed to self-organization processes of nanoparticles during ion irradiation of flat and curved solid-state interfaces. As an example of silicon nanocrystal application, the fabrication of silicon nanocrystal non-volatile memories will be described. Finally, the fabrication possibilities of nanostructures, such as nanowires and chains of nanoparticles (e.g. CoSi2), by ion beam synthesis using a focused Co+ ion beam will be demonstrated and possible applications will be mentioned.

  11. Fabrication of nanowires and nanostructures

    DEFF Research Database (Denmark)

    Mátéfi-Tempfli, Stefan; Mátéfi-Tempfli, M.; Piraux, L.

    2009-01-01

    We report on different approaches that we have adopted and developed for the fabrication of nanowires and nanostructures. Methods based on template synthesis and on self organization seem to be the most promising for the fabrication of nanomaterials and nanostructures due to their easiness and low...... cost. The development of a supported nanoporous alumina template and the possibility of using this template to combine electrochemical synthesis with lithographic methods open new ways for the fabrication of complex nanostructures. The numerous advantages of the supported template and its compatibility...

  12. Ultraflexible nanostructures and implications for future nanorobots

    Science.gov (United States)

    Cohn, Robert W.; Panchapakesan, Balaji

    2016-05-01

    Several high aspect ratio nanostructures have been made by capillary force directed self-assembly including polymeric nanofiber air-bridges, trampoline-like membranes, microsphere-beaded nanofibers, and intermetallic nanoneedles. Arrays of polymer air-bridges form in seconds by simply hand brushing a bead of polymeric liquid over an array of micropillars. The domination of capillary force that is thinning unstable capillary bridges leads to uniform arrays of nanofiber air-bridges. Similarly, arrays of vertically oriented Ag2Ga nanoneedles have been formed by dipping silvercoated arrays of pyramidal silicon into melted gallium. Force-displacement measurements of these structures are presented. These nanostructures, especially when compressively or torsionally buckled, have extremely low stiffnesses, motion due to thermal fluctuations that is relatively easily detected, and the ability to move great distances for very small changes in applied force. Nanofibers with bead-on-a-string structure, where the beads are micron diameter and loaded with magnetic iron oxide (maghemite), are shown to be simply viewable under optical microscopes, have micronewton/ m stiffness, and have ultralow torsional stiffnesses enabling the bead to be rotated numerous revolutions without breaking. Combination of these high aspect ratio structures with stretched elastomers offer interesting possibilities for robotic actuation and locomotion. Polydimethylsiloxane loaded with nanomaterials, e.g. nanotubes, graphene or MoS2, can be efficiently heated with directed light. Heating produces considerable force through the thermoelastic effect, and this force can be used for continuous translation or to trigger reversible elastic buckling of the nanostructures. The remote stimulation of motion with light provides a possible mechanism for producing cooperative behavior between swarms of semiautonomous nanorobots.

  13. Quantum theory of terahertz conductivity of semiconductor nanostructures

    Czech Academy of Sciences Publication Activity Database

    Ostatnický, T.; Pushkarev, Vladimir; Němec, Hynek; Kužel, Petr

    2018-01-01

    Roč. 97, č. 8 (2018), s. 1-8, č. článku 085426. ISSN 2469-9950 R&D Projects: GA ČR GA17-03662S EU Projects: European Commission(XE) 607521 - NOTEDEV Institutional support: RVO:68378271 Keywords : nanostructures * nanoparticles * terahertz conductivity * quantum theory * linear response Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.836, year: 2016

  14. Radiation emission from wrinkled SiGe/SiGe nanostructure

    Czech Academy of Sciences Publication Activity Database

    Fedorchenko, Alexander I.; Cheng, H. H.; Sun, G.; Soref, R. A.

    2010-01-01

    Roč. 96, č. 11 (2010), s. 113104-113107 ISSN 0003-6951 Institutional research plan: CEZ:AV0Z20760514 Keywords : SiGe wrinkled nanostructures * si-based optical emitter * synchrotron radiation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.820, year: 2010 http://apl.aip.org/resource/1/applab/v96/i11/p113104_s1?isAuthorized=no

  15. Spectroscopy and Biosensing with Optically Resonant Dielectric Nanostructures

    OpenAIRE

    Krasnok, Alex; Caldarola, Martin; Bonod, Nicolas; Alú, Andrea

    2017-01-01

    Resonant dielectric nanoparticles (RDNs) made of materials with large positive dielectric permittivity, such as Si, GaP, GaAs, have become a powerful platform for modern light science, enabling various fascinating applications in nanophotonics and quantum optics. In addition to light localization at the nanoscale, dielectric nanostructures provide electric and magnetic resonant responses throughout the visible and infrared spectrum, low dissipative losses and optical heating, low doping effec...

  16. Electrons in Nanostructures

    DEFF Research Database (Denmark)

    Flindt, Christian

    2007-01-01

    in the possibilities o®ered by the quantum mechanical behavior of electrons when it comes to informa- tion processing. This branch of research is also concerned with fundamental questions in physics. Besides an introduction to the above-mentioned subjects, the thesis con- tains a number of contributions to the ¯elds...... of coherent electron manip- ulation and the statistical description of electron transport through nano- devices. The physics of the electrons are described with a combination of numerical methods, developed and applied in the thesis, and more analytical approaches, which are also discussed. The thesis......-based communication. The statistical description of electron transport through nanostructures is based on rate equations, and the primary contribution of the thesis in that respect is the development of a method that allows for the calculation of the distribution of electrons passing through a device. The method...

  17. Critical sizes and critical characteristics of nanoclusters, nanostructures and nanomaterials

    International Nuclear Information System (INIS)

    Suzdalev, I.P.

    2005-01-01

    Full text: Critical sizes and characteristics of nanoclusters and nanostructures are introduced as the parameters of nanosystems and nanomaterials. The next critical characteristics are considered: atomic and electronic 'magic number', critical size of cluster nucleation, critical size of melting-freezing of cluster, critical size of quantum (laser) radiation, critical sizes for the single electron conductivity, critical energy and magnetic field for the magnetic tunneling, critical cluster sizes for the giant magnetic resistance, critical size of the first order magnetic phase transition. The critical characteristics are estimated by thermodynamic approaches, by Moessbauer spectroscopy, AFM, heat capacity, SQUID magnetometry and other technique, The influence of cluster-cluster interactions, cluster-matrix interactions and cluster defects on cluster atomic dynamics, cluster melting, cluster critical sizes, Curie or Neel points and the character of magnetic phase transitions were investigated. The applications of critical size and critical characteristic parameters for the nanomaterial characterization are considered

  18. Nanostructured Photovoltaics for Space Power

    Data.gov (United States)

    National Aeronautics and Space Administration — The NASA NSTRF proposal entitled Nanostructured Photovoltaics for Space Power is targeted towards research to improve the current state of the art photovoltaic...

  19. Quantum optics with semiconductor nanostructures

    CERN Document Server

    Jahnke, Frank

    2012-01-01

    A guide to the theory, application and potential of semiconductor nanostructures in the exploration of quantum optics. It offers an overview of resonance fluorescence emission.$bAn understanding of the interaction between light and matter on a quantum level is of fundamental interest and has many applications in optical technologies. The quantum nature of the interaction has recently attracted great attention for applications of semiconductor nanostructures in quantum information processing. Quantum optics with semiconductor nanostructures is a key guide to the theory, experimental realisation, and future potential of semiconductor nanostructures in the exploration of quantum optics. Part one provides a comprehensive overview of single quantum dot systems, beginning with a look at resonance fluorescence emission. Quantum optics with single quantum dots in photonic crystal and micro cavities are explored in detail, before part two goes on to review nanolasers with quantum dot emitters. Light-matter interaction...

  20. Nanostructured Materials for Renewable Energy

    Energy Technology Data Exchange (ETDEWEB)

    None

    2009-11-01

    This factsheet describes a research project whose overall objective is to advance the fundamental understanding of novel photoelectronic organic device structures integrated with inorganic nanostructures, while also expanding the general field of nanomaterials for renewable energy devices and systems.

  1. Quantum Nanostructures by Droplet Epitaxy

    OpenAIRE

    Somsak Panyakeow

    2009-01-01

    Droplet epitaxy is an alternative growth technique for several quantum nanostructures. Indium droplets are distributed randomly on GaAs substrates at low temperatures (120-350'C). Under background pressure of group V elements, Arsenic and Phosphorous, InAs and InP nanostructures are created. Quantum rings with isotropic shape are obtained at low temperature range. When the growth thickness is increased, quantum rings are transformed to quantum dot rings. At high temperature range, anisotropic...

  2. Nanostructures via DNA scaffold metallization

    OpenAIRE

    Ning, C.; Zinchenko, A.; Baigl, D.; Pyshkina, O.; Sergeyev, V.; Endo, Kazunaka; Yoshikawa, K.

    2005-01-01

    The critical role of polymers in process of noble metals nanostructures formation is well known, however, the use of DNA chain template in this process is yet largely unknown. In this study we demonstrate different ways of silver deposition on DNA template and report the influence of silver nanostructures formation on DNA conformational state. Metallization of DNA chain proceeds by two different scenarios depending on DNA conformation. If DNA chain is unfolded (elongated) chain, silver reduct...

  3. A solution phase fabrication of magnetic nanoparticles encapsulated in carbon

    International Nuclear Information System (INIS)

    Wei Xianwen; Zhu Guoxing; Xia Chuanjun; Ye Yin

    2006-01-01

    To avoid high energy consumption, intensive use of hardware and high cost in the manufacture of nanoparticles encapsulated in carbon, a simple, efficient and economical solution-phase method for the fabrication of FeNi at C nanostructures has been explored. The reaction to the magnetic metal at C structures here is conducted at a relatively low temperature (160 deg. C) and this strategy can be transferred to prepare other transition metal at C core-shell nanostructures. The saturation magnetization of metal in metal at C nanostructures is similar to those of the corresponding buck metals. Magnetic metal at C nanostructures with magnetic metal nanoparticles inside and a functionalized carbon surface outside may not only provide the opportunity to tailor the magnetic properties for magnetic storage devices and therapeutics but also make possible the loading of other functional molecules (e.g. enzymes, antigens) for clinic diagnostics, molecular biology, bioengineering, and catalysis

  4. Nanostructured porous silicon-mediated drug delivery.

    Science.gov (United States)

    Martín-Palma, Raúl J; Hernández-Montelongo, Jacobo; Torres-Costa, Vicente; Manso-Silván, Miguel; Muñoz-Noval, Álvaro

    2014-08-01

    The particular properties of nanostructured porous silicon (nanoPS) make it an attractive material for controlled and localized release of therapeutics within the body, aiming at increased efficacy and reduced risks of potential side effects. Since this is a rapidly evolving field as a consequence of the number of research groups involved, a critical review of the state of the art is necessary. In this work, the most promising and successful applications of nanoPS in the field of drug delivery are reviewed and discussed. Two key issues such as drug loading and release are also analyzed in detail. The development of multifunctional (hybrid) systems, aiming at imparting additional functionalities to the nanoPS particles such as luminescence, magnetic response and/or plasmonic effects (allowing simultaneous tracking and guiding), is also examined. Nanostructured materials based on silicon are promising platforms for pharmaceutical applications given their ability to degrade and low toxicity. However, a very limited number of clinical applications have been demonstrated so far.

  5. Synthesis of vertically aligned metal oxide nanostructures

    KAUST Repository

    Roqan, Iman S.

    2016-03-03

    Metal oxide nanostructure and methods of making metal oxide nanostructures are provided. The metal oxide nanostructures can be 1 -dimensional nanostructures such as nanowires, nanofibers, or nanotubes. The metal oxide nanostructures can be doped or undoped metal oxides. The metal oxide nanostructures can be deposited onto a variety of substrates. The deposition can be performed without high pressures and without the need for seed catalysts on the substrate. The deposition can be performed by laser ablation of a target including a metal oxide and, optionally, a dopant. In some embodiments zinc oxide nanostructures are deposited onto a substrate by pulsed laser deposition of a zinc oxide target using an excimer laser emitting UV radiation. The zinc oxide nanostructure can be doped with a rare earth metal such as gadolinium. The metal oxide nanostructures can be used in many devices including light-emitting diodes and solar cells.

  6. Mechanical design of DNA nanostructures

    Science.gov (United States)

    Castro, Carlos E.; Su, Hai-Jun; Marras, Alexander E.; Zhou, Lifeng; Johnson, Joshua

    2015-03-01

    Structural DNA nanotechnology is a rapidly emerging field that has demonstrated great potential for applications such as single molecule sensing, drug delivery, and templating molecular components. As the applications of DNA nanotechnology expand, a consideration of their mechanical behavior is becoming essential to understand how these structures will respond to physical interactions. This review considers three major avenues of recent progress in this area: (1) measuring and designing mechanical properties of DNA nanostructures, (2) designing complex nanostructures based on imposed mechanical stresses, and (3) designing and controlling structurally dynamic nanostructures. This work has laid the foundation for mechanically active nanomachines that can generate, transmit, and respond to physical cues in molecular systems.Structural DNA nanotechnology is a rapidly emerging field that has demonstrated great potential for applications such as single molecule sensing, drug delivery, and templating molecular components. As the applications of DNA nanotechnology expand, a consideration of their mechanical behavior is becoming essential to understand how these structures will respond to physical interactions. This review considers three major avenues of recent progress in this area: (1) measuring and designing mechanical properties of DNA nanostructures, (2) designing complex nanostructures based on imposed mechanical stresses, and (3) designing and controlling structurally dynamic nanostructures. This work has laid the foundation for mechanically active nanomachines that can generate, transmit, and respond to physical cues in molecular systems. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07153k

  7. Hybrid nanostructures: synthesis, morphology and functional properties

    International Nuclear Information System (INIS)

    Povolotskaya, A V; Povolotskiy, A V; Manshina, A A

    2015-01-01

    Hybrid nanostructures representing combinations of different materials and possessing properties that are absent in separate components forming the hybrid are discussed. Particular attention is given to hybrid structures containing plasmonic and magnetic nanoparticles, methods of their synthesis and the relationship between the composition, structure and properties. The functional features of the hybrid nanomaterials of various morphology (with core–shell structures, with encapsulated metal nanoparticles and with metal nanoparticles on the surface) are considered. The unique properties of these hybrid materials are demonstrated, which are of interest for solving problems of catalysis and photocatalysis, detecting impurities in various media, in vivo visualization, bioanalysis, as well as for the design of optical labels and multifunctional diagnostic nanoplatforms. The bibliography includes 182 references

  8. The nanostructure problem

    International Nuclear Information System (INIS)

    Billinge, S.

    2010-01-01

    Diffraction techniques are making progress in tackling the difficult problem of solving the structures of nanoparticles and nanoscale materials. The great gift of x-ray crystallography has made us almost complacent in our ability to locate the three-dimensional coordinates of atoms in a crystal with a precision of around 10 -4 nm. However, the powerful methods of crystallography break down for structures in which order only extends over a few nanometers. In fact, as we near the one hundred year mark since the birth of crystallography, we face a resilient frontier in condensed matter physics: our inability to routinely and robustly determine the structure of complex nanostructured and amorphous materials. Knowing the structure and arrangement of atoms in a solid is so fundamental to understanding its properties that the topic routinely occupies the early chapters of every solid-state physics textbook. Yet what has become clear with the emergence of nanotechnology is that diffraction data alone may not be enough to uniquely solve the structure of nanomaterials. As part of a growing effort to incorporate the results of other techniques to constrain x-ray refinements - a method called 'complex modeling' which is a simple but elegant approach for combining information from spectroscopy with diffraction data to solve the structure of several amorphous and nanostructured materials. Crystallography just works, so we rarely question how and why this is so, yet understanding the physics of diffraction can be very helpful as we consider the nanostructure problem. The relationship between the electron density distribution in three dimensions (i.e., the crystal structure) and an x-ray diffraction pattern is well established: the measured intensity distribution in reciprocal space is the square of the Fourier transform of the autocorrelation function of the electron density distribution ρ(r). The fact that we get the autocorrelation function (rather than just the density

  9. Multiscale modelling of nanostructures

    International Nuclear Information System (INIS)

    Vvedensky, Dimitri D

    2004-01-01

    Most materials phenomena are manifestations of processes that are operative over a vast range of length and time scales. A complete understanding of the behaviour of materials thereby requires theoretical and computational tools that span the atomic-scale detail of first-principles methods and the more coarse-grained description provided by continuum equations. Recent efforts have focused on combining traditional methodologies-density functional theory, molecular dynamics, Monte Carlo methods and continuum descriptions-within a unified multiscale framework. This review covers the techniques that have been developed to model various aspects of materials behaviour with the ultimate aim of systematically coupling the atomistic to the continuum descriptions. The approaches described typically have been motivated by particular applications but can often be applied in wider contexts. The self-assembly of quantum dot ensembles will be used as a case study for the issues that arise and the methods used for all nanostructures. Although quantum dots can be obtained with all the standard growth methods and for a variety of material systems, their appearance is a quite selective process, involving the competition between equilibrium and kinetic effects, and the interplay between atomistic and long-range interactions. Most theoretical models have addressed particular aspects of the ordering kinetics of quantum dot ensembles, with far fewer attempts at a comprehensive synthesis of this inherently multiscale phenomenon. We conclude with an assessment of the current status of multiscale modelling strategies and highlight the main outstanding issues. (topical review)

  10. Phonon engineering for nanostructures.

    Energy Technology Data Exchange (ETDEWEB)

    Aubry, Sylvie (Stanford University); Friedmann, Thomas Aquinas; Sullivan, John Patrick; Peebles, Diane Elaine; Hurley, David H. (Idaho National Laboratory); Shinde, Subhash L.; Piekos, Edward Stanley; Emerson, John Allen

    2010-01-01

    Understanding the physics of phonon transport at small length scales is increasingly important for basic research in nanoelectronics, optoelectronics, nanomechanics, and thermoelectrics. We conducted several studies to develop an understanding of phonon behavior in very small structures. This report describes the modeling, experimental, and fabrication activities used to explore phonon transport across and along material interfaces and through nanopatterned structures. Toward the understanding of phonon transport across interfaces, we computed the Kapitza conductance for {Sigma}29(001) and {Sigma}3(111) interfaces in silicon, fabricated the interfaces in single-crystal silicon substrates, and used picosecond laser pulses to image the thermal waves crossing the interfaces. Toward the understanding of phonon transport along interfaces, we designed and fabricated a unique differential test structure that can measure the proportion of specular to diffuse thermal phonon scattering from silicon surfaces. Phonon-scale simulation of the test ligaments, as well as continuum scale modeling of the complete experiment, confirmed its sensitivity to surface scattering. To further our understanding of phonon transport through nanostructures, we fabricated microscale-patterned structures in diamond thin films.

  11. Photoresponsive nanostructured membranes

    KAUST Repository

    Madhavan, Poornima

    2016-07-26

    The perspective of adding stimuli-response to isoporous membranes stimulates the development of separation devices with pores, which would open or close under control of environment chemical composition, temperature or exposure to light. Changes in pH and temperature have been previously investigated. In this work, we demonstrate for the first time the preparation of photoresponsive isoporous membranes, applying self-assembly non-solvent induced phase separation to a new light responsive block copolymer. First, we optimized the membrane formation by using poly(styrene-b-anthracene methyl methacrylate-b-methylmethacrylate) (PS-b-PAnMMA-b-PMMA) copolymer, identifying the most suitable solvent, copolymer block length, and other parameters. The obtained final triblock copolymer membrane morphologies were characterized using atomic force and electron microscopy. The microscopic analysis reveals that the PS-b-PAnMMA-b-PMMA copolymer can form both lamellar and ordered hexagonal nanoporous structures on the membrane top layer in appropriate solvent compositions. The nanostructured membrane emits fluorescence due to the presence of the anthracene mid-block. On irradiation of light the PS-b-PAnMMA-b-PMMA copolymer membranes has an additional stimuli response. The anthracene group undergoes conformational changes by forming [4 + 4] cycloadducts and this alters the membrane\\'s water flux and solute retention. © 2016 The Royal Society of Chemistry.

  12. Nanostructured Basaltfiberconcrete Exploitational Characteristics

    Science.gov (United States)

    Saraykina, K. A.; Shamanov, V. A.

    2017-11-01

    The article demonstrates that the mass use of basalt fiber concrete (BFC) is constrained by insufficient study of their durability and serviceability in a variety of environments. This research is aimed at the study of the basalt fiber corrosion processes in the cement stone of BFC, the control of the new products structure formation in order to protect the reinforcing fiber from alkaline destruction and thereby improve the exploitational characteristics of the composite. The research result revealed that the modification of basaltfiber concrete by the dispersion of MWNTs contributes to the directional formation of new products in the cement matrix. The HAM additive in basaltfiberconcrete provides for the binding of portlandite to low-basic calcium hydroaluminosilicates, thus reducing the aggressive effect of the cement environment on the reinforcing fibers properties. The complex modification of BFC with nanostructured additives provides for an increase in its durability and exploitational properties (strength, frost resistance and water resistance) due to basalt fiber protection from alkali corrosion on account of the compacting of the contact zone “basalt fiber - cement stone” and designing of the new products structure and morphology of cement matrix over the fiber surface.

  13. Photoresponsive nanostructured membranes

    KAUST Repository

    Madhavan, Poornima; Sutisna, Burhannudin; Sougrat, Rachid; Nunes, Suzana Pereira

    2016-01-01

    The perspective of adding stimuli-response to isoporous membranes stimulates the development of separation devices with pores, which would open or close under control of environment chemical composition, temperature or exposure to light. Changes in pH and temperature have been previously investigated. In this work, we demonstrate for the first time the preparation of photoresponsive isoporous membranes, applying self-assembly non-solvent induced phase separation to a new light responsive block copolymer. First, we optimized the membrane formation by using poly(styrene-b-anthracene methyl methacrylate-b-methylmethacrylate) (PS-b-PAnMMA-b-PMMA) copolymer, identifying the most suitable solvent, copolymer block length, and other parameters. The obtained final triblock copolymer membrane morphologies were characterized using atomic force and electron microscopy. The microscopic analysis reveals that the PS-b-PAnMMA-b-PMMA copolymer can form both lamellar and ordered hexagonal nanoporous structures on the membrane top layer in appropriate solvent compositions. The nanostructured membrane emits fluorescence due to the presence of the anthracene mid-block. On irradiation of light the PS-b-PAnMMA-b-PMMA copolymer membranes has an additional stimuli response. The anthracene group undergoes conformational changes by forming [4 + 4] cycloadducts and this alters the membrane's water flux and solute retention. © 2016 The Royal Society of Chemistry.

  14. Nanostructured graphene for spintronics

    DEFF Research Database (Denmark)

    Gregersen, Søren Schou; Power, Stephen; Jauho, Antti-Pekka

    2017-01-01

    Zigzag edges of the honeycomb structure of graphene exhibit magnetic polarization, making them attractive as building blocks for spintronic devices. Here, we show that devices with zigzag-edged triangular antidots perform essential spintronic functionalities, such as spatial spin splitting or spin...

  15. Effect of oxygen annealing on magnetic performance of (Nd,Eu,Gd)Ba.sub.2./sub.Cu.sub.3./sub.O.sub.y./sub. with a lamelar pinning nanostructure

    Czech Academy of Sciences Publication Activity Database

    Jirsa, Miloš; Rameš, Michal; Muralidhar, M.; Diko, P.

    2009-01-01

    Roč. 153, č. 1 (2009), 012015/1-012015/15 ISSN 1742-6588. [International Conference On Superconductivity and Magnetism (ICSM2008). Side-Antalya, 25.08.2008–29.08.2008] R&D Projects: GA ČR GA202/08/0722 Institutional research plan: CEZ:AV0Z10100520 Keywords : (Nd,Eu,Gd)Ba 2 Cu 3 O y * annealing effect * pinning * critical currents Subject RIV: BM - Solid Matter Physics ; Magnetism

  16. Two-Dimensional Programmable Manipulation of Magnetic Nanoparticles on-Chip

    DEFF Research Database (Denmark)

    Sarella, Anandakumar; Torti, Andrea; Donolato, Marco

    2014-01-01

    A novel device is designed for on-chip selective trap and two-dimensional remote manipulation of single and multiple fluid-borne magnetic particles using field controlled magnetic domain walls in circular nanostructures. The combination of different ring-shaped nanostructures and field sequences ...

  17. Nanostructures for Organic Solar Cells

    DEFF Research Database (Denmark)

    Goszczak, Arkadiusz Jarosław

    2016-01-01

    The experimental work in this thesis is focused on the fabrication of nanostructures that can be implemented in organic solar cell (OSC) architecture for enhancement of the device performance. Solar devices made from organic material are gaining increased attention, compared to their inorganic...... counterparts, due to the promising advantages, such as transparency, flexibility, ease of processing etc. But their efficiencies cannot be compared to the inorganic ones. Boosting the efficiency of OSCs by nanopatterning has thus been puzzling many researchers within the past years. Therefore various methods...... have been proposed to be used for developing efficient nanostructures for OSC devices such as, plasmonic structures, nanowires (NWs), gratings, nanorods etc. The nanostructuring methods applied though, do not offer the possibility of a cheap, rapid, reproducible and scalable fabrication. It is the aim...

  18. Nanostructuring of Solar Cell Surfaces

    DEFF Research Database (Denmark)

    Davidsen, Rasmus Schmidt; Schmidt, Michael Stenbæk

    Solar energy is by far the most abundant renewable energy source available, but the levelized cost of solar energy is still not competitive with that of fossil fuels. Therefore there is a need to improve the power conversion effciency of solar cells without adding to the production cost. The main...... objective of this PhD thesis is to develop nanostructured silicon (Si) solar cells with higher power conversion efficiency using only scalable and cost-efficient production methods. The nanostructures, known as 'black silicon', are fabricated by single-step, maskless reactive ion etching and used as front...... texturing of different Si solar cells. Theoretically the nanostructure topology may be described as a graded refractive index in a mean-field approximation between air and Si. The optical properties of the developed black Si were simulated and experimentally measured. Total AM1.5G-weighted average...

  19. Quantum Nanostructures by Droplet Epitaxy

    Directory of Open Access Journals (Sweden)

    Somsak Panyakeow

    2009-02-01

    Full Text Available Droplet epitaxy is an alternative growth technique for several quantum nanostructures. Indium droplets are distributed randomly on GaAs substrates at low temperatures (120-350'C. Under background pressure of group V elements, Arsenic and Phosphorous, InAs and InP nanostructures are created. Quantum rings with isotropic shape are obtained at low temperature range. When the growth thickness is increased, quantum rings are transformed to quantum dot rings. At high temperature range, anisotropic strain gives rise to quantum rings with square holes and non-uniform ring stripe. Regrowth of quantum dots on these anisotropic quantum rings, Quadra-Quantum Dots (QQDs could be realized. Potential applications of these quantum nanostructures are also discussed.

  20. Interfacing nanostructures to biological cells

    Science.gov (United States)

    Chen, Xing; Bertozzi, Carolyn R.; Zettl, Alexander K.

    2012-09-04

    Disclosed herein are methods and materials by which nanostructures such as carbon nanotubes, nanorods, etc. are bound to lectins and/or polysaccharides and prepared for administration to cells. Also disclosed are complexes comprising glycosylated nanostructures, which bind selectively to cells expressing glycosylated surface molecules recognized by the lectin. Exemplified is a complex comprising a carbon nanotube functionalized with a lipid-like alkane, linked to a polymer bearing repeated .alpha.-N-acetylgalactosamine sugar groups. This complex is shown to selectively adhere to the surface of living cells, without toxicity. In the exemplified embodiment, adherence is mediated by a multivalent lectin, which binds both to the cells and the .alpha.-N-acetylgalactosamine groups on the nanostructure.

  1. Zinc stannate nanostructures: hydrothermal synthesis

    International Nuclear Information System (INIS)

    Baruah, Sunandan; Dutta, Joydeep

    2011-01-01

    Nanostructured binary semiconducting metal oxides have received much attention in the last decade owing to their unique properties rendering them suitable for a wide range of applications. In the quest to further improve the physical and chemical properties, an interest in ternary complex oxides has become noticeable in recent times. Zinc stannate or zinc tin oxide (ZTO) is a class of ternary oxides that are known for their stable properties under extreme conditions, higher electron mobility compared to its binary counterparts and other interesting optical properties. The material is thus ideal for applications from solar cells and sensors to photocatalysts. Among the different methods of synthesizing ZTO nanostructures, the hydrothermal method is an attractive green process that is carried out at low temperatures. In this review, we summarize the conditions leading to the growth of different ZTO nanostructures using the hydrothermal method and delve into a few of its applications reported in the literature. (topical review)

  2. Nanostructures for protein drug delivery.

    Science.gov (United States)

    Pachioni-Vasconcelos, Juliana de Almeida; Lopes, André Moreni; Apolinário, Alexsandra Conceição; Valenzuela-Oses, Johanna Karina; Costa, Juliana Souza Ribeiro; Nascimento, Laura de Oliveira; Pessoa, Adalberto; Barbosa, Leandro Ramos Souza; Rangel-Yagui, Carlota de Oliveira

    2016-02-01

    Use of nanoscale devices as carriers for drugs and imaging agents has been extensively investigated and successful examples can already be found in therapy. In parallel, recombinant DNA technology together with molecular biology has opened up numerous possibilities for the large-scale production of many proteins of pharmaceutical interest, reflecting in the exponentially growing number of drugs of biotechnological origin. When we consider protein drugs, however, there are specific criteria to take into account to select adequate nanostructured systems as drug carriers. In this review, we highlight the main features, advantages, drawbacks and recent developments of nanostructures for protein encapsulation, such as nanoemulsions, liposomes, polymersomes, single-protein nanocapsules and hydrogel nanoparticles. We also discuss the importance of nanoparticle stabilization, as well as future opportunities and challenges in nanostructures for protein drug delivery.

  3. Nanostructured silicon for thermoelectric

    Science.gov (United States)

    Stranz, A.; Kähler, J.; Waag, A.; Peiner, E.

    2011-06-01

    Thermoelectric modules convert thermal energy into electrical energy and vice versa. At present bismuth telluride is the most widely commercial used material for thermoelectric energy conversion. There are many applications where bismuth telluride modules are installed, mainly for refrigeration. However, bismuth telluride as material for energy generation in large scale has some disadvantages. Its availability is limited, it is hot stable at higher temperatures (>250°C) and manufacturing cost is relatively high. An alternative material for energy conversion in the future could be silicon. The technological processing of silicon is well advanced due to the rapid development of microelectronics in recent years. Silicon is largely available and environmentally friendly. The operating temperature of silicon thermoelectric generators can be much higher than of bismuth telluride. Today silicon is rarely used as a thermoelectric material because of its high thermal conductivity. In order to use silicon as an efficient thermoelectric material, it is necessary to reduce its thermal conductivity, while maintaining high electrical conductivity and high Seebeck coefficient. This can be done by nanostructuring into arrays of pillars. Fabrication of silicon pillars using ICP-cryogenic dry etching (Inductive Coupled Plasma) will be described. Their uniform height of the pillars allows simultaneous connecting of all pillars of an array. The pillars have diameters down to 180 nm and their height was selected between 1 micron and 10 microns. Measurement of electrical resistance of single silicon pillars will be presented which is done in a scanning electron microscope (SEM) equipped with nanomanipulators. Furthermore, measurement of thermal conductivity of single pillars with different diameters using the 3ω method will be shown.

  4. Semi-automated quantification of living cells with internalized nanostructures

    KAUST Repository

    Margineanu, Michael B.

    2016-01-15

    Background Nanostructures fabricated by different methods have become increasingly important for various applications in biology and medicine, such as agents for medical imaging or cancer therapy. In order to understand their interaction with living cells and their internalization kinetics, several attempts have been made in tagging them. Although methods have been developed to measure the number of nanostructures internalized by the cells, there are only few approaches aimed to measure the number of cells that internalize the nanostructures, and they are usually limited to fixed-cell studies. Flow cytometry can be used for live-cell assays on large populations of cells, however it is a single time point measurement, and does not include any information about cell morphology. To date many of the observations made on internalization events are limited to few time points and cells. Results In this study, we present a method for quantifying cells with internalized magnetic nanowires (NWs). A machine learning-based computational framework, CellCognition, is adapted and used to classify cells with internalized and no internalized NWs, labeled with the fluorogenic pH-dependent dye pHrodo™ Red, and subsequently to determine the percentage of cells with internalized NWs at different time points. In a “proof-of-concept”, we performed a study on human colon carcinoma HCT 116 cells and human epithelial cervical cancer HeLa cells interacting with iron (Fe) and nickel (Ni) NWs. Conclusions This study reports a novel method for the quantification of cells that internalize a specific type of nanostructures. This approach is suitable for high-throughput and real-time data analysis and has the potential to be used to study the interaction of different types of nanostructures in live-cell assays.

  5. Massively parallel fabrication of repetitive nanostructures: nanolithography for nanoarrays

    International Nuclear Information System (INIS)

    Luttge, Regina

    2009-01-01

    This topical review provides an overview of nanolithographic techniques for nanoarrays. Using patterning techniques such as lithography, normally we aim for a higher order architecture similarly to functional systems in nature. Inspired by the wealth of complexity in nature, these architectures are translated into technical devices, for example, found in integrated circuitry or other systems in which structural elements work as discrete building blocks in microdevices. Ordered artificial nanostructures (arrays of pillars, holes and wires) have shown particular properties and bring about the opportunity to modify and tune the device operation. Moreover, these nanostructures deliver new applications, for example, the nanoscale control of spin direction within a nanomagnet. Subsequently, we can look for applications where this unique property of the smallest manufactured element is repetitively used such as, for example with respect to spin, in nanopatterned magnetic media for data storage. These nanostructures are generally called nanoarrays. Most of these applications require massively parallel produced nanopatterns which can be directly realized by laser interference (areas up to 4 cm 2 are easily achieved with a Lloyd's mirror set-up). In this topical review we will further highlight the application of laser interference as a tool for nanofabrication, its limitations and ultimate advantages towards a variety of devices including nanostructuring for photonic crystal devices, high resolution patterned media and surface modifications of medical implants. The unique properties of nanostructured surfaces have also found applications in biomedical nanoarrays used either for diagnostic or functional assays including catalytic reactions on chip. Bio-inspired templated nanoarrays will be presented in perspective to other massively parallel nanolithography techniques currently discussed in the scientific literature. (topical review)

  6. Diffusion slowdown in the nanostructured liquid Ga-Sn alloy

    International Nuclear Information System (INIS)

    Podorozhkin, Dmitri Y.; Charnaya, Elena V.; Lee, Min Kai; Chang, Lieh-Jeng; Haase, Juergen; Michel, Dieter; Kumzerov, Yurii A.; Fokin, Alexsandr V.

    2015-01-01

    The diffusion of gallium in liquid Ga-Sn alloy embedded into different porous silica matrices was studied by NMR. Spin relaxation was measured for two gallium isotopes, 71 Ga and 69 Ga, at two magnetic fields. Pronounced rise of quadrupole contribution to relaxation was observed for the nanostructured alloy which increased with decreasing the pore size. The correlation time of atomic mobility was evaluated and found to be much larger than in the relevant bulk melt which evidenced a pronounced diffusion slowdown in the Ga-Sn alloy under nanoconfinement. It is shown that the diffusion was slower by a factor of 30 for the alloy within 7 nm pores. The spectral densities of electric field gradients at zero frequency were found to double for the finest pores. The Knight shift was found to decrease but slightly for the nanostructured alloy. (copyright 2015 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Nanostructured Gas Sensors for Health Care: An Overview

    Science.gov (United States)

    Kaushik, Ajeet; Kumar, Rajesh; Jayant, Rahul Dev; Nair, Madhavan

    2015-01-01

    Nanostructured platforms have been utilized for fabrication of small, sensitive and reliable gas sensing devices owing to high functionality, enhanced charge transport and electro-catalytic property. As a result of globalization, rapid, sensitive and selective detection of gases in environment is essential for health care and security. Nonmaterial such as metal, metal oxides, organic polymers, and organic-inorganic hybrid nanocomposites exhibit interesting optical, electrical, magnetic and molecular properties, and hence are found potential gas sensing materials. Morphological, electrical, and optical properties of such nanostructures can be tailored via controlling the precursor concentration and synthesis conditions resulting to achieve desired sensing. This review presents applications of nano-enabling gas sensors to detect gases for environment monitoring. The recent update, challenges, and future vision for commercial applications of such sensor are also described here. PMID:26491544

  8. Vortex ice in nanostructured superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Reichhardt, Charles [Los Alamos National Laboratory; Reichhardt, Cynthia J [Los Alamos National Laboratory; Libal, Andras J [Los Alamos National Laboratory

    2008-01-01

    We demonstrate using numerical simulations of nanostructured superconductors that it is possible to realize vortex ice states that are analogous to square and kagome ice. The system can be brought into a state that obeys either global or local ice rules by applying an external current according to an annealing protocol. We explore the breakdown of the ice rules due to disorder in the nanostructure array and show that in square ice, topological defects appear along grain boundaries, while in kagome ice, individual defects appear. We argue that the vortex system offers significant advantages over other artificial ice systems.

  9. Spin-polarized scanning tunneling microscopy of magnetic nanostructures at the example of bcc-Co/Fe(110), Fe/Mo(110), and copper phthalocyanine/Fe(1110); Spinpolarisierte Rastertunnelmikroskopie magnetischer Nanostrukturen am Beispiel von bcc-Co/Fe(110), Fe/Mo(110) und Kupfer-Phthalocyanin/Fe(110)

    Energy Technology Data Exchange (ETDEWEB)

    Methfessel, Torsten

    2010-12-09

    This thesis provides an introduction into the technique of spin-polarized scanning tunnelling microscopy and spectroscopy as an experimental method for the investigation of magnetic nanostructures. Experimental results for the spin polarized electronic structure depending on the crystal structure of ultrathin Co layers, and depending on the direction of the magnetization for ultrathin Fe layers are presented. High-resolution measurements show the position-dependent spin polarization on a single copper-phthalocyanine molecule deposited on a ferromagnetic surface. Co was deposited by molecular beam epitaxy on the (110) surface of the bodycentered cubic metals Cr and Fe. In contrast to previous reports in the literature only two layers of Co can be stabilized in the body-centered cubic (bcc) structure. The bcc-Co films on the Fe(110) surface show no signs of epitaxial distortions. Thicker layers reconstruct into a closed-packed structure (hcp / fcc). The bcc structure increases the spin-polarization of Co to P=62 % in comparison to hcp-Co (P=45 %). The temperature-dependent spin-reorientation of ultrathin Fe/Mo(110) films was investigated by spin-polarized spectroscopy. A reorientation of the magnetic easy axis from the [110] direction along the surface normal to the in-plane [001] axis is observed at T (13.2{+-}0.5) K. This process can be identified as a discontinuous reorientation transition, revealing two simultaneous minima of the free energy in a certain temperature range. The electronic structure of mono- and double-layer Fe/Mo(110) shows a variation with the reorientation of the magnetic easy axis and with the direction of the magnetization. The investigation of the spin-polarized charge transport through a copper-phthalocyanine molecule on the Fe/Mo(110) surface provides an essential contribution to the understanding of spin-transport at the interface between metal and organic molecule. Due to the interaction with the surface of the metal the HOMO-LUMO energy

  10. Physicochemical and Electrophysical Properties of Metal/Semiconductor Containing Nanostructured Composites

    Science.gov (United States)

    Gerasimov, G. N.; Gromov, V. F.; Trakhtenberg, L. I.

    2018-06-01

    The properties of nanostructured composites based on metal oxides and metal-polymer materials are analyzed, along with ways of preparing them. The effect the interaction between metal and semiconductor nanoparticles has on the conductivity, photoconductivity, catalytic activity, and magnetic, dielectric, and sensor properties of nanocomposites is discussed. It is shown that as a result of this interaction, a material can acquire properties that do not exist in systems of isolated particles. The transfer of electrons between metal particles of different sizes in polymeric matrices leads to specific dielectric losses, and to an increase in the rate and a change in the direction of chemical reactions catalyzed by these particles. The interaction between metal-oxide semiconductor particles results in the electronic and chemical sensitization of sensor effects in nanostructured composite materials. Studies on creating molecular machines (Brownian motors), devices for magnetic recording of information, and high-temperature superconductors based on nanostructured systems are reviewed.

  11. Features of Magnetorefractive Effect in a [CoFe/Cu] n Multilayer Metallic Nanostructure

    Science.gov (United States)

    Yurasov, A. N.; Telegin, A. V.; Bannikova, N. S.; Milyaev, M. A.; Sukhorukov, Yu. P.

    2018-02-01

    The features of magnetorefractive effect (MRE) in metallic multilayer film Ni48Fe12Cr40(50 Å)/[Co90Fe10(14 Å)/Cu(22 Å)]8/Cr(20 Å) nanostructures, which exhibit giant magnetoresistance at room temperature, are investigated experimentally and theoretically. We show that the MRE in these structures reaches 1.5% in an applied magnetic field of 3.5 kOe, in a broad part of the IR region, and can change sign for both transmission and reflection of light. The refraction and extinction coefficients that are calculated for the nanostructures in an external magnetic field are in good agreement with our experimental data. The deduced formulas can be applied to estimating the MRE in multilayer metallic nanostructures.

  12. Modeling of hysteresis in magnetic multidomains

    International Nuclear Information System (INIS)

    Cardelli, E.; Carpentieri, M.; Faba, A.; Finocchio, G.

    2014-01-01

    In this paper, the analysis of multi-domain nanostructures is made by means of numerical approaches. The Landau–Lifshitz–Gilbert LLG equation is used to compute the magnetic hysteresis loops for different alternate scalar polarizations. The data computed are then used to identify the parameters of a phenomenological model, based on the extension of the Preisach model in 2-D. The identification in this case is the evaluation of the size and the position of the hysterons in the H-plane. Each hysteron is associated to a domain of the nanostructure and the assembly of hysterons reproduces with satisfactory accuracy the hysteretic behavior of the nanostructure computed by the LLG equation with an extremely reduced computational time. Some possible relationships between the magnetization nanostructure and the parameters of the hysteron are suggested. These relationship should be used for a “blind” prediction of the magnetization state of much larger magnetic structures, whose computation using the LLG equation is not possible in practice due to the enormous computational time, supposing that magnetic structures with the same aspect ratio exhibit a similar distribution of magnetic domains. The theory is applied here to an example of Permalloy nanostructure

  13. Computer Code for Nanostructure Simulation

    Science.gov (United States)

    Filikhin, Igor; Vlahovic, Branislav

    2009-01-01

    Due to their small size, nanostructures can have stress and thermal gradients that are larger than any macroscopic analogue. These gradients can lead to specific regions that are susceptible to failure via processes such as plastic deformation by dislocation emission, chemical debonding, and interfacial alloying. A program has been developed that rigorously simulates and predicts optoelectronic properties of nanostructures of virtually any geometrical complexity and material composition. It can be used in simulations of energy level structure, wave functions, density of states of spatially configured phonon-coupled electrons, excitons in quantum dots, quantum rings, quantum ring complexes, and more. The code can be used to calculate stress distributions and thermal transport properties for a variety of nanostructures and interfaces, transport and scattering at nanoscale interfaces and surfaces under various stress states, and alloy compositional gradients. The code allows users to perform modeling of charge transport processes through quantum-dot (QD) arrays as functions of inter-dot distance, array order versus disorder, QD orientation, shape, size, and chemical composition for applications in photovoltaics and physical properties of QD-based biochemical sensors. The code can be used to study the hot exciton formation/relation dynamics in arrays of QDs of different shapes and sizes at different temperatures. It also can be used to understand the relation among the deposition parameters and inherent stresses, strain deformation, heat flow, and failure of nanostructures.

  14. Passivating electron contact based on highly crystalline nanostructured silicon oxide layers for silicon solar cells

    Czech Academy of Sciences Publication Activity Database

    Stuckelberger, J.; Nogay, G.; Wyss, P.; Jeangros, Q.; Allebe, Ch.; Debrot, F.; Niquille, X.; Ledinský, Martin; Fejfar, Antonín; Despeisse, M.; Haug, F.J.; Löper, P.; Ballif, C.

    2016-01-01

    Roč. 158, Dec (2016), s. 2-10 ISSN 0927-0248 R&D Projects: GA MŠk LM2015087 Institutional support: RVO:68378271 Keywords : surface passivation * passivating contact * nanostructure * silicon oxide * nanocrystalline * microcrystalline * poly-silicon * crystallization * Raman * transmission line measurement Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.784, year: 2016

  15. Study on cellular adhesion of human osteoblasts on nano-structured diamond films

    Czech Academy of Sciences Publication Activity Database

    Kalbáčová, M.; Brož, A.; Babchenko, Oleg; Kromka, Alexander

    2009-01-01

    Roč. 246, 11-12 (2009), 2774-2777 ISSN 0370-1972 R&D Projects: GA AV ČR KAN400100701; GA AV ČR(CZ) KAN400480701 Institutional research plan: CEZ:AV0Z10100521 Keywords : cells adhesion * diamond nanostructures Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.150, year: 2009

  16. Superconductivity in nanostructured lead

    Science.gov (United States)

    Lungu, Anca; Bleiweiss, Michael; Amirzadeh, Jafar; Saygi, Salih; Dimofte, Andreea; Yin, Ming; Iqbal, Zafar; Datta, Timir

    2001-01-01

    Three-dimensional nanoscale structures of lead were fabricated by electrodeposition of pure lead into artificial porous opal. The size of the metallic regions was comparable to the superconducting coherence length of bulk lead. Tc as high as 7.36 K was observed, also d Tc/d H was 2.7 times smaller than in bulk lead. Many of the characteristics of these differ from bulk lead, a type I superconductor. Irreversibility line and magnetic relaxation rates ( S) were also studied. S( T) displayed two maxima, with a peak value about 10 times smaller than that of typical high- Tc superconductors.

  17. Fabrication, Characterization, Properties, and Applications of Low-Dimensional BiFeO3 Nanostructures

    Directory of Open Access Journals (Sweden)

    Heng Wu

    2014-01-01

    Full Text Available Low-dimensional BiFeO3 nanostructures (e.g., nanocrystals, nanowires, nanotubes, and nanoislands have received considerable attention due to their novel size-dependent properties and outstanding multiferroic properties at room temperature. In recent years, much progress has been made both in fabrications and (microstructural, electrical, and magnetic in characterizations of BiFeO3 low-dimensional nanostructures. An overview of the state of art in BiFeO3 low-dimensional nanostructures is presented. First, we review the fabrications of high-quality BiFeO3 low-dimensional nanostructures via a variety of techniques, and then the structural characterizations and physical properties of the BiFeO3 low-dimensional nanostructures are summarized. Their potential applications in the next-generation magnetoelectric random access memories and photovoltaic devices are also discussed. Finally, we conclude this review by providing our perspectives to the future researches of BiFeO3 low-dimensional nanostructures and some key problems are also outlined.

  18. Plasmonic Nanostructures for Biosensor Applications

    Science.gov (United States)

    Gadde, Akshitha

    Improving the sensitivity of existing biosensors is an active research topic that cuts across several disciplines, including engineering and biology. Optical biosensors are the one of the most diverse class of biosensors which can be broadly categorized into two types based on the detection scheme: label-based and label-free detection. In label-based detection, the target bio-molecules are labeled with dyes or tags that fluoresce upon excitation, indicating the presence of target molecules. Label-based detection is highly-sensitive, capable of single molecule detection depending on the detector type used. One method of improving the sensitivity of label-based fluorescence detection is by enhancement of the emission of the labels by coupling them with metal nanostructures. This approach is referred as plasmon-enhanced fluorescence (PEF). PEF is achieved by increasing the electric field around the nano metal structures through plasmonics. This increased electric field improves the enhancement from the fluorophores which in turn improves the photon emission from the fluorophores which, in turn, improves the limit of detection. Biosensors taking advantage of the plasmonic properties of metal films and nanostructures have emerged an alternative, low-cost, high sensitivity method for detecting labeled DNA. Localized surface plasmon resonance (LSPR) sensors employing noble metal nanostructures have recently attracted considerable attention as a new class of plasmonic nanosensors. In this work, the design, fabrication and characterization of plasmonic nanostructures is carried out. Finite difference time domain (FDTD) simulations were performed using software from Lumerical Inc. to design a novel LSPR structure that exhibit resonance overlapping with the absorption and emission wavelengths of quantum dots (QD). Simulations of a composite Au/SiO2 nanopillars on silicon substrate were performed using FDTD software to show peak plasmonic enhancement at QD emission wavelength

  19. Cluster-Assembled Soft Magnets for Power Electronics Applications

    National Research Council Canada - National Science Library

    Leslie-Pelecky, Diandra L

    2006-01-01

    This project used inert-gas condensation (IGC) to fabricate model nanostructured systems with the goal of better understanding the mechanisms responsible for decreasing the coercivity in soft magnetic materials...

  20. Selective Induction of Optical Magnetism.

    Science.gov (United States)

    Manna, Uttam; Lee, Jung-Hoon; Deng, Tian-Song; Parker, John; Shepherd, Nolan; Weizmann, Yossi; Scherer, Norbert F

    2017-12-13

    An extension of the Maxwell-Faraday law of electromagnetic induction to optical frequencies requires spatially appropriate materials and optical beams to create resonances and excitations with curl. Here we employ cylindrical vector beams with azimuthal polarization to create electric fields that selectively drive magnetic responses in dielectric core-metal nanoparticle "satellite" nanostructures. These optical frequency magnetic resonances are induced in materials that do not possess spin or orbital angular momentum. Multipole expansion analysis of the scattered fields obtained from electrodynamics simulations show that the excitation with azimuthally polarized beams selectively enhances magnetic vs electric dipole resonances by nearly 100-fold in experiments. Multipolar resonances (e.g., quadrupole and octupole) are enhanced 5-fold by focused azimuthally versus linearly polarized beams. We also selectively excite electric multipolar resonances in the same identical nanostructures with radially polarized light. This work opens new opportunities for spectroscopic investigation and control of "dark modes", Fano resonances, and magnetic modes in nanomaterials and engineered metamaterials.

  1. Spin–orbit induced electronic spin separation in semiconductor nanostructures

    Science.gov (United States)

    Kohda, Makoto; Nakamura, Shuji; Nishihara, Yoshitaka; Kobayashi, Kensuke; Ono, Teruo; Ohe, Jun-ichiro; Tokura, Yasuhiro; Mineno, Taiki; Nitta, Junsaku

    2012-01-01

    The demonstration of quantized spin splitting by Stern and Gerlach is one of the most important experiments in modern physics. Their discovery was the precursor of recent developments in spin-based technologies. Although electrical spin separation of charged particles is fundamental in spintronics, in non-uniform magnetic fields it has been difficult to separate the spin states of charged particles due to the Lorentz force, as well as to the insufficient and uncontrollable field gradients. Here we demonstrate electronic spin separation in a semiconductor nanostructure. To avoid the Lorentz force, which is inevitably induced when an external magnetic field is applied, we utilized the effective non-uniform magnetic field which originates from the Rashba spin–orbit interaction in an InGaAs-based heterostructure. Using a Stern–Gerlach-inspired mechanism, together with a quantum point contact, we obtained field gradients of 108 T m−1 resulting in a highly polarized spin current. PMID:23011136

  2. Spin-orbit induced electronic spin separation in semiconductor nanostructures.

    Science.gov (United States)

    Kohda, Makoto; Nakamura, Shuji; Nishihara, Yoshitaka; Kobayashi, Kensuke; Ono, Teruo; Ohe, Jun-ichiro; Tokura, Yasuhiro; Mineno, Taiki; Nitta, Junsaku

    2012-01-01

    The demonstration of quantized spin splitting by Stern and Gerlach is one of the most important experiments in modern physics. Their discovery was the precursor of recent developments in spin-based technologies. Although electrical spin separation of charged particles is fundamental in spintronics, in non-uniform magnetic fields it has been difficult to separate the spin states of charged particles due to the Lorentz force, as well as to the insufficient and uncontrollable field gradients. Here we demonstrate electronic spin separation in a semiconductor nanostructure. To avoid the Lorentz force, which is inevitably induced when an external magnetic field is applied, we utilized the effective non-uniform magnetic field which originates from the Rashba spin-orbit interaction in an InGaAs-based heterostructure. Using a Stern-Gerlach-inspired mechanism, together with a quantum point contact, we obtained field gradients of 10(8) T m(-1) resulting in a highly polarized spin current.

  3. Fabrication of zein nanostructure

    Science.gov (United States)

    Luecha, Jarupat

    resins. The soft lithography technique was mainly used to fabricate micro and nanostructures on zein films. Zein material well-replicated small structures with the smallest size at sub micrometer scale that resulted in interesting photonic properties. The bonding method was also developed for assembling portable zein microfluidic devices with small shape distortion. Zein-zein and zein-glass microfluidic devices demonstrated sufficient strength to facilitate fluid flow in a complex microfluidic design with no leakage. Aside from the fabrication technique development, several potential applications of this environmentally friendly microfluidic device were investigated. The concentration gradient manipulation of Rhodamine B solution in zein-glass microfluidic devices was demonstrated. The diffusion of small molecules such as fluorescent dye into the wall of the zein microfluidic channels was observed. However, with this formulation, zein microfluidic devices were not suitable for cell culture applications. This pioneer study covered a wide spectrum of the implementation of the two nanotechnology approaches to advance zein biomaterial which provided proof of fundamental concepts as well as presenting some limitations. The findings in this study can lead to several innovative research opportunities of advanced zein biomaterials with broad applications. The information from the study of zein nanocomposite structure allows the packaging industry to develop the low cost biodegradable materials with physical property improvement. The information from the study of the zein microfluidic devices allows agro-industry to develop the nanotechnology-enabled microfluidic sensors fabricated entirely from biodegradable polymer for on-site disease or contaminant detection in the fields of food and agriculture.

  4. Investigations on magnetic field induced optical transparency in magnetic nanofluids

    Science.gov (United States)

    Mohapatra, Dillip Kumar; Philip, John

    2018-02-01

    We study the magnetic field induced optical transparency and its origin in magnetic nanoemulsion of droplets of average size ∼200 nm containing superparamagnetic iron oxide nanoparticles. Beyond a certain volume fraction (Φ > 0.0021) of magnetic nanoemulsion and a critical magnetic field (Hc1), the transmitted light intensity increases drastically and reaches a maximum at another critical magnetic field (Hc2), beyond which the transmitted light intensity decreases and reaches a plateau. Interestingly, the transmitted light intensity at Hc2 is found to increase linearly with Φ and the critical magnetic fields Hc1 and Hc2 follow power law decay with Φ (i.e. Hc ∼ Φ-x), with exponents 0.48 and 0.27, respectively. The light intensity recovers to its initial value when the magnetic field is switched off, indicating the perfect reversibility of the field induced transparency process. The observed straight line scattered patterns above Hc2, on a screen placed perpendicular to the incident beam, confirms the formation of rod like anisotropic nanostructures perpendicular to the direction of light propagation. The magneto-optical measurements in the emulsion confirm that the observed field induced transparency in magnetic emulsions for Φ > 0.0021 is due to the optical birefringence caused by the rod like nanostructures. The reduced birefringence is found to be proportional to the square of the applied magnetic field. This finding offers several possibilities in using magnetic nanofluids in tunable optical devices.

  5. Nano-structure formation of Fe-Pt perpendicular magnetic recording media co-deposited with MgO, Al2O3 and SiO2 additives

    International Nuclear Information System (INIS)

    Safran, G.; Suzuki, T.; Ouchi, K.; Barna, P.B.; Radnoczi, G.

    2006-01-01

    Perpendicular magnetic recording media samples were prepared by sputter deposition on sapphire with a layer sequence of MgO seed-layer/Cr under-layer/FeSi soft magnetic under-layer/MgO intermediate layer/FePt-oxide recording layer. The effects of MgO, Al 2 O 3 and SiO 2 additives on the morphology and orientation of the FePt layer were investigated by transmission electron microscopy. The samples exhibited (001) orientation of the L1 FePt phase with the mutual orientations of sapphire substrate//MgO(100)[001]//Cr(100)[11-bar0]//FeSi(100)[11-bar0]//MgO(100) [001]//FePt(001)[100]. The morphology of the FePt films varied due to the co-deposited oxides: The FePt layers were continuous and segmented by stacking faults aligned at 54 o to the surface. Films with SiO 2 addition, beside the oriented columnar FePt grains, exhibited a fraction of misoriented crystallites due to random repeated nucleation. Al 2 O 3 addition resulted in a layered structure, i.e. an initial continuous epitaxial FePt layer covered by a secondary layer of FePt-Al 2 O 3 composite. Both components (FePt and MgO) of the MgO-added samples were grown epitaxially on the MgO intermediate layer, so that a nano-composite of intercalated (001) FePt and (001) MgO was formed. The revealed microstructures and formation mechanisms may facilitate the improvement of the structural and magnetic properties of the FePt-oxide composite perpendicular magnetic recording media

  6. Enhanced Energy Density in Permanent Magnets using Controlled High Magnetic Field during Processing

    Energy Technology Data Exchange (ETDEWEB)

    Carter, William G [ORNL; Rios, Orlando [ORNL; Constantinides, Steven [ORNL

    2016-05-05

    This ORNL Manufacturing Demonstraction Facility (MDF) technical collaboration focused on the use of high magnetic field processing (>2Tesla) using energy efficient large bore superconducting magnet technology and high frequency electromagnetics to improve magnet performance and reduce the energy budget associated with Alnico thermal processing. Alnico, alloys containing Al, Ni, Co and Fe, represent a class of functional nanostructured alloys, and show the greatest potential for supplementing or replacing commercial Nd-based rare-earth alloy magnets.

  7. Effective particle magnetic moment of multi-core particles

    NARCIS (Netherlands)

    Ahrentorp, F.; Astalan, A.; Blomgren, J.; Jonasson, C.; Wetterskog, E.; Svedlindh, P.; Lak, A.; Ludwig, F.; Van IJzendoorn, L.J.; Westphal, F.; Grüttner, C.; Gehrke, N.; Gustafsson, S.; Olsson, E.; Johansson, C.

    2015-01-01

    In this study we investigate the magnetic behavior of magnetic multi-core particles and the differences in the magnetic properties of multi-core and single-core nanoparticles and correlate the results with the nanostructure of the different particles as determined from transmission electron

  8. Elucidation of the electrochromic mechanism of nanostructured iron oxides films

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Lobato, M.A.; Martinez, Arturo I.; Castro-Roman, M. [Center for Research and Advanced Studies of the National Polytechnic Institute, Cinvestav Campus Saltillo, Carr. Saltillo-Monterrey Km. 13, Ramos Arizpe, Coah. 25900 (Mexico); Perry, Dale L. [Mail Stop 70A1150, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States); Zarate, R.A. [Departamento de Fisica, Facultad de Ciencias, Universidad Catolica del Norte, Casilla 1280, Antofagasta (Chile); Escobar-Alarcon, L. (Departamento de Fisica, Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, 11801 Mexico)

    2011-02-15

    Nanostructured hematite thin films were electrochemically cycled in an aqueous solution of LiOH. Through optical, structural, morphological, and magnetic measurements, the coloration mechanism of electrochromic iron oxide thin films was elucidated. The conditions for double or single electrochromic behavior are given in this work. During the electrochemical cycling, it was found that topotactic transformations of hexagonal crystal structures are favored; i.e. {alpha}-Fe{sub 2}O{sub 3} to Fe(OH){sub 2} and subsequently to {delta}-FeOOH. These topotactic redox reactions are responsible for color changes of iron oxide films. (author)

  9. Displacement Talbot lithography: an alternative technique to fabricate nanostructured metamaterials

    Science.gov (United States)

    Le Boulbar, E. D.; Chausse, P. J. P.; Lis, S.; Shields, P. A.

    2017-06-01

    Nanostructured materials are essential for many recent electronic, magnetic and optical devices. Lithography is the most common step used to fabricate organized and well calibrated nanostructures. However, feature sizes less than 200 nm usually require access to deep ultraviolet photolithography, e-beam lithography or soft lithography (nanoimprinting), which are either expensive, have low-throughput or are sensitive to defects. Low-cost, high-throughput and low-defect-density techniques are therefore of interest for the fabrication of nanostructures. In this study, we investigate the potential of displacement Talbot lithography for the fabrication of specific structures of interest within plasmonic and metamaterial research fields. We demonstrate that nanodash arrays and `fishnet'-like structures can be fabricated by using a double exposure of two different linear grating phase masks. Feature sizes can be tuned by varying the exposure doses. Such lithography has been used to fabricate metallic `fishnet'-like structures using a lift-off technique. This proof of principle paves the way to a low-cost, high-throughput, defect-free and large-scale technique for the fabrication of structures that could be useful for metamaterial and plasmonic metasurfaces. With the development of deep ultraviolet displacement Talbot lithography, the feature dimensions could be pushed lower and used for the fabrication of optical metamaterials in the visible range.

  10. Observation of the structural, optical and magnetic properties during the transformation from hexagonal NiS nano-compounds to cubic NiO nanostructures due to thermal oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Linganiso, E.C., E-mail: elinganiso@csir.co.za [National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, P.O. Box 395, Pretoria 0001 (South Africa); DST/NRF Centre of Excellence in Strong Materials, Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Private Bag 3, Johannesburg, Wits 2050 (South Africa); Mwakikunga, B.W., E-mail: bmwakikunga@csir.co.za [National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, P.O. Box 395, Pretoria 0001 (South Africa); Coville, N.J. [DST/NRF Centre of Excellence in Strong Materials, Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Private Bag 3, Johannesburg, Wits 2050 (South Africa); Mhlanga, S.D. [Department of Applied Chemistry, University of Johannesburg, PO Box 17011, Doornfontein, 2028 Johannesburg (South Africa)

    2015-04-25

    Graphical abstract: The transition temperature of 350 °C for the formation of c-NiO from h-NiS oxidation was obtained from structural and optical property studies and by calculating the number of spins obtained from the EPR data. Vibrating sample magnetometry (VSM) shows that this pure NiS has both ferromagnetic ordering and paramagnetic domains. Further, the transition temperature of −9 °C of the pure α-NiS nano-alloys was confirmed by performing electrical measurements on the as-synthesized material. - Highlights: • Single hexagonal phase NiS obtained by microwave assisted hydrothermal synthesis. • NiS nanoalloys show both ferromagnetic and paramagnetic domains by VSM. • Structural evolution of annealed NiS and temperature dependent NiS oxidation presented. • Phase transition from NiS to NiO studied and correlated to the EPR spin population data and crystallite size. • Ferromagnetic and paramagnetic ordering observed for the raw NiS nanostructures. - Abstract: Single phase α-NiS nano-compounds with uniformly distributed hierarchical networks were synthesized by a microwave-assisted hydrothermal technique. The materials were evaluated for thermal stability under an oxidative environment and at temperatures between 150 °C and 600 °C. NiS materials showed stability at 300 °C and NiO formation was observed from 350 °C to 600 °C. The annealing effect on the crystalline size and IR absorption of the annealed samples is reported by XRD and FTIR studied. The EPR properties of the annealed materials were studied and compared to the oxidized materials. The transition temperature of 350 °C for the formation of NiO from NiS oxidation was confirmed by calculating the number of spins obtained from the EPR data. Vibrating sample magnetometry (VSM) shows that this pure NiS has both ferromagnetic ordering and paramagnetic domains. Further, the transition temperature of −9 °C of the pure α-NiS nano-compounds was confirmed by performing electrical

  11. Plasmonics analysis of nanostructures for bioapplications

    Science.gov (United States)

    Xie, Qian

    geometries of different metallic nanostructures are drawn and simulated using finite element-based computational electromagnetics. The power absorption of the nanostructures is plotted as a function of wavelength to identify the LSPR wavelength, i.e. the wavelength of peak absorption. In Matlab, Mie scattering theory is programmed in terms of semi-analytical mathematical equations, which predict the power absorption for specific plasmonic geometries, i.e. nanospheres, nanorods and core-shell particles. These predictions, which are much faster than the Comsol analysis, are validated using corresponding numerical simulations. In chapter four, experiments involving novel magneto-plasmonic Nano platforms are described, and experimental data is presented to illustrate the use of the modeling in analyzing these particles. Simulations are performed to determine the influence on the laser absorption of magnetic nanospheres in proximity to metallic nanorods. These results are compared with experimental data. In the last chapter, experiments using a grating-based SPR sensor are described, and modeling results are also presented. In summary, this thesis discusses the physics of plasmonics, electromagnetic analysis for predicting the absorption spectra of metallic nanoparticles and bio-applications that utilize these effects.

  12. Control of polarization and dipole moment in low-dimensional semiconductor nanostructures

    International Nuclear Information System (INIS)

    Li, L. H.; Ridha, P.; Mexis, M.; Smowton, P. M.; Blood, P.; Bozkurt, M.; Koenraad, P. M.; Patriarche, G.; Fiore, A.

    2009-01-01

    We demonstrate the control of polarization and dipole moment in semiconductor nanostructures, through nanoscale engineering of shape and composition. Rodlike nanostructures, elongated along the growth direction, are obtained by molecular beam epitaxial growth. By varying the aspect ratio and compositional contrast between the rod and the surrounding matrix, we rotate the polarization of the dominant interband transition from transverse-electric to transverse-magnetic, and modify the dipole moment producing a radical change in the voltage dependence of absorption spectra. This opens the way to the optimization of quantum dot amplifiers and electro-optical modulators.

  13. Chemical Sensors Based on Metal Oxide Nanostructures

    Science.gov (United States)

    Hunter, Gary W.; Xu, Jennifer C.; Evans, Laura J.; VanderWal, Randy L.; Berger, Gordon M.; Kulis, Mike J.; Liu, Chung-Chiun

    2006-01-01

    This paper is an overview of sensor development based on metal oxide nanostructures. While nanostructures such as nanorods show significan t potential as enabling materials for chemical sensors, a number of s ignificant technical challenges remain. The major issues addressed in this work revolve around the ability to make workable sensors. This paper discusses efforts to address three technical barriers related t o the application of nanostructures into sensor systems: 1) Improving contact of the nanostructured materials with electrodes in a microse nsor structure; 2) Controling nanostructure crystallinity to allow co ntrol of the detection mechanism; and 3) Widening the range of gases that can be detected by using different nanostructured materials. It is concluded that while this work demonstrates useful tools for furt her development, these are just the beginning steps towards realizati on of repeatable, controlled sensor systems using oxide based nanostr uctures.

  14. Complex Nanostructures by Pulsed Droplet Epitaxy

    Directory of Open Access Journals (Sweden)

    Noboyuki Koguchi

    2011-06-01

    Full Text Available What makes three dimensional semiconductor quantum nanostructures so attractive is the possibility to tune their electronic properties by careful design of their size and composition. These parameters set the confinement potential of electrons and holes, thus determining the electronic and optical properties of the nanostructure. An often overlooked parameter, which has an even more relevant effect on the electronic properties of the nanostructure, is shape. Gaining a strong control over the electronic properties via shape tuning is the key to access subtle electronic design possibilities. The Pulsed Dropled Epitaxy is an innovative growth method for the fabrication of quantum nanostructures with highly designable shapes and complex morphologies. With Pulsed Dropled Epitaxy it is possible to combine different nanostructures, namely quantum dots, quantum rings and quantum disks, with tunable sizes and densities, into a single multi-function nanostructure, thus allowing an unprecedented control over electronic properties.

  15. Composite materials formed with anchored nanostructures

    Science.gov (United States)

    Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei

    2015-03-10

    A method of forming nano-structure composite materials that have a binder material and a nanostructure fiber material is described. A precursor material may be formed using a mixture of at least one metal powder and anchored nanostructure materials. The metal powder mixture may be (a) Ni powder and (b) NiAl powder. The anchored nanostructure materials may comprise (i) NiAl powder as a support material and (ii) carbon nanotubes attached to nanoparticles adjacent to a surface of the support material. The process of forming nano-structure composite materials typically involves sintering the mixture under vacuum in a die. When Ni and NiAl are used in the metal powder mixture Ni.sub.3Al may form as the binder material after sintering. The mixture is sintered until it consolidates to form the nano-structure composite material.

  16. Genesis of nanostructured, magnetically tunable ceramics from the pyrolysis of cross-linked polyferrocenylsilane networks and formation of shaped macroscopic objects and micron scale patterns by micromolding inside silicon wafers.

    Science.gov (United States)

    Ginzburg, Madlen; MacLachlan, Mark J; Yang, San Ming; Coombs, Neil; Coyle, Thomas W; Raju, Nandyala P; Greedan, John E; Herber, Rolfe H; Ozin, Geoffrey A; Manners, Ian

    2002-03-20

    The ability to form molded or patterned metal-containing ceramics with tunable properties is desirable for many applications. In this paper we describe the evolution of a ceramic from a metal-containing polymer in which the variation of pyrolysis conditions facilitates control of ceramic structure and composition, influencing magnetic and mechanical properties. We have found that pyrolysis under nitrogen of a well-characterized cross-linked polyferrocenylsilane network derived from the ring-opening polymerization (ROP) of a spirocyclic [1]ferrocenophane precursor gives shaped macroscopic magnetic ceramics consisting of alpha-Fe nanoparticles embedded in a SiC/C/Si(3)N(4) matrix in greater than 90% yield up to 1000 degrees C. Variation of the pyrolysis temperature and time permitted control over the nucleation and growth of alpha-Fe particles, which ranged in size from around 15 to 700 A, and the crystallization of the surrounding matrix. The ceramics contained smaller alpha-Fe particles when prepared at temperatures lower than 900 degrees C and displayed superparamagnetic behavior, whereas the materials prepared at 1000 degrees C contained larger alpha-Fe particles and were ferromagnetic. This flexibility may be useful for particular materials applications. In addition, the composition of the ceramic was altered by changing the pyrolysis atmosphere to argon, which yielded ceramics that contain Fe(3)Si(5). The ceramics have been characterized by a combination of physical techniques, including powder X-ray diffraction, TEM, reflectance UV-vis/near-IR spectroscopy, elemental analysis, XPS, SQUID magnetometry, Mössbauer spectroscopy, nanoindentation, and SEM. Micromolding of the spirocyclic [1]ferrocenophane precursor within soft lithographically patterned channels housed inside silicon wafers followed by thermal ROP and pyrolysis enabled the formation of predetermined micron scale designs of the magnetic ceramic.

  17. Imaging edges of nanostructured graphene

    DEFF Research Database (Denmark)

    Kling, Jens; Cagliani, Alberto; Booth, T. J.

    Graphene, as the forefather of 2D-materials, attracts much attention due to its extraordinary properties like transparency, flexibility and outstanding high conductivity, together with a thickness of only one atom. However, graphene also possesses no band gap, which makes it unsuitable for many...... electronic applications like transistors. It has been shown theoretically that by nanostructuring pristine graphene, e.g. with regular holes, the electronic properties can be tuned and a band gap introduced. The size, distance and edge termination of these “defects” influence the adaptability....... Such nanostructuring can be done experimentally, but especially characterization at atomic level is a huge challenge. High-resolution TEM (HRTEM) is used to characterize the atomic structure of graphene. We optimized the imaging conditions used for the FEI Titan ETEM. To reduce the knock-on damage of the carbon atoms...

  18. Nanostructured materials for water desalination

    Energy Technology Data Exchange (ETDEWEB)

    Humplik, T; Lee, J; O' Hern, S C; Fellman, B A; Karnik, R; Wang, E N [Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge (United States); Baig, M A; Hassan, S F; Atieh, M A; Rahman, F; Laoui, T, E-mail: tlaoui@kfupm.edu.sa, E-mail: karnik@mit.edu, E-mail: enwang@mit.edu [Departments of Mechanical Engineering and Chemical Engineering and Research Institute, King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia)

    2011-07-22

    Desalination of seawater and brackish water is becoming an increasingly important means to address the scarcity of fresh water resources in the world. Decreasing the energy requirements and infrastructure costs of existing desalination technologies remains a challenge. By enabling the manipulation of matter and control of transport at nanometer length scales, the emergence of nanotechnology offers new opportunities to advance water desalination technologies. This review focuses on nanostructured materials that are directly involved in the separation of water from salt as opposed to mitigating issues such as fouling. We discuss separation mechanisms and novel transport phenomena in materials including zeolites, carbon nanotubes, and graphene with potential applications to reverse osmosis, capacitive deionization, and multi-stage flash, among others. Such nanostructured materials can potentially enable the development of next-generation desalination systems with increased efficiency and capacity. (topical review)

  19. Nanostructured materials for water desalination

    International Nuclear Information System (INIS)

    Humplik, T; Lee, J; O'Hern, S C; Fellman, B A; Karnik, R; Wang, E N; Baig, M A; Hassan, S F; Atieh, M A; Rahman, F; Laoui, T

    2011-01-01

    Desalination of seawater and brackish water is becoming an increasingly important means to address the scarcity of fresh water resources in the world. Decreasing the energy requirements and infrastructure costs of existing desalination technologies remains a challenge. By enabling the manipulation of matter and control of transport at nanometer length scales, the emergence of nanotechnology offers new opportunities to advance water desalination technologies. This review focuses on nanostructured materials that are directly involved in the separation of water from salt as opposed to mitigating issues such as fouling. We discuss separation mechanisms and novel transport phenomena in materials including zeolites, carbon nanotubes, and graphene with potential applications to reverse osmosis, capacitive deionization, and multi-stage flash, among others. Such nanostructured materials can potentially enable the development of next-generation desalination systems with increased efficiency and capacity. (topical review)

  20. Nanostructured materials for water desalination

    Science.gov (United States)

    Humplik, T.; Lee, J.; O'Hern, S. C.; Fellman, B. A.; Baig, M. A.; Hassan, S. F.; Atieh, M. A.; Rahman, F.; Laoui, T.; Karnik, R.; Wang, E. N.

    2011-07-01

    Desalination of seawater and brackish water is becoming an increasingly important means to address the scarcity of fresh water resources in the world. Decreasing the energy requirements and infrastructure costs of existing desalination technologies remains a challenge. By enabling the manipulation of matter and control of transport at nanometer length scales, the emergence of nanotechnology offers new opportunities to advance water desalination technologies. This review focuses on nanostructured materials that are directly involved in the separation of water from salt as opposed to mitigating issues such as fouling. We discuss separation mechanisms and novel transport phenomena in materials including zeolites, carbon nanotubes, and graphene with potential applications to reverse osmosis, capacitive deionization, and multi-stage flash, among others. Such nanostructured materials can potentially enable the development of next-generation desalination systems with increased efficiency and capacity.

  1. Reactor casts light on nanostructures

    International Nuclear Information System (INIS)

    Garvey, C.

    2002-01-01

    Chris Garvey explains how the replacement research reactor will help scientists to design better materials by understanding how macromolecules behave. Australia is making a substantial financial commitment to providing scientists with facilities to scatter neutrons. Neutron scattering is one of the core areas of science in which the Australian Nuclear Science and Technology Organisation (ANSTO) invests its resources. His particular interest is to find out the way nature uses macromolecules, and how the shape and interaction of macromolecules with other molecules change their function. Biologists call aggregates of macromolecules, 'nanostructures'. Neutron probes are used at ANSTO for studying nanostructures, and in particular the organisation of the protein that is used to transport oxygen in the blood. Small angle neutron scattering was also allowed to understand at microscopic level, how humidity changes the mechanical properties of fibres

  2. Fibrin nanostructures for biomedical applications

    Czech Academy of Sciences Publication Activity Database

    Riedelová-Reicheltová, Zuzana; Brynda, Eduard; Riedel, Tomáš

    2016-01-01

    Roč. 65, Suppl. 2 (2016), S263-S272 ISSN 0862-8408 R&D Projects: GA MŠk(CZ) LQ1604 Institutional support: RVO:61389013 Keywords : fibrinogen * fibrin-bound thrombin * nanostructures Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 1.461, year: 2016 http://www.biomed.cas.cz/physiolres/pdf/65%20Suppl%202/65_S263.pdf

  3. Paramagnetic decoration of DNA origami nanostructures by Eu³⁺ coordination.

    Science.gov (United States)

    Opherden, Lars; Oertel, Jana; Barkleit, Astrid; Fahmy, Karim; Keller, Adrian

    2014-07-15

    The folding of DNA into arbitrary two- and three-dimensional shapes, called DNA origami, represents a powerful tool for the synthesis of functional nanostructures. Here, we present the first approach toward the paramagnetic functionalization of DNA origami nanostructures by utilizing postassembly coordination with Eu(3+) ions. In contrast to the usual formation of toroidal dsDNA condensates in the presence of trivalent cations, planar as well as rod-like DNA origami maintain their shape and monomeric state even under high loading with the trivalent lanthanide. Europium coordination was demonstrated by the change in Eu(3+) luminescence upon binding to the two DNA origami. Their natural circular dichroism in the Mg(2+)- and Eu(3+)-bound state was found to be very similar to that of genomic DNA, evidencing little influence of the DNA origami superstructure on the local chirality of the stacked base pairs. In contrast, the magnetic circular dichroism of the Mg(2+)-bound DNA origami deviates from that of genomic DNA. Furthermore, the lanthanide affects the magnetic properties of DNA in a superstructure-dependent fashion, indicative of the existence of superstructure-specific geometry of Eu(3+) binding sites in the DNA origami that are not formed in genomic DNA. This simple approach lays the foundation for the generation of magneto-responsive DNA origami nanostructures. Such systems do not require covalent modifications and can be used for the magnetic manipulation of DNA nanostructures or for the paramagnetic alignment of molecules in NMR spectroscopy.

  4. Synthesis of magnetic nanofibers using femtosecond laser material processing in air

    Directory of Open Access Journals (Sweden)

    Tan Bo

    2011-01-01

    Full Text Available Abstract In this study, we report formation of weblike fibrous nanostructure and nanoparticles of magnetic neodymium-iron-boron (NdFeB via femtosecond laser radiation at MHz pulse repetition frequency in air at atmospheric pressure. Scanning electron microscopy (SEM analysis revealed that the nanostructure is formed due to aggregation of polycrystalline nanoparticles of the respective constituent materials. The nanofibers diameter varies between 30 and 70 nm and they are mixed with nanoparticles. The effect of pulse to pulse separation rate on the size of the magnetic fibrous structure and the magnetic strength was reported. X-ray diffraction (XRD analysis revealed metallic and oxide phases in the nanostructure. The growth of magnetic nanostructure is highly recommended for the applications of magnetic devices like biosensors and the results suggest that the pulsed-laser method is a promising technique for growing nanocrystalline magnetic nanofibers and nanoparticles for biomedical applications.

  5. Synthesis of magnetic nanofibers using femtosecond laser material processing in air

    Science.gov (United States)

    2011-01-01

    In this study, we report formation of weblike fibrous nanostructure and nanoparticles of magnetic neodymium-iron-boron (NdFeB) via femtosecond laser radiation at MHz pulse repetition frequency in air at atmospheric pressure. Scanning electron microscopy (SEM) analysis revealed that the nanostructure is formed due to aggregation of polycrystalline nanoparticles of the respective constituent materials. The nanofibers diameter varies between 30 and 70 nm and they are mixed with nanoparticles. The effect of pulse to pulse separation rate on the size of the magnetic fibrous structure and the magnetic strength was reported. X-ray diffraction (XRD) analysis revealed metallic and oxide phases in the nanostructure. The growth of magnetic nanostructure is highly recommended for the applications of magnetic devices like biosensors and the results suggest that the pulsed-laser method is a promising technique for growing nanocrystalline magnetic nanofibers and nanoparticles for biomedical applications. PMID:21711890

  6. Nanotechnologies. Properties and applications of nanostructured materials

    International Nuclear Information System (INIS)

    Rempel, A A

    2007-01-01

    The review summarises the main methods for the preparation of nanostructured metals, alloys, semiconductors and ceramics. The formation mechanisms of nanostructures based on two different principles, viz. the assembly principle (bottom-up) and the disintegration principle (top-down), are analysed. Isolated nanoparticles, nanopowders and compact nanomaterials produced by these methods possess different properties. The scope of application of various classes of nanostructured materials is considered and the topicality of the development of nanoindustry is emphasised.

  7. Metal chalcogenide nanostructures for renewable energy applications

    CERN Document Server

    Qurashi, Ahsanulhaq

    2014-01-01

    This first ever reference book that focuses on metal chalcogenide semiconductor nanostructures for renewable energy applications encapsulates the state-of-the-art in multidisciplinary research on the metal chalcogenide semiconductor nanostructures (nanocrystals, nanoparticles, nanorods, nanowires,  nanobelts, nanoflowers, nanoribbons and more).  The properties and synthesis of a class of nanomaterials is essential to renewable energy manufacturing and this book focuses on the synthesis of metal chalcogendie nanostructures, their growth mechanism, optical, electrical, and other important prop

  8. Single-electron transport in graphene-like nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Chiu, Kuei-Lin, E-mail: klc43@mit.edu [Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Xu, Yang, E-mail: yangxu-isee@zju.edu.cn [Institute of Microelectronics and Optoelectronics, College of Information Science and Electronic Engineering, Zhejiang University, 310027 (China)

    2017-01-31

    Two-dimensional (2D) materials for their versatile band structures and strictly 2D nature have attracted considerable attention over the past decade. Graphene is a robust material for spintronics owing to its weak spin–orbit and hyperfine interactions, while monolayer transition metal dichalcogenides (TMDs) possess a Zeeman effect-like band splitting in which the spin and valley degrees of freedom are nondegenerate. The surface states of topological insulators (TIs) exhibit a spin–momentum locking that opens up the possibility of controlling the spin degree of freedom in the absence of an external magnetic field. Nanostructures made of these materials are also viable for use in quantum computing applications involving the superposition and entanglement of individual charge and spin quanta. In this article, we review a selection of transport studies addressing the confinement and manipulation of charges in nanostructures fabricated from various 2D materials. We supply the entry-level knowledge for this field by first introducing the fundamental properties of 2D bulk materials followed by the theoretical background relevant to the physics of nanostructures. Subsequently, a historical review of experimental development in this field is presented, from the early demonstration of graphene nanodevices on SiO{sub 2} substrate to more recent progress in utilizing hexagonal boron nitride to reduce substrate disorder. In the second part of this article, we extend our discussion to TMDs and TI nanostructures. We aim to outline the current challenges and suggest how future work will be geared towards developing spin qubits in 2D materials.

  9. Insulator coated magnetic nanoparticulate composites with reduced core loss and method of manufacture thereof

    Science.gov (United States)

    Zhang, Yide (Inventor); Wang, Shihe (Inventor); Xiao, Danny (Inventor)

    2004-01-01

    A series of bulk-size magnetic/insulating nanostructured composite soft magnetic materials with significantly reduced core loss and its manufacturing technology. This insulator coated magnetic nanostructured composite is comprises a magnetic constituent, which contains one or more magnetic components, and an insulating constituent. The magnetic constituent is nanometer scale particles (1-100 nm) coated by a thin-layered insulating phase (continuous phase). While the intergrain interaction between the immediate neighboring magnetic nanoparticles separated by the insulating phase (or coupled nanoparticles) provide the desired soft magnetic properties, the insulating material provides the much demanded high resistivity which significantly reduces the eddy current loss. The resulting material is a high performance magnetic nanostructured composite with reduced core loss.

  10. Reactor and method for production of nanostructures

    Science.gov (United States)

    Sunkara, Mahendra Kumar; Kim, Jeong H.; Kumar, Vivekanand

    2017-04-25

    A reactor and method for production of nanostructures, including metal oxide nanowires or nanoparticles, are provided. The reactor includes a regulated metal powder delivery system in communication with a dielectric tube; a plasma-forming gas inlet, whereby a plasma-forming gas is delivered substantially longitudinally into the dielectric tube; a sheath gas inlet, whereby a sheath gas is delivered into the dielectric tube; and a microwave energy generator coupled to the dielectric tube, whereby microwave energy is delivered into a plasma-forming gas. The method for producing nanostructures includes providing a reactor to form nanostructures and collecting the formed nanostructures, optionally from a filter located downstream of the dielectric tube.

  11. Is there a shift to 'active nanostructures'?

    International Nuclear Information System (INIS)

    Subramanian, Vrishali; Youtie, Jan; Porter, Alan L.; Shapira, Philip

    2010-01-01

    It has been suggested that an important transition in the long-run trajectory of nanotechnology development is a shift from passive to active nanostructures. Such a shift could present different or increased societal impacts and require new approaches for risk assessment. An active nanostructure 'changes or evolves its state during its operation,' according to the National Science Foundation's (2006) Active Nanostructures and Nanosystems grant solicitation. Active nanostructure examples include nanoelectromechanical systems (NEMS), nanomachines, self-healing materials, targeted drugs and chemicals, energy storage devices, and sensors. This article considers two questions: (a) Is there a 'shift' to active nanostructures? (b) How can we characterize the prototypical areas into which active nanostructures may emerge? We build upon the NSF definition of active nanostructures to develop a research publication search strategy, with a particular intent to distinguish between passive and active nanotechnologies. We perform bibliometric analyses and describe the main publication trends from 1995 to 2008. We then describe the prototypes of research that emerge based on reading the abstracts and review papers encountered in our search. Preliminary results suggest that there is a sharp rise in active nanostructures publications in 2006, and this rise is maintained in 2007 and through to early 2008. We present a typology that can be used to describe the kind of active nanostructures that may be commercialized and regulated in the future.

  12. Is there a shift to "active nanostructures"?

    Science.gov (United States)

    Subramanian, Vrishali; Youtie, Jan; Porter, Alan L.; Shapira, Philip

    2010-01-01

    It has been suggested that an important transition in the long-run trajectory of nanotechnology development is a shift from passive to active nanostructures. Such a shift could present different or increased societal impacts and require new approaches for risk assessment. An active nanostructure "changes or evolves its state during its operation," according to the National Science Foundation's (2006) Active Nanostructures and Nanosystems grant solicitation. Active nanostructure examples include nanoelectromechanical systems (NEMS), nanomachines, self-healing materials, targeted drugs and chemicals, energy storage devices, and sensors. This article considers two questions: (a) Is there a "shift" to active nanostructures? (b) How can we characterize the prototypical areas into which active nanostructures may emerge? We build upon the NSF definition of active nanostructures to develop a research publication search strategy, with a particular intent to distinguish between passive and active nanotechnologies. We perform bibliometric analyses and describe the main publication trends from 1995 to 2008. We then describe the prototypes of research that emerge based on reading the abstracts and review papers encountered in our search. Preliminary results suggest that there is a sharp rise in active nanostructures publications in 2006, and this rise is maintained in 2007 and through to early 2008. We present a typology that can be used to describe the kind of active nanostructures that may be commercialized and regulated in the future.

  13. Growth and BZO-doping of the nanostructured YBCO thin films on buffered metal substrates

    DEFF Research Database (Denmark)

    Huhtinen, H.; Irjala, M.; Paturi, P.

    2010-01-01

    The growth of the nanostructured YBa2Cu3O6+x (YBCO) films is investigated for the first time on biaxially textured NiW substrates used in coated conductor technology. The optimization process of superconducting layers is made in wide magnetic field and temperature range in order to understand...... the vortex pinning structure and mechanism in our films prepared from nanostructured material. Structural analysis shows that growth mechanism in YBCO films grown on NiW is completely different when compared to YBCO on STO. Films on NiW are much rougher, there is huge in-plane variation of YBCO crystals...... and moreover out-of-plane long range lattice ordering is greatly reduced. Magnetic measurements demonstrate that jc in films grown on NiW is higher in high magnetic fields and low temperatures. This effect is connected to the amount of pinning centres observed in films on metal substrates which are effective...

  14. Influence of DC arc current on the formation of cobalt-based nanostructures

    Science.gov (United States)

    Orpe, P. B.; Balasubramanian, C.; Mukherjee, S.

    2017-08-01

    The synthesis of cobalt-based magnetic nanostructures using DC arc discharge technique with varying arc current is reported here. The structural, morphological, compositional and magnetic properties of these nanostructures were studied as a function of applied arc current. Various techniques like X-ray diffraction, transmission electron microscopy, EDAX and vibrating sample magnetometry were used to carry out this study and the results are reported here. The results clearly indicate that for a given oxygen partial pressure, an arc current of 100 A favours the formation of unreacted cobalt atomic species. Also change in arc current leads to variation in phase, diversity in morphology etc. Other property changes such as thermal changes, mechanical changes etc. are not addressed here. The magnetic characterization further indicates that the anisotropy in shape plays a crucial role in deciding the magnetic properties of the nanostructured materials. We have quantified an interesting result in our experiment, that is, for a given partial pressure, 100 A arc current results in unique variation in structural and magnetic properties as compared to other arc currents.

  15. Electronic transport and magnetization dynamics in magnetic systems

    International Nuclear Information System (INIS)

    Borlenghi, Simone

    2011-01-01

    The aim of this thesis is to understand the mutual influence between electronic transport and magnetization dynamics in magnetic hybrid metallic nano-structures. At first, we have developed a theoretical model, based on random matrix theory, to describe at microscopic level spin dependent transport in a heterogeneous nano-structure. This model, called Continuous Random Matrix Theory (CRMT), has been implemented in a simulation code that allows one to compute local (spin torque, spin accumulation and spin current) and macroscopic (resistance) transport properties of spin valves. To validate this model, we have compared it with a quantum theory of transport based on the non equilibrium Green's functions formalism. Coupling the two models has allowed to perform a multi-scale description of metallic hybrid nano-structures, where ohmic parts are described using CRMT, while purely quantum parts are described using Green's functions. Then, we have coupled CRMT to a micro-magnetic simulation code, in order to describe the complex dynamics of the magnetization induced by spin transfer effect. The originality of this approach consists in modelling a spectroscopic experiment based on a mechanical detection of the ferromagnetic resonance, and performed on a spin torque nano-oscillator. This work has allowed us to obtain the dynamical phase diagram of the magnetization, and to detect the selection rules for spin waves induced by spin torque, as well as the competition between the Eigen-modes of the system when a dc current flows through the multilayer, in partial agreement with experimental data. (author)

  16. Microstructure and magnetic properties of nanostructured (Fe{sub 0.8}Al{sub 0.2}){sub 100–x}Si{sub x} alloy produced by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Boukherroub, N. [UR-MPE, M' hamed Bougara University, Boumerdes 35000 (Algeria); Guittoum, A., E-mail: aguittoum@gmail.com [Nuclear Research Centre of Algiers, 02 Bd Frantz Fanon, BP 399 Alger-Gare, Algiers (Algeria); Laggoun, A. [UR-MPE, M' hamed Bougara University, Boumerdes 35000 (Algeria); Hemmous, M. [Nuclear Research Centre of Algiers, 02 Bd Frantz Fanon, BP 399 Alger-Gare, Algiers (Algeria); Martínez-Blanco, D. [SCTs, University of Oviedo, EPM, 33600 Mieres (Spain); Blanco, J.A. [Department of Physics, University of Oviedo, Calvo Sotelo St., 33007 Oviedo (Spain); Souami, N. [Nuclear Research Centre of Algiers, 02 Bd Frantz Fanon, BP 399 Alger-Gare, Algiers (Algeria); Gorria, P. [Department of Physics and IUTA, EPI, University of Oviedo, 33203 Gijón (Spain); Bourzami, A. [Laboratoire d' Etudes des Surfaces et Interfaces des Matériaux Solides (LESIMS), Université Sétif1, 19000 Sétif (Algeria); Lenoble, O. [Institut Jean Lamour, CNRS-Université de Lorraine, Boulevard des aiguillettes, BP 70239, F-54506 Vandoeuvre lès Nancy (France)

    2015-07-01

    We report on how the microstructure and the silicon content of nanocrystalline ternary (Fe{sub 0.8}Al{sub 0.2}){sub 100–x}Si{sub x} powders (x=0, 5, 10, 15 and 20 at%) elaborated by high energy ball milling affect the magnetic properties of these alloys. The formation of a single-phase alloy with body centred cubic (bcc) crystal structure is completed after 72 h of milling time for all the compositions. This bcc phase is in fact a disordered Fe(Al,Si) solid solution with a lattice parameter that reduces its value almost linearly as the Si content is increased, from about 2.9 Å in the binary Fe{sub 80}Al{sub 20} alloy to 2.85 Å in the powder with x=20. The average nanocrystalline grain size also decreases linearly down to 10 nm for x=20, being roughly half of the value for the binary alloy, while the microstrain is somewhat enlarged. Mössbauer spectra show a sextet thus suggesting that the disordered Fe(Al,Si) solid solution is ferromagnetic at room temperature. However, the average hyperfine field diminishes from 27 T (x=0) to 16 T (x=20), and a paramagnetic doublet is observed for the powders with higher Si content. These results together with the evolution of both the saturation magnetization and the coercive field are discussed in terms of intrinsic and extrinsic properties. - Highlights: • Single-phase nanocrystalline (Fe{sub 0.8}Al{sub 0.2}){sub 100–x}Si{sub x} (x=0, 5, 10, 15 and 20 at%) powders were successfully fabricated by mechanical alloying for a milling time of 72 h. • The insertion of Si atoms leads to a unit-cell contraction and a decrease in the average crystallite size. • The hyperfine and magnetic properties of (Fe{sub 0.8}Al{sub 0.2}){sub 100–x}Si{sub x} were influenced by the Si content.

  17. Quantum information processing in nanostructures

    International Nuclear Information System (INIS)

    Reina Estupinan, John-Henry

    2002-01-01

    Since information has been regarded os a physical entity, the field of quantum information theory has blossomed. This brings novel applications, such as quantum computation. This field has attracted the attention of numerous researchers with backgrounds ranging from computer science, mathematics and engineering, to the physical sciences. Thus, we now have an interdisciplinary field where great efforts are being made in order to build devices that should allow for the processing of information at a quantum level, and also in the understanding of the complex structure of some physical processes at a more basic level. This thesis is devoted to the theoretical study of structures at the nanometer-scale, 'nanostructures', through physical processes that mainly involve the solid-state and quantum optics, in order to propose reliable schemes for the processing of quantum information. Initially, the main results of quantum information theory and quantum computation are briefly reviewed. Next, the state-of-the-art of quantum dots technology is described. In so doing, the theoretical background and the practicalities required for this thesis are introduced. A discussion of the current quantum hardware used for quantum information processing is given. In particular, the solid-state proposals to date are emphasised. A detailed prescription is given, using an optically-driven coupled quantum dot system, to reliably prepare and manipulate exciton maximally entangled Bell and Greenberger-Horne-Zeilinger (GHZ) states. Manipulation of the strength and duration of selective light-pulses needed for producing these highly entangled states provides us with crucial elements for the processing of solid-state based quantum information. The all-optical generation of states of the so-called Bell basis for a system of two quantum dots (QDs) is exploited for performing the quantum teleportation of the excitonic state of a dot in an array of three coupled QDs. Theoretical predictions suggest

  18. Debye screening length effects of nanostructured materials

    CERN Document Server

    Ghatak, Kamakhya Prasad

    2014-01-01

    This monograph solely investigates the Debye Screening Length (DSL) in semiconductors and their nano-structures. The materials considered are quantized structures of non-linear optical, III-V, II-VI, Ge, Te, Platinum Antimonide, stressed materials, Bismuth, GaP, Gallium Antimonide, II-V and Bismuth Telluride respectively. The DSL in opto-electronic materials and their quantum confined counterparts is studied in the presence of strong light waves and intense electric fields on the basis of newly formulated electron dispersion laws that control the studies of such quantum effect devices. The suggestions for the experimental determination of 2D and 3D DSL and the importance of measurement of band gap in optoelectronic materials under intense built-in electric field in nano devices and strong external photo excitation (for measuring photon induced physical properties) have also been discussed in this context. The influence of crossed electric and quantizing magnetic fields on the DSL and the DSL in heavily doped ...

  19. Model-based magnetization retrieval from holographic phase images

    Energy Technology Data Exchange (ETDEWEB)

    Röder, Falk, E-mail: f.roeder@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf, Institut für Ionenstrahlphysik und Materialforschung, Bautzner Landstr. 400, D-01328 Dresden (Germany); Triebenberg Labor, Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Vogel, Karin [Triebenberg Labor, Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Wolf, Daniel [Helmholtz-Zentrum Dresden-Rossendorf, Institut für Ionenstrahlphysik und Materialforschung, Bautzner Landstr. 400, D-01328 Dresden (Germany); Triebenberg Labor, Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Hellwig, Olav [Helmholtz-Zentrum Dresden-Rossendorf, Institut für Ionenstrahlphysik und Materialforschung, Bautzner Landstr. 400, D-01328 Dresden (Germany); AG Magnetische Funktionsmaterialien, Institut für Physik, Technische Universität Chemnitz, D-09126 Chemnitz (Germany); HGST, A Western Digital Company, 3403 Yerba Buena Rd., San Jose, CA 95135 (United States); Wee, Sung Hun [HGST, A Western Digital Company, 3403 Yerba Buena Rd., San Jose, CA 95135 (United States); Wicht, Sebastian; Rellinghaus, Bernd [IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden (Germany)

    2017-05-15

    The phase shift of the electron wave is a useful measure for the projected magnetic flux density of magnetic objects at the nanometer scale. More important for materials science, however, is the knowledge about the magnetization in a magnetic nano-structure. As demonstrated here, a dominating presence of stray fields prohibits a direct interpretation of the phase in terms of magnetization modulus and direction. We therefore present a model-based approach for retrieving the magnetization by considering the projected shape of the nano-structure and assuming a homogeneous magnetization therein. We apply this method to FePt nano-islands epitaxially grown on a SrTiO{sub 3} substrate, which indicates an inclination of their magnetization direction relative to the structural easy magnetic [001] axis. By means of this real-world example, we discuss prospects and limits of this approach. - Highlights: • Retrieval of the magnetization from holographic phase images. • Magnetostatic model constructed for a magnetic nano-structure. • Decomposition into homogeneously magnetized components. • Discretization of a each component by elementary cuboids. • Analytic solution for the phase of a magnetized cuboid considered. • Fitting a set of magnetization vectors to experimental phase images.

  20. Ultrathin magnetic structures II measurement techniques and novel magnetic properties

    CERN Document Server

    Heinrich, Bretislav

    2006-01-01

    The ability to understand and control the unique properties of interfaces has created an entirely new field of magnetism, with profound impact in technology and serving as the basis for a revolution in electronics. Our understanding of the physics of magnetic nanostructures has also advanced significantly. This rapid development has generated a need for a comprehensive treatment that can serve as an introduction to the field for those entering it from diverse fields, but which will also serve as a timely overview for those already working in this area. The four-volume work Ultra-Thin Magnetic

  1. Multi-periodic nanostructures for photon control

    DEFF Research Database (Denmark)

    Kluge, Christian; Adam, Jost; Barié, Nicole

    2014-01-01

    We propose multi-periodic nanostructures yielded by superposition of multiple binary gratings for wide control over photon emission in thin-film devices. We present wavelength- and angle-resolved photoluminescence measurements of multi-periodically nanostructured organic light-emitting layers...

  2. Spin tunneling and manipulation in nanostructures.

    Science.gov (United States)

    Sherman, E Ya; Ban, Yue; Gulyaev, L V; Khomitsky, D V

    2012-09-01

    The results for joint effects of tunneling and spin-orbit coupling on spin dynamics in nanostructures are presented for systems with discrete and continuous spectra. We demonstrate that tunneling plays the crucial role in the spin dynamics and the abilities of spin manipulation by external electric field. This result can be important for design of nanostructures-based spintronics devices.

  3. Structural, morphological, impedance and magnetic studies of nanostructured LiNi0.45M0.1Mn0.45O2 (MCu and Al cathode materials for lithium-ion batteries

    Directory of Open Access Journals (Sweden)

    N. Murali

    2017-12-01

    Full Text Available Layered structure LiNi0.45M0.1Mn0.45O2 (MCu and Al cathode materials for lithium-ion batteries are synthesized by sol–gel auto combustion method. The structural, morphological, electrical and magnetic properties are examined by X-ray diffraction (XRD, field effect scanning electron microscope FESEM, FT-IR, EIS and ESR. XRD data revealed the rhombohedral and α-NaFeO2 structure with a space group R-3m. The electrical conductivity, dielectric constant, and dielectric loss are measured in the room temperature at a frequency ranging from 20 Hz to 1 MHz. The electrical conductivity of the compound is measured by AC impedance. An effective improvement in the electrical conductivity of order 5.42 × 10−6 S/cm is observed for the copper doped LNMO compounds. ESR spectra is recorded at room temperature on a Bruker EMX model X-band spectrometer operating at a frequency of 9.50 GHz. The critical dopants of Cu, with minimum g-factor and maximum line-width (W are observed. Keywords: Sol–gel, FESEM, AC impedance, ESR

  4. Vicinal surfaces for functional nanostructures.

    Science.gov (United States)

    Tegenkamp, Christoph

    2009-01-07

    Vicinal surfaces are currently the focus of research. The regular arrangements of atomic steps on a mesoscopic scale reveal the possibility to functionalize these surfaces for technical applications, e.g. nanowires, catalysts, etc. The steps of the vicinal surface are well-defined defect structures of atomic size for nucleation of low-dimensional nanostructures. The concentration and therefore the coupling between the nanostructures can be tuned over a wide range by simply changing the inclination angle of the substrate. However, the coupling of these nano-objects to the substrate is just as important in controlling their electronic or chemical properties and making a functionality useable. On the basis of stepped insulating films, these aspects are fulfilled and will be considered in the first part of this review. Recent results for the epitaxial growth of wide bandgap insulating films (CaF(2), MgO, NaCl, BaSrO) on metallic and semiconducting vicinal substrates (Si(100), Ge(100), Ag(100)) will be presented. The change of the electronic structure, the adsorption behavior as well as the kinetics and energetics of color centers in the presence of steps is discussed. The successful bridging of the gap between the atomic and mesoscopic world, i.e. the functionalization of vicinal surfaces by nanostructures, is demonstrated in the second part by metal adsorption on semiconducting surfaces. For (sub)monolayer coverage these systems have in common that the surface states do not hybridize with the support, i.e. the semiconducting surfaces are insulating. Here I will focus on the latest results of macroscopic transport measurements on Pb quantum wires grown on vicinal Si(111) showing indeed a one-dimensional transport behavior.

  5. Vicinal surfaces for functional nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Tegenkamp, Christoph [Institut fuer Festkoerperphysik, Gottfried Wilhelm Leibniz Universitaet Hannover, Appelstrasse 2, D-30167 Hannover (Germany)], E-mail: tegenkamp@fkp.uni-hannover.de

    2009-01-07

    Vicinal surfaces are currently the focus of research. The regular arrangements of atomic steps on a mesoscopic scale reveal the possibility to functionalize these surfaces for technical applications, e.g. nanowires, catalysts, etc. The steps of the vicinal surface are well-defined defect structures of atomic size for nucleation of low-dimensional nanostructures. The concentration and therefore the coupling between the nanostructures can be tuned over a wide range by simply changing the inclination angle of the substrate. However, the coupling of these nano-objects to the substrate is just as important in controlling their electronic or chemical properties and making a functionality useable. On the basis of stepped insulating films, these aspects are fulfilled and will be considered in the first part of this review. Recent results for the epitaxial growth of wide bandgap insulating films (CaF{sub 2}, MgO, NaCl, BaSrO) on metallic and semiconducting vicinal substrates (Si(100), Ge(100), Ag(100)) will be presented. The change of the electronic structure, the adsorption behavior as well as the kinetics and energetics of color centers in the presence of steps is discussed. The successful bridging of the gap between the atomic and mesoscopic world, i.e. the functionalization of vicinal surfaces by nanostructures, is demonstrated in the second part by metal adsorption on semiconducting surfaces. For (sub)monolayer coverage these systems have in common that the surface states do not hybridize with the support, i.e. the semiconducting surfaces are insulating. Here I will focus on the latest results of macroscopic transport measurements on Pb quantum wires grown on vicinal Si(111) showing indeed a one-dimensional transport behavior. (topical review)

  6. Vicinal surfaces for functional nanostructures

    International Nuclear Information System (INIS)

    Tegenkamp, Christoph

    2009-01-01

    Vicinal surfaces are currently the focus of research. The regular arrangements of atomic steps on a mesoscopic scale reveal the possibility to functionalize these surfaces for technical applications, e.g. nanowires, catalysts, etc. The steps of the vicinal surface are well-defined defect structures of atomic size for nucleation of low-dimensional nanostructures. The concentration and therefore the coupling between the nanostructures can be tuned over a wide range by simply changing the inclination angle of the substrate. However, the coupling of these nano-objects to the substrate is just as important in controlling their electronic or chemical properties and making a functionality useable. On the basis of stepped insulating films, these aspects are fulfilled and will be considered in the first part of this review. Recent results for the epitaxial growth of wide bandgap insulating films (CaF 2 , MgO, NaCl, BaSrO) on metallic and semiconducting vicinal substrates (Si(100), Ge(100), Ag(100)) will be presented. The change of the electronic structure, the adsorption behavior as well as the kinetics and energetics of color centers in the presence of steps is discussed. The successful bridging of the gap between the atomic and mesoscopic world, i.e. the functionalization of vicinal surfaces by nanostructures, is demonstrated in the second part by metal adsorption on semiconducting surfaces. For (sub)monolayer coverage these systems have in common that the surface states do not hybridize with the support, i.e. the semiconducting surfaces are insulating. Here I will focus on the latest results of macroscopic transport measurements on Pb quantum wires grown on vicinal Si(111) showing indeed a one-dimensional transport behavior. (topical review)

  7. Sea-urchin-like iron oxide nanostructures for water treatment

    International Nuclear Information System (INIS)

    Lee, Hyun Uk; Lee, Soon Chang; Lee, Young-Chul; Vrtnik, Stane; Kim, Changsoo; Lee, SangGap; Lee, Young Boo; Nam, Bora; Lee, Jae Won; Park, So Young; Lee, Sang Moon; Lee, Jouhahn

    2013-01-01

    Highlights: • The u-MFN were synthesized via a ultrasound irradiation and/or calcinations process. • The u-MFN exhibited excellent adsorption capacities. • The u-MFN also displayed excellent adsorption of organic polluent after recycling. • The u-MFN has the potential to be used as an efficient adsorbent material. -- Abstract: To obtain adsorbents with high capacities for removing heavy metals and organic pollutants capable of quick magnetic separation, we fabricated unique sea-urchin-like magnetic iron oxide (mixed γ-Fe 2 O 3 /Fe 3 O 4 phase) nanostructures (called u-MFN) with large surface areas (94.1 m 2 g −1 ) and strong magnetic properties (57.9 emu g −1 ) using a simple growth process and investigated their potential applications in water treatment. The u-MFN had excellent removal capabilities for the heavy metals As(V) (39.6 mg g −1 ) and Cr(VI) (35.0 mg g −1 ) and the organic pollutant Congo red (109.2 mg g −1 ). The u-MFN also displays excellent adsorption of Congo red after recycling. Because of its high adsorption capacity, fast adsorption rate, and quick magnetic separation from treated water, the u-MFN developed in the present study is expected to be an efficient magnetic adsorbent for heavy metals and organic pollutants in aqueous solutions

  8. Transport Properties of Nanostructured Graphene

    DEFF Research Database (Denmark)

    Jauho, Antti-Pekka

    2017-01-01

    Despite of its many wonderful properties, pristine graphene has one major drawback: it does not have a band gap, which complicates its applications in electronic devices. Many routes have been suggested to overcome this difficulty, such as cutting graphene into nanoribbons, using chemical methods...... device operation. In this talk I elaborate these ideas and review the state-of-the-art both from the theoretical and the experimental points of view. I also introduce two new ideas: (1) triangular antidots, and (2) nanobubbles formed in graphene. Both of these nanostructuring methods are predicted...

  9. Field Emission from Carbon Nanostructures

    Directory of Open Access Journals (Sweden)

    Filippo Giubileo

    2018-03-01

    Full Text Available Field emission electron sources in vacuum electronics are largely considered to achieve faster response, higher efficiency and lower energy consumption in comparison with conventional thermionic emitters. Carbon nanotubes had a leading role in renewing attention to field emission technologies in the early 1990s, due to their exceptional electron emitting properties enabled by their large aspect ratio, high electrical conductivity, and thermal and chemical stability. In the last decade, the search for improved emitters has been extended to several carbon nanostructures, comprising carbon nanotubes, either individual or films, diamond structures, graphitic materials, graphene, etc. Here, we review the main results in the development of carbon-based field emitters.

  10. Nanostructured Y2O3

    International Nuclear Information System (INIS)

    Skandan, G.; Hahn, H.; Parker, J.C.

    1991-01-01

    It has been shown that a variety of nanostructured (n-) metal-oxide ceramics such as n-TiO 2 , n-ZrO 2 , n-Al 2 O 3 , n-ZnO and n-MgO can be produced using the inert gas condensation process. Amongst all the nanostructured oxides, the synthesis, microstructure, sintering, and mechanical properties of n-TiO 2 have been studied the most extensively. The gas condensation preparation of nanostructured metal-oxide ceramics involves evaporation of metal nanoparticles, collection and post- oxidation. The original synthesis studies of n-TiO 2 showed that in order to avoid formation of the many low oxidation state oxides in the Ti-O system, the post-oxidation had to be performed by rapidly exposing the Ti nanoparticles to pure oxygen gas. By doing so, the highest oxidation state and the most stable structure, rutile, was obtained. An undesired feature of this step is that the nanoparticles heat up to high temperatures for a brief period of time due to the exothermic nature of the oxidation. As a consequence, the particles with an average size of 12 nm tend to agglomerate into larger structures up to 50 nm. The agglomerated state of the powder is important since it determines the original density and pore size distribution after compaction, as well as the sintering characteristics and final microstructure of the bulk sample. As a consequence of the preparation procedure of n-TiO 2 and the resulting agglomeration, the pore size distribution of n-TiO 2 compacted at room temperature is very wide, with pore sizes ranging from 1 to 200 nm. Nevertheless, the n-TiO 2 sinters at temperatures several hundred degrees lower than conventional coarse grained ceramics. From the previous results on n- TiO 2 it is anticipated that better microstructures and properties can be achieved by reducing the agglomeration of nanostructured powders through a more controlled post- oxidation process

  11. Topological insulator materials and nanostructures for future electronics, spintronics and energy conversion

    International Nuclear Information System (INIS)

    Kantser, Valeriu

    2011-01-01

    Two fundamental electrons attributes in materials and nanostructures - charge and spin - determine their electronic properties. The processing of information in conventional electronic devices is based only on the charge of the electrons. Spin electronics, or spintronics, uses the spin of electrons, as well as their charge, to process information. Metals, semiconductors and insulators are the basic materials that constitute the components of electronic devices, and these have been transforming all aspects of society for over a century. In contrast, magnetic metals, half-metals, magnetic semiconductors, dilute magnetic semiconductors and magnetic insulators are the materials that will form the basis for spintronic devices. Materials with topological band structure attributes and having a zero-energy band gap surface states are a special class of these materials that exhibit some fascinating and superior electronic properties compared to conventional materials allowing to combine both charge and spin functionalities. This article reviews a range of topological insulator materials and nanostructures with tunable surface states, focusing on nanolayered and nanowire like structures. These materials and nanostructures all have intriguing physical properties and numerous potential practical applications in spintronics, electronics, optics and sensors.

  12. Spin splitting generated in a Y-shaped semiconductor nanostructure with a quantum point contact

    International Nuclear Information System (INIS)

    Wójcik, P.; Adamowski, J.; Wołoszyn, M.; Spisak, B. J.

    2015-01-01

    We have studied the spin splitting of the current in the Y-shaped semiconductor nanostructure with a quantum point contact (QPC) in a perpendicular magnetic field. Our calculations show that the appropriate tuning of the QPC potential and the external magnetic field leads to an almost perfect separation of the spin-polarized currents: electrons with opposite spins flow out through different output branches. The spin splitting results from the joint effect of the QPC, the spin Zeeman splitting, and the electron transport through the edge states formed in the nanowire at the sufficiently high magnetic field. The Y-shaped nanostructure can be used to split the unpolarized current into two spin currents with opposite spins as well as to detect the flow of the spin current. We have found that the separation of the spin currents is only slightly affected by the Rashba spin-orbit coupling. The spin-splitter device is an analogue of the optical device—the birefractive crystal that splits the unpolarized light into two beams with perpendicular polarizations. In the magnetic-field range, in which the current is carried through the edges states, the spin splitting is robust against the spin-independent scattering. This feature opens up a possibility of the application of the Y-shaped nanostructure as a non-ballistic spin-splitter device in spintronics

  13. Spin splitting generated in a Y-shaped semiconductor nanostructure with a quantum point contact

    Science.gov (United States)

    Wójcik, P.; Adamowski, J.; Wołoszyn, M.; Spisak, B. J.

    2015-07-01

    We have studied the spin splitting of the current in the Y-shaped semiconductor nanostructure with a quantum point contact (QPC) in a perpendicular magnetic field. Our calculations show that the appropriate tuning of the QPC potential and the external magnetic field leads to an almost perfect separation of the spin-polarized currents: electrons with opposite spins flow out through different output branches. The spin splitting results from the joint effect of the QPC, the spin Zeeman splitting, and the electron transport through the edge states formed in the nanowire at the sufficiently high magnetic field. The Y-shaped nanostructure can be used to split the unpolarized current into two spin currents with opposite spins as well as to detect the flow of the spin current. We have found that the separation of the spin currents is only slightly affected by the Rashba spin-orbit coupling. The spin-splitter device is an analogue of the optical device—the birefractive crystal that splits the unpolarized light into two beams with perpendicular polarizations. In the magnetic-field range, in which the current is carried through the edges states, the spin splitting is robust against the spin-independent scattering. This feature opens up a possibility of the application of the Y-shaped nanostructure as a non-ballistic spin-splitter device in spintronics.

  14. User-Friendly End Station at the ALS for Nanostructure Characterization

    International Nuclear Information System (INIS)

    F. J. Himpsel; P. Alivisatos; T. Callcott; J. Carlisle; J. D. Denlinger; D. E. Eastman; D. Ederer; Z. Hussain; L.J. Terminello; T. Van Buuren; R. S. Williams

    2006-01-01

    This is a construction project for an end station at the ALS, which is optimized for measuring NEXAFS of nanostructures with fluorescence detection. Compared to the usual electron yield detection, fluorescence is able to probe buried structures and is sensitive to dilute species, such as nanostructures supported on a substrate. Since the quantum yield for fluorescence is 10 -4 -10 -5 times smaller than for electrons in the soft x-ray regime, such an end station requires bright undulator beamlines at the ALS. In order to optimize the setup for a wide range of applications, two end stations were built: (1) A simple, mobile chamber with efficient photon detection (>10 4 times the solid angle collection of fluorescence spectrographs) and a built-in magnet for MCD measurements at EPU beamlines (Fig. 1 left). It allows rapid mapping the electronic states of nanostructures (nanocrystals, nanowires, tailored magnetic materials, buried interfaces, biologically-functionalized surfaces). It was used with BL 8.0 (linear polarized undulator) and BL 4.0 (variable polarization). (2) A sophisticated, stationary end station operating at Beamline 8.0 (Fig. 1 right). It contains an array of surface characterization instruments and a micro-focus capability for scanning across graded samples (wedges for thickness variation, stoichiometry gradients, and general variations of the sample preparation conditions for optimizing nanostructures)

  15. Generalized Synthesis of EAs [E = Fe, Co, Mn, Cr] Nanostructures and Investigating Their Morphology Evolution

    Directory of Open Access Journals (Sweden)

    P. Desai

    2015-01-01

    Full Text Available This paper illustrates a novel route for the synthesis of nanostructured transition metal arsenides including those of FeAs, CoAs, MnAs, and CrAs through a generalized protocol. The key feature of the method is the use of one-step hot-injection and the clever use of a combination of precursors which are low-melting and highly reactive such as metal carbonyls and triphenylarsine in a solventless setup. This method also facilitates the formation of one-dimensional nanostructures as we move across the periodic table from CrAs to CoAs. The chemical basis of this reaction is simple redox chemistry between the transition metals, wherein the transition metal is oxidized from elemental state (E0 to E3+in lieu of reduction of As3+ to As3−. While the thermodynamic analysis reveals that all these conversions are spontaneous, it is the kinetics of the process that influences morphology of the product nanostructures, which varies from extremely small nanoparticles to nanorods. Transition metal pnictides show interesting magnetic properties and these nanostructures can serve as model systems for the exploration of their intricate magnetism as well as their applications and can also function as starting materials for the arsenide based nanosuperconductors.

  16. Magnetic structures synthesized by controlled oxidative etching: Structural characterization and magnetic behavior

    Directory of Open Access Journals (Sweden)

    Álvaro de Jesús Ruíz-Baltazar

    Full Text Available A facile strategy for the fabrication Fe3O4 nanostructures at room temperature and with well-defined morphology is proposed. In this methodology, the iron precursors were reduced by sodium borohydride. Subsequently an oxidative etching process promotes the formation of Fe2O3 nanostructures. Magnetic measurements revealed a well-defined superparamagnetic behavior for the material. The Zero-Field-Cooled (ZFC and Field-Cooled (FC magnetization curves reveals that critical and blocking temperature were 24 and 350 °C respectively. The Fe3O4 nanostructures were characterized using aberration-corrected (Cs scanning transmission electron microscopy (STEM and energy dispersive spectroscopy (EDS. Additionally, Raman spectra support the Fe3O4 presence and corroborate the efficiency of the synthesis process to obtain magnetite. Keywords: Chemical synthesis, Fe3O4 nanoparticles, Structural characterization, Magnetic properties

  17. Chiral magnetism of magnetic adatoms generated by Rashba electrons

    Science.gov (United States)

    Bouaziz, Juba; dos Santos Dias, Manuel; Ziane, Abdelhamid; Benakki, Mouloud; Blügel, Stefan; Lounis, Samir

    2017-02-01

    We investigate long-range chiral magnetic interactions among adatoms mediated by surface states spin-splitted by spin-orbit coupling. Using the Rashba model, the tensor of exchange interactions is extracted wherein a thepseudo-dipolar interaction is found, in addition to the usual isotropic exchange interaction and the Dzyaloshinskii-Moriya interaction. We find that, despite the latter interaction, collinear magnetic states can still be stabilized by the pseudo-dipolar interaction. The interadatom distance controls the strength of these terms, which we exploit to design chiral magnetism in Fe nanostructures deposited on a Au(111) surface. We demonstrate that these magnetic interactions are related to superpositions of the out-of-plane and in-plane components of the skyrmionic magnetic waves induced by the adatoms in the surrounding electron gas. We show that, even if the interatomic distance is large, the size and shape of the nanostructures dramatically impacts on the strength of the magnetic interactions, thereby affecting the magnetic ground state. We also derive an appealing connection between the isotropic exchange interaction and the Dzyaloshinskii-Moriya interaction, which relates the latter to the first-order change of the former with respect to spin-orbit coupling. This implies that the chirality defined by the direction of the Dzyaloshinskii-Moriya vector is driven by the variation of the isotropic exchange interaction due to the spin-orbit interaction.

  18. Inorganic nanostructure-organic polymer heterostructures useful for thermoelectric devices

    Energy Technology Data Exchange (ETDEWEB)

    See, Kevin C.; Urban, Jeffrey J.; Segalman, Rachel A.; Coates, Nelson E.; Yee, Shannon K.

    2017-11-28

    The present invention provides for an inorganic nanostructure-organic polymer heterostructure, useful as a thermoelectric composite material, comprising (a) an inorganic nanostructure, and (b) an electrically conductive organic polymer disposed on the inorganic nanostructure. Both the inorganic nanostructure and the electrically conductive organic polymer are solution-processable.

  19. Process Development for Nanostructured Photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Elam, Jeffrey W.

    2015-01-01

    Photovoltaic manufacturing is an emerging industry that promises a carbon-free, nearly limitless source of energy for our nation. However, the high-temperature manufacturing processes used for conventional silicon-based photovoltaics are extremely energy-intensive and expensive. This high cost imposes a critical barrier to the widespread implementation of photovoltaic technology. Argonne National Laboratory and its partners recently invented new methods for manufacturing nanostructured photovoltaic devices that allow dramatic savings in materials, process energy, and cost. These methods are based on atomic layer deposition, a thin film synthesis technique that has been commercialized for the mass production of semiconductor microelectronics. The goal of this project was to develop these low-cost fabrication methods for the high efficiency production of nanostructured photovoltaics, and to demonstrate these methods in solar cell manufacturing. We achieved this goal in two ways: 1) we demonstrated the benefits of these coatings in the laboratory by scaling-up the fabrication of low-cost dye sensitized solar cells; 2) we used our coating technology to reduce the manufacturing cost of solar cells under development by our industrial partners.

  20. Space charge in nanostructure resonances

    Science.gov (United States)

    Price, Peter J.

    1996-10-01

    In quantum ballistic propagation of electrons through a variety of nanostructures, resonance in the energy-dependent transmission and reflection probabilities generically is associated with (1) a quasi-level with a decay lifetime, and (2) a bulge in electron density within the structure. It can be shown that, to a good approximation, a simple formula in all cases connects the density of states for the latter to the energy dependence of the phase angles of the eigen values of the S-matrix governing the propagation. For both the Lorentzian resonances (normal or inverted) and for the Fano-type resonances, as a consequence of this eigen value formula, the space charge due to filled states over the energy range of a resonance is just equal (for each spin state) to one electron charge. The Coulomb interaction within this space charge is known to 'distort' the electrical characteristics of resonant nanostructures. In these systems, however, the exchange effect should effectively cancel the interaction between states with parallel spins, leaving only the anti-parallel spin contribution.

  1. Quantitative Characterization of Nanostructured Materials

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Frank (Bud) Bridges, University of California-Santa Cruz

    2010-08-05

    The two-and-a-half day symposium on the "Quantitative Characterization of Nanostructured Materials" will be the first comprehensive meeting on this topic held under the auspices of a major U.S. professional society. Spring MRS Meetings provide a natural venue for this symposium as they attract a broad audience of researchers that represents a cross-section of the state-of-the-art regarding synthesis, structure-property relations, and applications of nanostructured materials. Close interactions among the experts in local structure measurements and materials researchers will help both to identify measurement needs pertinent to real-world materials problems and to familiarize the materials research community with the state-of-the-art local structure measurement techniques. We have chosen invited speakers that reflect the multidisciplinary and international nature of this topic and the need to continually nurture productive interfaces among university, government and industrial laboratories. The intent of the symposium is to provide an interdisciplinary forum for discussion and exchange of ideas on the recent progress in quantitative characterization of structural order in nanomaterials using different experimental techniques and theory. The symposium is expected to facilitate discussions on optimal approaches for determining atomic structure at the nanoscale using combined inputs from multiple measurement techniques.

  2. Lifetime of Nano-Structured Black Silicon for Photovoltaic Applications

    DEFF Research Database (Denmark)

    Plakhotnyuk, Maksym; Davidsen, Rasmus Schmidt; Schmidt, Michael Stenbæk

    2016-01-01

    In this work, we present recent results of lifetime optimization for nano-structured black silicon and its photovoltaic applications. Black silicon nano-structures provide significant reduction of silicon surface reflection due to highly corrugated nanostructures with excellent light trapping pro......, respectively. This is promising for use of black silicon RIE nano-structuring in a solar cell process flow......In this work, we present recent results of lifetime optimization for nano-structured black silicon and its photovoltaic applications. Black silicon nano-structures provide significant reduction of silicon surface reflection due to highly corrugated nanostructures with excellent light trapping...

  3. Silicon-embedded copper nanostructure network for high energy storage

    Science.gov (United States)

    Yu, Tianyue

    2016-03-15

    Provided herein are nanostructure networks having high energy storage, electrochemically active electrode materials including nanostructure networks having high energy storage, as well as electrodes and batteries including the nanostructure networks having high energy storage. According to various implementations, the nanostructure networks have high energy density as well as long cycle life. In some implementations, the nanostructure networks include a conductive network embedded with electrochemically active material. In some implementations, silicon is used as the electrochemically active material. The conductive network may be a metal network such as a copper nanostructure network. Methods of manufacturing the nanostructure networks and electrodes are provided. In some implementations, metal nanostructures can be synthesized in a solution that contains silicon powder to make a composite network structure that contains both. The metal nanostructure growth can nucleate in solution and on silicon nanostructure surfaces.

  4. Silicon-embedded copper nanostructure network for high energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Tianyue

    2018-01-23

    Provided herein are nanostructure networks having high energy storage, electrochemically active electrode materials including nanostructure networks having high energy storage, as well as electrodes and batteries including the nanostructure networks having high energy storage. According to various implementations, the nanostructure networks have high energy density as well as long cycle life. In some implementations, the nanostructure networks include a conductive network embedded with electrochemically active material. In some implementations, silicon is used as the electrochemically active material. The conductive network may be a metal network such as a copper nanostructure network. Methods of manufacturing the nanostructure networks and electrodes are provided. In some implementations, metal nanostructures can be synthesized in a solution that contains silicon powder to make a composite network structure that contains both. The metal nanostructure growth can nucleate in solution and on silicon nanostructure surfaces.

  5. Effect of surfactant for magnetic properties of iron oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Haracz, S. [Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89B, 61-614 Poznań (Poland); Hilgendorff, M. [Freie Universität Berlin, Fachbereich Physik, Arnimalle 14, 14195 Berlin (Germany); Rybka, J.D. [Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89B, 61-614 Poznań (Poland); Giersig, M. [Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89B, 61-614 Poznań (Poland); Freie Universität Berlin, Fachbereich Physik, Arnimalle 14, 14195 Berlin (Germany)

    2015-12-01

    Highlights: • Dynamic behavior of magnetic nanoparticles. • Synthesis of iron oxide nanoparticles. • Effect of surfactant for magnetic properties. - Abstract: For different medical applications nanoparticles (NPs) with well-defined magnetic properties have to be used. Coating ligand can change the magnetic moment on the surface of nanostructures and therefore the magnetic behavior of the system. Here we investigated magnetic NPs in a size of 13 nm conjugated with four different kinds of surfactants. The surface anisotropy and the magnetic moment of the system were changed due to the presence of the surfactant on the surface of iron oxide NPs.

  6. Tetrazole amphiphile inducing growth of conducting polymers hierarchical nanostructures and their electromagnetic absorption properties

    Science.gov (United States)

    Xie, Aming; Sun, Mengxiao; Zhang, Kun; Xia, Yilu; Wu, Fan

    2018-05-01

    Conducting polymers (CPs) at nano scales endow materials with special optical, electrical, and magnetic properties. The crucial factor to construct and regulate the micro-structures of CPs is the inducing reagent, particular in its chemical structure, such active sites, self-assembling properties. In this paper, we design and synthesize an amphiphile bearing tetrazole moiety on its skeleton, and use this amphiphile as an inducing reagent to prepare and regulate the micro-structures of a series of CPs including polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene) and poly(p-phenylenediamine). Because of the unique electric properties of CPs and size effect, we next explored the electromagnetic absorption performances of these CPs nanostructures. A synergetic combination of electric loss and magnetic loss is used to explain the absorption mechanism of these CPs nano-structures.

  7. Spin Hall magnetoresistance in Ta/CoFe2O4 nanostructures

    Science.gov (United States)

    Hui, Ya-Juan; Cheng, Wei-Ming; Zhang, Zhao-Bing; Ji, Hong-Kai; Cheng, Xiao-Min; You, Long; Miao, Xiang-Shui

    2016-07-01

    Spin Hall magnetoresistance (SMR) has been investigated in Ta/CoFe2O4 nanostructures grown on different substrates. Spin currents in CoFe2O4 films are electrically detected in adjacent Ta layers owing to inverse spin Hall effects. The sign of the magnetic-field-dependent resistivity signal shows different polarities along different axes, showing different spin-dependent electron transports. A cosinelike curve of the angular dependence signal with opposite polarity is observed in two orthogonal magnetization planes, whereas a basic line is observed in another plane, revealing the spin accumulation phenomenon. The roughness of the CoFe2O4 surface tuned by substrate strains is responsible for the extent of spin accumulations and the strength of the SMR signal in the nanostructures.

  8. Nanostructured transparent conducting oxide electrochromic device

    Science.gov (United States)

    Milliron, Delia; Tangirala, Ravisubhash; Llordes, Anna; Buonsanti, Raffaella; Garcia, Guillermo

    2016-05-17

    The embodiments described herein provide an electrochromic device. In an exemplary embodiment, the electrochromic device includes (1) a substrate and (2) a film supported by the substrate, where the film includes transparent conducting oxide (TCO) nanostructures. In a further embodiment, the electrochromic device further includes (a) an electrolyte, where the nanostructures are embedded in the electrolyte, resulting in an electrolyte, nanostructure mixture positioned above the substrate and (b) a counter electrode positioned above the mixture. In a further embodiment, the electrochromic device further includes a conductive coating deposited on the substrate between the substrate and the mixture. In a further embodiment, the electrochromic device further includes a second substrate positioned above the mixture.

  9. Nanostructured thin films and coatings functional properties

    CERN Document Server

    Zhang, Sam

    2010-01-01

    The second volume in ""The Handbook of Nanostructured Thin Films and Coatings"" set, this book focuses on functional properties, including optical, electronic, and electrical properties, as well as related devices and applications. It explores the large-scale fabrication of functional thin films with nanoarchitecture via chemical routes, the fabrication and characterization of SiC nanostructured/nanocomposite films, and low-dimensional nanocomposite fabrication and applications. The book also presents the properties of sol-gel-derived nanostructured thin films as well as silicon nanocrystals e

  10. Ceramic nanostructures and methods of fabrication

    Science.gov (United States)

    Ripley, Edward B [Knoxville, TN; Seals, Roland D [Oak Ridge, TN; Morrell, Jonathan S [Knoxville, TN

    2009-11-24

    Structures and methods for the fabrication of ceramic nanostructures. Structures include metal particles, preferably comprising copper, disposed on a ceramic substrate. The structures are heated, preferably in the presence of microwaves, to a temperature that softens the metal particles and preferably forms a pool of molten ceramic under the softened metal particle. A nano-generator is created wherein ceramic material diffuses through the molten particle and forms ceramic nanostructures on a polar site of the metal particle. The nanostructures may comprise silica, alumina, titania, or compounds or mixtures thereof.

  11. nanostructures

    Indian Academy of Sciences (India)

    Wintec

    In this method no special electrolytes, chemicals and surfactants are needed. ... tures collected from the bottom of the cell are either nanothreads embodying beads of different diameters,. ~10–40 nm or .... when copious oxygen produced through electrolysis at- ... corresponding bandgap calculations of the as synthesized.

  12. Direct Magnetic Relief Recording Using As40S60: Mn-Se Nanocomposite Multilayer Structures.

    Science.gov (United States)

    Stronski, A; Achimova, E; Paiuk, O; Meshalkin, A; Prisacar, A; Triduh, G; Oleksenko, P; Lytvyn, P

    2017-12-01

    Processes of holographic recording of surface relief structures using As 2 S 3 :Mn-Se multilayer nanostructures as registering media were studied in this paper. Optical properties of As 2 S 3 :Mn, Se layers, and As 2 S 3 :Mn-Se multilayer nanostructures were investigated. Values of optical bandgaps were obtained from Tauc dependencies. Surface relief diffraction gratings were recorded. Direct one-stage formation of surface relief using multilayer nanostructures is considered. For the first time, possibility of direct formation of magnetic relief simultaneous with surface relief formation under optical recording using As 2 S 3 :Mn-Se multilayer nanostructures is shown.

  13. Electrodeposited Ni-W magnetic thin films with columnar nanocrystallites

    International Nuclear Information System (INIS)

    Sulitanu, N.; Brinza, F.

    2002-01-01

    Nanocrystalline Ni-W thin films (140 nm) containing from zero to 18 wt % W were electrolytically prepared and structural and magnetic characterized. XRD, SEM and TEM investigations have revealed that all segregated Ni columns are fcc-type whose [111] axis is oriented perpendicular to the film plane and have 140 nm in height and 6-27 nm in diameter. Depending on film composition, two types of nanostructures were observed: (a) single-phase nanostructure ( i nterphases , namely W enriched particles boundaries, and (b) two-phase nanostructure (7-18 wt %) in which a second Ni-W amorphous phase or even amorphous-disordered mixture separates the magnetic columnar Ni nanocrystallites (d = 6-14 nm). The columnar crystallites have an easy magnetization direction along their long axis mainly due to the in-plane internal biaxial stresses. Magnetic characteristics of prepared thin films are presented. (Authors)

  14. Semiconductive Nanostructures - Materials for Spinelectronics: New Data Bank Requirement

    Directory of Open Access Journals (Sweden)

    Paata J Kervalishvili

    2007-12-01

    Full Text Available Nanoscience, the interdisciplinary science that draws on physics, chemistry, biology, and computational mathematics, is still in its infancy. Control and manipulation on a nanometric scale allow the fabrication of nanostructures, the properties of which are mainly determined by quantum mechanics and differ considerably from that of the common crystalline state. Nanostructures constructed from inorganic solids such as semiconductors have new electronic and optical properties because of their size and quantization effects [1, 2]. The quantization effects reflect the fundamental characteristics of structures as soon as their size falls below a certain limit. An example of the simplest nanostructure is the quantum dot formed from the energy well of certain semiconductor materials with 5-10nm thickness sandwiched between other semiconductors with normal properties. Quantum dots, for example, have led to important novel technology for lasers, optical sensors, and other electronic devices. The application of nanolayers to data storage, switching, lighting, and other devices can lead to substantially new hardware, for example, energy cells, and eventually to the quantum-based internet. Nanoscience and nanotechnology encompass the development of nano-spinelectronics, spinelectronics materials production, and nano-spinelectronic measuring devices and technologies. Nano-spinelectronics, based on usage of magnetic semiconductors, represents a new and emerging area of science and engineering of the 21st century. It is a primary example of the creation and enhancement of new materials and devices for information technologies, operating with charge and spin degrees of freedom of carriers, free from present-day limitations. This new multi-disciplinary direction of science and technology is very much in need of support from new data banks, which will function as a source of new ideas and approaches.

  15. Charge transport in nanostructured materials for solar energy conversion studied by time-resolved terahertz spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Němec, Hynek; Kužel, Petr; Sundström, V.

    2010-01-01

    Roč. 215, 2-3 (2010), s. 123-139 ISSN 1010-6030 R&D Projects: GA ČR(CZ) GP202/09/P099; GA AV ČR(CZ) IAA100100902; GA MŠk LC512 Institutional research plan: CEZ:AV0Z10100520 Keywords : time-resolved terahertz spectroscopy * ultrafast dynamics * bulk heterojunction * semiconductor nanostructures * transport * mobility Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.243, year: 2010

  16. Transfer of energy or charge between quasi-zero-dimensional nanostructures

    Czech Academy of Sciences Publication Activity Database

    Král, Karel; Menšík, Miroslav

    2016-01-01

    Roč. 45, č. 4 (2016), s. 243-255 ISSN 2332-4309 R&D Projects: GA ČR(CZ) GA14-05053S; GA MŠk(CZ) LD14011; GA MŠk LH12236 Institutional support: RVO:68378271 ; RVO:61389013 Keywords : charge transfer * electron-phonon interaction * energy transfer * nanostructures * quantum dots Subject RIV: BM - Solid Matter Physics ; Magnetism; CD - Macromolecular Chemistry (UMCH-V) Impact factor: 0.171, year: 2016

  17. Silicon vacancy-related centers in non-irradiated 6H-SiC nanostructur

    Czech Academy of Sciences Publication Activity Database

    Bagraev, N.T.; Danilovskii, E.Yu.; Gets, D.S.; Kalabukhova, E.N.; Klyachkin, L.E.; Koudryavtsev, A.A.; Malyarenko, A.M.; Mashkov, V.A.; Savchenko, Dariia; Shanina, B.D.

    2015-01-01

    Roč. 49, č. 5 (2015), 649-657 ISSN 1063-7826 R&D Projects: GA ČR GP13-06697P; GA MŠk(CZ) LM2011029 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : electron spin resonance * 6H-SiC nanostructures * silicon vacancy related centers * NV centers Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.701, year: 2015

  18. Electrically-detected electron paramagnetic resonance of point centers in 6H-SiC nanostructures

    Czech Academy of Sciences Publication Activity Database

    Bagraev, N.T.; Gets, D.S.; Kalabukhova, E.N.; Klyachkin, L.E.; Malyarenko, A.M.; Mashkov, V.A.; Savchenko, Dariia; Shanina, B.D.

    2014-01-01

    Roč. 48, č. 11 (2014), s. 1467-1480 ISSN 1063-7826 R&D Projects: GA MŠk(CZ) LM2011029 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : electron paramagnetic resonance * electrically- detected electron paramagnetic resonance * 6H -SiC nanostructures * nitrogen-vacancy defect * point defect Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.739, year: 2014

  19. Hydrothermal synthesis of nanostructured titania

    International Nuclear Information System (INIS)

    Yoshito, Walter Kenji; Ferreira, Nildemar A.M.; Rumbao, Ana Carolina S. Coutinho; Lazar, Dolores R.R.; Ussui, Valter

    2009-01-01

    Titania ceramics have many applications due to its surface properties and, recently, its nanostructured compounds, prepared by hydrothermal treatments, have been described to improve these properties. In this work, commercial titanium dioxide was treated with 10% sodium hydroxide solution in a pressurized reactor at 150°C for 24 hours under vigorous stirring and then washed following two different procedures. The first one consisted of washing with water and ethanol and the second with water and hydrochloric acid solution (1%). Resulting powders were characterized by X-ray diffraction, N 2 gas adsorption and field emission gun scanning and transmission electronic microscopy. Results showed that from an original starting material with mainly rutile phase, both anatase and H 2 Ti 3 O 7 phase could be identified after the hydrothermal treatment. Surface area of powders presented a notable increase of one order of magnitude and micrographs showed a rearrangement on the microstructure of powders. (author)

  20. Modelling nanostructures with vicinal surfaces

    International Nuclear Information System (INIS)

    Mugarza, A; Schiller, F; Kuntze, J; Cordon, J; Ruiz-Oses, M; Ortega, J E

    2006-01-01

    Vicinal surfaces of the (111) plane of noble metals are characterized by free-electron-like surface states that scatter at one-dimensional step edges, making them ideal model systems to test the electronic properties of periodic lateral nanostructures. Here we use high-resolution, angle-resolved photoemission to analyse the evolution of the surface state on a variety of vicinal surface structures where both the step potential barrier and the superlattice periodicity can vary. A transition in the electron dimensionality is found as we vary the terrace size in single-phase step arrays. In double-phase, periodic faceted surfaces, we observe surface states that characterize each of the phases

  1. Homoepitaxial Nanostructures of Zinc Oxide

    Directory of Open Access Journals (Sweden)

    Tatiana V. Plakhova

    2015-01-01

    Full Text Available The homoepitaxial ZnO nanostructures (HENS were obtained on different substrates using various techniques. The first type of homoepitaxial ZnO nanorod arrays was grown on Si or ITO substrates by using two alternative sequences: (a seeding → growth from solution → growth from vapor and contrariwise (b seeding → growth from vapor → growth from solution. As follows from transport and cathode luminescence measurements homoepitaxial growth allows enhancing electrical or luminescence properties. The second type of HENS was prepared by growth of vertically or horizontally oriented ZnO nanorod arrays depending on monocrystalline ZnO wafers with [0001] and [10-10] orientation. In all cases the growth occurs along the c-axis of fast growth.

  2. Optical Characterization of Nanostructured Surfaces

    DEFF Research Database (Denmark)

    Feidenhans'l, Nikolaj Agentoft

    Micro- and nanostructured surfaces are interesting due to the unique properties they add to the bulk material. One example is structural colors, where the interaction between surface structures and visible light produce bright color effects without the use of paints or dyes. Several research groups...... modeling to evaluate the dimensions of subwavelength gratings, by correlating the reflected light measured from the structures with a database of simulations. A new method is developed and termed color scatterometry, since compared to typical spectroscopic scatterometry, which evaluates the full reflection...... spectrum; the new method only evaluates the color of the reflected light using a standard RGB color camera. Color scatterometry provides the combined advantages of spectroscopic scatterometry, which provides fast evaluations, and imaging scatterometry that provides an overview image from which small...

  3. Hydrothermal synthesis of nanostructured titania

    International Nuclear Information System (INIS)

    Yoshito, W.K.; Ferreira, N.A.M.; Lazar, D.R.R.; Ussui, V.; Rumbao, A.C.S.

    2011-01-01

    Titania ceramics have many applications due to its surface properties and, recently, its nanostructured compounds, prepared by hydrothermal treatments, have been described to improve these properties. In this work, commercial titanium dioxide was treated with 10% sodium hydroxide solution in a pressurized reactor at 150 deg C for 24 hours under vigorous stirring and then washed following two different procedures. The first one consisted of washing with water and ethanol and the second with water and hydrochloric acid solution (1%). Resulting powders were characterized by X-ray diffraction, N 2 gas adsorption and field emission gun scanning and transmission electronic microscopy. Results showed that from an original starting material with mainly rutile phase, both anatase and H 2 Ti 3 O 7 phase could be identified after the hydrothermal treatment. Surface area of powders presented a notable increase of one order of magnitude and micrographs showed a rearrangement on the microstructure of powders. (author)

  4. Current-driven vortex domain wall motion in wire-tube nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Espejo, A. P. [Departamento de Física, Universidad de Santiago de Chile (USACH), Av. Ecuador 3493, 9170124 Santiago (Chile); Institute of Nanostructure and Solid State Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg (Germany); Vidal-Silva, N. [Departamento de Física, Universidad de Santiago de Chile (USACH), Av. Ecuador 3493, 9170124 Santiago (Chile); López-López, J. A. [Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Valparaíso (Chile); Goerlitz, D.; Nielsch, K. [Institute of Nanostructure and Solid State Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg (Germany); Escrig, J. [Departamento de Física, Universidad de Santiago de Chile (USACH), Av. Ecuador 3493, 9170124 Santiago (Chile); Center for the Development of Nanoscience and Nanotechnology (CEDENNA), Av. Ecuador 3493, 9170124 Santiago (Chile)

    2015-03-30

    We have investigated the current-driven domain wall motion in nanostructures comprised of a pair of nanotube and nanowire segments. Under certain values of external magnetic fields, it is possible to pin a vortex domain wall in the transition zone between the wire and tube segments. We explored the behavior of this domain wall under the action of an electron flow applied in the opposite direction to the magnetic field. Thus, for a fixed magnetic field, it is possible to release a domain wall pinned simply by increasing the intensity of the current density, or conversely, for a fixed current density, it is possible to release the domain wall simply decreasing the magnetic external field. When the domain wall remains pinned due to the competition between the current density and the magnetic external field, it exhibits a oscillation frequency close to 8 GHz. The amplitude of the oscillations increases with the current density and decreases over time. On the other hand, when the domain wall is released and propagated through the tube segment, this shows the standard separation between a steady and a precessional regime. The ability to pin and release a domain wall by varying the geometric parameters, the current density, or the magnetic field transforms these wire-tube nanostructures in an interesting alternative as an on/off switch nano-transistor.

  5. PREFACE: Domain wall dynamics in nanostructures Domain wall dynamics in nanostructures

    Science.gov (United States)

    Marrows, C. H.; Meier, G.

    2012-01-01

    forms of ordered phases such as antiferromagnetism and ferroelectricity. We would like to thank the scientists from all over the world who happily agreed to contribute their latest results to this special issue, and the Journal of Physics: Condensed Matter staff for their help, patience and professionalism. In such a fast-moving field it is not possible to give a definitive account, and this special issue can be no more than a snapshot of the current state of knowledge regarding this topic. Nevertheless, we hope that this collection of papers is a useful resource for experienced workers in the field, forms a useful introduction to researchers early in their careers and inspires others in related areas of nanotechnology to enter into the study of domain dynamics in nanostructures. Domain wall dynamics in nanostructures contents Temperature estimation in a ferromagnetic Fe-Ni nanowire involving a current-driven domain wall motionA Yamaguchi, A Hirohata, T Ono and H Miyajima Magnetization reversal in magnetic nanostripes via Bloch wall formation M Zeisberger and R Mattheis Magnetic soft x-ray microscopy of the domain wall depinning process in permalloy magnetic nanowiresMi-Young Im, Lars Bocklage, Guido Meier and Peter Fischer Domain wall propagation in meso- and nanoscale ferroelectrics R G P McQuaid, M McMillen, L-W Chang, A Gruverman and J M Gregg Transverse and vortex domain wall structure in magnetic nanowires with uniaxial in-plane anisotropyM T Bryan, S Bance, J Dean, T Schrefl and D A Allwood The stochastic nature of the domain wall motion along high perpendicular anisotropy strips with surface roughness Eduardo Martinez Temperature-dependent dynamics of stochastic domain-wall depinning in nanowiresClemens Wuth, Peter Lendecke and Guido Meier Controlled pinning and depinning of domain walls in nanowires with perpendicular magnetic anisotropyTheo Gerhardt, André Drews and Guido Meier The interaction of transverse domain wallsBenjamin Krüger The increase of the

  6. Robust Magnetic Properties of a Sublimable Single-Molecule Magnet.

    Science.gov (United States)

    Kiefl, Evan; Mannini, Matteo; Bernot, Kevin; Yi, Xiaohui; Amato, Alex; Leviant, Tom; Magnani, Agnese; Prokscha, Thomas; Suter, Andreas; Sessoli, Roberta; Salman, Zaher

    2016-06-28

    The organization of single-molecule magnets (SMMs) on surfaces via thermal sublimation is a prerequisite for the development of future devices for spintronics exploiting the richness of properties offered by these magnetic molecules. However, a change in the SMM properties due to the interaction with specific surfaces is usually observed. Here we present a rare example of an SMM system that can be thermally sublimated on gold surfaces while maintaining its intact chemical structure and magnetic properties. Muon spin relaxation and ac susceptibility measurements are used to demonstrate that, unlike other SMMs, the magnetic properties of this system in thin films are very similar to those in the bulk, throughout the full volume of the film, including regions near the metal and vacuum interfaces. These results exhibit the robustness of chemical and magnetic properties of this complex and provide important clues for the development of nanostructures based on SMMs.

  7. Hierarchically Nanostructured Materials for Sustainable Environmental Applications

    Directory of Open Access Journals (Sweden)

    Zheng eRen

    2013-11-01

    Full Text Available This article presents a comprehensive overview of the hierarchical nanostructured materials with either geometry or composition complexity in environmental applications. The hierarchical nanostructures offer advantages of high surface area, synergistic interactions and multiple functionalities towards water remediation, environmental gas sensing and monitoring as well as catalytic gas treatment. Recent advances in synthetic strategies for various hierarchical morphologies such as hollow spheres and urchin-shaped architectures have been reviewed. In addition to the chemical synthesis, the physical mechanisms associated with the materials design and device fabrication have been discussed for each specific application. The development and application of hierarchical complex perovskite oxide nanostructures have also been introduced in photocatalytic water remediation, gas sensing and catalytic converter. Hierarchical nanostructures will open up many possibilities for materials design and device fabrication in environmental chemistry and technology.

  8. Nanostructures for Electrical Energy Storage (NEES) EFRC

    Data.gov (United States)

    Federal Laboratory Consortium — The Nanostructures for Electrical Energy Storage (NEES) EFRC is a multi-institutional research center, one of 46 Energy Frontier Research Centers established by the...

  9. Sulfated glycopeptide nanostructures for multipotent protein activation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sungsoo S.; Fyrner, Timmy; Chen, Feng; Álvarez, Zaida; Sleep, Eduard; Chun, Danielle S.; Weiner, Joseph A.; Cook, Ralph W.; Freshman, Ryan D.; Schallmo, Michael S.; Katchko, Karina M.; Schneider, Andrew D.; Smith, Justin T.; Yun, Chawon; Singh, Gurmit; Hashmi, Sohaib Z.; McClendon, Mark T.; Yu, Zhilin; Stock, Stuart R.; Hsu, Wellington K.; Hsu, Erin L.; Stupp , Samuel I. (NWU)

    2017-06-19

    Biological systems have evolved to utilize numerous proteins with capacity to bind polysaccharides for the purpose of optimizing their function. A well-known subset of these proteins with binding domains for the highly diverse sulfated polysaccharides are important growth factors involved in biological development and tissue repair. We report here on supramolecular sulfated glycopeptide nanostructures, which display a trisulfated monosaccharide on their surfaces and bind five critical proteins with different polysaccharide-binding domains. Binding does not disrupt the filamentous shape of the nanostructures or their internal β-sheet backbone, but must involve accessible adaptive configurations to interact with such different proteins. The glycopeptide nanostructures amplified signalling of bone morphogenetic protein 2 significantly more than the natural sulfated polysaccharide heparin, and promoted regeneration of bone in the spine with a protein dose that is 100-fold lower than that required in the animal model. These highly bioactive nanostructures may enable many therapies in the future involving proteins.

  10. Metallic Nanostructures Based on DNA Nanoshapes

    Directory of Open Access Journals (Sweden)

    Boxuan Shen

    2016-08-01

    Full Text Available Metallic nanostructures have inspired extensive research over several decades, particularly within the field of nanoelectronics and increasingly in plasmonics. Due to the limitations of conventional lithography methods, the development of bottom-up fabricated metallic nanostructures has become more and more in demand. The remarkable development of DNA-based nanostructures has provided many successful methods and realizations for these needs, such as chemical DNA metallization via seeding or ionization, as well as DNA-guided lithography and casting of metallic nanoparticles by DNA molds. These methods offer high resolution, versatility and throughput and could enable the fabrication of arbitrarily-shaped structures with a 10-nm feature size, thus bringing novel applications into view. In this review, we cover the evolution of DNA-based metallic nanostructures, starting from the metallized double-stranded DNA for electronics and progress to sophisticated plasmonic structures based on DNA origami objects.

  11. Probing plasmonic nanostructures by photons and electrons

    DEFF Research Database (Denmark)

    Kneipp, Katrin; Kneipp, Harald; Kneipp, Janina

    2015-01-01

    We discuss recent developments for studying plasmonic metal nanostructures. Exploiting photons and electrons opens up new capabilities to probe the complete plasmon spectrum including bright and dark modes and related local optical fields at subnanometer spatial resolution. This comprehensive cha...

  12. Second harmonic spectroscopy of semiconductor nanostructures

    DEFF Research Database (Denmark)

    Østergaard, John Erland; Yu, Ping; Bozhevolnyi, Sergey I.

    1999-01-01

    Semiconductor nanostructures and their application to optoelectronic devices have attracted much attention recently. Lower-dimensional structures, and in particular quantum dots, are highly anisotropic resulting in broken symmetry as compared to their bulk counterparts. This is not only reflected...

  13. Packaging glass with hierarchically nanostructured surface

    KAUST Repository

    He, Jr-Hau

    2017-08-03

    An optical device includes an active region and packaging glass located on top of the active region. A top surface of the packaging glass includes hierarchical nanostructures comprised of honeycombed nanowalls (HNWs) and nanorod (NR) structures extending from the HNWs.

  14. Nanostructuring steel for injection molding tools

    DEFF Research Database (Denmark)

    Al-Azawi, A.; Smistrup, Kristian; Kristensen, Anders

    2014-01-01

    The production of nanostructured plastic items by injection molding with ridges down to 400 nm in width, which is the smallest line width replicated from nanostructured steel shims, is presented. Here we detail a micro-fabrication method where electron beam lithography, nano-imprint lithography...... and ion beam etching are combined to nanostructure the planar surface of a steel wafer. Injection molded plastic parts with enhanced surface properties, like anti-reflective, superhydrophobic and structural colors can be achieved by micro-and nanostructuring the surface of the steel molds. We investigate...... the minimum line width that can be realized by our fabrication method and the influence of etching angle on the structure profile during the ion beam etching process. Trenches down to 400 nm in width have been successfully fabricated into a 316 type electro-polished steel wafer. Afterward a plastic replica...

  15. Packaging glass with hierarchically nanostructured surface

    KAUST Repository

    He, Jr-Hau; Fu, Hui-Chun

    2017-01-01

    An optical device includes an active region and packaging glass located on top of the active region. A top surface of the packaging glass includes hierarchical nanostructures comprised of honeycombed nanowalls (HNWs) and nanorod (NR) structures

  16. Plant-derived nanostructures: types and applications

    Science.gov (United States)

    Plant-derived nanostructures and nanoparticles (NPs) have functional applications in numerous disciplines such as health care, food and feed, cosmetics, biomedical science, energy science, drug-gene delivery, environmental health, and so on. Consequently, it is imperative for res...

  17. Chemical modifications and reactions in DNA nanostructures

    DEFF Research Database (Denmark)

    Gothelf, Kurt Vesterager

    2017-01-01

    such as hydrocarbons or steroids have been introduced to change the surface properties of DNA origami structures, either to protect the DNA nanostructure or to dock it into membranes and other hydrophobic surfaces. DNA nanostructures have also been used to control covalent chemical reactions. This article provides......DNA nanotechnology has the power to form self-assembled and well-defined nanostructures, such as DNA origami, where the relative positions of each atom are known with subnanometer precision. Our ability to synthesize oligonucleotides with chemical modifications in almost any desired position...... provides rich opportunity to incorporate molecules, biomolecules, and a variety of nanomaterials in specific positions on DNA nanostructures. Several standard modifications for oligonucleotides are available commercially, such as dyes, biotin, and chemical handles, and such modified oligonucleotides can...

  18. Hollow Micro-/Nanostructures: Synthesis and Applications

    KAUST Repository

    Lou, Xiong Wen (David); Archer, Lynden A.; Yang, Zichao

    2008-01-01

    for Portland cement, to produce concrete with enhanced strength and durability. This review is devoted to the progress made in the last decade in synthesis and applications of hollow micro-nanostructures. We present a comprehensive overview of synthetic

  19. Optical Biosensors Based on Semiconductor Nanostructures

    Directory of Open Access Journals (Sweden)

    Raúl J. Martín-Palma

    2009-06-01

    Full Text Available The increasing availability of semiconductor-based nanostructures with novel and unique properties has sparked widespread interest in their use in the field of biosensing. The precise control over the size, shape and composition of these nanostructures leads to the accurate control of their physico-chemical properties and overall behavior. Furthermore, modifications can be made to the nanostructures to better suit their integration with biological systems, leading to such interesting properties as enhanced aqueous solubility, biocompatibility or bio-recognition. In the present work, the most significant applications of semiconductor nanostructures in the field of optical biosensing will be reviewed. In particular, the use of quantum dots as fluorescent bioprobes, which is the most widely used application, will be discussed. In addition, the use of some other nanometric structures in the field of biosensing, including porous semiconductors and photonic crystals, will be presented.

  20. Magnetization behavior of nanocrystalline systems combining ferromagnetic and antiferromagnetic phases

    Energy Technology Data Exchange (ETDEWEB)

    Loeffler, J.; Wagner, W.; Svygenhoven, H. van [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Meier, J.; Doudin, B.; Ansermet, J.P. [Ecole Polytechnique Federale, Lausanne (Switzerland)

    1997-09-01

    The magnetic properties of nanostructured materials on the basis of Fe and Ni have been investigated with a SQUID magnetometer, complementary to the small-angle neutron scattering study reported in the same volume. Measurements of the coercive field in a temperature range from 5 to 300 K confirm the validity of the random anisotropy model for our nanostructured systems. Furthermore, we obtain information about the presence and distribution of the antiferromagnetic oxides, joining the ferromagnetic grains. (author) 2 figs., 3 refs.

  1. Magnetization behavior of nanocrystalline systems combining ferromagnetic and antiferromagnetic phases

    International Nuclear Information System (INIS)

    Loeffler, J.; Wagner, W.; Svygenhoven, H. van; Meier, J.; Doudin, B.; Ansermet, J.P.

    1997-01-01

    The magnetic properties of nanostructured materials on the basis of Fe and Ni have been investigated with a SQUID magnetometer, complementary to the small-angle neutron scattering study reported in the same volume. Measurements of the coercive field in a temperature range from 5 to 300 K confirm the validity of the random anisotropy model for our nanostructured systems. Furthermore, we obtain information about the presence and distribution of the antiferromagnetic oxides, joining the ferromagnetic grains. (author) 2 figs., 3 refs

  2. Leafy nanostructure PANI for material of supercapacitors

    OpenAIRE

    XI Dong; CHEN Xinman

    2013-01-01

    Nanostructure conducting polyaniline(PANI) has great potential applications in supercapacitor electrode materials.In this paper,we report a template-free approach to synthesize PANI by a galvanostatic current procedure with a three-electrode configuration directly on indium-doped tin-oxide substrates (ITO).The morphology of product was characterized by Hitachi S-4800 field emission scanning electron microscope (FE-SEM).Due to the nanostructure,the specific capacitance of PANI film with the th...

  3. Directed spatial organization of zinc oxide nanostructures

    Science.gov (United States)

    Hsu, Julia [Albuquerque, NM; Liu, Jun [Richland, WA

    2009-02-17

    A method for controllably forming zinc oxide nanostructures on a surface via an organic template, which is formed using a stamp prepared from pre-defined relief structures, inking the stamp with a solution comprising self-assembled monolayer (SAM) molecules, contacting the stamp to the surface, such as Ag sputtered on Si, and immersing the surface with the patterned SAM molecules with a zinc-containing solution with pH control to form zinc oxide nanostructures on the bare Ag surface.

  4. Engineering metallic nanostructures for plasmonics and nanophotonics

    Science.gov (United States)

    Lindquist, Nathan C.; Nagpal, Prashant; McPeak, Kevin M.; Norris, David J.; Oh, Sang-Hyun

    2012-03-01

    Metallic nanostructures now play an important role in many applications. In particular, for the emerging fields of plasmonics and nanophotonics, the ability to engineer metals on nanometric scales allows the development of new devices and the study of exciting physics. This review focuses on top-down nanofabrication techniques for engineering metallic nanostructures, along with computational and experimental characterization techniques. A variety of current and emerging applications are also covered.

  5. Gold nanostructures and methods of use

    Science.gov (United States)

    Zhang, Jin Z [Santa Cruz, CA; Schwartzberg, Adam [Santa Cruz, CA; Olson, Tammy Y [Santa Cruz, CA

    2012-03-20

    The invention is drawn to novel nanostructures comprising hollow nanospheres and nanotubes for use as chemical sensors, conduits for fluids, and electronic conductors. The nanostructures can be used in microfluidic devices, for transporting fluids between devices and structures in analytical devices, for conducting electrical currents between devices and structure in analytical devices, and for conducting electrical currents between biological molecules and electronic devices, such as bio-microchips.

  6. Condensation on Superhydrophobic Copper Oxide Nanostructures

    OpenAIRE

    Enright, Ryan; Miljkovic, Nenad; Dou, Nicholas; Nam, Youngsuk; Wang, Evelyn N.

    2013-01-01

    Condensation is an important process in both emerging and traditional power generation and water desalination technologies. Superhydrophobic nanostructures promise enhanced condensation heat transfer by reducing the characteristic size of departing droplets via a surface-tension-driven mechanism [1]. In this work, we investigated a scalable synthesis technique to produce oxide nanostructures on copper surfaces capable of sustaining superhydrophobic condensation and characterized the growth an...

  7. Nanostructure symmetry: Relevance for physics and computing

    International Nuclear Information System (INIS)

    Dupertuis, Marc-André; Oberli, D. Y.; Karlsson, K. F.; Dalessi, S.; Gallinet, B.; Svendsen, G.

    2014-01-01

    We review the research done in recent years in our group on the effects of nanostructure symmetry, and outline its relevance both for nanostructure physics and for computations of their electronic and optical properties. The exemples of C3v and C2v quantum dots are used. A number of surprises and non-trivial aspects are outlined, and a few symmetry-based tools for computing and analysis are shortly presented

  8. Nanostructure symmetry: Relevance for physics and computing

    Energy Technology Data Exchange (ETDEWEB)

    Dupertuis, Marc-André; Oberli, D. Y. [Laboratory for Physics of Nanostructure, EPF Lausanne (Switzerland); Karlsson, K. F. [Department of Physics, Chemistry, and Biology (IFM), Linköping University (Sweden); Dalessi, S. [Computational Biology Group, Department of Medical Genetics, University of Lausanne (Switzerland); Gallinet, B. [Nanophotonics and Metrology Laboratory, EPF Lausanne (Switzerland); Svendsen, G. [Dept. of Electronics and Telecom., Norwegian University of Science and Technology, Trondheim (Norway)

    2014-03-31

    We review the research done in recent years in our group on the effects of nanostructure symmetry, and outline its relevance both for nanostructure physics and for computations of their electronic and optical properties. The exemples of C3v and C2v quantum dots are used. A number of surprises and non-trivial aspects are outlined, and a few symmetry-based tools for computing and analysis are shortly presented.

  9. Random laser action in 3-D ZnO nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Miao, L.; Tanemura, S. [Key Laboratory of Renewable Energy and Gas Hydrate, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, No. 2 Nengyuan Rd. Tianhe district, Guangzhou (China); Materials R and D Laboratory, Japan Fine Ceramics Centre, Mutsuno, Atsuta-ku, Nagoya 456-8587 (Japan); Yang, H.Y.; Lau, S.P. [School of Electrical and Electronic Engineering, Nanyang Technological University (Singapore); Xu, G. [Key Laboratory of Renewable Energy and Gas Hydrate, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, No. 2 Nengyuan Rd. Tianhe district, Guangzhou (China)

    2009-05-15

    Room-temperature ultraviolet random lasing with low threshold pumping power was successfully achieved by ZnO 3-D random-wall nanostructure fabricated on ZnO/SiO{sub 2}/Si substrate through a thermal chemical reaction and vapor transportation deposition method in a simple horizontal tube furnace from the mixed ZnO and graphite powders. The nanorods grown along c-axis on the substrate are coalesced to form the 3-D nano-wall with 80{proportional_to}100 nm in wall thickness and irregular height ranging of 95-250 nm. Mueller matrix spectroscopic ellipsometry reveals that evaluated refractive indices n(E) of ZnO nanowalls are well interpreted by taking account of the ratio between ZnO and void achieved by effective medium theory analysis and isotropic depolarization feature of the designated nanowalls. Random lasing action observed in the wide wavelength range between 375 and 395 nm is realized by coherent amplification of the closed-loop scattered light inside 3-D random-wall nanostructure. It is demonstrated that both transverse electric (TE) and transverse magnetic (TM) modes show the same threshold and pumping power dependent trend, while the intensity of TM lasing is weaker than that of TE due to the different scattering strength originated from the features of the inside of nanowall. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. DNA nanostructure-directed assembly of metal nanoparticle superlattices

    Science.gov (United States)

    Julin, Sofia; Nummelin, Sami; Kostiainen, Mauri A.; Linko, Veikko

    2018-05-01

    Structural DNA nanotechnology provides unique, well-controlled, versatile, and highly addressable motifs and templates for assembling materials at the nanoscale. These methods to build from the bottom-up using DNA as a construction material are based on programmable and fully predictable Watson-Crick base pairing. Researchers have adopted these techniques to an increasing extent for creating numerous DNA nanostructures for a variety of uses ranging from nanoelectronics to drug-delivery applications. Recently, an increasing effort has been put into attaching nanoparticles (the size range of 1-20 nm) to the accurate DNA motifs and into creating metallic nanostructures (typically 20-100 nm) using designer DNA nanoshapes as molds or stencils. By combining nanoparticles with the superior addressability of DNA-based scaffolds, it is possible to form well-ordered materials with intriguing and completely new optical, plasmonic, electronic, and magnetic properties. This focused review discusses the DNA structure-directed nanoparticle assemblies covering the wide range of different one-, two-, and three-dimensional systems.

  11. A novel nanostructure of cadmium oxide synthesized by mechanochemical method

    Energy Technology Data Exchange (ETDEWEB)

    Tadjarodi, A., E-mail: tajarodi@iust.ac.ir [Research Laboratory of Inorganic Materials Synthesis, Department of Chemistry, Iran University of Science and Technology, 16846-13114 Tehran (Iran, Islamic Republic of); Imani, M. [Research Laboratory of Inorganic Materials Synthesis, Department of Chemistry, Iran University of Science and Technology, 16846-13114 Tehran (Iran, Islamic Republic of)

    2011-11-15

    Highlights: {yields} A novel nanostructure of CdO was synthesized by mechanochemical reaction followed by calcination. {yields} Mechanochemical method is a simple and low-cost to synthesize nanomaterials. {yields} The obtained precursor was characterized by FT-IR, NMR techniques and elemental analysis. {yields} SEM images showed cauliflower-like shape of sample with components average diameter of 68 nm. {yields} The rods and tubes bundles with single crystalline nature were revealed by ED pattern and TEM images. -- Abstract: Cauliflower-like cadmium oxide (CdO) nanostructure was synthesized by mechanochemical reaction followed calcination procedure. Cadmium acetate dihydrate and acetamide were used as reagents and the resulting precursor was calcinated at 450 {sup o}C for 2 h in air. The structures of the precursor and resultant product of the heating treatment were characterized using Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and elemental analysis, X-ray powder diffraction (XRD), energy-dispersive X-ray spectroscopy analysis (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction pattern (ED). SEM and TEM images revealed the cauliflower-like morphology of the sample. This structure includes the bundles of rods and tubes in nanoscale, which combine with each other and form the resulting morphology with the average diameter, 68 nm of the components. ED pattern indicated the single crystal nature of the formed bundles.

  12. A novel nanostructure of cadmium oxide synthesized by mechanochemical method

    International Nuclear Information System (INIS)

    Tadjarodi, A.; Imani, M.

    2011-01-01

    Highlights: → A novel nanostructure of CdO was synthesized by mechanochemical reaction followed by calcination. → Mechanochemical method is a simple and low-cost to synthesize nanomaterials. → The obtained precursor was characterized by FT-IR, NMR techniques and elemental analysis. → SEM images showed cauliflower-like shape of sample with components average diameter of 68 nm. → The rods and tubes bundles with single crystalline nature were revealed by ED pattern and TEM images. -- Abstract: Cauliflower-like cadmium oxide (CdO) nanostructure was synthesized by mechanochemical reaction followed calcination procedure. Cadmium acetate dihydrate and acetamide were used as reagents and the resulting precursor was calcinated at 450 o C for 2 h in air. The structures of the precursor and resultant product of the heating treatment were characterized using Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and elemental analysis, X-ray powder diffraction (XRD), energy-dispersive X-ray spectroscopy analysis (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction pattern (ED). SEM and TEM images revealed the cauliflower-like morphology of the sample. This structure includes the bundles of rods and tubes in nanoscale, which combine with each other and form the resulting morphology with the average diameter, 68 nm of the components. ED pattern indicated the single crystal nature of the formed bundles.

  13. Spin Coherence in Semiconductor Nanostructures

    National Research Council Canada - National Science Library

    Flatte, Michael E

    2006-01-01

    ... dots, tuning of spin coherence times for electron spin, tuning of dipolar magnetic fields for nuclear spin, spontaneous spin polarization generation and new designs for spin-based teleportation and spin transistors...

  14. Nanostructured gold microelectrodes for extracellular recording

    Energy Technology Data Exchange (ETDEWEB)

    Brueggemann, Dorothea; Wolfrum, Bernhard; Maybeck, Vanessa; Offenhaeusser, Andreas [CNI Center of Nanoelectronic Systems for Information Technology and Institute of Bio- and Nanosystems 2, Forschungszentrum Juelich (Germany)

    2010-07-01

    Electrophysiological activity of electrogenic cells is currently recorded with planar bioelectronic interfaces such as microelectrode arrays (MEAs). In this work, a novel concept of biocompatible nanostructured gold MEAs for extracellular signal recording is presented. MEAs were fabricated using clean room technologies, e.g. photolithography and metallization. Subsequently, they were modified with gold nanopillars of approximately 300 to 400 nm in height and 60 nm width. The nanostructuring process was carried out with a template-assisted approach using nanoporous aluminium oxide. Impedance spectroscopy of the resulting nanostructures showed higher capacitances compared to planar gold. This confirmed the expected increase of the surface area via nanostructuring. We used the nanostructured microelectrodes to record extracellular potentials from heart muscle cells (HL1), which were plated onto the chips. Good coupling between the HL1 cells and the nanostructured electrodes was observed. The resulting signal-to-noise ratio of nanopillar-MEAs was increased by a factor of 2 compared to planar MEAs. In future applications this nanopillar concept can be adopted for distinct interface materials and coupling to cellular and molecular sensing components.

  15. Structural peculiarities in magnetic small particles

    International Nuclear Information System (INIS)

    Haneda, K.; Morrish, A.H.

    1993-01-01

    Nanostructured magnetic materials, consisting of nanometer-sized crystallites, are currently a developing subject. Evidence has been accumulating that they possess properties that can differ substantially from those of bulk materials. This paper illustrates how Moessbauer spectroscopy can yield useful information on the structural peculiarities associated with these small particles. As illustrations, metallic iron and iron-oxide systems are considered in detail. The subjects discussed include: (1) Phase stabilities in small particles, (2) deformed or nonsymmetric atomic arrangements in small particles, and (3) peculiar magnetic structures or non-collinear spin arrangements in small magnetic oxide particles that are correlated with lower specific magnetizations as compared to the bulk values. (orig.)

  16. Platinum dendritic nanoparticles with magnetic behavior

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wenxian, E-mail: wl240@uowmail.edu.au [Institute for Superconducting and Electronic Materials, University of Wollongong, NSW 2522 (Australia); Solar Energy Technologies, School of Computing, Engineering, and Mathematics, University of Western Sydney, Penrith NSW 2751 (Australia); Sun, Ziqi; Nevirkovets, Ivan P.; Dou, Shi-Xue [Institute for Superconducting and Electronic Materials, University of Wollongong, NSW 2522 (Australia); Tian, Dongliang [Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of the Ministry of Education, School of Chemistry and the Environment, Beihang University, Beijing 100191 (China)

    2014-07-21

    Magnetic nanoparticles have attracted increasing attention for biomedical applications in magnetic resonance imaging, high frequency magnetic field hyperthermia therapies, and magnetic-field-gradient-targeted drug delivery. In this study, three-dimensional (3D) platinum nanostructures with large surface area that features magnetic behavior have been demonstrated. The well-developed 3D nanodendrites consist of plentiful interconnected nano-arms ∼4 nm in size. The magnetic behavior of the 3D dendritic Pt nanoparticles is contributed by the localization of surface electrons due to strongly bonded oxygen/Pluronic F127 and the local magnetic moment induced by oxygen vacancies on the neighboring Pt and O atoms. The magnetization of the nanoparticles exhibits a mixed paramagnetic and ferromagnetic state, originating from the core and surface, respectively. The 3D nanodendrite structure is suitable for surface modification and high amounts of drug loading if the transition temperature was enhanced to room temperature properly.

  17. Platinum dendritic nanoparticles with magnetic behavior

    International Nuclear Information System (INIS)

    Li, Wenxian; Sun, Ziqi; Nevirkovets, Ivan P.; Dou, Shi-Xue; Tian, Dongliang

    2014-01-01

    Magnetic nanoparticles have attracted increasing attention for biomedical applications in magnetic resonance imaging, high frequency magnetic field hyperthermia therapies, and magnetic-field-gradient-targeted drug delivery. In this study, three-dimensional (3D) platinum nanostructures with large surface area that features magnetic behavior have been demonstrated. The well-developed 3D nanodendrites consist of plentiful interconnected nano-arms ∼4 nm in size. The magnetic behavior of the 3D dendritic Pt nanoparticles is contributed by the localization of surface electrons due to strongly bonded oxygen/Pluronic F127 and the local magnetic moment induced by oxygen vacancies on the neighboring Pt and O atoms. The magnetization of the nanoparticles exhibits a mixed paramagnetic and ferromagnetic state, originating from the core and surface, respectively. The 3D nanodendrite structure is suitable for surface modification and high amounts of drug loading if the transition temperature was enhanced to room temperature properly.

  18. Quest for high-Curie temperature MnxGe1-x diluted magnetic semiconductors for room-temperature spintronics applications

    Science.gov (United States)

    Nie, Tianxiao; Tang, Jianshi; Wang, Kang L.

    2015-09-01

    In this paper, we report the non-equilibrium growth of various Mn-doped Ge dilute magnetic semiconductor nanostructures using molecular-beam epitaxy, including quantum dots, nanodisks and nanowires. Their detailed structural and magnetic properties are characterized. By comparing the results with those in MnxGe1-x thin films, it is affirmed that the use of nanostructures helps eliminate crystalline defects and meanwhile enhance the carrier-mediate ferromagnetism from substantial quantum confinements. Our systematic studies provide a promising platform to build nonvolatile spinFET and other novel spintronic devices based upon dilute magnetic semiconductor nanostructures.

  19. Commercial Implementation of Model-Based Manufacturing of Nanostructured Metals

    Energy Technology Data Exchange (ETDEWEB)

    Lowe, Terry C. [Los Alamos National Laboratory

    2012-07-24

    Computational modeling is an essential tool for commercial production of nanostructured metals. Strength is limited by imperfections at the high strength levels that are achievable in nanostructured metals. Processing to achieve homogeneity at the micro- and nano-scales is critical. Manufacturing of nanostructured metals is intrinsically a multi-scale problem. Manufacturing of nanostructured metal products requires computer control, monitoring and modeling. Large scale manufacturing of bulk nanostructured metals by Severe Plastic Deformation is a multi-scale problem. Computational modeling at all scales is essential. Multiple scales of modeling must be integrated to predict and control nanostructural, microstructural, macrostructural product characteristics and production processes.

  20. Attosecond experiments on plasmonic nanostructures principles and experiments

    CERN Document Server

    Schötz, Johannes

    2016-01-01

    Johannes Schötz presents the first measurements of optical electro-magnetic near-fields around nanostructures with subcycle-resolution. The ability to measure and understand light-matter interactions on the nanoscale is an important component for the development of light-wave-electronics, the control and steering of electron dynamics with the frequency of light, which promises a speed-up by several orders of magnitude compared to conventional electronics. The experiments presented here on metallic nanotips, widely used in experiments and applications, do not only demonstrate the feasibility of attosecond streaking as a unique tool for fundamental studies of ultrafast nanophotonics but also represent a first important step towards this goal. Contents Electron Scattering in Solids Attosecond Streaking from Metal Nanotips Target Groups Lecturers and students of physics, especially in the area of nanophotonics and attosecond physics About the Author Johannes Schötz received his Master's degree in physics and cu...

  1. Properties of self-assembled diluted magnetic semiconductor nanostructures =

    Science.gov (United States)

    Ankiewicz, Amelia Olga Goncalves

    Este trabalho centra-se na investigacao da possibilidade de se conseguir um semicondutor magnetico diluido (SMD) baseado em ZnO. Foi levado a cabo um estudo detalhado das propriedades magneticas e estruturais de estruturas de ZnO, nomeadamente nanofios (NFs), nanocristais (NCs) e filmes finos, dopadas com metais de transicao (MTs). Foram usadas varias tecnicas experimentais para caracterizar estas estruturas, designadamente difraccao de raios-X, microscopia electronica de varrimento, ressonancia magnetica, SQUID, e medidas de transporte. Foram incorporados substitucionalmente nos sitios do Zn ioes de Mn2+ e Co2+ em ambos os NFs e NCs de ZnO. Revelou-se para ambos os ioes dopantes, que a incorporacao e heterogenea, uma vez que parte do sinal de ressonancia paramagnetica electronica (RPE) vem de ioes de MTs em ambientes distorcidos ou enriquecidos com MTs. A partir das intensidades relativas dos espectros de RPE e de modificacoes da superficie, demonstra-se ainda que os NCs exibem uma estrutura core-shell. Os resultados, evidenciam que, com o aumento da concentracao de MTs, a dimensao dos NCs diminui e aumentam as distorcoes da rede. Finalmente, no caso dos NCs dopados com Mn, obteve-se o resultado singular de que a espessura da shell e da ordem de 0.3 nm e de que existe uma acumulacao de Mn na mesma. Com o objectivo de esclarecer o papel dos portadores de carga na medicao das interaccoes ferromagneticas, foram co-dopados filmes de ZnO com Mn e Al ou com Co e Al. Os filmes dopados com Mn, revelaram-se simplesmente paramagneticos, com os ioes de Mn substitucionais nos sitios do Zn. Por outro lado, os filmes dopados com Co exibem ferromagnetismo fraco nao intrinseco, provavelmente devido a decomposicao spinodal. Foram ainda efectuados estudos comparativos com filmes de ligas de Zn1-xFexO. Como era de esperar, detectaram-se segundas fases de espinela e de oxido de ferro nestas ligas; todas as amostras exibiam curvas de histerese a 300 K. Estes resultados suportam a hipotese de que as segundas fases sao responsaveis pelo comportamento magnetico observado em muitos sistemas baseados em ZnO. Nao se observou nenhuma evidencia de ferromagnetismo mediado por portadores de carga. As experiencias mostram que a analise de RPE permite demonstrar directamente se e onde estao incorporados os ioes de MTs e evidenciam a importancia dos efeitos de superficie para dimensoes menores que 15 nm, para as quais se formam estruturas core-shell. As investigacoes realizadas no ambito desta tese demonstram que nenhuma das amostras de ZnO estudadas exibiram propriedades de um SMD intrinseco e que, no futuro, sao necessarios estudos teoricos e experimentais detalhados das interaccoes de troca entre os ioes de MTs e os atomos do ZnO para determinar a origem das propriedades magneticas observadas.

  2. Plastic deformation of indium nanostructures

    International Nuclear Information System (INIS)

    Lee, Gyuhyon; Kim, Ju-Young; Burek, Michael J.; Greer, Julia R.; Tsui, Ting Y.

    2011-01-01

    Highlights: → Indium nanopillars display two different deformation mechanisms. → ∼80% exhibited low flow stresses near that of bulk indium. → Low strength nanopillars have strain rate sensitivity similar to bulk indium. → ∼20% of compressed indium nanopillars deformed at nearly theoretical strengths. → Low-strength samples do not exhibit strength size effects. - Abstract: Mechanical properties and morphology of cylindrical indium nanopillars, fabricated by electron beam lithography and electroplating, are characterized in uniaxial compression. Time-dependent deformation and influence of size on nanoscale indium mechanical properties were investigated. The results show two fundamentally different deformation mechanisms which govern plasticity in these indium nanostructures. We observed that the majority of indium nanopillars deform at engineering stresses near the bulk values (Type I), with a small fraction sustaining flow stresses approaching the theoretical limit for indium (Type II). The results also show the strain rate sensitivity and flow stresses in Type I indium nanopillars are similar to bulk indium with no apparent size effects.

  3. Semiconductor nanostructures for artificial photosynthesis

    Science.gov (United States)

    Yang, Peidong

    2012-02-01

    Nanowires, with their unique capability to bridge the nanoscopic and macroscopic worlds, have already been demonstrated as important materials for different energy conversion. One emerging and exciting direction is their application for solar to fuel conversion. The generation of fuels by the direct conversion of solar energy in a fully integrated system is an attractive goal, but no such system has been demonstrated that shows the required efficiency, is sufficiently durable, or can be manufactured at reasonable cost. One of the most critical issues in solar water splitting is the development of a suitable photoanode with high efficiency and long-term durability in an aqueous environment. Semiconductor nanowires represent an important class of nanostructure building block for direct solar-to-fuel application because of their high surface area, tunable bandgap and efficient charge transport and collection. Nanowires can be readily designed and synthesized to deterministically incorporate heterojunctions with improved light absorption, charge separation and vectorial transport. Meanwhile, it is also possible to selectively decorate different oxidation or reduction catalysts onto specific segments of the nanowires to mimic the compartmentalized reactions in natural photosynthesis. In this talk, I will highlight several recent examples in this lab using semiconductor nanowires and their heterostructures for the purpose of direct solar water splitting.

  4. Chemical scissors cut phosphorene nanostructures

    International Nuclear Information System (INIS)

    Peng, Xihong; Wei, Qun

    2014-01-01

    Phosphorene, a recently fabricated two-dimensional puckered honeycomb structure of phosphorus, showed promising properties for applications in nano-electronics. In this work, we report a chemical scissors effect on phosphorene, using first-principles method. It was found that chemical species, such as H, OH, F, and Cl, can act as scissors to cut phosphorene. Phosphorus nanochains and nanoribbons can be obtained. The scissors effect results from the strong bonding between the chemical species and phosphorus atoms. Other species such as O, S and Se fail to cut phosphorene nanostructures due to their weak bonding with phosphorus. The electronic structures of the produced P-chains reveal that the hydrogenated chain is an insulator while the pristine chain is a one-dimensional Dirac material, in which the charge carriers are massless fermions travelling at an effective speed of light ∼8 × 10 5 m s −1 . The obtained zigzag phosphorene nanoribbons show either metallic or semiconducting behaviors, depending on the treatment of the edge phosphorus atoms. (paper)

  5. Sea-urchin-like iron oxide nanostructures for water treatment

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyun Uk, E-mail: leeho@kbsi.re.kr [Division of Materials Science, Korea Basic Science Institute, Daejeon 305-333 (Korea, Republic of); Lee, Soon Chang [Department of Fine Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Lee, Young-Chul [Department of Biological Engineering, College of Engineering, Inha University, Incheon 402-751 (Korea, Republic of); Vrtnik, Stane; Kim, Changsoo; Lee, SangGap [Division of Materials Science, Korea Basic Science Institute, Daejeon 305-333 (Korea, Republic of); Lee, Young Boo; Nam, Bora [Jeonju Center, Korea Basic Science Institute, Jeonju 561-756 (Korea, Republic of); Lee, Jae Won [Department of Energy Engineering, Dankook University, Cheonan 330-714 (Korea, Republic of); Park, So Young; Lee, Sang Moon [Division of Materials Science, Korea Basic Science Institute, Daejeon 305-333 (Korea, Republic of); Lee, Jouhahn, E-mail: jouhahn@kbsi.re.kr [Division of Materials Science, Korea Basic Science Institute, Daejeon 305-333 (Korea, Republic of)

    2013-11-15

    Highlights: • The u-MFN were synthesized via a ultrasound irradiation and/or calcinations process. • The u-MFN exhibited excellent adsorption capacities. • The u-MFN also displayed excellent adsorption of organic polluent after recycling. • The u-MFN has the potential to be used as an efficient adsorbent material. -- Abstract: To obtain adsorbents with high capacities for removing heavy metals and organic pollutants capable of quick magnetic separation, we fabricated unique sea-urchin-like magnetic iron oxide (mixed γ-Fe{sub 2}O{sub 3}/Fe{sub 3}O{sub 4} phase) nanostructures (called u-MFN) with large surface areas (94.1 m{sup 2} g{sup −1}) and strong magnetic properties (57.9 emu g{sup −1}) using a simple growth process and investigated their potential applications in water treatment. The u-MFN had excellent removal capabilities for the heavy metals As(V) (39.6 mg g{sup −1}) and Cr(VI) (35.0 mg g{sup −1}) and the organic pollutant Congo red (109.2 mg g{sup −1}). The u-MFN also displays excellent adsorption of Congo red after recycling. Because of its high adsorption capacity, fast adsorption rate, and quick magnetic separation from treated water, the u-MFN developed in the present study is expected to be an efficient magnetic adsorbent for heavy metals and organic pollutants in aqueous solutions.

  6. Facile Growth of Multi-twined Au Nanostructures

    Indian Academy of Sciences (India)

    like nanostructures undergo spontaneous transformation into multi-twined nanostructures within 24 h. These nanocrystalline ... reactions,1 and a color indicating reagent for the sensing of biomolecules.2 ... Two-compartment, three electrode ...

  7. Mapping the nanostructures in human adult and baby tooth enamel

    International Nuclear Information System (INIS)

    Low, I.M.; Mahmood, U.; Duraman, N.

    2005-01-01

    This paper investigates and compares the variations in crystal structure, composition, and nanostructures within the human adult and deciduous teeth. The similarities and differences in the nanostructure of both types of teeth are highlighted and discussed. (author)

  8. Terminating DNA Tile Assembly with Nanostructured Caps.

    Science.gov (United States)

    Agrawal, Deepak K; Jiang, Ruoyu; Reinhart, Seth; Mohammed, Abdul M; Jorgenson, Tyler D; Schulman, Rebecca

    2017-10-24

    Precise control over the nucleation, growth, and termination of self-assembly processes is a fundamental tool for controlling product yield and assembly dynamics. Mechanisms for altering these processes programmatically could allow the use of simple components to self-assemble complex final products or to design processes allowing for dynamic assembly or reconfiguration. Here we use DNA tile self-assembly to develop general design principles for building complexes that can bind to a growing biomolecular assembly and terminate its growth by systematically characterizing how different DNA origami nanostructures interact with the growing ends of DNA tile nanotubes. We find that nanostructures that present binding interfaces for all of the binding sites on a growing facet can bind selectively to growing ends and stop growth when these interfaces are presented on either a rigid or floppy scaffold. In contrast, nucleation of nanotubes requires the presentation of binding sites in an arrangement that matches the shape of the structure's facet. As a result, it is possible to build nanostructures that can terminate the growth of existing nanotubes but cannot nucleate a new structure. The resulting design principles for constructing structures that direct nucleation and termination of the growth of one-dimensional nanostructures can also serve as a starting point for programmatically directing two- and three-dimensional crystallization processes using nanostructure design.

  9. Nanostructuring steel for injection molding tools

    International Nuclear Information System (INIS)

    Al-Azawi, A; Smistrup, K; Kristensen, A

    2014-01-01

    The production of nanostructured plastic items by injection molding with ridges down to 400 nm in width, which is the smallest line width replicated from nanostructured steel shims, is presented. Here we detail a micro-fabrication method where electron beam lithography, nano-imprint lithography and ion beam etching are combined to nanostructure the planar surface of a steel wafer. Injection molded plastic parts with enhanced surface properties, like anti-reflective, superhydrophobic and structural colors can be achieved by micro- and nanostructuring the surface of the steel molds. We investigate the minimum line width that can be realized by our fabrication method and the influence of etching angle on the structure profile during the ion beam etching process. Trenches down to 400 nm in width have been successfully fabricated into a 316 type electro-polished steel wafer. Afterward a plastic replica has been produced by injection molding with good structure transfer fidelity. Thus we have demonstrated that by utilizing well-established fabrication techniques, nanostructured steel shims that are used in injection molding, a technique that allows low cost mass fabrication of plastic items, are produced. (paper)

  10. Mn-based nanostructured building blocks: Synthesis, characterization and applications

    Science.gov (United States)

    Beltran Huarac, Juan

    The quest for smaller functional elements of devices has stimulated increased interest in charge-transfer phenomena at the nanoscale. Mn-based nanostructured building blocks are particularly appealing given that the excited states of high-spin Mn2+ ions induce unusual d-d energy transfer processes, which is critical for better understanding the performance of electronic and spintronic devices. These nanostructures also exhibit unique properties superior to those of common Fe- and Co-based nanomaterials, including: excellent structural flexibility, enhanced electrochemical energy storage, effective ion-exchange dynamics, more comprehensive transport mechanisms, strong quantum yield, and they act as effective luminescent centers for more efficient visible light emitters. Moreover, Mn-based nanostructures (MBNs) are crucial for the design and assembly of inexpensive nanodevices in diluted magnetic semiconductors (DMS), optoelectronics, magneto-optics, and field-effect transistors, owing to the great abundance and low-cost of Mn. Nonetheless, the paucity of original methods and techniques to fabricate new multifunctional MBNs that fulfill industrial demands limits the sustainable development of innovative technology in materials sciences. In order to meet this critical need, in this thesis we develop and implement novel methods and techniques to fabricate zero- and one-dimensional highly-crystalline new-generation MBNs conducive to the generation of new technology, and provide alternative and feasible miniaturization strategies to control and devise at nanometric precision their size, shape, structure and composition. Herein, we also establish the experimental conditions to grow Mn-based nanowires (NWs), nanotubes (NTs), nanoribbons (NRs), nanosaws (NSs), nanoparticles (NPs) and nanocomposites (NCs) via chemical/physical deposition and co-precipitation chemical routes, and determine the pertinent arrangements to our experimental schemes in order to extend our bottom

  11. Review on the progress in synthesis and application of magnetic carbon nanocomposites

    Science.gov (United States)

    Zhu, Maiyong; Diao, Guowang

    2011-07-01

    This review focuses on the synthesis and application of nanostructured composites containing magnetic nanostructures and carbon-based materials. Great progress in fabrication of magnetic carbon nanocomposites has been made by developing methods including filling process, template-based synthesis, chemical vapor deposition, hydrothermal/solvothermal method, pyrolysis procedure, sol-gel process, detonation induced reaction, self-assembly method, etc. The applications of magnetic carbon nanocomposites expanded to a wide range of fields such as environmental treatment, microwave absorption, magnetic recording media, electrochemical sensor, catalysis, separation/recognization of biomolecules and drug delivery are discussed. Finally, some future trends and perspectives in this research area are outlined.

  12. Sm and Y radiolabeled magnetic fluids: magnetic and magneto-optical characterization

    Energy Technology Data Exchange (ETDEWEB)

    Aquino, R. [Complex Fluids Group, Instituto de Quimica, Universidade de Brasilia, Caixa Postal 04478, 70919-970 Brasilia (DF) (Brazil) and Laboratoire des Milieux Deet Heterogenes, Universite Pierre et Marie Curie (Paris 6), Site de Boucicaut, case 86, 140, Rue de Lourmel, 75015 Paris (France)]. E-mail: reaquino@unb.br; Gomes, J.A. [Complex Fluids Group, Instituto de Fisica, Universidade de Brasilia, 70919-970 Brasilia (DF) (Brazil); Tourinho, F.A. [Complex Fluids Group, Instituto de Quimica, Universidade de Brasilia, Caixa Postal 04478, 70919-970 Brasilia (DF) (Brazil); Dubois, E. [Laboratoire des Liquides Ioniques et Interfaces Chargees, Universite Pierre et Marie Curie (Paris 6), Batiment F, Case 63, 4 place Jussieu, 75252 Paris Cedex 05 (France); Perzynski, R. [Laboratoire des Milieux Deet Heterogenes, Universite Pierre et Marie Curie (Paris 6), Site de Boucicaut, case 86, 140, Rue de Lourmel, 75015 Paris (France); Silva, G.J. da [Complex Fluids Group, Instituto de Fisica, Universidade de Brasilia, 70919-970 Brasilia (DF) (Brazil); Depeyrot, J. [Complex Fluids Group, Instituto de Fisica, Universidade de Brasilia, 70919-970 Brasilia (DF) (Brazil)

    2005-03-15

    We report on magnetic fluids based on samarium and ytrium-doped nanoparticles. The nanostructures chemical composition is checked and X-ray diffraction provides both their mean size and a structural characterization. Magnetization and magneto-optical birefringence results are presented and well agree with the pure maghemite behavior. Since these particles can become radioactive after neutron activation, they could therefore represent a new perspective for biomedical applications in the radiation therapy of cancer.

  13. Sm and Y radiolabeled magnetic fluids: magnetic and magneto-optical characterization

    Science.gov (United States)

    Aquino, R.; Gomes, J. A.; Tourinho, F. A.; Dubois, E.; Perzynski, R.; da Silva, G. J.; Depeyrot, J.

    2005-03-01

    We report on magnetic fluids based on samarium and ytrium-doped nanoparticles. The nanostructures chemical composition is checked and X-ray diffraction provides both their mean size and a structural characterization. Magnetization and magneto-optical birefringence results are presented and well agree with the pure maghemite behavior. Since these particles can become radioactive after neutron activation, they could therefore represent a new perspective for biomedical applications in the radiation therapy of cancer.

  14. Sm and Y radiolabeled magnetic fluids: magnetic and magneto-optical characterization

    International Nuclear Information System (INIS)

    Aquino, R.; Gomes, J.A.; Tourinho, F.A.; Dubois, E.; Perzynski, R.; Silva, G.J. da; Depeyrot, J.

    2005-01-01

    We report on magnetic fluids based on samarium and ytrium-doped nanoparticles. The nanostructures chemical composition is checked and X-ray diffraction provides both their mean size and a structural characterization. Magnetization and magneto-optical birefringence results are presented and well agree with the pure maghemite behavior. Since these particles can become radioactive after neutron activation, they could therefore represent a new perspective for biomedical applications in the radiation therapy of cancer

  15. Metal films with imprinted nanostructures by template stripping

    DEFF Research Database (Denmark)

    Eriksen, René Lynge; Pors, Anders; Dreier, Jes

    We present a novel template stripping procedure for fabricating metal films with imprinted nanostructures. The basic idea is to deposit a gold film onto a nano-structured substrate and subsequently strip the film from the substrate surface thereby revealing imprinted nanostructures in the film...... result is a thin gold film with imprinted nano-cavities....

  16. Science and Technology of Nanostructures in the Department of Defense

    International Nuclear Information System (INIS)

    Murday, James S.

    1999-01-01

    The United States Department of Defense maintains a research and development program in nanostructures with special attention to miniaturization of information technology devices, nanostructured materials, and nanobiotechnology for detection of biological agents. This article provides a brief guide to those DoD funding officers and research scientists actively interested in nanostructures

  17. Synthesis and processing of nanostructured materials

    International Nuclear Information System (INIS)

    Siegel, R.W.

    1992-12-01

    Significant and growing interest is being exhibited in the novel and enhanced properties of nanostructured materials. These materials, with their constituent phase or grain structures modulated on a length scale less than 100 nm, are artificially synthesized by a wide variety of physical, chemical, and mechanical methods. In this NATO Advanced Study Institute, where mechanical behavior is emphasized, nanostructured materials with modulation dimensionalities from one (multilayers) to three (nanophase materials) are mainly considered. No attempt is made in this review to cover in detail all of the diverse methods available for the synthesis of nanostructured materials. Rather, the basic principles involved in their synthesis are discussed in terms of the special properties sought using examples of particular synthesis and processing methodologies. Some examples of the property changes that can result from one of these methods, cluster assembly of nanophase materials, are presented

  18. Synthesis and AFM visualization of DNA nanostructures

    International Nuclear Information System (INIS)

    Mizuno, Rika; Haruta, Hirotaka; Morii, Takashi; Okada, Takao; Asakawa, Takeshi; Hayashi, Kenshi

    2004-01-01

    We propose a novel bottom-up approach for the fabrication of various desired nanostructures, based on self-assembly of oligonucleotides governed by Watson-Crick base pairing. Using this approach, we designed Y-shaped, closed Y-shaped, H-shaped, and hexagonal structures with oligonucleotides. These structures were autonomously fabricated simply by mixing equimolar solutions of oligonucleotides and performing hybridization. After synthesis of the nanostructures, we confirmed their validity by agarose gel electrophoresis and atomic force microscope (AFM) visualization. We detected bands of the desired molecular sizes in the gel electrophoresis and observed the desired structures by AFM analysis. We concluded that the synthesized structures were consistent with our intended design and that AFM visualization is a very useful tool for the observation of nanostructures

  19. Transport and dynamics of nanostructured graphene

    DEFF Research Database (Denmark)

    Gunst, Tue

    This thesis is concerned with the heating and electronic properties of nanoscale devices based on nanostructured graphene. As electronic devices scale down to nanometer dimensions, the operation depends on the detailed atomic structure. Emerging carbon nano-materials such as graphene, carbon...... nanotubes and graphene nanoribbons, exhibit promising electronic and heat transport properties. Much research addresses the electron mobility of pristine graphene devices. However, the thermal transport properties, as well as the effects of e-ph interaction, in nanoscale devices, based on nanostructured...... graphene, have received much less attention. This thesis contributes to the understanding of the thermal properties of nanostructured graphene. The computational analysis is based on DFT/TB-NEGF. We show how a regular nanoperforation of a graphene layer - a graphene antidot lattice (GAL) - may...

  20. Fractal like charge transport in polyaniline nanostructures

    International Nuclear Information System (INIS)

    Nath, Chandrani; Kumar, A.

    2013-01-01

    The structural and electrical properties of camphorsulfonic acid (CSA) doped nanotubes, and hydrochloric acid (HCl) doped nanofibers and nanoparticles of polyaniline have been studied as a function of doping level. The crystallinity increases with doping for all the nanostructures. Electrical transport measurements in the temperature range of 5–300 K show an increase in conductivity with doping for the nanostructures. All the nanostructures exhibit metal to insulator (MIT) transition below 40 K. The metallic behavior is ascribed to the electron–electron interaction effects. In the insulating regime of the nanotubes conduction follows the Mott quasi-1D variable range hopping model, whereas the conduction in the nanofibers and nanoparticles occur by variable range hopping of charge carriers among superlocalized states without and with Coulomb interaction, respectively. The smaller dopant size in case of HCl makes the polymer fractal resulting in superlocalization of electronic wave-functions. The confined morphology of the nanoparticles results in effective Coulomb interaction dominating the intersite hopping

  1. Electrode Nanostructures in Lithium‐Based Batteries

    Science.gov (United States)

    Mahmood, Nasir

    2014-01-01

    Lithium‐based batteries possessing energy densities much higher than those of the conventional batteries belong to the most promising class of future energy devices. However, there are some fundamental issues related to their electrodes which are big roadblocks in their applications to electric vehicles (EVs). Nanochemistry has advantageous roles to overcome these problems by defining new nanostructures of electrode materials. This review article will highlight the challenges associated with these chemistries both to bring high performance and longevity upon considering the working principles of the various types of lithium‐based (Li‐ion, Li‐air and Li‐S) batteries. Further, the review discusses the advantages and challenges of nanomaterials in nanostructured electrodes of lithium‐based batteries, concerns with lithium metal anode and the recent advancement in electrode nanostructures. PMID:27980896

  2. Metal oxide nanostructures as gas sensing devices

    CERN Document Server

    Eranna, G

    2016-01-01

    Metal Oxide Nanostructures as Gas Sensing Devices explores the development of an integrated micro gas sensor that is based on advanced metal oxide nanostructures and is compatible with modern semiconductor fabrication technology. This sensor can then be used to create a compact, low-power, handheld device for analyzing air ambience. The book first covers current gas sensing tools and discusses the necessity for miniaturized sensors. It then focuses on the materials, devices, and techniques used for gas sensing applications, such as resistance and capacitance variations. The author addresses the issues of sensitivity, concentration, and temperature dependency as well as the response and recovery times crucial for sensors. He also presents techniques for synthesizing different metal oxides, particularly those with nanodimensional structures. The text goes on to highlight the gas sensing properties of many nanostructured metal oxides, from aluminum and cerium to iron and titanium to zinc and zirconium. The final...

  3. Electron Microscopy of Nanostructures in Cells

    DEFF Research Database (Denmark)

    Købler, Carsten

    with cells is therefore increasingly more relevant from both an engineering and a toxicological viewpoint. My work involves developing and exploring electron microscopy (EM) for imaging nanostructures in cells, for the purpose of understanding nanostructure-cell interactions in terms of their possibilities...... in science and concerns in toxicology. In the present work, EM methods for imaging nanostructure-cell interactions have been explored, and the complex interactions documented and ordered. In particular the usability of the focused ion beam scanning electron microscope (FIB-SEM) was explored. Using EM...... in literature. Furthermore, EM proved valuable as it revealed an unnoticed CNT effect. FIB-SEM helped establish that the effect was linked to eosionophilic crystalline pneumonia (ECP)....

  4. Optical properties of nitride nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Cantarero, A.; Cros, A.; Garro, N.; Gomez-Gomez, M.I.; Garcia, A.; Lima, M.M. de [Materials Science Institute, University of Valencia, PO Box 22085, 46071 Valencia (Spain); Daudin, B. [Departement de Recherche Fondamentale sur la Matiere Condensee, SPMM, CEA/Grenoble, 17 Rue des Martyrs, 38054 Grenoble (France); Rizzi, A.; Denker, C.; Malindretos, J. [IV. Physikalisches Institut, Georg August Universitaet Goettingen, 37073 Goettingen (Germany)

    2011-01-15

    In this paper we review some recent results on the optical properties of nitride nanostructures, in particular on GaN quantum dots (QDs) and InN nanocolumns (NCs). First, we will give a brief introduction on the particularities of vibrational modes of wurtzite. The GaN QDs, embedded in AlN, were grown by molecular beam epitaxy (MBE) in the Stransky-Krastanov mode on c- and a-plane 6H-SiC. We have studied the optical properties by means of photoluminescence (PL) and performed Raman scattering measurements to analyze the strain relaxation in the dots and the barrier, the effect of the internal electric fields, and the influence of specific growth parameters, like the influence of capping or the spacer on the relaxation of the QDs. A theoretical model, based on continuous elastic theory, were developed to interpret the Raman scattering results. On the other hand, InN NCs have been grown by MBE in the vapor-liquid-solid mode using Au as a catalyst. The nanocolumns have different morphology depending on the growth conditions. The optical properties can be correlated to the morphology of the samples and the best growth conditions can be selected. We observe, from the analysis of the Raman data in InN NCs, the existence of two space regions contributing to the scattering: the surface and the inner region. From the inner region, uncoupled phonon modes are clearly observed, showing the high crystal quality and the complete relaxation of the NCs (no strain). The observation of a LO-phonon-plasmon couple in the same spectra is a fingerprint of the accumulation layer predicted at the surface of the nanocolumns. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Nanostructured Diclofenac Sodium Releasing Material

    Science.gov (United States)

    Nikkola, L.; Vapalahti, K.; Harlin, A.; Seppälä, J.; Ashammakhi, N.

    2008-02-01

    Various techniques have been developed to produce second generation biomaterials for tissue repair. These include extrusion, molding, salt leaching, spinning etc, but success in regenerating tissues has been limited. It is important to develop porous material, yet with a fibrous structure for it to be biomimetic. To mimic biological tissues, the extra-cellular matrix usually contains fibers in nano scale. To produce nanostructures, self-assembly or electrospinning can be used. Adding a drug release function to such a material may advance applications further for use in controlled tissue repair. This turns the resulting device into a multifunctional porous, fibrous structure to support cells and drug releasing properties in order to control tissue reactions. A bioabsorbable poly(ɛ-caprolactone-co-D,L lactide) 95/5 (PCL) was made into diluted solution using a solvent, to which was added 2w-% of diclofenac sodium (DS). Nano-fibers were made by electrospinning onto substrate. Microstructure of the resulting nanomat was studied using SEM and drug release profiles with UV/VIS spectroscopy. Thickness of the electrospun nanomat was about 2 mm. SEM analysis showed that polymeric nano-fibers containing drug particles form a highly interconnected porous nano structure. Average diameter of the nano-fibers was 130 nm. There was a high burst peak in drug release, which decreased to low levels after one day. The used polymer has slow a degradation rate and though the nanomat was highly porous with a large surface area, drug release rate is slow. It is feasible to develop a nano-fibrous porous structure of bioabsorbable polymer, which is loaded with test drug. Drug release is targeted at improving the properties of biomaterial for use in controlled tissue repair and regeneration.

  6. 2009 Clusters, Nanocrystals & Nanostructures GRC

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lai-Sheng [Washington State Univ., Pullman, WA (United States)

    2009-07-19

    For over thirty years, this Gordon Conference has been the premiere meeting for the field of cluster science, which studies the phenomena that arise when matter becomes small. During its history, participants have witnessed the discovery and development of many novel materials, including C60, carbon nanotubes, semiconductor and metal nanocrystals, and nanowires. In addition to addressing fundamental scientific questions related to these materials, the meeting has always included a discussion of their potential applications. Consequently, this conference has played a critical role in the birth and growth of nanoscience and engineering. The goal of the 2009 Gordon Conference is to continue the forward-looking tradition of this meeting and discuss the most recent advances in the field of clusters, nanocrystals, and nanostructures. As in past meetings, this will include new topics that broaden the field. In particular, a special emphasis will be placed on nanomaterials related to the efficient use, generation, or conversion of energy. For example, we anticipate presentations related to batteries, catalysts, photovoltaics, and thermoelectrics. In addition, we expect to address the controversy surrounding carrier multiplication with a session in which recent results addressing this phenomenon will be discussed and debated. The atmosphere of the conference, which emphasizes the presentation of unpublished results and lengthy discussion periods, ensures that attendees will enjoy a valuable and stimulating experience. Because only a limited number of participants are allowed to attend this conference, and oversubscription is anticipated, we encourage all interested researchers from academia, industry, and government institutions to apply as early as possible. An invitation is not required. We also encourage all attendees to submit their latest results for presentation at the poster sessions. We anticipate that several posters will be selected for 'hot topic' oral

  7. Three-dimensional flowerlike iron oxide nanostructures: Morphology, composition and metal ion removal capability

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Dan [School of Material Science and Engineering, University of Jinan, 250022 Jinan (China); Yang, Ping, E-mail: mse_yangp@ujn.edu.cn [School of Material Science and Engineering, University of Jinan, 250022 Jinan (China); Huang, Baibiao [State Key Laboratory of Crystal Materials, Shandong University, 250100 Jinan (China)

    2016-01-15

    Graphical abstract: The iron alkoxide precursors are calcined into α-Fe{sub 2}O{sub 3}, Fe{sub 3}O{sub 4} microstructures with different morphologies by changing calcination atmosphere, reaction time of precursors and calcination temperature simply. The Fe{sub 2}O{sub 3}/Ag hybrid composites prepared through aqueous synthesis and light irradiation. - Highlights: • α-Fe{sub 2}O{sub 3} and Fe{sub 3}O{sub 4} microstructures with different morphologies were created. • Solvents play an important role for the solvothermal treatment of precursors. • The α-Fe{sub 2}O{sub 3} microstructures show excellent adsorption properties. • Fe{sub 2}O{sub 3}/Ag hybrid composites were prepared to improve their properties. - Abstract: The flower-like precursors of Fe alkoxide constructed by the self-assembly of nanoflakes were prepared. Time-dependent experiments confirmed the formation mechanism of flower-like precursors. After calcination, α-Fe{sub 2}O{sub 3} and Fe{sub 3}O{sub 4} nanostructures with different morphologies were created. Fe{sub 3}O{sub 4} nanostructures containing blocks with a truncated octahedron structure were obtained under N{sub 2} protection. α-Fe{sub 2}O{sub 3} nanostructures were prepared in an air atmosphere. The values of maximum adsorption capacity of α-Fe{sub 2}O{sub 3} nanostructures for Cr{sup 6+} ions were much higher than that of commercial bulk α-Fe{sub 2}O{sub 3}. Ag NPs were deposited on α-Fe{sub 2}O{sub 3} nanostructures through an aqueous synthesis and light irradiation using L-cysteine as a linker. Such procedure is utilizable for the preparation of the composites of noble metals and magnetic materials.

  8. Characterization of ZnO nanostructures: A challenge to positron annihilation spectroscopy and other methods

    Energy Technology Data Exchange (ETDEWEB)

    Brauer, Gerhard; Anwand, Wolfgang; Grambole, Dieter; Skorupa, Wolfgang [Institut fuer Ionenstrahlphysik und Materialforschung, Forschungszentrum Dresden-Rossendorf, Dresden (Germany); Egger, Werner; Sperr, Peter [Institut fuer Angewandte Physik und Messtechnik LRT2, Fakultaet fuer Luft- und Raumfahrttechnik, Werner-Heisenberg-Weg 39, Universitaet der Bundeswehr, Neubiberg (Germany); Beinik, Igor; Wang, Lin; Teichert, Christian [Institut fuer Physik, Montanuniversitaet Leoben (Austria); Kuriplach, Jan; Lang, Jan [Department of Low Temperature Physics, Charles University, Prague (Czech Republic); Zviagin, Sergei; Cizmar, Erik [Institut Hochfeld-Magnetlabor, Forschungszentrum Dresden-Rossendorf, Dresden (Germany); Ling, Chi Chung; Hsu, Yuk Fan; Xi, Yan Yan; Chen, Xinyi; Djurisic, Aleksandra B. [Department of Physics, University of Hong Kong, Hong Kong (China)

    2009-11-15

    ZnO nanostructures are of special interest for device applications. However, their structural characterization remains an ongoing challenge. This paper reviews recent efforts and latest achievements in this direction. Results comprise PAS in the form of Slow Positron Implantation Spectroscopy (SPIS) and Pulsed Low Energy Positron Lifetime Spectroscopy (PLEPS), Nuclear Reaction Analysis (NRA), Atomic Force Microscopy (AFM), conductive AFM (C-AFM), Nuclear Magnetic Resonance (NMR), Electron Spin Resonance (ESR), Photoluminescence (PL) spectroscopy, and latest theoretical investigations of structure-related and positron properties of selected defects. The fundamental importance of a relationship between fabrication conditions, native defect formation, and resulting optical and electronic properties is demonstrated by getting either inferior (nanorods) or significantly improved (tetrapods) optical properties compared to single crystal samples, depending on the nanostructure fabrication method. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Polymer Masks for nanostructuring of graphene

    DEFF Research Database (Denmark)

    Shvets, Violetta

    This PhD project is a part of Center for Nanostructured Graphene (CNG) activities. The aim of the project is to develop a new lithography method for creation of highly ordered nanostructures with as small as possible feature and period sizes. The method should be applicable for graphene nanostruc...... demonstrated the opening of what could be interpreted as a band gap....... polymer masks is developed. Mask fabrication is realized by microtoming of 30-60 nm thin sections from pre-aligned polymer monoliths with different morphologies. The resulting polymer masks are then transferred to both silicon and graphene substrates. Hexagonally packed hole patterns with 10 nm hole...

  10. Research of Self-Formation Nanostructures

    Directory of Open Access Journals (Sweden)

    Romas Petrauskas

    2011-08-01

    Full Text Available Lateral etching processes for the modeling of the geometry of self-formation nanostructures with Silvaco TCAD Athena program are analyzed. Self-formation nanostructures is modeled with different mask selectivity values equal to 2, 10, 40 and 100 with respect to the etching layer, with the etching duration of 0–180 s. The etching rates are constant – 1.33 nm/s. The analysis of the dependence of the etching systematic error on its thickness has been carried out. The computer modeled results are close to the ones produced by means of the application of the analytical calculation models by other authors.Article in Lithuanian

  11. Nanowires and nanostructures fabrication using template methods

    DEFF Research Database (Denmark)

    Mátéfi-Tempfli, Stefan; Mátéfi-Tempfli, M.; Vlad, A.

    2009-01-01

    One of the great challenges of today is to find reliable techniques for the fabrication of nanomaterials and nanostructures. Methods based on template synthesis and on self organization are the most promising due to their easiness and low cost. This paper focuses on the electrochemical synthesis ...... of nanowires and nanostructures using nanoporous host materials such as supported anodic aluminum considering it as a key template for nanowires based devices. New ways are opened for applications by combining such template synthesis methods with nanolithographic techniques....

  12. About possible technologies of creation nanostructures blankets

    International Nuclear Information System (INIS)

    Blednova, Zh.M.; Chaevskij, M.I.; Rusinov, P.O.

    2008-01-01

    Possible technologies of formation nanostructures blankets are considered: a method of thermal carrying over of weights in the conditions of a high gradient of temperatures; the combined method including cathode-plasma nitriding in the conditions of low pressure and drawing of nitride of the titan in a uniform work cycle; the combined method including high-frequency ionic nitriding and drawing of carbide of chrome by pyrolysis chrome and organic of connections in plasma of the decaying category. Possibility of formation layered nanostructures layers is shown.

  13. Engineered Metallic Nanostructures: Fabrication, Characterization, and Applications

    Science.gov (United States)

    Bohloul, Arash

    Metallic nanostructures have garnered a great deal of attention due to their fascinating optical properties, which differ from the bulk metal. They have been proven to exceed expectations in wide variety of applications including chemical and biological sensing. Nevertheless, high-throughput and low cost nanofabrication techniques are required to implant metallic nanostructures in widespread applications. With that vision, this thesis presents a versatile and reliable method for scalable fabrication of gold nanostructures. In this approach, a plasma-treated ordered array of polystyrene nanospheres acts as an initial mask. The key step in this process is the vapor-deposition of nickel as a sacrificial mask. Thereby, gold nanostructures are directly formed on the substrate through the nickel mask. This is an easy, powerful, and straightforward method that offers several degrees of freedom to precisely control the shape and size of nanostructures. We made a library of nanostructures including gold nanocrescents, double crescents, nanorings, and nanodisks with the ability to tune the size in the range of 150 to 650 nm. The fabricated nanostructures are highly packed and uniformly cover the centimeter scale substrate. The optical properties of metallic nanostructures were extensively studied by a combination of UV-Vis-NIR and Fourier transform infrared (FTIR) spectroscopies, and correlation between optical response and geometrical parameters were investigated. In the next part of this thesis, highly sensitive surface enhanced infrared absorption (SEIRA) analysis was demonstrated on gold nanocrescent arrays. Theoretical modeling was confirmed that these substrates provide highly dense and strong hot-spots over the substrate, which is required for surface enhanced spectroscopic studies. Gold nanocrescent arrays exhibit highly tunable plasmon resonance to cover desired molecular vibrational bands. These substrates experimentally illustrated 3 orders of magnitude

  14. On the possibility of room temperature ferromagnetism on chunk-shape BaSnO3/ZnO core/shell nanostructures

    Science.gov (United States)

    Rajamanickam, N.; Jayakumar, K.; Ramachandran, K.

    2018-04-01

    Core/shell BaSnO3/ZnO (BS-ZO) nanostructures were prepared by oxalate precipitation method and wet-chemical method. BaSnO3 (BSO) cubic perovskite structure and ZnO hexagonal wurtzite structure were confirmed by X-ray diffraction (XRD). The crystallite sizes is 23 nm, 29 nm and 27 nm for BSO, ZnO and BS-ZO, respectively. Chunk-shape and cuboids morphology observed from scanning electron microscopy (SEM) analysis. The magnetic properties were studied by VSM for bare and core-shell nano systems and the room temperature ferromagnetism observed for core-shell nanostructures. The BSO/ZnO shows enhanced coercivity and saturated magnetization as compared with BSO and ZnO nanostructures.

  15. Magneto-Plasmonics and Resonant Interaction of Light with Dynamic Magnetisation in Metallic and All-Magneto-Dielectric Nanostructures.

    Science.gov (United States)

    Maksymov, Ivan S

    2015-04-09

    A significant interest in combining plasmonics and magnetism at the nanoscale gains momentum in both photonics and magnetism sectors that are concerned with the resonant enhancement of light-magnetic-matter interaction in nanostructures. These efforts result in a considerable amount of literature, which is difficult to collect and digest in limited time. Furthermore, there is insufficient exchange of results between the two research sectors. Consequently, the goal of this review paper is to bridge this gap by presenting an overview of recent progress in the field of magneto-plasmonics from two different points of view: magneto-plasmonics, and magnonics and magnetisation dynamics. It is expected that this presentation style will make this review paper of particular interest to both general physical audience and specialists conducting research on photonics, plasmonics, Brillouin light scattering spectroscopy of magnetic nanostructures and magneto-optical Kerr effect magnetometry, as well as ultrafast all-optical and THz-wave excitation of spin waves. Moreover, readers interested in a new, rapidly emerging field of all-dielectric nanophotonics will find a section about all-magneto-dielectric nanostructures.

  16. Magneto-Plasmonics and Resonant Interaction of Light with Dynamic Magnetisation in Metallic and All-Magneto-Dielectric Nanostructures

    Directory of Open Access Journals (Sweden)

    Ivan S. Maksymov

    2015-04-01

    Full Text Available A significant interest in combining plasmonics and magnetism at the nanoscale gains momentum in both photonics and magnetism sectors that are concerned with the resonant enhancement of light-magnetic-matter interaction in nanostructures. These efforts result in a considerable amount of literature, which is difficult to collect and digest in limited time. Furthermore, there is insufficient exchange of results between the two research sectors. Consequently, the goal of this review paper is to bridge this gap by presenting an overview of recent progress in the field of magneto-plasmonics from two different points of view: magneto-plasmonics, and magnonics and magnetisation dynamics. It is expected that this presentation style will make this review paper of particular interest to both general physical audience and specialists conducting research on photonics, plasmonics, Brillouin light scattering spectroscopy of magnetic nanostructures and magneto-optical Kerr effect magnetometry, as well as ultrafast all-optical and THz-wave excitation of spin waves. Moreover, readers interested in a new, rapidly emerging field of all-dielectric nanophotonics will find a section about all-magneto-dielectric nanostructures.

  17. Application of nanostructural materials in electro optical measuring sets of big powers based on usage of optical effects

    Science.gov (United States)

    Salihov, Aidar I.; Tljavlin, Anfar Z.; Kusimov, Salavat M.

    2005-06-01

    Optically transparent nanostructural materials show to themselves a heightened interest owing to display in them the new physic mechanical properties. Variation of structure of the materials received by methods of intensive plastic deformation, results in variation of many fundamental parameters. Among them special interest was caused with variations of fundamental magnetic characteristics. One of them is the magnetization of saturation, which is usually structurally tolerant, but reflects changes in an atomic-crystal structure of solids. Even in the first probing of the transparent nanostructures, received by intensive deformation by torsion of samples, was found that the magnetization of saturation was revealed at room temperature in comparison with coarse-grained samples. High-power measuring devices are based on Faraday effect, representing itself rotation of a plane of polarization of linearly polarized light in optical active substances under action of a magnetic field. Application of nanostructural materials in the optical insulator, which is the main part of the measuring device, allows improving the measuring characteristics of instruments qualitatively. Brought losses in Faraday cell make 0,35 -0,89 dB instead of 0,7 - I,2 dB, and value of the backward losses makes not less than 62 dB instead of 55 dB. Undoubtedly, improvement of the given parameters allows making the measuring operations with the greater accuracy, reducing both absolute, and relative errors.

  18. Positronium formation in nanostructured metals

    Czech Academy of Sciences Publication Activity Database

    Čížek, J.; Melikhova, O.; Hruška, P.; Vlček, M.; Anwand, W.; Liedke, M.O.; Novotný, Michal; Bulíř, Jiří

    2017-01-01

    Roč. 132, č. 5 (2017), s. 1579-1584 ISSN 0587-4246 R&D Projects: GA ČR GBP108/12/G043 Institutional support: RVO:68378271 Keywords : positronium * positron annihilation spectroscopy * black gold Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 0.469, year: 2016

  19. Mn-doped ZnO nanocrystals synthesized by sonochemical method: Structural, photoluminescence, and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Othman, A.A., E-mail: aaelho@yahoo.com [Assiut University, Faculty of Science, Department of Physics, Assiut 71516 (Egypt); Osman, M.A. [Assiut University, Faculty of Science, Department of Physics, Assiut 71516 (Egypt); Ibrahim, E.M.M. [Sohag University, Faculty of Science, Department of Physics, Sohag 82524 (Egypt); Ali, Manar A.; Abd-Elrahim, A.G. [Assiut University, Faculty of Science, Department of Physics, Assiut 71516 (Egypt)

    2017-05-15

    Highlights: • Mn-doped ZnO nanostructures were synthesized by the sonochemical method. • Structural, morphological, optical, photoluminescence and magnetic properties were investigated. • Mn-doped ZnO nanostructures reveal a blue shift of the optical band gap. • Photoluminescence spectra of Mn-doped ZnO nanostructures show quenching in the emission intensity. • Mn-doped ZnO nanostructures exhibit ferromagnetic ordering at room temperature. - Abstract: This work reports the synthesis of Mn-doped ZnO nanostructures using ice-bath assisted sonochemical technique. The impact of Mn-doping on structural, morphological, optical, and magnetic properties of ZnO nanostructures is studied. The morphological study shows that the lower doped samples possess mixtures of nanosheets and nanorods while the increase in Mn content leads to improvement of an anisotropic growth in a preferable orientation to form well-defined edge rods at Mn content of 0.04. UV–vis absorption spectra show that the exciton peak in the UV region is blue shifted due to Mn incorporation into the ZnO lattice. Doping ZnO with Mn ions leads to a reduction in the PL intensity due to a creation of more non-radiative recombination centers. The magnetic measurements show that the Mn-doped ZnO nanostructures exhibit ferromagnetic ordering at room temperature, as well as variation of the Mn content can significantly affect the ferromagnetic behavior of the samples.

  20. The 2013 Clusters, Nanocrystals & Nanostructures Gordon Research Conference/Gordon Research Seminar

    Energy Technology Data Exchange (ETDEWEB)

    Krauss, Todd D. [University of Rochester

    2014-11-25

    The fundamental properties of small particles and their potential for groundbreaking applications are among the most exciting areas of study in modern physics, chemistry, and materials science. The Clusters, Nanocrystals & Nanostructures Gordon ResearchConference and Gordon Research Seminar synthesize contributions from these inter-related fields that reflect the pivotal role of nano-particles at the interface between these disciplines. Size-dependent optical, electronic, magnetic and catalytic properties offer prospects for applications in many fields, and possible solutions for many of the grand challenges facing energy generation, consumption, delivery, and storage in the 21st century. The goal of the 2013 Clusters, Nanocrystals & Nanostructures Gordon Research Conference and Gordon Research Seminar is to continue the historical interdisciplinary tradition of this series and discuss the most recent advances, basic scientific questions, and emerging applications of clusters, nanocrystals, and nanostructures. The Clusters, Nanocrystals & Nanostructures GRC/GRS traditionally brings together the leading scientific groups that have made significant recent advances in one or more fundamental nanoscience or nanotechnology areas. Broad interests of the DOE BES and Solar Photochemistry Program addressed by this meeting include the areas of solar energy to fuels conversion, new photovoltaic systems, fundamental characterization of nanomaterials, magnetism, catalysis, and quantum physics. The vast majority of speakers and attendees will address either directly the topic of nanotechnology for photoinduced charge transfer, charge transport, and catalysis, or will have made significant contributions to related areas that will impact these fields indirectly. These topics have direct relevance to the mission of the DOE BES since it is this cutting-edge basic science that underpins our energy future.