AVS2011 Session MI-ThP: Magnetic Interfaces and Nanostructures Poster Session

Thursday, November 3, 2011 6:00 PM in Room East Exhibit Hall
Thursday Evening

Time Period ThP Sessions | Topic MI Sessions | Time Periods | Topics | AVS2011 Schedule

MI-ThP-1 Investigations of Ni and Co Magnetic Overlayers at the Advanced Photon Source
Dan Waddill, Takashi Komesu (Missouri University of Science and Technology); Sung Woo Yu, James G. Tobin (Lawrence Livermore National Laboratory)
Magnetic overlayers and bilayers of Ni and Co on Cu(001) have been investigated as a function of coverage, using X-ray Magnetic Circular Dichroism in X-ray Absorption Spectroscopy (XMCD-XAS) and Photoelectron Spectroscopy (PES). These studies were pursued at Beamline 4 at the Advanced Photon Source (APS).

Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344. This work is funded by the DOE Office of Science, Office of Basic Energy Science, Division of Materials Sciences and Engineering. The Advanced Photon Source (APS) is supported by the Director, Office of Science, Office of Basic Energy Sciences.

MI-ThP-3 A Facile and Controllable Two-Step Electrodeposition Technique in Synthesis of Nanostructures of Metal Oxides on Carbon Nanotube S
Jiang Yang, Sundaram Gunasekaran (University of Wisconsin-Madison)

The nano dimensions of materials are comparable to the size of the target analyte biomolecule, higher catalytic reaction, better affinity binding or more efficient molecule-capturing may occur, leading to high sensitivity. And it is possible to use nanoparticle tags for designing electrical bioaffinity assays with remarkable sensitivity and multiplexing ability. So far, efforts have always been made to design novel nanomaterials useful in solving emerging bioanalytical problems such as rapidness, anti-interfering ability, specificity, stability and sensitivity. Synergies of nanocomposite materials, generally retaining the functional properties of each component and possibly yield synergistic effects via cooperative interactions, have exploited a new area to miniaturize and optimize nano-scale sensors and electronics. The synergistic interesting new features include but not limited to increased surface area, enhanced electrocatalytic activities, improved biocompatibility, promoted electron transfer and better invulnerability against intermediate species. A lot of efforts have been made to fabricate nanocomposite materials of metals/metal oxides nanostructures and carbon materials, using a number of techniques, including sputtering, sol–gel, hydrothermal, microwave and electrodeposition from different precursor solutions containing complex agents. Among these, electrodeposition is the easiest, most controllable, environment-friendly and robust technique for synthesis of metal/ metal oxides NPs, in which, the size, density, composition and even the shape of NPs could be well-controlled by electrodeposition potential, time, concentration and composition of metal precursor solutions.

Herein, we report a general two-step approach of electrodeposition useful in facile, controllable and 'green' electrochemical synthesis of metal oxide NPs onto carbon supports, using carbon nanotubes (CNTs) as an example. First, metal nanostructures were electrochemically deposited onto carbon supports at a constant potential with the density, size, shape and elctrocatalytic activities of the produced nanostructures well-controlled by the time and deposition potential applied as well as the concentration of the precursor solution. Then the as-deposited metallic nanostructures were oxidized into metal oxide nanostructures by repetitive potential cycling with extent of oxidation and generation of metal oxides controlled by the number of potential circles.The as-synthesized metal oxides-CNTs composites were characterized and applied as a glucose sensor for illustration of their electrocatalytic properties.

MI-ThP-4 Magnetic Properties and Size Control of Zn0.95Mn0.05O Nanorods Deposited by Pulsed Laser Deposition
Tzung-Chen Wu, Yi-Chen Yeh, Da-Ren Liu, Don-Yau Chiang (National Applied Research Laboratories, Taiwan, Republic of China)
The well-aligned ZnO nanorods with 5 at.% of Mn doping (Zn0.95Mn0.05O) were deposited on silicon (100) substrates by pulsed laser deposition at three different substrate temperatures ranged from 600 ℃ to 700 ℃, while the structure with and without a ZnO seed layer were both considered. The magnetic and structural properties of Zn0.95Mn0.05O nanorods has been characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and superconducting quantum interference device (SQUID). We demonstrate that the distribution and diameter of well-aligned Zn0.95Mn0.05O nanorods are controllable, which strongly depend on the substrate temperature. Also, the magnetic properties are directly controlled by the morphologies of Zn0.95Mn0.05O nanorods, and are thus appropriate for further applications.
MI-ThP-5 Characterization of Metal Oxides Tunnel Barriers for use in a Non-Local Spin Detection Device
Akitomo Matsubayashi (College of Nanoscale Science and Engineering, the University at Albany-SUNY)
Metal oxides can be utilized as interfacial layers between ferromagnetic metals and graphene to achieve spin injection into graphene. Utilizing the spin of the electron as well as its charge has the potential to be utilized for logic devices in the post CMOS era. The goal of our research is to inject and readout spins using a non-local measurement device. However the efficient spin injection has been realized its difficulty due to the conductivity mismatch problem1,2. In order to achieve the efficient spin injection, it has been determined that the insertion of a few nanometers of a tunnel barrier between the ferromagnetic metal and the graphene increases the contact resistance and measured spin lifetime3. However, non-uniformity of the tunnel barriers (pinholes)4 lowers the quality of the interface barrier. In this study, we investigate the fabrication of tunnel barrier on graphene using various metal oxides such as aluminum oxide grown under UHV conditions directly on the graphene. Graphene samples were loaded into an ultrahigh vacuum MBE (Molecular Beam Epitaxy) machine. D esired thickness of metals were deposited from a Knudsen cell. Samples were then transferred back into the load lock and exposed to approximately 130 mTorr of pure O2 for 20 min. Several measurements were performed including scanning electron microscopy, X-ray photoelectron spectroscopy, and angle resolved XPS characterize the electrical and structural quality of the films and their suitability for to be utilized as a tunnel barrier in graphene spin measurements.
 
References:
[1] P. C. van Son, H. van Kempen, and P. Wyder, Phys. Rev. Lett. 58, 2271 (1987)
[2] G.Schmidt, D. Ferrand, L. W. Molenkamp, A. T. Filip, and B. J. van Wees, Phys. Rev. B 62, 4790 (2000)
[3] E. I. Rashba, Phys. Rev. B 62, 16267 (2000)
[4] W. Han, K. Pi, K. M. McCreary, Y. Li, J. J. I. Wong, A. G. Swartz, and R. K. Kawakami, Phys. Rev. Lett. 105, 167202 (2010)
 
 
MI-ThP-7 Promise of New Multiferroics: Synthesis and Characterization of Epitaxial NiTiO3 Films
Tamas Varga, Tim Droubay, Mark Bowden, Scott Chambers, Bernd Kabius, William Shelton, Ponnusamy Nachimuthu, Vaithiyalingam Shutthanandan (Pacific Northwest National Laboratory)

In a search for new multiferroic materials where the direction of magnetization can be switched by an applied electric field, we have looked for materials in which polarization and magnetization are strongly coupled. Recent theory calculations predicted that the family of compounds MTiO 3 (M = Mn, Fe, Ni), in a certain polymorphic structure (acentric R3c), are promising candidates where a polar lattice distortion can induce weak ferromagnetism. Guided by these insights, a rhombohedral phase of Ni TiO3 has been prepared in epitaxial thin film form, whose structure is very close to that predicted to be a multiferroic. The synthesis of such new epitaxial films, their full structural characterization along with our first-principles DFT calculations to predict the desired NiTiO3 structure and its stability are reported .

Time Period ThP Sessions | Topic MI Sessions | Time Periods | Topics | AVS2011 Schedule