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Articles 1 - 11 of 11

Full-Text Articles in Physics

Structure And Dynamics Of Model Systems: From Ferrofluids To Brain Membranes, Matthew A. Barrett Oct 2013

Structure And Dynamics Of Model Systems: From Ferrofluids To Brain Membranes, Matthew A. Barrett

Matthew J. Barrett

Soft condensed matter systems are a very diverse and challenging subject to study. To understand the complex macro-properties of such systems one approach is to characterize the microscopic structure and dynamics. A powerful technique for determining micro and nanoscale properties is scattering of radiation sources. Light, electron and neutron scattering techniques provide insight into the complicated molecular structures and the processes happening on these small scales. We have used neutron and x-ray scattering techniques to determine structural and dynamical information from two different types of soft condensed matter systems. The microscopic nature of a cobalt magnetic fluid was studied using …


Reflectance Anisotropy Of Gd5si2ge2 And Tb5si2.2ge1.8, S. J. Lee, Joong Mok Park, J. E. Snyder, David C. Jiles, Deborah L. Schlagel, Thomas A. Lograsso, A. O. Pecharsky, David W. Lynch Oct 2013

Reflectance Anisotropy Of Gd5si2ge2 And Tb5si2.2ge1.8, S. J. Lee, Joong Mok Park, J. E. Snyder, David C. Jiles, Deborah L. Schlagel, Thomas A. Lograsso, A. O. Pecharsky, David W. Lynch

Professor David Lynch

Reflectance difference (RD) spectra for the a–b plane of the single crystals of Gd5Si2Ge2and b–c planes of Gd5Si2Ge2 and Tb5Si2.2Ge1.8 were obtained in the photon energy range of 1.5–5.5 eV. Several peaks were observed for these crystals in the measured spectrum range. Similar features were observed in the RD spectra for the b–c planes ofGd5Si2Ge2 and Tb5Si2.2Ge1.8, while different features were observed for the a–b plane and b–c plane of Gd5Si2Ge2. The RD spectra for the crystals arise not only from the surface anisotropy but also from the bulk anisotropy due to the monoclinic structure of the bulk crystal.


Novel Nanostructured Rare-Earth-Free Magnetic Materials With High Energy Products, Bhaskar Das Aug 2013

Novel Nanostructured Rare-Earth-Free Magnetic Materials With High Energy Products, Bhaskar Das

B. Das

Novel nanostructured Zr2Co11-based magnetic materials are fabricated in a single step process using cluster-deposition method. The composition, atomic ordering, and spin structure are precisely controlled to achieve a substantial magnetic remanence and coercivity, as well as the highest energy product for non-rare-earth and Pt-free permanent-magnet alloys.


Bulk Fermi Surface And Momentum Density In Heavily Doped La₂₋ₓsrₓcuo₄ Using High-Resolution Compton Scattering And Positron Annihilation Spectroscopies, W. Al-Sawai, B. Barbiellini, Y. Sakurai, M. Itou, P. E. Mijnarends, R. S. Markiewicz, S. Kaprzyk, S. Wakimoto, M. Fujita, S. Basak, H. Lin, Yung Jui Wang, S. W. H. Eijt, H. Schut, K. Yamada, A. Bansil Aug 2013

Bulk Fermi Surface And Momentum Density In Heavily Doped La₂₋ₓsrₓcuo₄ Using High-Resolution Compton Scattering And Positron Annihilation Spectroscopies, W. Al-Sawai, B. Barbiellini, Y. Sakurai, M. Itou, P. E. Mijnarends, R. S. Markiewicz, S. Kaprzyk, S. Wakimoto, M. Fujita, S. Basak, H. Lin, Yung Jui Wang, S. W. H. Eijt, H. Schut, K. Yamada, A. Bansil

Susmita Basak

We have observed the bulk Fermi surface (FS) in an overdoped (x=0.3) single crystal of La₂₋ₓSrₓCuO₄ by using Compton scattering. A two-dimensional (2D) momentum density reconstruction from measured Compton profiles yields a clear FS signature in the third Brillouin zone along [100]. The quantitative agreement between density functional theory (DFT) calculations and momentum density experiment suggests that Fermi-liquid physics is restored in the overdoped regime. In particular the predicted FS topology is found to be in good accord with the corresponding experimental data. We find similar quantitative agreement between the measured 2D angular correlation of positron annihilation radiation (2D-ACAR) spectra …


Electrostatic Discharge Properties Of Fused Silica Coatings, Allen Andersen, Charles Sim, Jr Dennison Jul 2013

Electrostatic Discharge Properties Of Fused Silica Coatings, Allen Andersen, Charles Sim, Jr Dennison

Allen Andersen

The electric field value at which electrostatic discharge (ESD) occurs was studied for thin coatings of fused silica (highly disordered SiO2/SiOx) on conductive substrates, such as those encountered as optical coatings and in Si microfabrication. The electrostatic breakdown field was determined using an increasing voltage, while monitoring the leakage current. A simple parallel-plate capacitor geometry was used, under medium vacuum and at temperatures down to ~150 K using a liquid N2 reservoir. The breakdown field, pre-breakdown arcing and I-V curves for fused silica samples are compared for ~60 nm and ~80 μm thick, room and low temperature, and untreated and …


Hfco7-Based Rare-Earth-Free Permanent-Magnet Alloys, Bhaskar Das Jun 2013

Hfco7-Based Rare-Earth-Free Permanent-Magnet Alloys, Bhaskar Das

B. Das

This study presents the structural and magnetic properties of melt-spun HfCo7,HfCo7-xFex (0.25 ≤ × ≤ 1) and HfCo7Six(0.2 ≤ × ≤1.2) alloys. Appreciable permanent-magnet properties with a magnetocrystalline anisotropy of about 9.6-16.5 Mergs/cm3, a magnetic polarization Js ≈ 7.2-10.6 kG, and coercivities Hc = 0.5-3.0 kOe were obtained by varying the composition of these alloys. Structural analysis reveals that the positions of x-ray diffraction peaks of HfCo7 show good agreement with those corresponding to an orthorhombic structure having lattice parameters of about α = 4.719 Å, b = 4.278 Å, and c = 8.070 Å. Based on these results, a …


Modeling Complex Properties Of Ferroelectric Nanocomposites, Raymond T. Walter Apr 2013

Modeling Complex Properties Of Ferroelectric Nanocomposites, Raymond T. Walter

Raymond Walter

No abstract provided.


Proton Transfer In Surface-Stabilized Chiral And Polar Motifs Of Croconic Acid, Axel Enders Dec 2012

Proton Transfer In Surface-Stabilized Chiral And Polar Motifs Of Croconic Acid, Axel Enders

Axel Enders

No abstract provided.


Vortex-Glass Phase Transition And Enhanced Flux Pinning In C 4+-Irradiated Bafe1.9ni0.1as2 Superconducting Single Crystals, M Shahbazi, X Wang, S Ghorbani, M Ionescu, Olga Shcherbakova, Frederick Wells, Alexey Pan, S Dou, K Choi Dec 2012

Vortex-Glass Phase Transition And Enhanced Flux Pinning In C 4+-Irradiated Bafe1.9ni0.1as2 Superconducting Single Crystals, M Shahbazi, X Wang, S Ghorbani, M Ionescu, Olga Shcherbakova, Frederick Wells, Alexey Pan, S Dou, K Choi

Frederick S Wells

We report the effects of C4+-irradiation on the superconducting properties of BaFe1.9Ni0.1As2 single crystal. The BaFe1.9Ni0.1As2 single crystal before and after C4+-irradiation was characterized by magnetic, magneto-transport and magneto-optical techniques over a wide range of magnetic fields (0-13 T) and temperatures (2-200 K). We demonstrate that the C 4+-irradiation significantly enhances the in-field critical current density (by a factor of up to 1.5 at 5 K) and induces enhanced flux jumping at 2 K, with only a small degradation (by 0.5 K) of the critical temperature, T c. The vortex phase diagram describing the evolution of the vortex-glass transition temperature …


Tuning Of Magnetization In Vertical Graphenes By Plasma-Enabled Chemical Conversion Of Organic Precursors With Different Oxygen Content, Zengji Yue Dec 2012

Tuning Of Magnetization In Vertical Graphenes By Plasma-Enabled Chemical Conversion Of Organic Precursors With Different Oxygen Content, Zengji Yue

Zengji Yue

Different magnetization in vertical graphenes fabricated by plasma-enabled chemical conversion of organic precursors with various oxygen atom contents and bonding energies was achieved. The graphenes grown from fat-like precursors exhibit magnetization up to 8 emu g−1, whereas the use of sugar-containing precursors results in much lower numbers. A relatively high Curie temperature exceeding 600 K was also demonstrated.


Spin Scattering In Manganese Doped Nickel, Ken Podolak Dec 2012

Spin Scattering In Manganese Doped Nickel, Ken Podolak

Dr. Ken Podolak

Spin scattering characteristics of nickel doped with manganese are compared to nickel doped with iron and chromium in nickel. Conclusions are made based on the spin characteristics of the nickel samples doped with manganese with varying percentages in a host nickel crystal. Manganese doping increases the magnetic exchange splitting of nickel, similar to doping with iron and opposite to doping with chromium. On the other hand, manganese doping behaves different from iron with respect the ratio of the majority to minority spin carriers and the ratio of their lifetimes. While iron doping affects both ratios strongly, manganese and chromium doping …