Transcript of Commission on Wartime Contracting in Iraq & Afghanistan Hearing: February 18. 2009 (open access)

Transcript of Commission on Wartime Contracting in Iraq & Afghanistan Hearing: February 18. 2009

Transcript of a public hearing held by the Commission on Wartime Contracting in Iraq & Afghanistan held December 18, 2009 in Washington, D.C. This hearing includes testimony from federal officials and government contractors on the adequacy and oversight of contract training for Afghanistan's national army and police forces.
Date: December 18, 2009
Creator: CQ Transcriptions
Object Type: Text
System: The UNT Digital Library
VisIt: a component based parallel visualization package (open access)

VisIt: a component based parallel visualization package

We are currently developing a component based, parallel visualization and graphical analysis tool for visualizing and analyzing data on two- and three-dimensional (20, 30) meshes. The tool consists of three primary components: a graphical user interface (GUI), a viewer, and a parallel compute engine. The components are designed to be operated in a distributed fashion with the GUI and viewer typically running on a high performance visualization server and the compute engine running on a large parallel platform. The viewer and compute engine are both based on the Visualization Toolkit (VTK), an open source object oriented data manipulation and visualization library. The compute engine will make use of parallel extensions to VTK, based on MPI, developed by Los Alamos National Laboratory in collaboration with the originators of P K . The compute engine will make use of meta-data so that it only operates on the portions of the data necessary to generate the image. The meta-data can either be created as the post-processing data is generated or as a pre-processing step to using VisIt. VisIt will be integrated with the VIEWS' Tera-Scale Browser, which will provide a high performance visual data browsing capability based on multi-resolution techniques.
Date: December 18, 2000
Creator: Ahern, S; Bonnell, K; Brugger, E; Childs, H; Meredith, J & Whitlock, B
Object Type: Article
System: The UNT Digital Library
Engineered Defects for Investigation of Laser-Induced Damage of Fused Silica at 355nm (open access)

Engineered Defects for Investigation of Laser-Induced Damage of Fused Silica at 355nm

Embedded gold and mechanical deformation in silica were used to investigate initiation of laser-induced damage at 3.55-nm (7.6 ns). The nanoparticle-covered surfaces were coated with between 0 and 500 nm of SiO{sub 2} by e-beam deposition. The threshold for observable damage and initiation site morphology for these ''engineered'' surfaces was determined. The gold nanoparticle coated surfaces with 500nm SiO{sub 2} coating exhibited pinpoint damage threshold of <0.7 J/cm{sup 2} determined by light scattering and Nomarski microscopy. The gold nanoparticle coated surfaces with the 100nm SiO{sub 2} coatings exhibited what nominally appeared to be film exfoliation damage threshold of 19 J/cm{sup 2} via light scattering and Nomarski microscopy. With atomic force microscopy pinholes could be detected at fluences greater than 7 J/cm{sup 2} and blisters at fluences greater than 3 J/cm{sup 2} on the 100 nm-coated surfaces. A series of mechanical indents and scratches were made in the fused silica substrates using a nano-indentor. Plastic deformation without cracking led to damage thresholds of -25 J/cm{sup 2}, whereas indents and scratches with cracking led to damage thresholds of only {approx}5 J/cm{sup 2}. Particularly illuminating was the deterministic damage of scratches at the deepest end of the scratch, as if the scratch acted …
Date: December 18, 2001
Creator: Hamza, A V; Siekhaus, W J; Rubenchik, A M; Feit, M; Chase, L L; Savina, M et al.
Object Type: Article
System: The UNT Digital Library
Effects of Globally Waste-Disturbing Activities on Gas Generation, Retention, and Release in Hanford Waste Tanks (open access)

Effects of Globally Waste-Disturbing Activities on Gas Generation, Retention, and Release in Hanford Waste Tanks

Various operations are authorized in Hanford single- and double-shell tanks that disturb all or a large fraction of the waste. These globally waste-disturbing activities have the potential to release a large fraction of the retained flammable gas and to affect future gas generation, retention, and release behavior. This report presents analyses of the expected flammable gas release mechanisms and the potential release rates and volumes resulting from these activities. The background of the flammable gas safety issue at Hanford is summarized, as is the current understanding of gas generation, retention, and release phenomena. Considerations for gas monitoring and assessment of the potential for changes in tank classification and steady-state flammability are given.
Date: December 18, 2002
Creator: Stewart, Charles W.; Huckaby, James L. & Meyer, Perry A.
Object Type: Report
System: The UNT Digital Library
Simulated (n,f) cross section of isomeric 235m-U (open access)

Simulated (n,f) cross section of isomeric 235m-U

The neutron-induced fission cross section on the {sup 235}U, T{sub 1/2} {approx} 26 min isomer has been deduced for incident neutron energies in the range E{sub n}=0.1-2.5 MeV, using the surrogate-reaction technique. In this technique, {sup 236}U fission probabilities measured in the {sup 234}U(t, pf) reaction have been converted into {sup 235}U(n,f) and {sup 235m}U(n,f) cross sections, using reaction theory to compensate for the differences in angular-momentum and parity distributions in the fissioning systems, transferred by the (t,p) and neutron-induced reactions. Based on the comparison between the {sup 235}U(n,f) cross section extracted in this work and independent experimental data, the deduced {sup 235m}U(n,f) cross section is believed to be reliable to 20% below E{sub n} {approx} 0.5 MeV and 10% at higher energies. The surrogate-reaction technique, its validation in the case of the {sup 235}U(n,f) cross section, and the deduced {sup 235m}U(n,f) cross section are discussed. Validation of this method allows (n,f) cross sections for many short-lived nuclei, as well as isomeric nuclei, to be extracted from measured fission probabilities.
Date: December 18, 2003
Creator: Becker, J; Britt, H & Younes, W
Object Type: Article
System: The UNT Digital Library
Annual Energy Consumption Analysis Report for Richland Middle School (open access)

Annual Energy Consumption Analysis Report for Richland Middle School

Richland Middle School is a single story, 90,000 square feet new school located in Richland, WA. The design team proposed four HVAC system options to serve the building. The proposed HVAC systems are listed as following: (1) 4-pipe fan coil units served by electrical chiller and gas-fired boilers, (2) Ground-source closed water loop heat pumps with water loop heat pumps with boiler and cooling tower, and (3) VAV system served by electrical chiller and gas-fired boiler. This analysis estimates the annual energy consumptions and costs of each system option, in order to provide the design team with a reasonable basis for determining which system is most life-cycle cost effective. eQuest (version 3.37), a computer-based energy simulation program that uses the DOE-2 simulation engine, was used to estimate the annual energy costs.
Date: December 18, 2003
Creator: Liu, Bing
Object Type: Report
System: The UNT Digital Library
Removal of Nickel and Vanadium From Heavy Crude Oils by Exchange Reactions (open access)

Removal of Nickel and Vanadium From Heavy Crude Oils by Exchange Reactions

None
Date: December 18, 2003
Creator: Reynolds, J G
Object Type: Article
System: The UNT Digital Library
Device Assembly Facility (DAF) Glovebox Radioactive Waste Characterization (open access)

Device Assembly Facility (DAF) Glovebox Radioactive Waste Characterization

The Device Assembly Facility (DAF) at the Nevada Test Site (NTS) provides programmatic support to the Joint Actinide Shock Physics Experimental Research (JASPER) Facility in the form of target assembly. The target assembly activities are performed in a glovebox at DAF and include Special Nuclear Material (SNM). Currently, only activities with transuranic SNM are anticipated. Preliminary discussions with facility personnel indicate that primarily two distributions of SNM will be used: Weapons Grade Plutonium (WG-Pu), and Pu-238 enhanced WG-Pu. Nominal radionuclide distributions for the two material types are included in attachment 1. Wastes generated inside glove boxes is expected to be Transuranic (TRU) Waste which will eventually be disposed of at the Waste Isolation Pilot Plant (WIPP). Wastes generated in the Radioactive Material Area (RMA), outside of the glove box is presumed to be low level waste (LLW) which is destined for disposal at the NTS. The process knowledge quantification methods identified herein may be applied to waste generated anywhere within or around the DAF and possibly JASPER as long as the fundamental waste stream boundaries are adhered to as outlined below. The method is suitable for quantification of waste which can be directly surveyed with the Blue Alpha meter or …
Date: December 18, 2001
Creator: Dominick, J L
Object Type: Report
System: The UNT Digital Library
Phase I Source Investigation, Heckathorn Superfund Site, Richmond, California (open access)

Phase I Source Investigation, Heckathorn Superfund Site, Richmond, California

This report represents Phase I of a multi-phase approach to a source investigation of DDT at the Heckathorn Superfund Site, Richmond, California, the former site of a pesticide packaging plant, and the adjacent waterway, the Lauritzen Channel. Potential identified sources of contamination were from sloughed material from undredged areas (such as side banks) and from outfall pipes. Objectives of Phase I included the (1) evaluation of pesticide concentrations associated with discharge from outfalls, (2) identification of additional outfalls in the area, (3) identification of type, quantity, and distribution of sediment under the Levin pier, (4) quantification of pesticide concentrations in sediment under the pier, and (5) evaluation of sediment structure and slope stability under the pier. Field operations included the collection of sediment directly from inside the mouths of outfall pipes, when possible, or the deployment of specially designed particle traps where direct sampling was problematic. Passive water samplers were placed at the end of known outfall pipes and analyzed for DDT and other pesticides of concern. Underwater dive surveys were conducted beneath the Levin pier to document type, slope, and thickness of sediment. Samples were collected at locations of interest and analyzed for contaminants. Also sampled was soil from …
Date: December 18, 2002
Creator: Kohn, Nancy P. & Evans, Nathan R.
Object Type: Report
System: The UNT Digital Library
Decontamination of U-metal Surface by an Oxidation Etching System (open access)

Decontamination of U-metal Surface by an Oxidation Etching System

A surface oxidation treatment is described to remove surface contamination from uranium (U) metal and/or hydrides of uranium and heavy metals (HM) from U-metal parts. In the case of heavy metal atomic contamination on a surface, and potentially several atomic layers beneath, the surface oxidation treatment combines both chemical and chemically driven mechanical processes. The chemical process is a controlled temperature-time oxidization process that creates a thin film of uranium oxide (UO{sub 2} and higher oxides) on the U-metal surface. The chemically driven mechanical process is strain induced by the volume increase as the U-metal surface transforms to a UO{sub 2} surface film. These volume strains are sufficiently large to cause surface failure spalling/scale formation and thus, removal of a U-oxide film that contains the HM-contaminated surface. The case of a HM-hydride surface contamination layer can be treated similarly by using inert hot gas to decompose the U-hydrides and/or HM-hydrides that are contiguous with the surface. A preliminary analysis to design and to plan for a sequence of tests is developed. The tests will provide necessary and sufficient data to evaluate the effective implementation and operational characteristics of a safe and reliable system. The following description is limited to only …
Date: December 18, 2000
Creator: Stout, R B; Kansa, E J; Shaffer, R J & Weed, H C
Object Type: Article
System: The UNT Digital Library
Transformation Crystallography and Plasticity of the Delta to Alpha Prime Transformation in Plutonium Alloys (open access)

Transformation Crystallography and Plasticity of the Delta to Alpha Prime Transformation in Plutonium Alloys

In delta phase Pu-Ga alloys, the transformation from the ductile face-centered cubic (fcc) {delta} phase that is retained at room temperature to the brittle low-temperature monoclinic alpha' phase is a thermally activated diffusionless transformation with double-c kinetics. Accurate modeling of the phase transformation requires detailed understanding of the role of plastic flow during the transformation and of the crystallographic transformation path. Using transmission electron microscopy (TEM), we find a significant increase in dislocation density in {delta} near the {alpha}' plates, which suggests that plastic deformation contributes to the accommodation of the 20% reduction in volume during the transformation. Analysis of a series of optical micrographs of partially transformed alloys suggests that the {alpha}' habit plane is usually nearly perpendicular to <111> {delta}. However, a small number of TEM observations support a habit plane near <112> or <123>, in agreement with earlier work.
Date: December 18, 2003
Creator: Krenn, C R; Wall, M A & Schwartz, A J
Object Type: Article
System: The UNT Digital Library
Effective determination of coexistence curves using reversible-scaling molecular dynamics simulations (open access)

Effective determination of coexistence curves using reversible-scaling molecular dynamics simulations

We present a simulation technique that allows the calculation of a phase coexistence curve from a single nonequilibrium molecular dynamics (MD) simulation. The approach is based on the simultaneous simulation of two coexisting phases, each in its own computational cell, and the integration of the relevant Clausius-Clapeyron equation starting from a known coexistence point. As an illustration of the effectiveness of our approach we apply the method to explore the melting curve in the Lennard-Jones phase diagram.
Date: December 18, 2000
Creator: de Koning, M; Antonelli, A & Yip, S
Object Type: Article
System: The UNT Digital Library
Mechanisms to Explain Damage Growth in Optical Materials (open access)

Mechanisms to Explain Damage Growth in Optical Materials

Damage growth in optical materials used in large aperture laser systems is an issue of great importance when determining component lifetime and therefore cost of operation. Understanding the mechanisms and photophysical processes associated with damage growth are important in order to devise mitigation techniques. In this work we examined plasma-modified material and cracks for their correlation to damage growth on fused silica and DKDP samples. We employ an in-situ damage testing optical microscope that allows the acquisition of light scattering and fluorescence images of the area of interest prior to, and following exposure to a high fluence, 355-nm, 3-ns laser pulse. In addition, high-resolution images of the damage event are recorded using the associated plasma emission. Experimental results indicate that both aforementioned features can initiate plasma formation at fluences as low as 2 J/cm{sup 2}. The intensity of the recorded plasma emission remains low for fluences up to approximately 5 J/cm{sup 2} but rapidly increases thereafter. Based on the experimental results, we propose as possible mechanisms leading to damage growth the initiation of avalanche ionization by defects at the damage modified material and presence of field intensification due to cracks.
Date: December 18, 2000
Creator: Demos, S G; Kozlowski, M R; Staggs, M; Chase, L L; Burnham, A & Radousky, H B
Object Type: Article
System: The UNT Digital Library
Texas Disease Prevention News, Volume 60, Number 26, December 2000 (open access)

Texas Disease Prevention News, Volume 60, Number 26, December 2000

Newsletter of the Texas Department of Health discussing the news, activities, and events of the organization and other information related to health in Texas. This issue contains the annual index for 2000.
Date: December 18, 2000
Creator: Texas. Department of Health.
Object Type: Journal/Magazine/Newsletter
System: The Portal to Texas History
Debuncher Momentum Cooling Systems Signal to Noise Measurements (open access)

Debuncher Momentum Cooling Systems Signal to Noise Measurements

The Debuncher Momentum cooling systems were carefully measured for signal to noise. It was observed that cooling performance was not optimum. Closer inspection shows that the installed front-end bandpass filters are wider than the pickup response. (The original filters were specified to be wider so that none of the available bandwidth would be clipped.) The end result is excess noise is amplified and passed onto the kickers unimpeded, hence, reducing the achievable system gain. From this data, new filters should be designed to improve performance. New system bandwidths are specified on the data figures. Also included are the transfer function measurements that clearly show adjacent band response. In band 4 upper, the adjacent lobes are strong and out of phase. This is also degrading the system performance. The correlation between spectrum analyzer signal to noise and network analyzer system transfer functions is very strong. The table below has a calculation of expected improvement of front noise reduction by means of building new front-end bandpass filters. The calculation is based on a flat input noise spectrum and is a linear estimation of improvement. The listed 3dB bandwidths of the original filters are from measured data. The expected bandwidth is taken from …
Date: December 18, 2001
Creator: Pasquinelli, Ralph J.
Object Type: Report
System: The UNT Digital Library
Demonstration of Datacenter Automation Software and Hardware (DASH) at the California Franchise Tax Board (open access)

Demonstration of Datacenter Automation Software and Hardware (DASH) at the California Franchise Tax Board

Control software and wireless sensors designed for closed-loop, monitoring and control of IT equipment's inlet air temperatures in datacenters were evaluated and tested while other datacenter cooling best practices were implemented. The controls software and hardware along with each best practice were installed sequentially and evaluated using a measurement and verification procedure between each measure. The results show that the overall project eliminates 475,239 kWh per year, which is 21.3percent of the baseline energy consumption of the data center. The total project, including the best practices will save $42,772 per year and cost $134,057 yielding a simple payback of 3.1 years. However, the control system alone eliminates 59.6percent of the baseline energy used to move air in the datacenter and 13.6percent of the baseline cooling energy, which is 15.2percent of the baseline energy consumption (see Project Approach, Task 1, below, for additional information) while keeping temperatures substantially within the limits recommended by ASHRAE. Savings attributed to the control system are $30,564 per year with a cost $56,824 for a simple payback of 1.9 years.
Date: December 18, 2009
Creator: Bell, Geoffrey C. & Federspiel, Clifford
Object Type: Report
System: The UNT Digital Library
A detailed kinetic modeling study of toluene oxidation in a premixed laminar flame (open access)

A detailed kinetic modeling study of toluene oxidation in a premixed laminar flame

An improved chemical kinetic model for the toluene oxidation based on experimental data obtained in a premixed laminar low-pressure flame with vacuum ultraviolet (VUV) photoionization and molecular beam mass spectrometry (MBMS) techniques has been proposed. The present mechanism consists of 273 species up to chrysene and 1740 reactions. The rate constants of reactions of toluene, decomposition, reaction with oxygen, ipso-additions and metatheses with abstraction of phenylic H-atom are updated; new pathways of C{sub 4} + C{sub 2} species giving benzene and fulvene are added. Based on the experimental observations, combustion intermediates such as fulvenallene, naphtol, methylnaphthalene, acenaphthylene, 2-ethynylnaphthalene, phenanthrene, anthracene, 1-methylphenanthrene, pyrene and chrysene are involved in the present mechanism. The final toluene model leads to an overall satisfactory agreement between the experimentally observed and predicted mole fraction profiles for the major products and most combustion intermediates. The toluene depletion is governed by metathese giving benzyl radicals, ipso-addition forming benzene and metatheses leading to C{sub 6}H{sub 4}CH{sub 3} radicals. A sensitivity analysis indicates that the unimolecular decomposition via the cleavage of a C-H bond has a strong inhibiting effect, while decomposition via C-C bond breaking, ipso-addition of H-atom to toluene, decomposition of benzyl radicals and reactions related to C{sub 6}H{sub …
Date: December 18, 2009
Creator: Tian, Zhenyu; Pitz, William J.; Fournet, Rene; Glaude, Pierre-Alexander & Battin-Leclerc, Frederique
Object Type: Article
System: The UNT Digital Library
Use of a Submarine in Ice-Covered Arctic Waters to Help Delimit the U.S. Extended Continental Shelf (open access)

Use of a Submarine in Ice-Covered Arctic Waters to Help Delimit the U.S. Extended Continental Shelf

"This White Paper describes the roles, value, and preparation requirements for a U.S. Navy nuclear submarine (SSN) to collect geophysical data, and especially multi-channel seismic reflection (MCS) data, in the Arctic Ocean that are necessary to delimit the U.S. extended continental shelf (ECS)."
Date: December 18, 2007
Creator: U.S. Arctic Research Commission
Object Type: Text
System: The UNT Digital Library
Dworshak Kokanee Population and Engrainment Assessment : 2006 Annual Report, March 1, 2006 - February 28, 2007. (open access)

Dworshak Kokanee Population and Engrainment Assessment : 2006 Annual Report, March 1, 2006 - February 28, 2007.

During this contract, we continued testing underwater strobe lights to determine their effectiveness at repelling kokanee Oncorhynchus nerka away from Dworshak Dam. Strobe light tests were conducted on four nights from April 24-27, 2006, in front of the middle reservoir outlet (RO) 2. The density and distribution of fish, (thought to be mostly kokanee), were monitored with a split-beam echo sounder. We then compared fish counts and densities during nights when the lights were flashing to counts and densities during adjacent nights without the lights on. On two nights, April 25 and 27, 2006, when no lights were present, fish counts near RO 2 averaged 12.4 fish and densities averaged 31.0 fish/ha. When strobe lights were turned on during the nights of April 24 and 26, mean counts dropped to 4.7 fish and densities dropped to 0.5 fish/ha. The decline in counts (62%) and densities (99%) was statistically significant (p = 0.009 and 0.002, respectively). Test results indicated that strobe lights were able to reduce fish densities by at least 50% in front of a discharging reservoir outlet, which would be sufficient to improve sport fish harvest. We also used split-beam hydroacoustics to monitor the kokanee population in Dworshak Reservoir …
Date: December 18, 2008
Creator: Stark, Eric J.
Object Type: Report
System: The UNT Digital Library
Measured Off-Grid LED Lighting System Performance (open access)

Measured Off-Grid LED Lighting System Performance

This report is a product of our ongoing effort to support the development of high-quality yet affordable products for off-grid lighting in the developing world that have good potential to succeed in the market. The effort includes work to develop low-cost testing procedures, to identify useful performance metrics, and to facilitate the development of industry standards and product rating protocols. We conducted laboratory testing of nine distinct product lines. In some cases we also tested multiple generations of a single product line and/or operating modes for a product. The resultsare summarized in Table 1. We found that power consumption and light output varied by nearly a factor of 12, with efficacy varying by a factor of more than six. Of particular note, overall luminous efficacy varied from 8.2 to 53.1 lumens per watt. Color quality indices variedmaterially, especially for correlated color temperature. Maximum illuminance, beamcandlepower, and luminance varied by 8x, 32x, and 61x respectively, suggesting considerable differences among products in terms of service levels and visual comfort. Glare varied by1.4x, and was above acceptable thresholds in most cases. Optical losses play a role in overall performance, varying by a factor of 3.2 and ranging as high as 24percent. These findings …
Date: December 18, 2008
Creator: Granderson, Jessica; Galvin, James; Bolotov, Dmitriy; Clear, Robert; Jacobson, Arne & Mills, Evan
Object Type: Report
System: The UNT Digital Library
New Materials for NGNP/Gen IV (open access)

New Materials for NGNP/Gen IV

The bounding conditions were briefly summarized for the Next Generation Nuclear Plant (NGNP) that is the leading candidate in the Department of Energy Generation IV reactor program. Metallic materials essential to the successful development and proof of concept for the NGNP were identified. The literature bearing on the materials technology for high-temperature gas-cooled reactors was reviewed with emphasis on the needs identified for the NGNP. Several materials were identified for a more thorough study of their databases and behavioral features relative to the requirements ASME Boiler and Pressure Vessel Code, Section III, Division 1, Subsection NH.
Date: December 18, 2009
Creator: Swindeman, Robert W. & Marriott, Douglas L.
Object Type: Report
System: The UNT Digital Library
Status Report on Phase Identification in Hanford Tank Sludges (open access)

Status Report on Phase Identification in Hanford Tank Sludges

The U.S. Department of Energy plans to vitrify Hanford's underground storage tank wastes. The vitrified wastes will be divided into low-activity and high-level fractions. There is an effort to reduce the quantity of high-activity wastes by removing nonradioactive components because of the high costs involved in treating high-level waste. Pretreatment options, such as caustic leaching, to selectively remove nonradioactive components are being investigated. The effectiveness of these proposed processes for removing nonradioactive components depends on the chemical phases in the tank sludges. This review summarizes the chemical phases identified to date in Hanford tank sludges.
Date: December 18, 2000
Creator: Rapko, Brian M. & Lumetta, Gregg J.
Object Type: Report
System: The UNT Digital Library
Real time imaging of live cell ATP leaking or release events by chemiluminescence microscopy (open access)

Real time imaging of live cell ATP leaking or release events by chemiluminescence microscopy

The purpose of this research was to expand the chemiluminescence microscopy applications in live bacterial/mammalian cell imaging and to improve the detection sensitivity for ATP leaking or release events. We first demonstrated that chemiluminescence (CL) imaging can be used to interrogate single bacterial cells. While using a luminometer allows detecting ATP from cell lysate extracted from at least 10 bacterial cells, all previous cell CL detection never reached this sensitivity of single bacteria level. We approached this goal with a different strategy from before: instead of breaking bacterial cell membrane and trying to capture the transiently diluted ATP with the firefly luciferase CL assay, we introduced the firefly luciferase enzyme into bacteria using the modern genetic techniques and placed the CL reaction substrate D-luciferin outside the cells. By damaging the cell membrane with various antibacterial drugs including antibiotics such as Penicillins and bacteriophages, the D-luciferin molecules diffused inside the cell and initiated the reaction that produces CL light. As firefly luciferases are large protein molecules which are retained within the cells before the total rupture and intracellular ATP concentration is high at the millmolar level, the CL reaction of firefly luciferase, ATP and D-luciferin can be kept for a relatively …
Date: December 18, 2008
Creator: Zhang, Yun
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Correlation between Crystallographic and Magnetic Domains at Co/NiO(001) Interfaces (open access)

Correlation between Crystallographic and Magnetic Domains at Co/NiO(001) Interfaces

Using soft x-ray spectromicroscopy we show that NiO(001) exhibits a crystallographic and magnetic domain structure near the surface identical to that of the bulk. Upon Co deposition a perpendicular coupling between the Ni and Co moments is observed that persists even after formation of uncompensated Ni spins at the interface through annealing. The chemical composition at the interface alters its crystallographic structure and leads to a reorientation of the Ni moments from the <112> to the <110> direction. We show that this reorientation is driven by changes in the magnetocrystalline anisotropy rather than exchange coupling mediated by residual uncompensated spins.
Date: December 18, 2008
Creator: Ohldag, H.; van der Laan, G. & Arenholz, E.
Object Type: Article
System: The UNT Digital Library