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Articles 1 - 10 of 10

Full-Text Articles in Nanoscience and Nanotechnology

Multiscale Nature Of Hysteretic Phenomena: Application To Copt-Type Magnets, Kirill D. Belashchenko, Vladimir P. Antropov Oct 2002

Multiscale Nature Of Hysteretic Phenomena: Application To Copt-Type Magnets, Kirill D. Belashchenko, Vladimir P. Antropov

Faculty Publications from Nebraska Center for Materials and Nanoscience

We suggest a workable approach for the description of multiscale magnetization reversal phenomena in nanoscale magnets and apply it to CoPt-type alloys. We show that their hysteretic properties are governed by two effects originating at different length scales: a peculiar splitting of domain walls at twin boundaries and their strong pinning at antiphase boundaries. We emphasize that such multiscale nature of hysteretic phenomena is a generic feature of nanoscale magnetic materials.


Spontaneous Planarization Of Nanoscale Phase Separated Thin Film, Ravi F. Saraf, Sanjun Niu, Eric Stumb Jun 2002

Spontaneous Planarization Of Nanoscale Phase Separated Thin Film, Ravi F. Saraf, Sanjun Niu, Eric Stumb

Papers in Nanotechnology

Structure of complex fluid at mesoscales is influenced by interfacial effects. We describe the dynamic response in such films to sudden change in interfacial tension. In a self-assembled block copolymer film, the monolayer of 15 nm diam cylindrical discrete phases close to the surface commence to sink at an average rate of 0.16 nm/day in response to the interfacial tension change. Surprisingly, this spontaneous planarization occurs, even though the cylinders are covalently stitched to the matrix. A simple model explains the observed behavior. The observation may lead to approaches to tailor the structure of mesoscale thin films of ...


Nanofatigue Studies Of Ultrathin Hard Carbon Overcoats Used In Magnetic Storage Devices, Xiaodong Li, Bharat Bhushan May 2002

Nanofatigue Studies Of Ultrathin Hard Carbon Overcoats Used In Magnetic Storage Devices, Xiaodong Li, Bharat Bhushan

Faculty Publications

A technique to perform nanofatigue experiments was developed. This technique utilizes a depth-sensing nanoindenter with harmonic force. The nanofatigue behavior of 20 nm thick amorphous carbon coatings was studied. The contact stiffness was monitored continuously throughout the test. The abrupt decrease in the contact stiffness indicates fatigue damage has occurred. The critical load amplitude, below which no fatigue damage occurs, was identified. It was found that the filtered cathodic arc coating exhibits longer fatigue life than a direct ion beam coating. Failure mechanisms of the coatings during fatigue are also discussed in conjunction with the hardness,elastic modulus, and fracture ...


Structure Of Macrodomain Walls In Polytwinned Magnets, Kirill D. Belashchenko, Vladimir P. Antropov May 2002

Structure Of Macrodomain Walls In Polytwinned Magnets, Kirill D. Belashchenko, Vladimir P. Antropov

Faculty Publications from Nebraska Center for Materials and Nanoscience

We propose a microscopic approach to the studies of magnetic configurations in hard magnets which may be conveniently used for nanoscale systems; the microstructure of the magnet is easily and naturally included in the calculations. This approach is applied to find the structure of macrodomain walls in polytwinned magnets of the CoPt family. Magnetostatic fields are small compared to the anisotropy field in these magnets; direct simulation shows that in this case the macrodomain wall is not continuous, but rather comprised of segments held together by relatively small magnetostatic forces. This segmentation is expected to have a strong effect on ...


Magnetization Reversal Of Individual Nanowires With Controlled Defects, Andrei Sokolov, Renat F. Sabirianov, W. Wernsdorfer, Bernard Doudin May 2002

Magnetization Reversal Of Individual Nanowires With Controlled Defects, Andrei Sokolov, Renat F. Sabirianov, W. Wernsdorfer, Bernard Doudin

Faculty Publications from Nebraska Center for Materials and Nanoscience

Low temperature magnetization reversal measurements were performed on individual permalloy nanowires of diameters between 30 and 60 nm. During the electrochemical growth of the wire, a defect was induced by a short pulse in the deposition potential modifying locally the microstructure and composition. Magnetic measurements performed with micro-superconducting quantum interference devices were performed. The angular dependence of switching field revealed significant deviations from classical predictions. For specific angles, magnetization curves indicate a reversal occurring in two steps.


Performance Projections For Ballistic Carbon Nanotube Field-Effect Transistors, Jing Guo, Mark Lundstrom, Supriyo Datta Apr 2002

Performance Projections For Ballistic Carbon Nanotube Field-Effect Transistors, Jing Guo, Mark Lundstrom, Supriyo Datta

Other Nanotechnology Publications

The performance limits of carbon nanotube field-effect transistors 􏰎CNTFETs􏰁 are examined theoretically by extending a one-dimensional treatment used for silicon metal – oxide – semiconductor field-effect transistors 􏰎MOSFETs􏰁. Compared to ballistic MOSFETs, ballistic CNTFETs show similar I–V characteristics but the channel conductance is quantized. For low-voltage, digital applications, the CNTFET with a planar gate geometry provides an on-current that is comparable to that expected for a ballistic MOSFET. Significantly better performance, however, could be achieved with high gate capacitance structures. Because the computed performance limits greatly exceed the performance of recently reported CNTFETs, there is considerable opportunity for progress in device ...


Characterization Of Crbn Films Deposited By Ion Beam Assisted Deposition, S.M. Aouadi, F. Namavar, E. Tobin, N. Finnegan, R.T. Haasch, R. Nilchiani, Joseph A. Turner, S. L. Rohde Feb 2002

Characterization Of Crbn Films Deposited By Ion Beam Assisted Deposition, S.M. Aouadi, F. Namavar, E. Tobin, N. Finnegan, R.T. Haasch, R. Nilchiani, Joseph A. Turner, S. L. Rohde

Faculty Publications from Nebraska Center for Materials and Nanoscience

This article reports on the growth and analysis of CrBN nanocrystalline materials using an ion beam assisted deposition process. In addition, this article addresses the utilization of spectroscopic ellipsometry for in situ analysis of ternary nitrides. Coatings, with a total thickness of 1.5 ±0.2 μm, were deposited at low temperatures (<200 °C) on silicon substrates using ion beam assisted deposition. These coatings were characterized postdeposition using x-ray diffraction (XRD), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), visible-light spectroscopic ellipsometry (VIS-SE), infrared spectroscopic ellipsometry (IR-SE), and nanoindentation. The primary phases in the films were investigated using XRD. The surface morphology and nanocrystalline nature of the coatings (grain size of 5–7 nm) were deduced using AFM. The elemental composition and phase composition of the samples were determined from XPS and AES measurements and were subsequently deduced from the analysis of the VIS-SE data, and these correlated well. XPS, AES, and IR-SE revealed the crystal structure of the BN phase in the ternary compounds. The correlation of the results from these various techniques indicates that in situ SE may be a potential technique to control the growth of ternary nitride coatings in the future. The mechanical properties of the coatings were evaluated using nanohardness testing. The hardness and elastic modulus were measured to be 19–22 GPa and 250–270 GPa, respectively.


Synthesis And Magnetic Properties Of Copt–Poly(Methylmethacrylate) Nanostructured Composite Material, Jiye Fang, Kevin L. Stokes, Jibao He, Weillie L. Zhou, Charles J. O'Connor, Daniela Caruntu Jan 2002

Synthesis And Magnetic Properties Of Copt–Poly(Methylmethacrylate) Nanostructured Composite Material, Jiye Fang, Kevin L. Stokes, Jibao He, Weillie L. Zhou, Charles J. O'Connor, Daniela Caruntu

Physics Faculty Publications

We have prepared nanometer-sized CoPt particles dispersed in a poly~methyl methacrylate~PMMA!matrix, as a novel nanostructured magnetic plastic, through a soft chemical processing route. In this work, CoPt nanoparticles were successfully synthesized from a solution phase reduction system in the presence of capping ligands and stabilizing agents at high temperature. The CoPt nanoparticles were annealed at 400 °C for 3 h, and were subsequently re-dispersed inmethylmethacrylate~monomer! . The polymerization was induced by a UV source and the hardness of final product was adjusted by varying the amount of monomeric cross-link agent. Annealed bare CoPt nanoparticles as a ‘‘core ...


Diagnostic Of Critical Circuits Of Kraft Pulp Production Process Considering The Environmental Aspects, João F. Gomes Jan 2002

Diagnostic Of Critical Circuits Of Kraft Pulp Production Process Considering The Environmental Aspects, João F. Gomes

João F Gomes

This paper describes systematic work done in the field of atmospheric emissions from Portuguese Kraft pulp mills. This study led to the determination of emission factors from stationary sources that proved to be an important tool to assess the need for investment on air pollution abatement equipment, namely in what concerns mal-odorous gases.


121.6 Nm Radiation Source For Advanced Lithography, Jianxun Yan, Ashraf El-Dakrouri, Mounir Laroussi, Mool C. Gupta Jan 2002

121.6 Nm Radiation Source For Advanced Lithography, Jianxun Yan, Ashraf El-Dakrouri, Mounir Laroussi, Mool C. Gupta

Electrical & Computer Engineering Faculty Publications

A vacuum ultraviolet (VUV) light source based on a high-pressure cylindrical dielectric barrier discharge (DBD) has been developed. Intense and spectrally clean Lyman-α line at 121.6 nm was obtained by operating a DBD discharge in neon with a small admixture of hydrogen. The spectrum, optical power, stability, and efficiency of the source were measured. The influence of the gas mixture and total gas pressure on the VUV intensity has been investigated. Maximum optical power of 3.2 W and spectral width 0.03 nm was achieved. Power stability of 2% for 100 h of operation has also been obtained ...