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2002

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Articles 451 - 480 of 572

Full-Text Articles in Physics

Effect Of The Zn Concentration On The Characteristic Parameters Of Zn_{X}Cd_{1 - X}S Thin Films Developed By Spraying Pyrolysis Method Under The Nitrogen Atmosphere, Meti̇n Bedi̇r, Refi̇k Kayali, Mustafa Öztaş Jan 2002

Effect Of The Zn Concentration On The Characteristic Parameters Of Zn_{X}Cd_{1 - X}S Thin Films Developed By Spraying Pyrolysis Method Under The Nitrogen Atmosphere, Meti̇n Bedi̇r, Refi̇k Kayali, Mustafa Öztaş

Turkish Journal of Physics

The electronic and optical properties of Zn_{x}Cd _{(1- x)}S thin films (0.0 \le x \le 0.7) fabricated using the chemical spray method have been investigated in nitrogen atmosphere. The films are deposited on glass substrates at 420^oC substrate temperature. The related optical data are recorded in the wavelength range 200-700 nm. In addition, the absorption coefficient is determined and correlated with the photon energy in order to estimate the direct transition energy bandgap. The crystallite size and degree of preferential orientation were found to decrease with the increase of x and to improve upon annealing in vacuum at \cong 600^oC. …

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The B --> S G G Decay In The General Two Higgs Doublet Model, E. O. İltan Jan 2002

The B --> S G G Decay In The General Two Higgs Doublet Model, E. O. İltan

Turkish Journal of Physics

We study the decay width of the inclusive process b --> s g g in the two Higgs doublet model with three-level flavor changing neutral currents (model III). We analyse the dependencies of the differential decay width to the s- quark energy E_s and model III parameters, charged Higgs mass m_H_{^{±}} and Yukawa coupling \bar{\xi}_{N,bb}^D. We observe that there exist a considerable enhancement in the decay width for the relevant process. This enhancement can be reduced by choosing C_7^{eff} as negative or increasing the lower bound of m_H_{^{±}} to the large values. This is an interesting result which gives an …

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Spin Polarized Cold And Hot Dense Neutron Matter, S. A. Moharrm, Azza O. El-Shal Jan 2002

Spin Polarized Cold And Hot Dense Neutron Matter, S. A. Moharrm, Azza O. El-Shal

Turkish Journal of Physics

The Thomas-Fermi (TF) model is used to calculate the equation of state of thermal polarized neutron matter. The properties of cold and hot neutron matter have been investigated. A realistic density-dependent M3Y effective nucleon-nucleon (NN) interaction where the Yukawa strengthes are based on the G-matrix of the Paris interaction has been used. Special attention is devoted to the effect of the spin excess parameter on these properties. Moreover, the effect of some realistic density dependence has been studied. The results obtained are in reasonable agreement with previous theoretical estimates using different methods of calculation.

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Tsl-Epr Correlation Study Of Lapo_4 : Ce, Tb, B. S. Chakrabarty, K. V. R. Murthy, T. R. Joshi Jan 2002

Tsl-Epr Correlation Study Of Lapo_4 : Ce, Tb, B. S. Chakrabarty, K. V. R. Murthy, T. R. Joshi

Turkish Journal of Physics

Gamma irradiated TSL glow curves of laboratory made phosphor samples of LaPO_{4}:Ce, Tb exhibited one intense peak around 408 K and two smaller peaks around 508 K and 613 K. The spectrum of the first glow peak gives spectral peaks around 480 nm and 540 nm, which can be attributed to the thermal destruction of F^{++} centres and PO_4^{2-} radicals. The luminescense centre has been thought to be Cerium and Terbium ions. The glow peak around 413 K for UV irradiated samples has been attributed to aggregates of dopant ions. The photoluminescence study of the samples exhibited one intense peak …

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On The Numerical Solution And Limitations Of Energy Equation For Vertical Bridgman System With Varying Temperature Gradient At The Boundary, Ergün Taşarkuyu, Evren Akar, Bülent Gülteki̇n Akinoğlu Jan 2002

On The Numerical Solution And Limitations Of Energy Equation For Vertical Bridgman System With Varying Temperature Gradient At The Boundary, Ergün Taşarkuyu, Evren Akar, Bülent Gülteki̇n Akinoğlu

Turkish Journal of Physics

In vertical Bridgman crystal growth systems solid-liquid interface shape is one of the most important factors affecting the product quality. Most of the theoretical studies to determine the interface shape consider the numerical solution to the heat-conduction and the energy equation. The purpose of this work is to present and discuss a numerical solution to the energy equation (also called the convection-diffusion equation) for a vertical Bridgman system with varying temperature gradient at the boundary. Different system parameters are examined and the importance of the pulling rate for different materials in the utilization of the energy equation is emphasized. The …

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Contribution To The Relationship Between Solar Radiation And Sunshine Duration In The Tropics: A Case Study Of Experimental Data At Ilorin, Nigeria, Sunday O. Udo Jan 2002

Contribution To The Relationship Between Solar Radiation And Sunshine Duration In The Tropics: A Case Study Of Experimental Data At Ilorin, Nigeria, Sunday O. Udo

Turkish Journal of Physics

From monthly average daily values of clearness index and relative sunshine spanning a period of two years, two equations (linear and quadratic) of the Angstrom-Prescott model have been developed for the estimation of global solar irradiation at Ilorin (Lat. 8°32'N, Long. 4°34'E), a tropical location. Comparison of the regression coefficients of the linear type model showed that the values are quite consistent with those quoted in the literature for the Tropics. The predictive efficiencies of these two models are also compared with those which are believed to be applicable globally, and those developed for the Nigerian environment. Although some of …

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Short-Range Correlations In Coupled Quantum-Wire Systems, A. Yurtsever, B. Tanatar Jan 2002

Short-Range Correlations In Coupled Quantum-Wire Systems, A. Yurtsever, B. Tanatar

Turkish Journal of Physics

We study the contact values of the inter-wire pair-correlation function in electron-electron and electron-hole double-wire systems. For this purpose the ladder approximation as generalized to multicomponent systems is used. The ladder approximation yields positive values for the inter-wire g_{ee}(0) and g_{eh}(0) for all values of the density parameter r_s and distance d between the wires. This allows us to infer possible instabilities in the system more reliably compared to other approaches. We also investigate the effects of quantum-wire width and screening on the inter-wire pair-correlation functions. PACS numbers: 05.30.Fk, 73.20.Dx, 71.45.Gm, 73.40.Kp

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Excess Properties Of Alcohol - Water Systems At 298.15 K, Hülya Yilmaz Jan 2002

Excess Properties Of Alcohol - Water Systems At 298.15 K, Hülya Yilmaz

Turkish Journal of Physics

Dielectric constants \varepsilon, viscosities \eta, refractive indices n and densities d have been measured over the entire mole fraction range for the water - methyl, ethyl, n-propyl alcohol binary systems at 298.15 K. From the experimental data excess dielectric constants \varepsilon^E, excess viscosities \eta^E and Kirkwood correlation factors g_k have been calculated and studied. Their behaviour suggests the existence of intermolecular interactions and plotted curves show that excess dielectric constant and g_k values decrease with the increasing of carbon atom number, while excess viscosity increases.

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Interface Roughness-Induced Intrassubband Scattering In A Quantum Well Under An Electric Field, Guseyn Behbudoglu Ibragimov Jan 2002

Interface Roughness-Induced Intrassubband Scattering In A Quantum Well Under An Electric Field, Guseyn Behbudoglu Ibragimov

Turkish Journal of Physics

The scattering rates in the lowest subband in a quantum well are calculated for interface roughness scattering when an electric field is applied perpendicular to the layer plane. It is found that the interface roughness scattering rate increases with increase in the electric field. The electric field changes the interface roughness scattering rates drastically in thick QWs compared with those for the zero-field case. This behaviour in the scattering rate gives a new degree of freedom in regions of interest in device applications.

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Effects Of Substrate Temperature On Properties Of A-Sin_X:H Films, Tayyar Güngör, Hüseyi̇n Tolunay Jan 2002

Effects Of Substrate Temperature On Properties Of A-Sin_X:H Films, Tayyar Güngör, Hüseyi̇n Tolunay

Turkish Journal of Physics

Hydrogenated amorphous silicon nitride films were prepared in an rf glow-discharge system by the decomposition of silane + nitrogen gas mixture at various substrate temperatures. The effects of substrate temperature on the electrical and optical properties of the films have been studied.

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Monte Carlo Simulation Of Electron Transport In Insb, Ö. Özbaş, M. Akarsu Jan 2002

Monte Carlo Simulation Of Electron Transport In Insb, Ö. Özbaş, M. Akarsu

Turkish Journal of Physics

Transport properties of indium antimonide in an electric field have been calculated at 77 K. The calculation shows that ionized impurity scattering plays a dominant role in InSb at low electric field. The mobility, mean energy, and drift velocity are calculated as a function of the electric field strength, and comparison is made with previous theoretical results. Types of the scattering mechanisms and percentage of each mechanism in the total scattering events are determined.

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The Ibm-2 Study For Some Even - Even Platinum Isotopes, Mehmet Baylan, Mehmet Altay Atlihan Jan 2002

The Ibm-2 Study For Some Even - Even Platinum Isotopes, Mehmet Baylan, Mehmet Altay Atlihan

Turkish Journal of Physics

The structure of some even -- even Pt isotopes have been studied within the framework of the interacting boson model. The B(E2), B(M1) and Q(I) values of the above nuclei have been calculated. The numerical results obtained for Pt have been compared with the previous experimental and theoretical values obtained on the basis of the interacting boson model (IBA-2).

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The Single Step Vmhnc Calculations For Liquid Alkali Metals In The Inverse Problem, Serap Şentürk Dalgiç, Seyfetti̇n Dalgiç, Mehmet Tomak Jan 2002

The Single Step Vmhnc Calculations For Liquid Alkali Metals In The Inverse Problem, Serap Şentürk Dalgiç, Seyfetti̇n Dalgiç, Mehmet Tomak

Turkish Journal of Physics

An effective pair potential \phi (r) for liquid alkali metals close totheir melting points is extracted from an experimental structure factor using the inverse method based on the variational modified hypernetted-chain integral equation theory of liquids (VMHNC). The first order pair potential according to the procedure suggested by de Angelis and March is also presented for comparison. It has been found that the inverted pair potentials of liquid alkali metals scale well.

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Single And Double-Layer Antireflection Coatings On Silicon, İpek Gi̇rgi̇n Kavakli, Kayhan Kantarli Jan 2002

Single And Double-Layer Antireflection Coatings On Silicon, İpek Gi̇rgi̇n Kavakli, Kayhan Kantarli

Turkish Journal of Physics

In this study, the effect of single and double-layer thin film coatings on the reflectance spectrum of silicon surfaces has been investigated. Thin film coatings have been prepared by vacuum evaporation of the materials with suitable refractive index. Reflectance measurements in the visible and near infrared have shown that the coated samples acquire antireflection properties. Thickness and wavelength dependence of the antireflection properties of SiO, CeO_2 and ZnS single-layer coatings with optical thickness of one quarter wavelength has been studied. In double-layer coatings, a thin film of SiO, CeO_2 and ZnS with optical thickness of quarter wavelength were used as …

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The Effects Of Nonstoichiometry In High - T_C Superconducting Properties Of Yba_2cu_{3 + X}O_{7 - \Delta}, Beniah Ndudim Onwuagba Jan 2002

The Effects Of Nonstoichiometry In High - T_C Superconducting Properties Of Yba_2cu_{3 + X}O_{7 - \Delta}, Beniah Ndudim Onwuagba

Turkish Journal of Physics

Polycrystalline samples of high T_c superconductor YBa_2Cu_{3 + x}O_{7 - \delta} with 0 \leqslant x \leqslant 0.5 were grown. The effects of nonstoichiometry on the resistance slope above transition temperature T_c and X-ray diffraction patterns for these samples were investigated. In the diffraction patterns obtained, apart from some new features in the peaks, these polycrystalline samples show predominantly 123 phase.

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Some Characteristic Properties, Vithal Bhivaba Pujari, V. B. Gaikwad, E. U. Masumdar, P. D. More, L. P. Deshmukh Jan 2002

Some Characteristic Properties, Vithal Bhivaba Pujari, V. B. Gaikwad, E. U. Masumdar, P. D. More, L. P. Deshmukh

Turkish Journal of Physics

This paper presents some information regarding (Cd, Hg) Se materials synthesized by a simple chemical growth process and the structural, optical and electrical transport properties. The growth of these films depends on various preparative parameters and deposition conditions such as concentration of the starting materials, pH, temperature, time, speed of mechanical churning, etc., and the reaction kinetics suggests that the films grow into two different phases: one, initialy an almost linear phase; and second, a saturation phase. The deposits were analysed chemically and by an EDS techniques. It has been seen that more than 70% of the materials taken in …

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Mathematical Modeling Of Plasmachemical Processes, Meli̇k-Aslanova Tamilla Jan 2002

Mathematical Modeling Of Plasmachemical Processes, Meli̇k-Aslanova Tamilla

Turkish Journal of Physics

In this research, we studied the kinetics of plasmachemical processes in quasiequilibrium and nonequilibrium conditions. The example of methane conversion into acetylene showed that the most efficient plasmachemical process may be achieved under nonequilibrium conditions, especially, when the reaction was stimulated by vibrational excitation of molecules.

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Paramagnetic Defects In \Gamma-Irradiated, Pure And Doped (With As, Cl And Br) Selenium, Ibrahimgizi Salima Mekhtieva, Ibrahimogli Namig Ibragimov, Isaogli Abasat Isaev, Zeinalogli Vasif Zeinalov, Arifogli Eldar Mamedov Jan 2002

Paramagnetic Defects In \Gamma-Irradiated, Pure And Doped (With As, Cl And Br) Selenium, Ibrahimgizi Salima Mekhtieva, Ibrahimogli Namig Ibragimov, Isaogli Abasat Isaev, Zeinalogli Vasif Zeinalov, Arifogli Eldar Mamedov

Turkish Journal of Physics

This paper presents results of an EPR spectrum investigation of \gamma-irradiated (Co^{60} dose 10^{7} Rad) glasses Se, SeCl_{x}, Se_{0.95}As_{0.05}Cl_{x} and Se_{0.95}As_{0.05}Br_{x} (x=0.001--0.1) at 77 K. An analysis of spectra reveals that two types of paramagnetic radiation-induced defects arise (broken bonds localized on Se and As atoms) from the irradiation of such chalcogenide glasses.

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Monitoring The Effect Of Recrystallization And Quenching In Almg_{X} Alloy By Pat, A. Ashour, Nour Zaki El-Said, Emad A. Badawi Jan 2002

Monitoring The Effect Of Recrystallization And Quenching In Almg_{X} Alloy By Pat, A. Ashour, Nour Zaki El-Said, Emad A. Badawi

Turkish Journal of Physics

Positron annihilation technique (PAT) lifetime measurements have been carried out on AlMg_{x} samples (x = 0.23, 0.85, 1.27 and 1.4 at %) with point defects and dislocations introduced by plastic deformation at room temperature. Clustering of vacancies was observed by quenching using PAT. The samples were annealed at 573 K for 12 hours to homogenize and divided into two sets. The first set of AlMg_{x} (x = 0.23, 0.85 and 1.4 at %) was deformed to 10, 25 and 35% thickness reduction. Isochronal annealing was studied in the range of 300-550 K. In the second set of measurements, AlMg_{x} (x …

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Unifying Lectures, Recitations & Laboratories As A Part Of The Humanized Physics Project, Vicki L. Plano Clark, Robert G. Fuller Jan 2002

Unifying Lectures, Recitations & Laboratories As A Part Of The Humanized Physics Project, Vicki L. Plano Clark, Robert G. Fuller

Robert G. Fuller Publications

As a part of our work in the Humanized Physics Project, we have made the content of the physics laboratories the keystone of our physics content coverage. After having selected an appropriate human application of physics for the laboratory each week, we have shaped the lecture, recitation and homework assignments to support the laboratory. Our poster will provide examples from both semesters of our general physics course.

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Cross Section And Heavy Quark Composition Of Γ+Μ Events Produced In Pp̅ Collisions, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Jan 2002

Cross Section And Heavy Quark Composition Of Γ+Μ Events Produced In Pp̅ Collisions, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present a measurement of the cross section and the first measurement of the heavy flavor content of associated direct photon + muon events produced in hadronic collisions. These measurements come from a sample of 1.8 TeV pp̅ collisions recorded with the Collider Detector at Fermilab. Quantum chromodynamics (QCD) predicts that these events are primarily due to the Compton scattering process cg→cγ , with the final-state charm quark producing a muon. The cross section for events with a photon transverse momentum between 12 and 40 GeV/c is measured to be 46.8±6.3±7.5 pb, which is two standard deviations below the …

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Neutron Powder Diffraction Studies Of The La0.65Pb0.35Mno3 Perovskite, Camelia Borca, Shireen Adenwalla, Sy-Hwang Liou, Q.L. Xu, J. L. Robertson, Peter A. Dowben Jan 2002

Neutron Powder Diffraction Studies Of The La0.65Pb0.35Mno3 Perovskite, Camelia Borca, Shireen Adenwalla, Sy-Hwang Liou, Q.L. Xu, J. L. Robertson, Peter A. Dowben

Peter Dowben Publications

The structure of La0.65Pb0.35MnO3 has been studied by neutron powder diffraction. From the temperature dependence of the lattice parameters, we observe that La0.65Pb0.35MnO3 remains single phase in the temperature interval from 25 to 400 K, with a rhombohedral (R3c) structure. The collinear Mn spins suffer a thermally driven reorientation transition close to the Curie temperature, as obtained from powder samples (using neutron diffraction) and from thin films [using ferromagnetic resonance (FMR)]. The reorientation transition may indicate the presence of local Jahn–Teller (JT) lattice distortions, which are prevented from …

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Observational Limits On Quantum Geometry Effects, Tomasz J. Konopka '02, Seth Major Jan 2002

Observational Limits On Quantum Geometry Effects, Tomasz J. Konopka '02, Seth Major

Articles

Using a form of modified dispersion relations derived in the context of quantum geometry, we investigate limits set by current observations on potential corrections to Lorentz invariance. We use a phenomological model in which there are separate parameters for photons, leptons and hadrons. Constraints on these parameters are derived using thresholds for the processes of photon stability, photon absorption, vacuum Cerenkov radiation, pion stability and the GZK cutoff. Although the allowed region in parameter space is tightly constrained, non-vanishing corrections to Lorentz symmetry due to quantum geometry are consistent with current astrophysical observations.

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Structural Transition In (C60)N Clusters, W. Branz, N. Malinowski, Axel Enders, T. P. Martin Jan 2002

Structural Transition In (C60)N Clusters, W. Branz, N. Malinowski, Axel Enders, T. P. Martin

Axel Enders Publications

The structure of (C60) n clusters (n = 1– 150) was investigated by heating them to definite temperatures in a helium bath (heating cell) with subsequent characterization in a time-of-flight mass spectrometer. The intensity anomalies in the resulting mass spectra reflect particularly stable configurations that resisted evaporation. However, the set of enhanced peaks (magic numbers) turned out to be temperature dependent. Clusters heated to a moderate temperature of 490 K yielded mass spectra indicating the presence of icosahedral structures that can be characterized by a set of unusually strong peaks, namely n = 13, 19, 23, 26, …

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Adsorbate And Thermally Induced Spin Reorientation Transition In Low-Temperature-Grown Fe/Cu(001), D. Peterka, Axel Enders, G. Haas, K. Kern Jan 2002

Adsorbate And Thermally Induced Spin Reorientation Transition In Low-Temperature-Grown Fe/Cu(001), D. Peterka, Axel Enders, G. Haas, K. Kern

Axel Enders Publications

Adsorbate and thermally induced changes of the spin reorientation transition in Fe wedges grown at 140 K on Cu(001) substrates are investigated by the magneto-optical Kerr effect and Kerr microscopy. The adsorption of oxygen causes a complete reorientation of the easy axis of magnetization into the film plane. In contrast to that carbon monoxide decreases the critical thickness for the reorientation transition of the film by 0.7 monolayer down to 3.6 monolayers, while films thinner than 3.6 monolayers remain magnetized perpendicularly. These adsorbate-induced changes can be ascribed to a change in the surface magnetic anisotropy. Also annealing of the films …

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Revealing The Superfluid–Mott-Insulator Transition In An Optical Lattice, V Kashurnikov, Nikolai Prokof'ev, Boris Svistunov Jan 2002

Revealing The Superfluid–Mott-Insulator Transition In An Optical Lattice, V Kashurnikov, Nikolai Prokof'ev, Boris Svistunov

Physics Department Faculty Publication Series

We study (by an exact numerical scheme) the single-particle density matrix of ∼103 ultracold atoms in an optical lattice with a parabolic confining potential. Our simulation is directly relevant to the interpretation and further development of the recent pioneering experiment by Greiner et al., Nature, (London) 415, 39 (2002). In particular, we show that restructuring of the spatial distribution of the superfluid component when a domain of Mott-insulator phase appears in the system, results in a fine structure of the particle momentum distribution. This feature may be used to locate the point of the superfluid–Mott-insulator transition.

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Some Irrational Generalised Moonshine From Orbifolds, Rossen Ivanov, Michael Tuite Jan 2002

Some Irrational Generalised Moonshine From Orbifolds, Rossen Ivanov, Michael Tuite

Articles

We verify the Generalised Moonshine conjectures for some irrational modular functions for theMonster centralisers related to the Harada-Norton, Held, M12 and L3(3) simple groups based on certain orbifolding constraints. We find explicitly the fixing groups of the hauptmoduls arising in each case.

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The Magnetism-Nanostructure Interface In Advanced Magnetic Materials, David J. Sellmyer Jan 2002

The Magnetism-Nanostructure Interface In Advanced Magnetic Materials, David J. Sellmyer

David Sellmyer Publications

The critical relationship between microstructure and nanostructure of materials and their magnetic properties has been appreciated for decades. Electromagnetic machinery, permanent magnets, and data recording and electronic devices all have seen steady and sometimes spectacular advances over this period. At the present time the most interesting research in magnetism and magnetic materials arises from new developments in structuring materials on the nanometer length scale. This talk will present recent advances and challenges in furthering this work, with particular attention paid to extremely high density magnetic recording films, exchange-coupled high-energy-product permanent-magnet materials, high-temperature permanent-magnet materials, and self-organized and patterned magnetic nanoarrays.

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Elemental Mapping Of Co-Pr Nanostructured Powders By Eels Image Filtering, Yi Liu, C. Nelson, H. Tang, David J. Sellmyer Jan 2002

Elemental Mapping Of Co-Pr Nanostructured Powders By Eels Image Filtering, Yi Liu, C. Nelson, H. Tang, David J. Sellmyer

David Sellmyer Publications

In current extremely high density recording media design, the signal to noise ratio SNR is related to the number of magnetic grains N in a recording bit by
SNR = 10 logl0 N .................................... (1)
In earlier studies we have found that a metallurgical grain can act as a magnetic grain when grains are magnetically decoupled by a non-magnetic phase [1,2]. Alternatively, several metallurgical grains can be exchange-coupled together when they are small [3]. An ideal morphology is one in which the non-magnetic atoms are segregated at the grain boundaries forming the non-magnetic phase while keeping the grains closely …

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Determination Of Hexadecapole Moments For The 3p4(1D) Core Of Argon Ii Excited In Polarized E--Ar Collisions, B. G. Birdsey, H. M. Al-Khateeb, Timothy J. Gay Jan 2002

Determination Of Hexadecapole Moments For The 3p4(1D) Core Of Argon Ii Excited In Polarized E--Ar Collisions, B. G. Birdsey, H. M. Al-Khateeb, Timothy J. Gay

Timothy J. Gay Publications

We report on measurements of the integrated Stokes parameters of the light emitted from four well-LS coupled states of the 3p4(1D)4p manifold of Aril, following the simultaneous ionization and excitation of neutral argon by polarized electrons. As for all states, the state multipoles of J can be expanded in terms of the total orbital (L ) and the total spin (S) state multipoles. By splitting each L and S state multipole into multipoles for the core and outer electron, we have experimentally obtained for the first time the normalized integrated state multipole of rank 4 (hexadecapole …

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