Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 9 of 9
Full-Text Articles in Physics
Theoretical Study Of The Magnetic Ordering In Rare-Earth Compounds With Face-Centered-Cubic Structure, Chun-Gang Duan, Renat F. Sabirianov, Jianjun Liu, Wai-Ning Mei, Peter A. Dowben, John R. Hardy
Theoretical Study Of The Magnetic Ordering In Rare-Earth Compounds With Face-Centered-Cubic Structure, Chun-Gang Duan, Renat F. Sabirianov, Jianjun Liu, Wai-Ning Mei, Peter A. Dowben, John R. Hardy
Peter Dowben Publications
We present a detailed theoretical study of the magnetic ordering in heavy rare-earth compounds with a face-centered-cubic structure. In addition to the exchange interactions which are counted up to the third nearest neighbors, the effect of the dipolar interactions and magnetic anisotropic effect are also included in our model Hamiltonian. The interactions parameters are obtained from first-principles band-structure calculations by fitting the total energies of different magnetic configurations to the Heisenberg Model. Thus from utilizing the Monte Carlo simulations, we explained the formation of different magnetic structures in the rare-earth compounds.
Noncollinear Spin States And Competing Interactions In Half-Metals, Ralph Skomski, Jian Zhou, Peter A. Dowben, David J. Sellmyer
Noncollinear Spin States And Competing Interactions In Half-Metals, Ralph Skomski, Jian Zhou, Peter A. Dowben, David J. Sellmyer
Peter Dowben Publications
The high-field spin structure of magnetic perovskites and related magnetoresistive materials is investigated by model calculations. Competing exchange as well as real-structure-dependent random field, random anisotropy, and Dzyaloshinskii–Moriya interactions yield a noncollinear magnetic structure that may be called a spin colloid. The noncollinear structure, which contributes to the zero- and finite-temperature spin mixing and reduces the magnetoresistance, is strongly field dependent. © 2005 American Institute of Physics. [DOI: 10.1063/1.1851412]
N-Type Boron-Carbide Semiconductor Polytype And Method Of Fabricating The Same, Peter A. Dowben, Anthony N. Caruso, Yaroslav B. Losovyj
N-Type Boron-Carbide Semiconductor Polytype And Method Of Fabricating The Same, Peter A. Dowben, Anthony N. Caruso, Yaroslav B. Losovyj
Peter Dowben Publications
A non-doped n-type boron carbide semiconductor polytype and a method of fabricating the same is provided. The n-type boron carbide polytype may be used in a device for detecting neutrons, electric power conversion, and pulse counting. Such a device may include an n-type boron carbide layer coupled with a substrate where the boron carbide may be an electrically active part of the device. This n-type boron carbide layer may be fabricated through the use of closo-1, 7-dicarbadodecaborane (metacarborane). Specifically, the non-doped n-type polytype may be fabricated using SR-CVD by placing the substrate in a vacuum chamber, cooling the substrate, introducing …
Boron-Carbide Solid State Neutron Detector And Method Of Using The Same, Peter A. Dowben, Shireen Adenwalla, Brian W. Robertson, Mengjun Bai
Boron-Carbide Solid State Neutron Detector And Method Of Using The Same, Peter A. Dowben, Shireen Adenwalla, Brian W. Robertson, Mengjun Bai
Peter Dowben Publications
A boron carbide solid state neutron detector and method of using the detector is disclosed, wherein the detector includes a layer of boron carbide wherein the boron carbide layer is an electrically active part of the detection device, a sensing mechanism inherent to said boron carbide layer, wherein the sensing mechanism detects changes in the boron carbide layer caused by the interception of neutrons and a monitoring device coupled to the sensing mechanics.
The Elimination Of The Influence Of Ambient Environmental Effects On The Structure Of `Inert' Polymers, Luis G. Rosa, P.A. Jacobson, Raymond Lemoine, Peter A. Dowben
The Elimination Of The Influence Of Ambient Environmental Effects On The Structure Of `Inert' Polymers, Luis G. Rosa, P.A. Jacobson, Raymond Lemoine, Peter A. Dowben
Peter Dowben Publications
The construction and use of a vacuum chamber suitable for conventional X-ray diffraction has revealed the influence of the ambient environment, including moisture, on the bulk structure of very thin polymer films. It is concluded that studies of thin film organic systems, even those thought not to be perturbed by ambient water vapor and other contaminants, may benefit from undertaking some studies in such small sample vacuum chambers.
Surface Photovoltage Effects On The Isomeric Semiconductors Of Boron-Carbide, A. N. Caruso, Snjezana Balaz, Bo Xu, Peter A. Dowben, A.S. Mcmullen-Gunn, Jennifer I. Brand, Yaroslav B. Losovyj, D.N. Mcilroy
Surface Photovoltage Effects On The Isomeric Semiconductors Of Boron-Carbide, A. N. Caruso, Snjezana Balaz, Bo Xu, Peter A. Dowben, A.S. Mcmullen-Gunn, Jennifer I. Brand, Yaroslav B. Losovyj, D.N. Mcilroy
Peter Dowben Publications
During exposure to synchrotron radiation, closo 1,7-dicarbadodecaborane (metacarborane) and closo 1,2-dicarbadodecaborane (orthocarborane) decompose, and are accompanied by increasingly evident photoemission surface photovoltage effects. We show that metacarborane and orthocarborane form self-doped n-type and p-type boron-carbides, respectively. Surface photovoltage effects dominate the photoemission final state, not the changes in electronic structure due to decomposition. © 2004 American Institute of Physics. [DOI: 10.1063/1.1648136]
The Surface Band Structure Of W(112), Yaroslav B. Losovyj, I. N. Yakovkin, Hae-Kyung Jeong, Peter A. Dowben
The Surface Band Structure Of W(112), Yaroslav B. Losovyj, I. N. Yakovkin, Hae-Kyung Jeong, Peter A. Dowben
Peter Dowben Publications
Both the experimental and theoretical band structure of the W(112) surface are presented, with the theoretical band structure calculated by the film–LAPW (linearized augmented plane waves) method. The results permit one to compare the W(112) and Mo(112) band structures and illuminate the similarities. It is found that for the W(112) surface the main photoemission features combine contributions from both the surface and bulk, as has been previously noted for Mo(112). The main differences between the electronic structures of the furrowed W(112) and Mo(112) surfaces are seen in the width of occupied bands. The differences are attributed to the extent of …
Are Half-Metallic Ferromagnets Half Metals? (Invited), Peter A. Dowben, Ralph Skomski
Are Half-Metallic Ferromagnets Half Metals? (Invited), Peter A. Dowben, Ralph Skomski
Peter Dowben Publications
Several classes of materials are currently under investigation as potential high-spin-polarization materials. Unfortunately, the proposed half-metallic materials, including the semi-Heusler alloys, the manganese perovskites, and the "simpler" oxides such as chromium dioxide and magnetite, suffer from fundamental limitations. First, the postulated half-metallic systems lose their full (T = 0) spin polarization at finite temperatures and, second, surfaces, interfaces, and structural inhomogenities destroy the complete spin polarization of half-metallic systems even at zero temperature. In a strict sense, half-metallic ferromagnetism is limited to zero temperature since magnon and phonon effects lead to reductions in polarization at finite temperatures. ©2004 American Institute …
Water Absorption And Dielectric Changes In Crystalline Poly(Vinylidene Fluoride-Trifluoroethylene) Copolymer Films, P.A. Jacobson, Luis G. Rosa, Christina M. Othon, Kristin L. Kraemer, A.V. Sorokin, Stephen Ducharme, Peter A. Dowben
Water Absorption And Dielectric Changes In Crystalline Poly(Vinylidene Fluoride-Trifluoroethylene) Copolymer Films, P.A. Jacobson, Luis G. Rosa, Christina M. Othon, Kristin L. Kraemer, A.V. Sorokin, Stephen Ducharme, Peter A. Dowben
Peter Dowben Publications
Crystalline Langmuir–Blodgett copolymer films of vinylidene fluoride with trifluoroethylene (70%:30% and 80%:20%) absorb water. Water absorption is accompanied by film swelling, as indicated by an increase in lattice spacing, sometimes by as much as 5%. This water absorption, between 0 and 40 °C, is a result of intercalation or occupation of interstitial sites between the layers of the film, not just water molecules filling voids and defect sites alone. An increase in the film capacitance is observed, although the polymer chains retain all trans configuration of the ferroelectric phase. © 2004 American Institute of Physics.