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Articles 1 - 30 of 62
Full-Text Articles in Physics
Efficacy Of Multimedia Learning Modules As Preparation For Lecture-Based Tutorials In Electromagnetism, James Christopher Moore
Efficacy Of Multimedia Learning Modules As Preparation For Lecture-Based Tutorials In Electromagnetism, James Christopher Moore
Physics Faculty Publications
We have investigated the efficacy of on-line, multimedia learning modules (MLMs) as preparation for in-class, lecture-based tutorials in electromagnetism in a physics course for natural science majors (biology and marine science). Specifically, we report the results of a multiple-group pre/post-test research design comparing two groups receiving different treatments with respect to activities preceding participation in Tutorials in Introductory Physics. The different pre-tutorial activities were as follows: (1) students were assigned reading from a traditional textbook, followed by a traditional lecture; and (2) students completed on-line MLMs developed by the Physics Education Research Group at the University of Illinois at Urbana …
Kinematics Of Subluminous O And B Stars By Surface Helium Abundance, P. Martin, C. S. Jeffery, Naslim N., V. M. Woolf
Kinematics Of Subluminous O And B Stars By Surface Helium Abundance, P. Martin, C. S. Jeffery, Naslim N., V. M. Woolf
Physics Faculty Publications
The majority of hot subdwarf stars are low-mass core-helium-burning stars. Their atmospheres are generally helium deficient; however, a minority have extremely helium-rich surfaces. An additional fraction have an intermediate surface-helium abundance, occasionally accompanied by peculiar abundances of other elements. We have identified a sample of 88 hot subdwarfs including 38 helium-deficient, 27 intermediate-helium and 23 extreme-helium stars for which radial-velocity and proper-motion measurements, together with distances, allow a calculation of galactic space velocities. We have investigated the kinematics of these three groups to determine whether they belong to similar or different Galactic populations. The majority of helium-deficient subdwarfs in our …
Surface-Enhanced Raman Scattering-Based Immunoassay Technologies For Detection Of Disease Biomarkers, Joseph Smolsky, Sukhwinder Kaur, Chihiro Hayashi, Surinder K. Batra, Alexey Krasnoslobodtsev
Surface-Enhanced Raman Scattering-Based Immunoassay Technologies For Detection Of Disease Biomarkers, Joseph Smolsky, Sukhwinder Kaur, Chihiro Hayashi, Surinder K. Batra, Alexey Krasnoslobodtsev
Physics Faculty Publications
Detection of biomarkers is of vital importance in disease detection, management, and monitoring of therapeutic efficacy. Extensive efforts have been devoted to the development of novel diagnostic methods that detect and quantify biomarkers with higher sensitivity and reliability, contributing to better disease diagnosis and prognosis. When it comes to such devastating diseases as cancer, these novel powerful methods allow for disease staging as well as detection of cancer at very early stages. Over the past decade, there have been some advances in the development of platforms for biomarker detection of diseases. The main focus has recently shifted to the development …
Subaru And Salt Spectroscopy Of Chemically Peculiar Hot Subdwarfs, C. Simon Jeffery, Naslim Neelamkodan, Vincent M. Woolf, Steven M. Crawford, Roy H. Østensen
Subaru And Salt Spectroscopy Of Chemically Peculiar Hot Subdwarfs, C. Simon Jeffery, Naslim Neelamkodan, Vincent M. Woolf, Steven M. Crawford, Roy H. Østensen
Physics Faculty Publications
The majority of hot subdwarfs lie on or close to the helium main-sequence. Many have hydrogen-rich surfaces, but a substantial fraction of the hotter subdwarfs have hydrogen-depleted or hydrogen-deficient surfaces. Amongst the former, three were known to show extraordinary overabundances of heavy elements including zirconium and lead. Using Subaru/HDS,we commenced a high-resolution survey of hydrogen-depleted subdwarfs to discover new members of the class. UVO 0825+15, was found to exhibit strong lead lines, to be an intrinsic variable in K2 field 5, and to have a relatively high space motion. Two other lead-rich subdwarfs have been found in the Subaru sample. …
Discovery Of A Variable Lead-Rich Hot Subdwarf: Uvo 0825+15, C. S. Jeffery, A. S. Baran, N. T. Behara, A. Kvammen, P. Martin, Naslim N., R. H. Østensen, H. P. Preece, M. D. Reed, J. H. Telting, V. M. Woolf
Discovery Of A Variable Lead-Rich Hot Subdwarf: Uvo 0825+15, C. S. Jeffery, A. S. Baran, N. T. Behara, A. Kvammen, P. Martin, Naslim N., R. H. Østensen, H. P. Preece, M. D. Reed, J. H. Telting, V. M. Woolf
Physics Faculty Publications
UVO 0825+15 is a hot bright helium-rich subdwarf which lies in K2 Field 5 and in a sample of intermediate helium-rich subdwarfs observed the Subaru High Dispersion Spectrograph. The K2 light curve shows low-amplitude variations, whilst the Subaru spectrum shows Pb IV absorption lines, indicative of a very high lead overabundance. UVO 0825+15 also has a high proper motion with kinematics typical for a thick disc star. Analyses of ultraviolet and intermediate dispersion optical spectra rule out a short-period binary companion and provide fundamental atmospheric parameters of Teff=38 900±270 K, logg/cms−2=5.97±0.11, log nHe/nH = −0.57 ± …
Magnetic And Magneto-Transport Studies Of Substrate Effect On The Martensitic Transformation In A Nimnin Shape Memory Alloy, Andrei Sokolov, Eugene Kirianov, Albina Zlenko, Abdiel Quetz, Anil Aryal, Sudip Pandey, Igor Dubenko, Shane Stadler, Naushad Ali, Nabil Al-Aqtash, Renat Sabirianov
Magnetic And Magneto-Transport Studies Of Substrate Effect On The Martensitic Transformation In A Nimnin Shape Memory Alloy, Andrei Sokolov, Eugene Kirianov, Albina Zlenko, Abdiel Quetz, Anil Aryal, Sudip Pandey, Igor Dubenko, Shane Stadler, Naushad Ali, Nabil Al-Aqtash, Renat Sabirianov
Physics Faculty Publications
The effect of substrates on the magnetic and transport properties of Ni2Mn1.5In0.5 ultra-thin films were studied theoretically and experimentally. High quality 8-nm films were grown by laser-assisted molecular beam epitaxy deposition. Magneto-transport measurements revealed that the films undergo electronic structure transformation similar to those of bulk materials at the martensitic transformation. The temperature of the transformation depends strongly on lattice parameters of the substrate. To explain this behavior, we performed DFT calculations on the system and found that different substrates change the relative stability of the ferromagnetic (FM) austenite and ferrimagnetic (FiM) martensite states. We conclude that the energy difference …
Electronic Structures Of Lanthanum, Samarium, And Gadolinium Sulfides, Lu Wang, Chris M. Marin, Wai-Ning Mei, Chin Li Cheung
Electronic Structures Of Lanthanum, Samarium, And Gadolinium Sulfides, Lu Wang, Chris M. Marin, Wai-Ning Mei, Chin Li Cheung
Physics Faculty Publications
In this study, we report our efforts to elucidate the electronic structures of two lattice structures of lanthanide sulfides (LnS and Ln3S4) and for three lanthanides (Ln = La, Sm and Gd) using density functional theory calculations performed with the CASTEP code. A DFT+U method was used for the corrections of on-site Coulomb interactions with U = 6 eV. The calculated electronic structures show that both lanthanum and gadolinium sulfides have metallic properties, consistent with the available experimental results. However, the calculated electronic structure of Sm3S4 is considerably different from those of the La3S4 and Gd3S4 and is predicted to …
Rare Earth Dopant (Nd, Gd, Dy, And Er) Hybridization In Lithium Tetraborate, Tony D. Kelly, James C. Petrosky, John W. Mcclory, Volodymyr T. Adamiv, Yaroslav V. Burak, Bohdan V. Padlyak, Ihor M. Teslyuk, Ning Lu, Lu Wang, Wai-Ning Mei, Peter A. Dowben
Rare Earth Dopant (Nd, Gd, Dy, And Er) Hybridization In Lithium Tetraborate, Tony D. Kelly, James C. Petrosky, John W. Mcclory, Volodymyr T. Adamiv, Yaroslav V. Burak, Bohdan V. Padlyak, Ihor M. Teslyuk, Ning Lu, Lu Wang, Wai-Ning Mei, Peter A. Dowben
Physics Faculty Publications
The four dopants (Nd, Gd, Dy, and Er) substitutionally occupy the Li+ sites in lithium tetraborate (Li2B4O7: RE) glasses as determined by analysis of the extended X-ray absorption fine structure. The dopants are coordinated by 6-8 oxygen at a distance of 2.3 to 2.5 Å, depending on the rare earth. The inverse relationship between the RE-O coordination distance and rare earth (RE) atomic number is consistent with the expected lanthanide atomic radial contraction with increased atomic number. Through analysis of the X-ray absorption near edge structure, the rare earth dopants adopt the RE3+ valence state. There are indications of strong …
Searching For Electrical Properties, Phenomena And Mechanisms In The Construction And Function Of Chromosomes, Ivan Kanev, Wai-Ning Mei, Akira Mizuno, Kristi Dehaai, Jennifer Sanmann, Michelle Hess, Lois Starr, Jennifer Grove, Bhavana Dave, Warren Sanger
Searching For Electrical Properties, Phenomena And Mechanisms In The Construction And Function Of Chromosomes, Ivan Kanev, Wai-Ning Mei, Akira Mizuno, Kristi Dehaai, Jennifer Sanmann, Michelle Hess, Lois Starr, Jennifer Grove, Bhavana Dave, Warren Sanger
Physics Faculty Publications
Our studies reveal previously unidentified electrical properties of chromosomes: (1) chromosomes are amazingly similar in construction and function to electrical transformers; (2) chromosomes possess in their construction and function, components similar to those of electric generators, conductors, condensers, switches, and other components of electrical circuits; (3) chromosomes demonstrate in nano-scale level electromagnetic interactions, resonance, fusion and other phenomena similar to those described by equations in classical physics. These electrical properties and phenomena provide a possible explanation for unclear and poorly understood mechanisms in clinical genetics including: (a) electrically based mechanisms responsible for breaks, translocations, fusions, and other chromosomal abnormalities associated …
The Helium-Rich Subdwarf Cpd−20°1123: A Post-Common-Envelope Binary Evolving On To The Extended Horizontal Branch, Naslim N., S. Geier, C. S. Jeffery, N. T. Behara, V. M. Woolf, L. Classen
The Helium-Rich Subdwarf Cpd−20°1123: A Post-Common-Envelope Binary Evolving On To The Extended Horizontal Branch, Naslim N., S. Geier, C. S. Jeffery, N. T. Behara, V. M. Woolf, L. Classen
Physics Faculty Publications
Subluminous B stars come in a variety of flavours including single stars, close and wide binaries, and pulsating and non-pulsating variables. A majority have helium-poor surfaces (helium by number nHe < 1 per cent), whilst a minority have extremely helium rich surfaces (nHe > 90 per cent). A small number have an intermediate surface helium abundance (≈10–30 per cent), accompanied by peculiar abundances of other elements. The questions posed are (i) whether these abundance peculiarities are associated with radiatively driven and time-dependent stratification of elements within the photosphere as the star evolves from a helium-enriched progenitor to become a normal helium-poor sdB star and (ii) whether these phenomena occur only in …
The M Dwarf Problem In The Galaxy, Vincent M. Woolf, Andrew A. West
The M Dwarf Problem In The Galaxy, Vincent M. Woolf, Andrew A. West
Physics Faculty Publications
We present evidence that there is an M dwarf problem similar to the previously identified G dwarf and K dwarf problems: the number of low-metallicity M dwarfs is not sufficient to match simple closed-box models of local Galactic chemical evolution. We estimated the metallicity of 4141 M dwarf stars with spectra from the Sloan Digital Sky Survey (SDSS) using a molecular band strength versus metallicity calibration developed using high resolution spectra of nearby M dwarfs. Using a sample of M dwarfs with measured magnitudes, parallaxes and metallicities, we derived a relation that describes the absolute magnitude variation as a function …
Structural, Magnetic, And Electron Transport Properties Of Mnbi:Fe Thin Films, Parashu Kharel, X. Z. Li, V. R. Shah, N. Al-Aqtash, K. Tarawneh, Renat F. Sabirianov, R. Skomski, D. J. Sellmyer
Structural, Magnetic, And Electron Transport Properties Of Mnbi:Fe Thin Films, Parashu Kharel, X. Z. Li, V. R. Shah, N. Al-Aqtash, K. Tarawneh, Renat F. Sabirianov, R. Skomski, D. J. Sellmyer
Physics Faculty Publications
The structural, magnetic, and electron transport properties ofMn55=xFexBi45 (x¼0, 2, 4, 5, 8, 11, 13, 16) films prepared by multilayer deposition and annealing using e-beam evaporation have been investigated. Fe doping has produced a significant change in the magnetic properties of the samples including the decrease in saturation magnetization and magnetocrystalline anisotropy and increase in coercivity. Although the magnetization shows a smooth decrease with increasing Fe concentration, the coercivity jumps abruptly from 8.5 kOe to 22 kOe as Fe content changes from 4% to 5%, but the change in coercivity is small as the concentration goes beyond 5%. The temperature …
Optical Properties Of Antiferroelectric Cs2nb4o11: Absorption Spectra And First-Principles Calculations, H. L. Liu, C. R. Huang, G. F. Luo, Wai-Ning Mei
Optical Properties Of Antiferroelectric Cs2nb4o11: Absorption Spectra And First-Principles Calculations, H. L. Liu, C. R. Huang, G. F. Luo, Wai-Ning Mei
Chemistry Faculty Publications
We report a joint experimental and theoretical investigation of the optical properties of Cs2Nb4O11. In room temperature optical absorption spectra, we found a direct gap about 3.5560.05 eV and charge transfer excitations at about 4.96 and 6.08 eV, which are in good agreement with the first-principles calculations. Upon passing through the 165 C antiferroelectric to paraelectric phase transition, the peak energies of two charge transfer bands display almost no temperature dependence, yet they become even broader and exhibit enhanced oscillator strength. We infer this intriguing behavior as the manifestation of Nb cation distortions due to the charge-lattice interaction.
The Local Structure Of Transition Metal Doped Semiconducting Boron Carbides, Jing Liu, Guangfu Luo, Wai-Ning Mei, Orhan Kizilkaya, Eric D. Shepherd, J. I. Brand, Peter A. Dowben
The Local Structure Of Transition Metal Doped Semiconducting Boron Carbides, Jing Liu, Guangfu Luo, Wai-Ning Mei, Orhan Kizilkaya, Eric D. Shepherd, J. I. Brand, Peter A. Dowben
Physics Faculty Publications
Transition metal doped boron carbides produced by plasma enhanced chemical vapour deposition of orthocarborane (closo-1,2-C2B10H12) and 3d metal metallocenes were investigated by performing K-edge extended x-ray absorption fine structure and x-ray absorption near edge structure measurements. The 3d transition metal atom occupies one of the icosahedral boron or carbon atomic sites within the icosahedral cage. Good agreement was obtained between experiment and models for Mn, Fe and Co doping, based on the model structures of two adjoined vertex sharing carborane cages, each containing a transition metal. The local spin configurations of all …
What Is Wrong With Water Barometers?, Dan Sullivan, Robert W. Smith, E. J. Kemnitz, Kevin Barton, Robert M. Graham, Raymond A. Guenther, Larry Webber
What Is Wrong With Water Barometers?, Dan Sullivan, Robert W. Smith, E. J. Kemnitz, Kevin Barton, Robert M. Graham, Raymond A. Guenther, Larry Webber
Chemistry Faculty Publications
Every student who studies atmospheric pressure in physics or chemistry learns the principles behind the construction of barometers. Cistern barometers, such as those found in most laboratories, consist of a long glass tube containing an inverted column of liquid having an open end in a cistern of the liquid. Students learn that the column of liquid is supported by air pressure and is equal in weight to a column of air of the same diameter.
The Surface Relaxation And Band Structure Of Mo(112), Ning Wu, Ya. B. Losovyj, Zhaoxian Yu, Renat F. Sabirianov, Wai-Ning Mei, N. Lozova, J. A. Colón Santana, Peter Dowben
The Surface Relaxation And Band Structure Of Mo(112), Ning Wu, Ya. B. Losovyj, Zhaoxian Yu, Renat F. Sabirianov, Wai-Ning Mei, N. Lozova, J. A. Colón Santana, Peter Dowben
Physics Faculty Publications
The experimental and theoretical surface band structures of Mo(112) are compared. This surface band structure mapping is presented with corrections included for the lattice relaxation of the Mo(112) surface. Quantitative low energy electron diffraction (LEED) has been used to determine the details of the Mo(112) surface structure. The first layer contraction is 14.9% by LEED intensity versus voltage analysis and is in general agreement with the 17.6% contraction found from total surface energy optimization. The electronic band structure is mapped out along ¯– ¯ X and ¯–¯Y of the surface Brillouin zone (SBZ). There is strong evidence of electron–phonon coupling …
Voltage-Induced Switching With Magnetoresistance Signature In Magnetic Nano-Filaments, Andrei Sokolov, Renat F. Sabirianov, Ildar F. Sabiryanov, Bernard Doudin
Voltage-Induced Switching With Magnetoresistance Signature In Magnetic Nano-Filaments, Andrei Sokolov, Renat F. Sabirianov, Ildar F. Sabiryanov, Bernard Doudin
Physics Faculty Publications
Large hysteretic resistance changes are reported on sub-100 nm diameter metallic nanowires including thin dielectric junctions. Bi-stable 50% switching in a double junction geometry is modeled in terms of an occupation-driven metal–insulator transition in one of the two junctions, using the generalized Poisson expressions of Oka and Nagaosa (2005 Phys. Rev. Lett. 95 266403). It illustrates how a band bending scheme can be generalized for strongly correlated electron systems. The magnetic constituents of the nanowires provide a magnetoresistive signature of the two resistance states, confirming our model and enabling a four states device application.
Surface Magnetoelectric Effect In Ferromagnetic Metal Films, Chun-Gang Duan, Julian P. Velev, Renat F. Sabirianov, Zigiang Zhu, Junhao Chu, Sitaram Jaswal, Evgeny Y. Tsymbal
Surface Magnetoelectric Effect In Ferromagnetic Metal Films, Chun-Gang Duan, Julian P. Velev, Renat F. Sabirianov, Zigiang Zhu, Junhao Chu, Sitaram Jaswal, Evgeny Y. Tsymbal
Physics Faculty Publications
A surface magnetoelectric effect is revealed by density-functional calculations that are applied to ferromagnetic Fe(001), Ni(001), and Co(0001) films in the presence of an external electric field. The effect originates from spin-dependent screening of the electric field which leads to notable changes in the surface magnetization and the surface magnetocrystalline anisotropy. These results are of considerable interest in the area of electrically controlled magnetism and magnetoelectric phenomena.
The Surface Stability Of Cos2(100), Ning Wu, Renat F. Sabirianov, Chun-Gang Duan, Wai-Ning Mei, David Wisbey, Ya B. Losovyj, M. Manno, Christopher Leighton, En Cai, Jiandi Zhang, Peter Dowben
The Surface Stability Of Cos2(100), Ning Wu, Renat F. Sabirianov, Chun-Gang Duan, Wai-Ning Mei, David Wisbey, Ya B. Losovyj, M. Manno, Christopher Leighton, En Cai, Jiandi Zhang, Peter Dowben
Physics Faculty Publications
The stability of various possible terminations of the CoS2 (1 × 1) surface have been explored and theoretical expectations are found to agree with experiment. With extensive annealing, there is a phase separation at the (100) surface of CoS2. Sulfur segregation to the surface leads to a significant change in the largely sulfur bands due to changes in the hybridized bands, with cobalt. Resonant photoemission spectra indicate clearly that the hybridized cobalt and sulfur bands, characteristic of the CoS2 bulk, lie at higher binding energies than those of segregated sulfur layers. This is discussed in terms of the stability of …
Electronic And Magnetic Properties Of Endohedrally Doped Fullerene Mn@C60: A Total Energy Study, Guangping Li, Renat F. Sabirianov, Jing Lu, Xiao Cheng Zeng, Wai-Ning Mei
Electronic And Magnetic Properties Of Endohedrally Doped Fullerene Mn@C60: A Total Energy Study, Guangping Li, Renat F. Sabirianov, Jing Lu, Xiao Cheng Zeng, Wai-Ning Mei
Physics Faculty Publications
We perform total energy calculations on a manganese atom encapsulated inside a C60 cage using density functional theory with the generalized gradient approximation through three optimization schemes and along four paths inside the cage. We find that when Mn is located in the central region, its electronic and magnetic properties are not exactly the same as those of a free Mn atom due to weak coupling between Mn and the cage. As Mn is shifted toward to the edge, the total energy and spin start to change significantly when Mn is situated about one-third of the way between the …
Theory Of The Piezomagnetic Effect In Mn-Based Antiperovskites, Pavel Lukashev, Renat F. Sabirianov, Kirill Belashchenko
Theory Of The Piezomagnetic Effect In Mn-Based Antiperovskites, Pavel Lukashev, Renat F. Sabirianov, Kirill Belashchenko
Physics Faculty Publications
Recent experimental and theoretical studies of the magnetoelectric ME effect in the nanocomposite structures and in laminates show an enhanced ME coefficient. These materials combine piezoelectric properties of the paramagnetic phase and piezomagnetic properties of the magnetic phase. We propose to fabricate heterostructures formed by piezoelectric materials and magnetic antiperovskites as magnetoelectric materials. We show that the magnetic structure of antiperovskite, such as Mn3GaN, can be controlled by a small applied biaxial strain. The lowering of symmetry with the strain causes the local magnetic moments of Mn atoms to rotate from the trigonal 5g structure with symmetric curl of spin …
Local Structures Surrounding Zr In Nanostructurally Stabilized Cubic Zirconia: Structural Origin Of Phase Stability, Y. L. Soo, P. J. Chen, S. H. Huang, T. J. Shiu, T Y. Tsai, Y. H. Chow, Y. C. Lin, S. C, Weng, S. L. Chang, G. Wang, Chin Li Cheung, Renat F. Sabirianov, Wai-Ning Mei, Fereydoon Namavar, Hani Haider, Kevin L. Garvin, J. F. Lee, H. Y. Lee, P. P. Chu
Local Structures Surrounding Zr In Nanostructurally Stabilized Cubic Zirconia: Structural Origin Of Phase Stability, Y. L. Soo, P. J. Chen, S. H. Huang, T. J. Shiu, T Y. Tsai, Y. H. Chow, Y. C. Lin, S. C, Weng, S. L. Chang, G. Wang, Chin Li Cheung, Renat F. Sabirianov, Wai-Ning Mei, Fereydoon Namavar, Hani Haider, Kevin L. Garvin, J. F. Lee, H. Y. Lee, P. P. Chu
Physics Faculty Publications
Local environment surrounding Zr atoms in the thin films of nanocrystalline zirconia (ZrO2) has been investigated by using the extended x-ray absorption fine structure (EXAFS) technique. These films prepared by the ion beam assisted deposition exhibit long-range structural order of cubic phase and high hardness at room temperature without chemical stabilizers. The local structure around Zr probed by EXAFS indicates a cubic Zr sublattice with O atoms located on the nearest tetragonal sites with respect to the Zr central atoms, as well as highly disordered locations. Similar Zr local structure was also found in a ZrO2 nanocrystal …
Tailoring Magnetic Anisotropy At The Ferromagnetic/Ferroelectric Interface, Chun-Gang Duan, Julian P. Velev, R. F. Sabirianov, W. N. Mei, S. S. Jaswal, E. Y. Tsymbal
Tailoring Magnetic Anisotropy At The Ferromagnetic/Ferroelectric Interface, Chun-Gang Duan, Julian P. Velev, R. F. Sabirianov, W. N. Mei, S. S. Jaswal, E. Y. Tsymbal
Physics Faculty Publications
It is predicted that magnetic anisotropy of a thin magnetic film may be affected by the polarization of a ferroelectric material. Using a Fe∕BaTiO3 bilayer as a representative model and performing first-principles calculations, we demonstrate that a reversal of the electric polarization of BaTiO3 produces a sizable change in magnetic anisotropy energy of Fe films. Tailoring the magnetic anisotropy of a nanomagnet by an adjacent ferroelectric material may yield entirely new device concepts, such as electric-field controlled magnetic data storage.
We thank Ruqian Wu for fruitful discussions. This work was supported by the NSF and the Nanoelectronics Research Initiative through …
Effect Of Tip Resonances On Tunnelling Anisotropic Magnetoresistance In Ferromagnetic Break Junctions: A First-Principles Study, J. D. Burton, Renat F. Sabirianov, Julian P. Velev, Oleg N. Mryasov, Evgeny Y. Tsymbal
Effect Of Tip Resonances On Tunnelling Anisotropic Magnetoresistance In Ferromagnetic Break Junctions: A First-Principles Study, J. D. Burton, Renat F. Sabirianov, Julian P. Velev, Oleg N. Mryasov, Evgeny Y. Tsymbal
Physics Faculty Publications
First-principles calculations of electron tunneling transport in nanoscale Ni and Co break-junctions reveal strong dependence of the conductance on the magnetization direction, an effect known as tunneling anisotropic magnetoresistance TAMR. An important aspect of this phenomenon stems from resonant states localized in the electrodes near the junction break. The energy and broadening of these states is strongly affected by the magnetization orientation due to spin-orbit coupling, causing TAMR to be sensitive to bias voltage on a scale of a few millivolts. Our results bear a resemblance to recent experimental data and suggest that TAMR driven by resonant states is a …
Thermal Stability Of Nanostructurally Stabilized Zirconium Oxide, Fereydoon Namavar, Gonghua Wang, Chin Li Cheung, Xiao Cheng Zeng, Renat F. Sabirianov, Wai-Ning Mei, Jaeil Bai, Joseph R. Brewer, Hani Haider, Kevin L. Garvin
Thermal Stability Of Nanostructurally Stabilized Zirconium Oxide, Fereydoon Namavar, Gonghua Wang, Chin Li Cheung, Xiao Cheng Zeng, Renat F. Sabirianov, Wai-Ning Mei, Jaeil Bai, Joseph R. Brewer, Hani Haider, Kevin L. Garvin
Physics Faculty Publications
Nanostructurally stabilized zirconium oxide (NSZ) hard transparent films were produced without chemical stabilizers by the ion beam assisted deposition technique (IBAD). A transmission electron microscopy study of the samples produced below 150 °C revealed that these films are composed of zirconium oxide (ZrO2) nanocrystallites of diameters 7.5 ± 2.3 nm. X-ray and selected-area electron diffraction studies suggested that the as-deposited films are consistent with cubic phase ZrO2. Rutherford backscattering spectroscopy (RBS) indicated the formation of stoichiometric ZrO2. The phase identity of these optically transparent NSZ films was in agreement with cubic ZrO2, …
Correlation Effects And Electronic Structure Of Gd@C60, Renat F. Sabirianov, Wai-Ning Mei, Jing Lu, Yi Gao, Xiao Cheng Zeng, Robert D. Bolskar, P. Jeppson, Ning Wu, A. N. Caruso, Peter Dowben
Correlation Effects And Electronic Structure Of Gd@C60, Renat F. Sabirianov, Wai-Ning Mei, Jing Lu, Yi Gao, Xiao Cheng Zeng, Robert D. Bolskar, P. Jeppson, Ning Wu, A. N. Caruso, Peter Dowben
Physics Faculty Publications
We have investigated the electronic structure of Gd@C60 using ab initio calculations, photoemission and resonant photoemission (constant initial state spectroscopy). In comparing our calculations based on the local spin density approximation and the Hubbard model description with the observed photoemission spectra, we conclude that Gd 4f states exhibit enhanced correlation energies. These correlation energies have values larger than those normally observed in metallic gadolinium and gadolinium compounds. We attributed the enhanced correlation to the diminished screening of the encapsulated Gd. Both calculation and experiment confi rm a strong hybridization between the valence states of Gd and the C 2p states …
Nonvolatile Two-Terminal Molecular Memory, Jason Snodgrass, Glen Kennedy, Wai-Ning Mei, Renat F. Sabirianov
Nonvolatile Two-Terminal Molecular Memory, Jason Snodgrass, Glen Kennedy, Wai-Ning Mei, Renat F. Sabirianov
Physics Faculty Proceedings & Presentations
We propose a nonvolatile two-terminal memory with two resistance states based on the molecular tunnel junctions. This tunnel junction is composed of one or few monolayers of polar molecules sandwiched between two electrodes made of materials with different screening length. As a prototype model system we study rare earth endohedral metallofullerene molecule with reversible dipole moment sandwiched by metal and semiconducting electrodes forming a double barrier junction. We use the Thomas-Fermi model to calculate the potential profile across the device. Calculated tunneling conductance through the proposed structure changes by order of magnitude upon the reversal of the dipole orientation (due …
An Abundance Analysis Of A Chemically Peculiar B Star – Jl 87*,**, A. Ahmad, N. T. Behara, C. S. Jeffery, T. Sahin, V. M. Woolf
An Abundance Analysis Of A Chemically Peculiar B Star – Jl 87*,**, A. Ahmad, N. T. Behara, C. S. Jeffery, T. Sahin, V. M. Woolf
Physics Faculty Publications
Aims. The aim of this study is to understand the nature and origin of a chemically peculiar star JL 87 by measuring its physical parameters and chemical abundances.
Methods. Physical parameters – effective temperature, surface gravity and helium abundance were measured from a moderate resolution optical spectrum using fully line-blanketed LTE model atmospheres. The effective temperature and extinction were verified by comparing FUSE, IUE spectrophotometry and optical/IR broadband photometry with theoretical flux distributions from LTE model atmospheres. The photospheric chemical abundances were measured from a high-resolution optical spectrum using LTE model atmospheres and spectral synthesis.
Results. On the basis of …
Magnetic Moment Softening And Domain Wall Resistance In Ni Nanowires, J. D. Burton, Renat F. Sabirianov, Sitaram Jaswal, Evgeny Y. Tsymbal, Oleg N. Mryasov
Magnetic Moment Softening And Domain Wall Resistance In Ni Nanowires, J. D. Burton, Renat F. Sabirianov, Sitaram Jaswal, Evgeny Y. Tsymbal, Oleg N. Mryasov
Physics Faculty Publications
We perform ab initio calculations of the electronic structure and conductance of atomic-size Ni nanowires with domain walls only a few atomic lattice constants wide. We show that the hybridization between noncollinear spin states leads to a reduction of the magnetic moments in the domain wall resulting in the enhancement of the domain wall resistance. Experimental studies of the magnetic moment softening may be feasible with modern techniques such as scanning tunneling spectroscopy.
Magnetic Ordering In Gd Monopnictides: Indirect Exchange Versus Superexchange Interaction, Chun-Gang Duan, Renat F. Sabirianov, Wai-Ning Mei, Peter Dowben, Sitaram Jaswal, Evgeny Y. Tsymbal
Magnetic Ordering In Gd Monopnictides: Indirect Exchange Versus Superexchange Interaction, Chun-Gang Duan, Renat F. Sabirianov, Wai-Ning Mei, Peter Dowben, Sitaram Jaswal, Evgeny Y. Tsymbal
Physics Faculty Publications
The exchange interaction parameters of Gd monopnictides are deduced from fitting the total energies of different magnetic configurations to those computed within the Heisenberg model. The magnetic structures predicted by first-principles calculations as well as the Curie (Néel) temperatures obtained from Monte Carlo simulations are both in good agreement with experiments. A detailed analysis of the exchange parameters suggests that the Ruderman-Kittel-Kasuya-Yosida-type indirect exchange interactions and antiferromagnetic superexchange interactions coexist in these compounds. The magnetic order changes from ferromagnetic in GdN to antiferromagnetic in other Gd pnictides as a result of the increased ionic radius of a pnictide in the …