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Full-Text Articles in Nanoscience and Nanotechnology
Wave Propagation In Nanofibers, Xiangfa Wu, Yuris A. Dzenis
Wave Propagation In Nanofibers, Xiangfa Wu, Yuris A. Dzenis
Nebraska Center for Materials and Nanoscience: Faculty Publications
Surface effect on the longitudinal and flexural wave propagation in straight nanofibers/nanowires is studied within the framework of continuum mechanics. Modified Euler-Bernoulli and Rayleigh-Love rod equations and modified Timoshenko beam equation were developed to take into account the surface effect. It was found that surface tension/stress plays appreciable influence on the wave propagation in nanofibers/nanowires at very small diameters. Wave dispersion relations were presented in closed form, and numerical calculations were performed to show the variation of the phase velocity with the wave number at varying surface property and fiber diameter. The given results can be used as the theoretical …
Effect Of Nb And C Additives On The Microstructures And Magnetic Properties Of Rapidly Solidified Sm-Co Alloys, S. Aich, Jeffrey E. Shield
Effect Of Nb And C Additives On The Microstructures And Magnetic Properties Of Rapidly Solidified Sm-Co Alloys, S. Aich, Jeffrey E. Shield
Nebraska Center for Materials and Nanoscience: Faculty Publications
Highly coercive Sm-Co-based permanent magnets have been achieved through simple modification of binary Sm12Co88 alloys with Nb, C or combined Nb and C at concentrations ranging from 1 to 10 atomic percent processed via rapid solidification. Melt spinning at 40 m/s resulted in the formation of the metastable TbCu7-type structure in all alloys. While the unalloyed, as-solidified Sm12Co88 alloy displayed a coercivity of 0.5 kOe, alloying additions resulted in a systematic and profound increase in coercivity. Nb additions resulted in as-solidified coercivities up to 9 kOe, C additions up to 37 kOe, and combined NbC …
Jecp—A Java Electron Crystallography Project, Xingzhong Li
Jecp—A Java Electron Crystallography Project, Xingzhong Li
Nebraska Center for Materials and Nanoscience: Faculty Publications
JECP stands for a java electron crystallography project that includes a series of practical java stand-alone programs for electron diffraction/microscopy and crystallography applications. The aim of the JECP project is twofold, i) as teaching tools to show students the principles of electron diffraction/microscopy and crystallography, ii) as research tools to analyze experimental results. Although there are commercial and public domain computer programs available that allow a user to simulate electron diffraction patterns or processing HREM images, there are always situations when we need to perform operations that are not a feature of any of the existing programs. The programs in …
Refractive Indices And Band-Gap Properties Of Rocksalt Mg XZn Sub>1-XO (0.68 ≤X≤1), RüDiger Schmidt-Grund, Anke Carstens, Bernd Rheinländer, Daniel Spemann, Holger Hochmut, Gregor Zimmermann, Michael Lorenz, Marius Grundmann, Craig M. Herzinger, Mathias Schubert
Refractive Indices And Band-Gap Properties Of Rocksalt Mg XZn Sub>1-XO (0.68 ≤X≤1), RüDiger Schmidt-Grund, Anke Carstens, Bernd Rheinländer, Daniel Spemann, Holger Hochmut, Gregor Zimmermann, Michael Lorenz, Marius Grundmann, Craig M. Herzinger, Mathias Schubert
Nebraska Center for Materials and Nanoscience: Faculty Publications
The room-temperature optical pseudo-dielectric-functions of single-phase, single-crystalline rocksalt-structure MgxZn1-xO with Mg-content x between 0.68 and 1 were determined in the photon energy range from 0.75 to 9.10 eV using spectroscopic ellipsometry. The refractive index determined in the spectral region below the fundamental absorption edge decreases with increasing Mg content. The pseudo-dielectric-functions reveal structures caused in critical points due to electronic band-to-band transitions and free exciton formation at the fundamental band-gap transition. Standard model dielectric function approaches were applied for line shape analysis. Upon increase of the bond ionicity with increasing Mg content the energies of …
Infrared Optical Properties Of MgX-1Zn1-XO Thin Films (0≤X≤1): Long-Wavelength Optical Phonons And Dielectric Constants, C. Bundemann, A. Rahm, M. Lorenz, M. Grundmann, Mathias Schubert
Infrared Optical Properties Of MgX-1Zn1-XO Thin Films (0≤X≤1): Long-Wavelength Optical Phonons And Dielectric Constants, C. Bundemann, A. Rahm, M. Lorenz, M. Grundmann, Mathias Schubert
Nebraska Center for Materials and Nanoscience: Faculty Publications
Infrared spectroscopic ellipsometry in the spectral range from ω =360 cm-1 to ω =1500 cm-1 and Raman scattering spectroscopy are applied to study the long-wavelength optical phonon modes and dielectric constants of MgxZn1-xO thin films in the composition range 0≤x≤1. The samples were grown by pulsed laser deposition on sapphire substrates. X-ray diffraction measurements of the thin film samples reveal the hexagonal wurtzite crystal structure for x≤0.53 and the cubic rocksalt crystal structure for x≥0.67. A systematic variation of the phonon mode frequencies with Mg-mole fraction x is found …
United States Patent: Nano-Crystalline, Homo-Metallic, Protective Coatings, Fereydoon Namavar
United States Patent: Nano-Crystalline, Homo-Metallic, Protective Coatings, Fereydoon Namavar
Nebraska Center for Materials and Nanoscience: Faculty Publications
The present invention provides orthopedic prosthesis having at least one metallic component that includes a metallic substrate on which an integrally formed nano-crystalline coating is formed. The coating and the substrate have at least one metallic constituent in common having an average atomic concentration in the coating that differs from an average atomic concentration in the substrate by less than about 10 percent. Further, the nano-crystalline coatings includes crystalline grains with an average size in a range of about 1 to 999 nanometers, and more preferably in a range of about 10 to 200 nanometers. A transition region that exhibits …
Effect Of Oxygen Vacancies On Interlayer Exchange Coupling In Fe/Mgo/Fe Tunnel Junctions, Mikhail Ye Zhuravlev, Julian P. Velev, A. V. Vedyayev, Evgeny Y. Tsymbal
Effect Of Oxygen Vacancies On Interlayer Exchange Coupling In Fe/Mgo/Fe Tunnel Junctions, Mikhail Ye Zhuravlev, Julian P. Velev, A. V. Vedyayev, Evgeny Y. Tsymbal
Nebraska Center for Materials and Nanoscience: Faculty Publications
We have investigated the interlayer exchange coupling (IEC) in Fe/MgO/Fe(0 0 1) tunnel junctions with and without oxygen vacancies in MgO, using model and density functional calculations. The model predicts that IEC changes sign from ferromagnetic to antiferromagnetic if a defect level matches the Fermi energy. Ab initio calculations show that for perfect junctions, IEC is ferromagnetic and decreases exponentially with MgO thickness. Oxygen vacancies placed in the middle of MgO make IEC antiferromagnetic for three monolayers (MLs) of MgO, but do not change the sign of IEC for five MLs. The latter fact is explained within the model, which …
Magnetic Anisotropy And Anisotropic Ballistic Conductance Of Thin Magnetic Wires, Ildar F. Sabiryanov
Magnetic Anisotropy And Anisotropic Ballistic Conductance Of Thin Magnetic Wires, Ildar F. Sabiryanov
Nebraska Center for Materials and Nanoscience: Faculty Publications
The magnetocrystalline anisotropy of thin magnetic wires of iron and cobalt is quite different from the bulk phases. The spin moment of monatomic Fe wire may be as high as 3.4 μB, while the orbital moment as high as 0.5 μB. The magnetocrystalline anisotropy energy (MAE) was calculated for wires up to 0.6 nm in diameter starting from monatomic wire and adding consecutive shells for thicker wires. I observe that Fe wires exhibit the change sign with the stress applied along the wire. It means that easy axis may change from the direction along the wire …
Highly Coercive Rapidly Solidified Sm–Co Alloys, Shampa Aich, V.K. Ravindran, Jeffrey E. Shield
Highly Coercive Rapidly Solidified Sm–Co Alloys, Shampa Aich, V.K. Ravindran, Jeffrey E. Shield
Nebraska Center for Materials and Nanoscience: Faculty Publications
Highly coercive (Hc up to 37 kOe at 300 K), high remanent permanent magnets have been achieved by rapid solidification of binary Sm–Co alloys and Sm–Co alloys modified with Nb and C. Rapidly solidified SmCox alloys with x ranging from 5 to 11.5 formed predominantly a solid solution TbCu7-type SmCo7 phase, although hcp Co was observed for x>7.3. A coercivity value of 10 kOe was observed for xx, as primary dendrites. Additions of 3 at. % Nb or 3 and 5 at. % C profoundly affected the coercivity values. Transmission electron microscopy (TEM) investigations revealed …
Magnetic Behavior Of Rapidly Solidified Pr–Co Alloys With The Tbcu7-Type Structure, J. Kostogorova, Jeffrey E. Shield
Magnetic Behavior Of Rapidly Solidified Pr–Co Alloys With The Tbcu7-Type Structure, J. Kostogorova, Jeffrey E. Shield
Nebraska Center for Materials and Nanoscience: Faculty Publications
Rapid solidification has been utilized to produce a series of Pr–Co alloys between the Pr2Co17 and PrCo5 stoichiometries. In this system, PrCo5 has easy axis magnetization while Pr2Co17 has easy-plane magnetization. Alloys of the form (PrxCo1-x)94Ti3C3 with x ranging from 0.105 corresponding to the Pr2Co17 compound tox=0.167 corresponding to the PrCo5 compound were produced by melt spinning at a tangential wheel speed of 40 m/ s. The rapid solidification and alloying additions were found to suppress …
Structural And Magnetic Properties Of Laves Compounds Dy1-XPrX(Fe0.35Co0.55B0.1)2 (0≤X≤1), W.J. Ren, D. Li, Yucheng Sui, W. Liu, X.G. Zhao, J.J. Liu, J. Li, Z.D. Zhang
Structural And Magnetic Properties Of Laves Compounds Dy1-XPrX(Fe0.35Co0.55B0.1)2 (0≤X≤1), W.J. Ren, D. Li, Yucheng Sui, W. Liu, X.G. Zhao, J.J. Liu, J. Li, Z.D. Zhang
Nebraska Center for Materials and Nanoscience: Faculty Publications
Dy1-xPrx(Fe0.35Co0.55B0.1)2 (0≤x≤1) Laves compounds with a cubic MgCu2-type structure were synthesized by arc melting and subsequent annealing. The lattice parameter of the Laves compounds linearly increases, while the Curie temperature Tc decreases with increasing Pr content. The saturation magnetization M5 at 5 K or 295 K for the Dy1-xPrx(Fe0.35Co0.55B0.1)2 alloys decreases to reach a minimum, then increases with increasing Pr content. The composition for magnetic moment compensation is about x …
Comment On ‘‘Destructive Effect Of Disorder And Bias Voltage On Interface Resonance Transmission In Symmetric Tunnel Junctions’’, Julian P. Velev, Kirill D. Belashchenko, Evgeny Y. Tsymbal
Comment On ‘‘Destructive Effect Of Disorder And Bias Voltage On Interface Resonance Transmission In Symmetric Tunnel Junctions’’, Julian P. Velev, Kirill D. Belashchenko, Evgeny Y. Tsymbal
Nebraska Center for Materials and Nanoscience: Faculty Publications
In a recent Letter Tusche et al. [1] showed that a complete and coherent FeO layer forms on both interfaces of a FejMgOjFe|001| magnetic tunnel junction (MTJ) when using oxygen-assisted growth. Their ab initio model for these MTJs predicted tunneling magnetoresistance (TMR) of several thousand percent due to the contribution from interface resonances (IRs) perfectly matched at the two interfaces. In this Comment, we show that in practice the predicted giant TMR is unfeasible because the IRs are mismatched by structural disorder and/or by applied bias voltage resulting in a moderate TMR.
The Effective Magnetoelectroelastic Moduli Of Matrix-Based Multiferroic Composites, Shashidhar Srinivas, Jiangyu Li, Y.C. Zhou, A.K. Soh
The Effective Magnetoelectroelastic Moduli Of Matrix-Based Multiferroic Composites, Shashidhar Srinivas, Jiangyu Li, Y.C. Zhou, A.K. Soh
Nebraska Center for Materials and Nanoscience: Faculty Publications
In this paper, we develop a mean field Mori-Tanaka model [T. Mori and K. Tanaka, Acta. Metall. 21, 571 (1973)] to calculate the effective magnetoelectroelastic moduli of matrix-based multiferroic composites, emphasizing the effects of shape and orientation distribution of second phase particles that have not been investigated before. Through a systematic study, it is observed that laminated composites are optimal for magnetoelectric coefficient a11, while fibrous composites are optimal for a33. In addition, these coupling coefficients are maximum when the second phase particles are aligned. It is also postulated that the large discrepancy between theoretical predictions …
Self-Consistent Local Gw Method: Application To 3D And 4D Metals, Kirill D. Belashchenko, Vladimir P. Antropov, N.E. Zein
Self-Consistent Local Gw Method: Application To 3D And 4D Metals, Kirill D. Belashchenko, Vladimir P. Antropov, N.E. Zein
Nebraska Center for Materials and Nanoscience: Faculty Publications
The spectral densities for 3d and 4d transition metals are calculated using the simplified version of the self-consistent GW method employing the local (one-site) approximation and the self-consistent quasiparticle basis set. The results are compared with those given by the traditional local density approximation (LDA) and also with experimental x-ray photoemission and inverse photoemission spectra. While no systematic improvements over LDA are observed, this fully self-consistent many-body technique generates quite reasonable results and can serve as a practical prototype for further development of the many-body electronic structure theory.
Conduction-Band Electron Effective Mass In Zn0.87Mn0.13Se Measured By Terahertz And Far-Infrared Magnetooptic Ellipsometry, Tino Hofmann, U. Schade, K.C. Agarwal, B. Daniel, C. Klingshirn, M. Hetterich, C.M. Herzinger, Mathias Schubert
Conduction-Band Electron Effective Mass In Zn0.87Mn0.13Se Measured By Terahertz And Far-Infrared Magnetooptic Ellipsometry, Tino Hofmann, U. Schade, K.C. Agarwal, B. Daniel, C. Klingshirn, M. Hetterich, C.M. Herzinger, Mathias Schubert
Nebraska Center for Materials and Nanoscience: Faculty Publications
We determine the electron effective mass parameter m*=0.086±0.004 m0 of thin-film n-type low-chlorine-doped Zn0.87Mn0.13Se with free-charge-carrier concentration N=4.5x1017 cm-3 and optical mobility ) =300±20 cm2 / (V s) using magneto-optic generalized ellipsometry in the terahertz and far-infrared spectral domain for wave numbers from ω =30–650 cm-1. The room-temperature measurements were carried out with magnetic fields up to 3 T. We employ synchrotron and black-body radiation sources for the terahertz and far-infrared spectral regions, respectively. Comparison with previous experimental results from samples with considerably higher free electron …