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- Electron diffraction (4)
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- X-ray diffraction (XRD) (1)
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- Computer simulation (1)
- Computer software (1)
- Discrete pinning (1)
- Exchange interaction (1)
- Finite-temperature magnetism (1)
- HOLZ line (1)
- Impurity (1)
- Interlayer exchange coupling (1)
- L10 magnets (1)
- L10 phase (1)
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- Magnetic anisotropy; Magnetic properties of nanostructures (1)
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- Mechanical milling (1)
- Microstructure (1)
- Noncollinearity (1)
- O vacancy (1)
- Ordering (1)
- Polycrystalline phase (1)
- Precession technique (1)
- Pt–Bi (1)
- Resistivity (1)
- Rietveld method (1)
Articles 31 - 60 of 93
Full-Text Articles in Engineering
Effect Of Ferroelectricity On Electron Transport In Pt/Batio3/Pt Tunnel Junctions, Julian P. Velev, Chun-Gang Duan, Kirill D. Belashchenko, Sitaram Jaswal, Evgeny Y. Tsymbal
Effect Of Ferroelectricity On Electron Transport In Pt/Batio3/Pt Tunnel Junctions, Julian P. Velev, Chun-Gang Duan, Kirill D. Belashchenko, Sitaram Jaswal, Evgeny Y. Tsymbal
Nebraska Center for Materials and Nanoscience: Faculty Publications
Based on first-principles calculations, we demonstrate the impact of the electric polarization on electron transport in ferroelectric tunnel junctions (FTJs). Using a Pt/BaTiO3 /Pt FTJ as a model system, we show that the polarization of the BaTiO3 barrier leads to a substantial drop in the tunneling conductance due to changes in the electronic structure driven by ferroelectric displacements. We find a sizable change in the transmission probability across the Pt/BaTiO3 interface with polarization reversal, a signature of the electroresistance effect. These results reveal exciting prospects that FTJs offer as resistive switches in nanoscale electronic devices.
Calculations Of Spin-Disorder Resistivity From First Principles, Aleksander L. Wysocki, Kirill D. Belashchenko, Julian P. Velev, Mark Van Schilfgaarde
Calculations Of Spin-Disorder Resistivity From First Principles, Aleksander L. Wysocki, Kirill D. Belashchenko, Julian P. Velev, Mark Van Schilfgaarde
Nebraska Center for Materials and Nanoscience: Faculty Publications
Spin-disorder resistivity of Fe and Ni is studied using the noncollinear density functional theory. The Landauer conductance is averaged over random disorder configurations and fitted to Ohm’s law. The distribution function is approximated by the mean-field theory. The dependence of spin-disorder resistivity on magnetization in Fe is found to be in excellent agreement with the results for the isotropic s-d model. In the fully disordered state, spin-disorder resistivity for Fe is close to experiment, while for fcc Ni it exceeds the experimental value by a factor of 2.3. This result indicates strong magnetic short-range order in Ni at …
Determination Of Young’S Modulus Of Individual Electrospun Nanofibers, Philip A. Yuya, Yongkui Wen, Joseph A. Turner, Yuris A. Dzenis, Zheng Li
Determination Of Young’S Modulus Of Individual Electrospun Nanofibers, Philip A. Yuya, Yongkui Wen, Joseph A. Turner, Yuris A. Dzenis, Zheng Li
Nebraska Center for Materials and Nanoscience: Faculty Publications
The authors report a technique for measuring Young’s modulus of a single electrospun nanofiber using the vibrations of two microcantilevers coupled with the nanofiber. The modulus is calculated from the resonant frequency shift resulting from the nanofiber. Polyacrylonitrile nanofibers (200 nm diameter) were collected during electrospinning and wrapped on two similar microcantilevers causing a shift in first resonance from 10.0 to 19.4 kHz. Finite element analysis was used to analyze the frequency shift using images from a scanning electron microscope giving a modulus of the as-spun polyacrylonitrile nanofiber of 26.8 GPa.
Effect Of Oxygen Vacancies On Spin-Dependent Tunneling In Fe/Mgo/Fe, Julian P. Velev, Kirill D. Belashchenko, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Effect Of Oxygen Vacancies On Spin-Dependent Tunneling In Fe/Mgo/Fe, Julian P. Velev, Kirill D. Belashchenko, Sitaram S. Jaswal, Evgeny Y. Tsymbal
Nebraska Center for Materials and Nanoscience: Faculty Publications
First-principles calculations based on density functional theory are used to elucidate the effect of O vacancies, forming F centers, on spin-dependent tunneling in Fe/MgO/Fe(001) magnetic tunnel junctions. O vacancies produce occupied localized s states and unoccupied resonant p states, which is consistent with available experimental data. The authors find that O vacancies affect the conductance by nonresonant scattering of tunneling electrons causing a substantial reduction of tunneling magnetoresistance (TMR). Improving the quality of the MgO barrier to reduce O vacancy concentration would improve TMR in these and similar junctions.
Granular Layers On Vibrating Plates: Effective Bending Stiffness And Particle-Size Effects, Wonmo Kang, Joseph A. Turner, Florin Bobaru, Liyong Yang, Kitti Rattanidit
Granular Layers On Vibrating Plates: Effective Bending Stiffness And Particle-Size Effects, Wonmo Kang, Joseph A. Turner, Florin Bobaru, Liyong Yang, Kitti Rattanidit
Nebraska Center for Materials and Nanoscience: Faculty Publications
Acoustic methods of land mine detection rely on the vibrations of the top plate of the mine in response to sound. For granular soil (e.g., sand), the particle size is expected to influence the mine response. This hypothesis is studied experimentally using a plate loaded with dry sand of various sizes from hundreds of microns to a few millimeters. For low values of sand mass, the plate resonance decreases with added mass and eventually reaches a minimum without particle size dependence. After the minimum, a frequency increase is observed with additional mass that includes a particle-size effect. Analytical nondissipative continuum …
Tunneling Anisotropic Magnetoresistance Driven By Resonant Surface States: First-Principles Calculations On An Fe(001) Surface, Athanasios N. Chantis, Kirill D. Belashchenko, Evgeny Y. Tsymbal, Mark Van Schilfgaarde
Tunneling Anisotropic Magnetoresistance Driven By Resonant Surface States: First-Principles Calculations On An Fe(001) Surface, Athanasios N. Chantis, Kirill D. Belashchenko, Evgeny Y. Tsymbal, Mark Van Schilfgaarde
Nebraska Center for Materials and Nanoscience: Faculty Publications
Fully relativistic first-principles calculations of the Fe(001) surface demonstrate that resonant surface (interface) states may produce sizable tunneling anisotropic magnetoresistance in magnetic tunnel junctions with a single magnetic electrode. The effect is driven by the spin-orbit coupling. It shifts the resonant surface band via the Rashba effect when the magnetization direction changes. We find that spin-flip scattering at the interface is controlled not only by the strength of the spin-orbit coupling, but depends strongly on the intrinsic width of the resonant surface states.
Ultrasonic Characterization Of Microstructure Evolution During Processing, Liyong Yang, Joseph A. Turner, Zheng Li
Ultrasonic Characterization Of Microstructure Evolution During Processing, Liyong Yang, Joseph A. Turner, Zheng Li
Nebraska Center for Materials and Nanoscience: Faculty Publications
Many cold-working processes for polycrystalline metals cause alignment of the grains with a single symmetry axis. This type of microstructure is called fiber texture. The existence of a preferred orientation of the grains has a significant influence on the propagation and scattering of ultrasonic waves, which are often used for material inspection. Knowledge of the wave attenuation of such textured materials is of both theoretical and practical interest to nondestructive testing and materials characterization. In this article, the quantitative relations between fiber texture and wave attenuations of hexagonal crystals are presented. The texture is characterized by a Gaussian distribution function …
Quantitative Analysis Of Polycrystalline Electron Diffraction Patterns, Xingzhong Li
Quantitative Analysis Of Polycrystalline Electron Diffraction Patterns, Xingzhong Li
Nebraska Center for Materials and Nanoscience: Faculty Publications
Image processing and computer-assisted analysis are very important in electron microscopy/crystallography, e.g., computer programs have been well developed for image processing and simulation for high-resolution electron microscopy images, and are widely used in research. Unfortunately, few computer programs have been developed for analysis and processing electron diffraction ring patterns. Facing this situation, Labar [1] developed ProcessDiffraction, a computer program to process electron diffraction patterns from polycrystalline and amorphous samples, with an aim to provides good angular resolution, quantified intensities, and reproducible identification of discontinuous and/or faint rings. For phase identification, it is to compare the generated diffractogram to the X-ray …
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 …
Magnetization Reversal In Particulate L10 Nanostructures, Jian Zhou, Ralph Skomski, Kory D. Sorge, David J. Sellmyer
Magnetization Reversal In Particulate L10 Nanostructures, Jian Zhou, Ralph Skomski, Kory D. Sorge, David J. Sellmyer
Nebraska Center for Materials and Nanoscience: Faculty Publications
Magnetization processes in particulate L10 FePt nanostructures are investigated by model calculations and numerical simulations. The systems considered include anisotropic nanograins embedded in non-magnetic matrix; randomly oriented nanoclusters embedded in a C matrix, and nanocomposites of FePt particles in a semi-hard matrix. The reversal mechanisms depend on both intra- and intergranular features. Quasi-coherent rotation dominates the reversal in weakly-coupled granular magnets, but interface imperfections yield a disproportionately strong coercivity reduction. Strong intergranular exchange leads to a transition to a discrete pinning regime, which is accompanied by a coercivity maximum.
Phase Transformations And Thermodynamic Properties Of Nanocrystalline Fept Powders , J. Lyubina, O. Gutfleisch, Ralph Skomski, K.-H. Müller, L. Schultz
Phase Transformations And Thermodynamic Properties Of Nanocrystalline Fept Powders , J. Lyubina, O. Gutfleisch, Ralph Skomski, K.-H. Müller, L. Schultz
Nebraska Center for Materials and Nanoscience: Faculty Publications
The solid state reactions and structural evolution in nanocrystalline FePt powders during mechanical ball milling at 77 K and subsequent annealing have been investigated. Above 310 °C the formation of L10 FePt is observed. As the milling time increases, the enthalpy evolved during the transformations is reduced, whereas the corresponding activation energy increases. For accelerating the ordering process a fine lamellar structure of Fe and Pt is favourable.
Atomic And Micromagnetic Aspects Of L10 Magnetism, Ralph Skomski, Arti Kashyap, Jian Zhou
Atomic And Micromagnetic Aspects Of L10 Magnetism, Ralph Skomski, Arti Kashyap, Jian Zhou
Nebraska Center for Materials and Nanoscience: Faculty Publications
Atomic and continuum effects in L10 magnets are investigated. Emphasis is on the competition between ferromagnetism, antiferromagnetism, and noncollinear order in both perfect and imperfect structures, and on the temperature dependence of the magnetic anisotropy. The applicability of micromagnetic and atomistic approaches depends on the length scales involved, but there is a broad range of phenomena where both can be used.
Effective Electromechanical Moduli Of Ferroelectric Ceramics With Fiber Textures, Y.C. Zhou, J. Liu, Jiangyu Li
Effective Electromechanical Moduli Of Ferroelectric Ceramics With Fiber Textures, Y.C. Zhou, J. Liu, Jiangyu Li
Nebraska Center for Materials and Nanoscience: Faculty Publications
In this letter, we report the predictions on the effective piezoelectric coefficients and electromechanical coupling factors of ferroelectric ceramics BaTiO 3 and Pb(Mg 1/3Nb 2/3)O 3–PbTiO 3 (PMN-PT) with various fiber textures, including [001], [011], and [111], using a two-scale micromechanical model that accounts for microstructural phenomena at both domain and grain levels. It was observed that for BaTiO 3 the [011] texture is optimal with highest d 31 and d 33, while for PMN-PT [001] texture is optimal despite the fact that [011]-oriented single-crystalline PMN-PT has higher d 32 than that of [001]-oriented PMN-PT single …
Jecp/Holz — An Interactive Computer Program For Simulation Of Holz Patterns, Xingzhong Li
Jecp/Holz — An Interactive Computer Program For Simulation Of Holz Patterns, Xingzhong Li
Nebraska Center for Materials and Nanoscience: Faculty Publications
In the present work, an interactive computer program for simulation of the HOLZ line patterns, JECP/HOLZ, is reported. A feature of this program is the integration of the simulation of the HOLZ reflections and the HOLZ (curved and straight) lines, which is interactive with respect to changes of the lattice parameter, the accelerator voltage, the zone axis, and the beam tilt. The program can be used as a teaching aid for students as well as a tool for scientists working on electron diffraction experiments.
Influence Of Nitrogen Growth Pressure On The Ferromagnetic Properties Of Cr-Doped Aln Thin Films, Jun Zhang, Xingzhong Li, B. Xu, David J. Sellmyer
Influence Of Nitrogen Growth Pressure On The Ferromagnetic Properties Of Cr-Doped Aln Thin Films, Jun Zhang, Xingzhong Li, B. Xu, David J. Sellmyer
Nebraska Center for Materials and Nanoscience: Faculty Publications
We report the magnetic properties of Cr-doped AlN thin films grown by reactive magnetron sputtering under various nitrogen pressures. Ferromagnetism is observed up to the highest temperature measured, 400 K, and shows strong dependence on the Cr concentration and, especially, the nitrogen growth pressure. By varying the nitrogen pressure during film growth, the magnetic properties of the films can be changed while keeping a constant Cr concentration. The ferromagnetism is enhanced in the films that were grown at low nitrogen pressures and thus nitrogen deficient, suggesting an important role of defects in the ferromagnetism of this material.
Magnetic Behavior Of Sm-Co-Based Permanent Magnets During Order/Disorder Phase Transformations, Shampa Aich, J. Kostogorova, Jeffrey E. Shield
Magnetic Behavior Of Sm-Co-Based Permanent Magnets During Order/Disorder Phase Transformations, Shampa Aich, J. Kostogorova, Jeffrey E. Shield
Nebraska Center for Materials and Nanoscience: Faculty Publications
The structural transformation from the metastable disordered TbCu7-type SmCo7 structure to the equilibrium ordered Th2Zn17-type Sm2Co17 structure was revealed by x-ray diffraction analysis using Reitveld refinement. The magnetic properties depended strongly on the stage of the transformation, as the coercivity strongly depended on the annealing temperature. The as-solidified alloy in the TbCu7-type structure had a coercivity of 4 kOe, which increased to greater than 9 kOe. The coercivity decreased to around 5 kOe as the transformation neared completion upon annealing at higher temperatures. The magnetization processes were also strongly influenced …