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Articles 1 - 30 of 1339

Full-Text Articles in Physics

Uncompensated Polarization In Incommensurate Modulations Of Perovskite Antiferroelectrics, Tao Ma, Zhongming Fan, Bin Xu, Tae-Hoon Kim, Ping Lu, Laurent Bellaiche, Matthew J. Kramer, Xiaoli Tan, Lin Zhou Sep 2019

Uncompensated Polarization In Incommensurate Modulations Of Perovskite Antiferroelectrics, Tao Ma, Zhongming Fan, Bin Xu, Tae-Hoon Kim, Ping Lu, Laurent Bellaiche, Matthew J. Kramer, Xiaoli Tan, Lin Zhou

Xiaoli Tan

Complex polar structures of incommensurate modulations (ICMs) are revealed in chemically modified PbZrO3 perovskite antiferroelectrics using advanced transmission electron microscopy techniques. The Pb-cation displacements, previously assumed to arrange in a fully-compensated antiparallel fashion, are found to be either antiparallel but with different magnitudes, or in a nearly orthogonal arrangement in adjacent stripes in the ICMs. Ab initio calculations corroborate the low-energy state of these arrangements. Our discovery corrects the atomic understanding of ICMs in PbZrO3-based perovskite antiferroelectrics.


Fatigue-Resistant High-Performance Elastocaloric Materials Via Additive Manufacturing, Huilong Hou, Emrah Simsek, Tao Ma, Nathan S. Johnson, Suxin Qian, Cheikh Cissé, Drew Stasak, Naila Al Hasan, Lin Zhou, Yunho Hwang, Reinhard Radermacher, Valery I. Levitas, Matthew J. Kramer, Mohsen Asle Zaeem, Aaron P. Stebner, Ryan T. Ott, Jun Cui, Ichiro Takeuchi Aug 2019

Fatigue-Resistant High-Performance Elastocaloric Materials Via Additive Manufacturing, Huilong Hou, Emrah Simsek, Tao Ma, Nathan S. Johnson, Suxin Qian, Cheikh Cissé, Drew Stasak, Naila Al Hasan, Lin Zhou, Yunho Hwang, Reinhard Radermacher, Valery I. Levitas, Matthew J. Kramer, Mohsen Asle Zaeem, Aaron P. Stebner, Ryan T. Ott, Jun Cui, Ichiro Takeuchi

Valery I. Levitas

Elastocaloric cooling, which exploits the latent heat released and absorbed as stress-induced phase transformations are reversibly cycled in shape memory alloys, has recently emerged as a frontrunner in non-vapor-compression cooling technologies. The intrinsically high thermodynamic efficiency of elastocaloric materials is limited only by work hysteresis. Here, we report on creating high-performance low-hysteresis elastocaloric cooling materials via additive manufacturing of Titanium-Nickel (Ti-Ni) alloys. Contrary to established knowledge of the physical metallurgy of Ti-Ni alloys, intermetallic phases are found to be beneficial to elastocaloric performances when they are combined with the binary Ti-Ni compound in nanocomposite configurations. The resulting microstructure gives rise ...


Composition-Dependent Stability Of The Medium-Range Order Responsible For Metallic Glass Formation, Feng Zhang, Min Ji, Xiao-Wei Fang, Yang Sun, Cai-Zhuang Wang, Mikhail I. Mendelev, Matthew J. Kramer, Ralph E. Napolitano, Kai-Ming Ho Aug 2019

Composition-Dependent Stability Of The Medium-Range Order Responsible For Metallic Glass Formation, Feng Zhang, Min Ji, Xiao-Wei Fang, Yang Sun, Cai-Zhuang Wang, Mikhail I. Mendelev, Matthew J. Kramer, Ralph E. Napolitano, Kai-Ming Ho

Ralph E. Napolitano

The competition between the characteristic medium-range order corresponding to amorphous alloys and that in ordered crystalline phases is central to phase selection and morphology evolution under various processing conditions. We examine the stability of a model glass system, Cu–Zr, by comparing the energetics of various medium-range structural motifs over a wide range of compositions using first-principles calculations. We focus specifically on motifs that represent possible building blocks for competing glassy and crystalline phases, and we employ a genetic algorithm to efficiently identify the energetically favored decorations of each motif for specific compositions. Our results show that a Bergman-type motif ...


A Computational Study Of Diffusion In A Glass-Forming Metallic Liquid, T. Wang, F. Zhang, L. Yang, X. W. Fang, S. H. Zhou, Matthew J. Kramer, Cai-Zhuang Wang, Kai-Ming Ho, Ralph E. Napolitano Aug 2019

A Computational Study Of Diffusion In A Glass-Forming Metallic Liquid, T. Wang, F. Zhang, L. Yang, X. W. Fang, S. H. Zhou, Matthew J. Kramer, Cai-Zhuang Wang, Kai-Ming Ho, Ralph E. Napolitano

Ralph E. Napolitano

Liquid phase diffusion plays a critical role in phase transformations (e.g. glass transformation and devitrification) observed in marginal glass forming systems such as Al-Sm. Controlling transformation pathways in such cases requires a comprehensive description of diffusivity, including the associated composition and temperature dependencies. In the computational study reported here, we examine atomic diffusion in Al-Sm liquids using ab initio molecular dynamics (AIMD) and determine the diffusivities of Al and Sm for selected alloy compositions. Non-Arrhenius diffusion behavior is observed in the undercooled liquids with an enhanced local structural ordering. Through assessment of our AIMD result, we construct a general ...


Fatigue-Resistant High-Performance Elastocaloric Materials Via Additive Manufacturing, Huilong Hou, Emrah Simsek, Tao Ma, Nathan S. Johnson, Suxin Qian, Cheikh Cissé, Drew Stasak, Naila Al Hasan, Lin Zhou, Yunho Hwang, Reinhard Radermacher, Valery I. Levitas, Matthew J. Kramer, Mohsen Asle Zaeem, Aaron P. Stebner, Ryan T. Ott, Jun Cui, Ichiro Takeuchi Aug 2019

Fatigue-Resistant High-Performance Elastocaloric Materials Via Additive Manufacturing, Huilong Hou, Emrah Simsek, Tao Ma, Nathan S. Johnson, Suxin Qian, Cheikh Cissé, Drew Stasak, Naila Al Hasan, Lin Zhou, Yunho Hwang, Reinhard Radermacher, Valery I. Levitas, Matthew J. Kramer, Mohsen Asle Zaeem, Aaron P. Stebner, Ryan T. Ott, Jun Cui, Ichiro Takeuchi

Aerospace Engineering Publications

Elastocaloric cooling, which exploits the latent heat released and absorbed as stress-induced phase transformations are reversibly cycled in shape memory alloys, has recently emerged as a frontrunner in non-vapor-compression cooling technologies. The intrinsically high thermodynamic efficiency of elastocaloric materials is limited only by work hysteresis. Here, we report on creating high-performance low-hysteresis elastocaloric cooling materials via additive manufacturing of Titanium-Nickel (Ti-Ni) alloys. Contrary to established knowledge of the physical metallurgy of Ti-Ni alloys, intermetallic phases are found to be beneficial to elastocaloric performances when they are combined with the binary Ti-Ni compound in nanocomposite configurations. The resulting microstructure gives rise ...


Dependence Of The Absolute Value Of The Penetration Depth In (Ba1–X Kx) Fe2 As2 On Doping, Avior Almoalem, Alon Yagil, Kyuil Cho, Serafim Teknowijoyo, Makariy A. Tanatar, Ruslan Prozorov, Yong Liu, Thomas A. Lograsso, Ophir M. Auslaender Aug 2019

Dependence Of The Absolute Value Of The Penetration Depth In (Ba1–X Kx) Fe2 As2 On Doping, Avior Almoalem, Alon Yagil, Kyuil Cho, Serafim Teknowijoyo, Makariy A. Tanatar, Ruslan Prozorov, Yong Liu, Thomas A. Lograsso, Ophir M. Auslaender

Thomas A. Lograsso

We report magnetic force microscopy (MFM) measurements on the iron-based superconductor Ba1−xKxFe2As2. By measuring locally the Meissner repulsion with the magnetic MFM tip, we determine the absolute value of the in-plane magnetic penetration depth (λab) in underdoped, optimally doped, and overdoped samples. The results suggest an abrupt increase of λab as doping is increased from xopt, which is potentially related to the presence of a quantum critical point. The response of superconducting vortices to magnetic forces exerted by the MFM tip for x=0.19 and 0.58 is compatible with previously observed structural symmetries at those doping levels.


Non-Fermi-Liquid Behaviors Associated With A Magnetic Quantum-Critical Point In Sr(Co{1-X}Ni{X})2as2 Single Crystals, Nediadath S. Sangeetha, Lin-Lin Wang, Andrei V. Smirnov, Volodymyr Smetana, A.-V. Mudring, Duane D. Johnson, Makariy A. Tanatar, Ruslan Prozorov, David C. Johnston Jul 2019

Non-Fermi-Liquid Behaviors Associated With A Magnetic Quantum-Critical Point In Sr(Co{1-X}Ni{X})2as2 Single Crystals, Nediadath S. Sangeetha, Lin-Lin Wang, Andrei V. Smirnov, Volodymyr Smetana, A.-V. Mudring, Duane D. Johnson, Makariy A. Tanatar, Ruslan Prozorov, David C. Johnston

Duane D. Johnson

Electron-doped Sr(Co{1-x}Ni{x})2As2 single crystals with compositions x = 0 to 0.9 were grown out of self-flux and SrNi2As2 single crystals out of Bi flux. The crystals were characterized using single-crystal x-ray diffraction (XRD), magnetic susceptibility chi(H,T), isothermal magnetization M(H,T), heat capacity Cp(H,T), and electrical resistivity ho(H,T) measurements versus applied magnetic field H and temperature T. The chi(T) data show that the crystals exhibit an antiferromagnetic (AFM) ground state almost immediately upon Ni doping on the Co site. Ab-initio electronic-structure calculations for x = 0 and x = 0 ...


Single Pair Of Weyl Fermions In The Half-Metallic Semimetal Eucd2as2, Lin-Lin Wang, Na Hyun Jo, Brinda Kuthanazhi, Yun Wu, Robert J. Mcqueeney, Adam Kaminski, Paul C. Canfield Jul 2019

Single Pair Of Weyl Fermions In The Half-Metallic Semimetal Eucd2as2, Lin-Lin Wang, Na Hyun Jo, Brinda Kuthanazhi, Yun Wu, Robert J. Mcqueeney, Adam Kaminski, Paul C. Canfield

Paul C. Canfield

Materials with the ideal case of a single pair of Weyl points (WPs) are highly desirable for elucidating the unique properties of Weyl fermions. EuC d 2 A s 2 is an antiferromagnetic topological insulator or Dirac semimetal depending on the different magnetic configurations. Using first-principles band-structure calculations, we show that inducing ferromagnetism in EuC d 2 A s 2 can generate a single pair of WPs from splitting the single pair of antiferromagnetic Dirac points due to its half-metallic nature. Analysis with a low-energy effective Hamiltonian shows that a single pair of WPs is obtained in EuC d 2 ...


Interplay Between Superconductivity And Itinerant Magnetism In Underdoped Ba1−Xkxfe2as2 (X = 0.2) Probed By The Response To Controlled Point-Like Disorder, Ruslan Prozorov, Marcin Kończykowski, Makariy A. Tanatar, Hai-Hu Wen, Rafael M. Fernandes, Paul C. Canfield Jul 2019

Interplay Between Superconductivity And Itinerant Magnetism In Underdoped Ba1−Xkxfe2as2 (X = 0.2) Probed By The Response To Controlled Point-Like Disorder, Ruslan Prozorov, Marcin Kończykowski, Makariy A. Tanatar, Hai-Hu Wen, Rafael M. Fernandes, Paul C. Canfield

Paul C. Canfield

The response of superconductors to controlled introduction of point-like disorder is an important tool to probe their microscopic electronic collective behavior. In the case of iron-based superconductors, magnetic fluctuations presumably play an important role in inducing high-temperature superconductivity. In some cases, these two seemingly incompatible orders coexist microscopically. Therefore, understanding how this unique coexistence state is affected by disorder can provide important information about the microscopic mechanisms involved. In one of the most studied pnictide family, hole-doped Ba1−xKxFe2As2 (BaK122), this coexistence occurs over a wide range of doping levels, 0.16 ≲ x ≲ 0.25. We used ...


Ultrahigh Elastically Compressible And Strain-Engineerable Intermetallic Compounds Under Uniaxial Mechanical Loading, Gyuho Song, Vladislav Borisov, William Meier, Mingyu Xu, Keith J. Dusoe, John T. Sypek, Roser Valentí, Paul C. Canfield, Seok-Woo Lee Jul 2019

Ultrahigh Elastically Compressible And Strain-Engineerable Intermetallic Compounds Under Uniaxial Mechanical Loading, Gyuho Song, Vladislav Borisov, William Meier, Mingyu Xu, Keith J. Dusoe, John T. Sypek, Roser Valentí, Paul C. Canfield, Seok-Woo Lee

Paul C. Canfield

Intermetallic compounds possess unique atomic arrangements that often lead to exceptional material properties, but their extreme brittleness usually causes fracture at a limited strain of less than 1% and prevents their practical use. Therefore, it is critical for them to exhibit either plasticity or some form of structural transition to absorb and release a sufficient amount of mechanical energy before failure occurs. This study reports that the ThCr2Si2-structured intermetallic compound (CaFe2As2) and a hybrid of its structure (CaKFe4As4) with 2 µm in diameter and 6 µm in height can exhibit superelasticity with strain up to 17% through a reversible, deformation-induced ...


Lack Of Superconductivity In The Phase Diagram Of Single-Crystalline Eu(Fe1-Xcox)(2)As-2 Grown By Transition Metal Arsenide Flux, Gang Wang, William R. Meier, Warren E. Straszheim, Joshua Slagle, Sergey L. Bud’Ko, Paul C. Canfield Jul 2019

Lack Of Superconductivity In The Phase Diagram Of Single-Crystalline Eu(Fe1-Xcox)(2)As-2 Grown By Transition Metal Arsenide Flux, Gang Wang, William R. Meier, Warren E. Straszheim, Joshua Slagle, Sergey L. Bud’Ko, Paul C. Canfield

Paul C. Canfield

The interplay of magnetism and superconductivity (SC) has been a focus of interest in condensed matter physics for decades. EuF e 2 A s 2 has been identified as a potential platform to investigate interactions between structural, magnetic, and electronic effects as well as the coexistence of magnetism and SC with similar transition temperatures. However, there are obvious inconsistencies in the reported phase diagrams of Eu ( F e 1 − x C o x ) 2 A s 2 crystals grown by different methods. For transition metal arsenide (TMA)-flux-grown crystals, even the existence of SC is uncertain. Here we reexamine the ...


Is It Possible To Stabilize The 1144-Phase Pnictides With Tri-Valence Cations?, Boqun Song, Manh Cuong Nguyen, Cai-Zhuang Wang, Paul C. Canfield, Kai-Ming Ho Jul 2019

Is It Possible To Stabilize The 1144-Phase Pnictides With Tri-Valence Cations?, Boqun Song, Manh Cuong Nguyen, Cai-Zhuang Wang, Paul C. Canfield, Kai-Ming Ho

Paul C. Canfield

A lately discovered 1144 phase has generated significant interest for its high superconducting temperatures, disorder-free doping, and various chemical substitutions. However, it has only been found in iron arsenides ( A B Fe 4 As 4 ), and cations are limited to +1 or +2 valence states (e.g., alkali metals, alkaline earth elements, and Eu). Whether more 1144 phases could be stabilized and whether intriguing properties exist are questions of general interest. In this work, we investigate 1144 iron and cobalt arsenides with tri-valence cations (La, Y, In, Tl, Sm, Gd). We study phase stability among other competing phases: 122 solution ...


Enhanced Thermoelectric Performance Of Mg2 Si1−X Snx Codoped With Bi And Cr, Vikram, Duane D. Johnson, Aftab Alam Jul 2019

Enhanced Thermoelectric Performance Of Mg2 Si1−X Snx Codoped With Bi And Cr, Vikram, Duane D. Johnson, Aftab Alam

Duane D. Johnson

Magnesium silicides are favorable thermoelectric materials considering resource abundance and cost. Chromium (Cr) doping in magnesium silicides has not yet been explored. Using first-principles calculations, we have studied the stability of Mg2Si with chromium (1.85, 3.7, 5.55, and 6.25% Cr) and tin (12.5 and 50% Sn). Three Mg2Si compounds doped with Sn, (Sn + Bi), and (Sn + Bi + Cr) are used to explain doping effects on thermoelectric performance. Notably, Cr behaves nonmagnetically for ≤2%Cr, after which ferromagnetic ordering is favored (≤12.96% Cr), despite its elemental antiferromagnetic state. With alloying of Sn (70.4%), Mg2Si ...


Suppression Of Antiferromagnetic Spin Fluctuations In Superconducting Cr0.8 Ru0.2, M. Ramazanoglu, Benjamin G. Ueland, D. K. Pratt, L. W. Harringer, J. W. Lynn, G. Ehlers, G. E. Granroth, Sergey L. Bud’Ko, Paul C. Canfield, Deborah L. Schlagel, Alan I. Goldman, Thomas A. Lograsso, Robert J. Mcqueeney Jul 2019

Suppression Of Antiferromagnetic Spin Fluctuations In Superconducting Cr0.8 Ru0.2, M. Ramazanoglu, Benjamin G. Ueland, D. K. Pratt, L. W. Harringer, J. W. Lynn, G. Ehlers, G. E. Granroth, Sergey L. Bud’Ko, Paul C. Canfield, Deborah L. Schlagel, Alan I. Goldman, Thomas A. Lograsso, Robert J. Mcqueeney

Deborah L. Schlagel

Unconventional superconductivity (SC) often develops in magnetic metals on the cusp of static antiferromagnetic (AFM) order where spin fluctuations are strong. This association is so compelling that many SC materials are labeled as unconventional by proximity to an ordered AFM state. The Cr-Ru alloy system possesses such a phase diagram [see Fig. 1(a)]. Here we use inelastic neutron scattering to show that spin fluctuations are present in a SC Cr0.8Ru0.2 alloy (Tc=1.35 K). However, the neutron spin resonance, a possible signature of unconventional SC, is not observed. Instead, data indicate a spin gap of order ...


Suppression Of Antiferromagnetic Spin Fluctuations In Superconducting Cr0.8 Ru0.2, M. Ramazanoglu, Benjamin G. Ueland, D. K. Pratt, L. W. Harringer, J. W. Lynn, G. Ehlers, G. E. Granroth, Sergey L. Bud’Ko, Paul C. Canfield, Deborah L. Schlagel, Alan I. Goldman, Thomas A. Lograsso, Robert J. Mcqueeney Jul 2019

Suppression Of Antiferromagnetic Spin Fluctuations In Superconducting Cr0.8 Ru0.2, M. Ramazanoglu, Benjamin G. Ueland, D. K. Pratt, L. W. Harringer, J. W. Lynn, G. Ehlers, G. E. Granroth, Sergey L. Bud’Ko, Paul C. Canfield, Deborah L. Schlagel, Alan I. Goldman, Thomas A. Lograsso, Robert J. Mcqueeney

A. I. Goldman

Unconventional superconductivity (SC) often develops in magnetic metals on the cusp of static antiferromagnetic (AFM) order where spin fluctuations are strong. This association is so compelling that many SC materials are labeled as unconventional by proximity to an ordered AFM state. The Cr-Ru alloy system possesses such a phase diagram [see Fig. 1(a)]. Here we use inelastic neutron scattering to show that spin fluctuations are present in a SC Cr0.8Ru0.2 alloy (Tc=1.35 K). However, the neutron spin resonance, a possible signature of unconventional SC, is not observed. Instead, data indicate a spin gap of order ...


Suppression Of Antiferromagnetic Spin Fluctuations In Superconducting Cr0.8 Ru0.2, M. Ramazanoglu, Benjamin G. Ueland, D. K. Pratt, L. W. Harringer, J. W. Lynn, G. Ehlers, G. E. Granroth, Sergey L. Bud’Ko, Paul C. Canfield, Deborah L. Schlagel, Alan I. Goldman, Thomas A. Lograsso, Robert J. Mcqueeney Jul 2019

Suppression Of Antiferromagnetic Spin Fluctuations In Superconducting Cr0.8 Ru0.2, M. Ramazanoglu, Benjamin G. Ueland, D. K. Pratt, L. W. Harringer, J. W. Lynn, G. Ehlers, G. E. Granroth, Sergey L. Bud’Ko, Paul C. Canfield, Deborah L. Schlagel, Alan I. Goldman, Thomas A. Lograsso, Robert J. Mcqueeney

Thomas A. Lograsso

Unconventional superconductivity (SC) often develops in magnetic metals on the cusp of static antiferromagnetic (AFM) order where spin fluctuations are strong. This association is so compelling that many SC materials are labeled as unconventional by proximity to an ordered AFM state. The Cr-Ru alloy system possesses such a phase diagram [see Fig. 1(a)]. Here we use inelastic neutron scattering to show that spin fluctuations are present in a SC Cr0.8Ru0.2 alloy (Tc=1.35 K). However, the neutron spin resonance, a possible signature of unconventional SC, is not observed. Instead, data indicate a spin gap of order ...


Interplay Between Superconductivity And Itinerant Magnetism In Underdoped Ba1−Xkxfe2as2 (X = 0.2) Probed By The Response To Controlled Point-Like Disorder, Ruslan Prozorov, Marcin Kończykowski, Makariy A. Tanatar, Hai-Hu Wen, Rafael M. Fernandes, Paul C. Canfield Jul 2019

Interplay Between Superconductivity And Itinerant Magnetism In Underdoped Ba1−Xkxfe2as2 (X = 0.2) Probed By The Response To Controlled Point-Like Disorder, Ruslan Prozorov, Marcin Kończykowski, Makariy A. Tanatar, Hai-Hu Wen, Rafael M. Fernandes, Paul C. Canfield

Ames Laboratory Accepted Manuscripts

The response of superconductors to controlled introduction of point-like disorder is an important tool to probe their microscopic electronic collective behavior. In the case of iron-based superconductors, magnetic fluctuations presumably play an important role in inducing high-temperature superconductivity. In some cases, these two seemingly incompatible orders coexist microscopically. Therefore, understanding how this unique coexistence state is affected by disorder can provide important information about the microscopic mechanisms involved. In one of the most studied pnictide family, hole-doped Ba1−xKxFe2As2 (BaK122), this coexistence occurs over a wide range of doping levels, 0.16 ≲ x ≲ 0.25. We used ...


60th Annual Rocky Mountain Conference On Magnetic Resonance Jul 2019

60th Annual Rocky Mountain Conference On Magnetic Resonance

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 60th annual meeting of the Rocky Mountain Conference on Magnetic Resonance, co-endorsed by the Colorado Section of the American Chemical Society and the Society for Applied Spectroscopy. Held in Denver, Colorado, July 21-25, 2019.


Investigation Of Fundamental Principles Of Rigid Body Impact Mechanics, Khalid Alluhydan Jul 2019

Investigation Of Fundamental Principles Of Rigid Body Impact Mechanics, Khalid Alluhydan

Mechanical Engineering Research Theses and Dissertations

In impact mechanics, the collision between two or more bodies is a common, yet a very challenging problem. Producing analytical solutions that can predict the post-collision motion of the colliding bodies require consistent modeling of the dynamics of the colliding bodies. This dissertation presents a new method for solving the two and multibody impact problems that can be used to predict the post-collision motion of the colliding bodies. Also, we solve the rigid body collision problem of planar kinematic chains with multiple contacts with external surfaces.

In the first part of this dissertation, we study planar collisions of Balls and ...


Interaction Dynamics Between Ferroelectric And Antiferroelectric Domains In A Pbzro3-Based Ceramic, Zhongming Fan, Fei Xue, Goknur Tutuncu, Long-Qing Chen, Xiaoli Tan Jun 2019

Interaction Dynamics Between Ferroelectric And Antiferroelectric Domains In A Pbzro3-Based Ceramic, Zhongming Fan, Fei Xue, Goknur Tutuncu, Long-Qing Chen, Xiaoli Tan

Xiaoli Tan

The antiferroelectric-ferroelectric phase transition in PbZrO3-based oxides is of both fundamental and practical importance. In ceramics in which such a transition readily occurs, the antiferroelectric and the ferroelectric phases often coexist in individual grains with a coherent interphase interface. In this work, the electric biasing in situ transmission electron microscopy technique is employed to directly observe a unique microstructural dynamic when ferroelectric and antiferroelectric domains are driven by a moderate electric field to interact. It is found that, under monotonic loading, the ferroelectric domain grows until it is blocked by the ferroelectric-antiferroelectric interface. At the same time, a kink is ...


Single-Crystal Permanent Magnets: Extraordinary Magnetic Behavior In The Ta-,Cu-, And Fe-Substituted Ceco 5 Systems, Tej N. Lamichhane, Michael T. Onyszczak, Olena Palasyuk, Saba Sharikadze, Tae-Hoon Kim, Qisheng Lin, Matthew J. Kramer, R. W. Mccallum, Aleksander L. Wysocki, Manh Cuong Nguyen, Vladimir P. Antropov, Tribhuwan Pandey, David Parker, Sergey L. Bud’Ko, Paul C. Canfield, Andriy Palasyuk Jun 2019

Single-Crystal Permanent Magnets: Extraordinary Magnetic Behavior In The Ta-,Cu-, And Fe-Substituted Ceco 5 Systems, Tej N. Lamichhane, Michael T. Onyszczak, Olena Palasyuk, Saba Sharikadze, Tae-Hoon Kim, Qisheng Lin, Matthew J. Kramer, R. W. Mccallum, Aleksander L. Wysocki, Manh Cuong Nguyen, Vladimir P. Antropov, Tribhuwan Pandey, David Parker, Sergey L. Bud’Ko, Paul C. Canfield, Andriy Palasyuk

Paul C. Canfield

To reduce material and processing costs of commercial permanent magnets and to attempt to fill the empty niche of energy products, 10–20 MGOe, between low-flux (ferrites, alnico) and high-flux (Nd2Fe14B- and SmCo5-type) magnets, we report the synthesis, structure, magnetic properties, and modeling of Ta-, Cu-, and Fe-substituted CeCo5. Using a self-flux technique, we grow single crystals of Ce15.1Ta1.0Co74.4Cu9.5, Ce16.3Ta0.6Co68.9Cu14.2, Ce15.7Ta0.6Co67.8Cu15.9, Ce16.3Ta0.3Co61.7Cu21.7, and Ce14.3Ta1.0Co62.0Fe12.3Cu10.4. X-ray-diffraction analysis shows that these materials retain a CaCu5 substructure and incorporate small amounts of ...


Equation Of State Of Boron Nitride Combining Computation, Modeling, And Experiment, Shuai Zhang, Amy Lazicki, Burkhard Militzer, Lin H. Yang, Kyle Caspersen, Jim A. Gaffney, Markus W. Däne, John E. Pask, Walter R. Johnson, Abhiraj Sharma, Phanish Suryanarayana, Duane D. Johnson, Andrey V. Smirnov, Philip A. Sterne, David Erskine, Richard A. London, Federica Coppari, Damian Swift, Joseph Nilsen, Art J. Nelson, Heather D. Whitley Jun 2019

Equation Of State Of Boron Nitride Combining Computation, Modeling, And Experiment, Shuai Zhang, Amy Lazicki, Burkhard Militzer, Lin H. Yang, Kyle Caspersen, Jim A. Gaffney, Markus W. Däne, John E. Pask, Walter R. Johnson, Abhiraj Sharma, Phanish Suryanarayana, Duane D. Johnson, Andrey V. Smirnov, Philip A. Sterne, David Erskine, Richard A. London, Federica Coppari, Damian Swift, Joseph Nilsen, Art J. Nelson, Heather D. Whitley

Duane D. Johnson

The equation of state (EOS) of materials at warm dense conditions poses significant challenges to both theory and experiment. We report a combined computational, modeling, and experimental investigation leveraging new theoretical and experimental capabilities to investigate warm-dense boron nitride (BN). The simulation methodologies include path integral Monte Carlo (PIMC), several density functional theory (DFT) molecular dynamics methods [plane-wave pseudopotential, Fermi operator expansion (FOE), and spectral quadrature (SQ)], activity expansion (actex), and all-electron Green's function Korringa-Kohn-Rostoker (mecca), and compute the pressure and internal energy of BN over a broad range of densities and temperatures. Our experiments were conducted at the ...


Single Pair Of Weyl Fermions In The Half-Metallic Semimetal Eucd2as2, Lin-Lin Wang, Na Hyun Jo, Brinda Kuthanazhi, Yun Wu, Robert J. Mcqueeney, Adam Kaminski, Paul C. Canfield Jun 2019

Single Pair Of Weyl Fermions In The Half-Metallic Semimetal Eucd2as2, Lin-Lin Wang, Na Hyun Jo, Brinda Kuthanazhi, Yun Wu, Robert J. Mcqueeney, Adam Kaminski, Paul C. Canfield

Ames Laboratory Accepted Manuscripts

Materials with the ideal case of a single pair of Weyl points (WPs) are highly desirable for elucidating the unique properties of Weyl fermions. EuC d 2 A s 2 is an antiferromagnetic topological insulator or Dirac semimetal depending on the different magnetic configurations. Using first-principles band-structure calculations, we show that inducing ferromagnetism in EuC d 2 A s 2 can generate a single pair of WPs from splitting the single pair of antiferromagnetic Dirac points due to its half-metallic nature. Analysis with a low-energy effective Hamiltonian shows that a single pair of WPs is obtained in EuC d 2 ...


Interaction Dynamics Between Ferroelectric And Antiferroelectric Domains In A Pbzro3-Based Ceramic, Zhongming Fan, Fei Xue, Goknur Tutuncu, Long-Qing Chen, Xiaoli Tan Jun 2019

Interaction Dynamics Between Ferroelectric And Antiferroelectric Domains In A Pbzro3-Based Ceramic, Zhongming Fan, Fei Xue, Goknur Tutuncu, Long-Qing Chen, Xiaoli Tan

Materials Science and Engineering Publications

The antiferroelectric-ferroelectric phase transition in PbZrO3-based oxides is of both fundamental and practical importance. In ceramics in which such a transition readily occurs, the antiferroelectric and the ferroelectric phases often coexist in individual grains with a coherent interphase interface. In this work, the electric biasing in situ transmission electron microscopy technique is employed to directly observe a unique microstructural dynamic when ferroelectric and antiferroelectric domains are driven by a moderate electric field to interact. It is found that, under monotonic loading, the ferroelectric domain grows until it is blocked by the ferroelectric-antiferroelectric interface. At the same time, a kink is ...


Ultrahigh Elastically Compressible And Strain-Engineerable Intermetallic Compounds Under Uniaxial Mechanical Loading, Gyuho Song, Vladislav Borisov, William Meier, Mingyu Xu, Keith J. Dusoe, John T. Sypek, Roser Valentí, Paul C. Canfield, Seok-Woo Lee Jun 2019

Ultrahigh Elastically Compressible And Strain-Engineerable Intermetallic Compounds Under Uniaxial Mechanical Loading, Gyuho Song, Vladislav Borisov, William Meier, Mingyu Xu, Keith J. Dusoe, John T. Sypek, Roser Valentí, Paul C. Canfield, Seok-Woo Lee

Ames Laboratory Accepted Manuscripts

Intermetallic compounds possess unique atomic arrangements that often lead to exceptional material properties, but their extreme brittleness usually causes fracture at a limited strain of less than 1% and prevents their practical use. Therefore, it is critical for them to exhibit either plasticity or some form of structural transition to absorb and release a sufficient amount of mechanical energy before failure occurs. This study reports that the ThCr2Si2-structured intermetallic compound (CaFe2As2) and a hybrid of its structure (CaKFe4As4) with 2 µm in diameter and 6 µm in height can exhibit superelasticity with strain up to 17% through a reversible, deformation-induced ...


Revealing The Nature Of Antiferroquadrupolar Ordering In Cerium Hexaboride: Ceb6, C. K. Barman, Prashant Singh, Duane Johnson, Aftab Alam Jun 2019

Revealing The Nature Of Antiferroquadrupolar Ordering In Cerium Hexaboride: Ceb6, C. K. Barman, Prashant Singh, Duane Johnson, Aftab Alam

Duane D. Johnson

The cerium hexaboride (CeB6) f-electron compound displays a rich array of low-temperature magnetic phenomena, including a “magnetically hidden” order, identified as multipolar in origin via advanced x-ray scattering. From first-principles electronic-structure results, we find that the antiferroquadrupolar(AFQ) ordering in CeB6 arises from crystal-field splitting and yields a band structure in agreement with experiments. With interactions of p electrons between Ce and B6 being small, the electronic state of CeB6 is suitably described as Ce(4f1)3+(e−)(B6)2−. The AFQ state of orbital spins is caused by an exchange interaction induced through spin-orbit interaction, which also splits the ...


Mechanisms Of Enhanced Thermal Stability Of Polarization In Lead-Free (Bi 1/2na 1/2) 0.94ba 0.06tio 3/Zno Ceramic Composites, Zhongming Fan, Lin Zhou, Tae-Hoon Kim, Ji Zhang, Shan-Tao Zhang, Xiaoli Tan Jun 2019

Mechanisms Of Enhanced Thermal Stability Of Polarization In Lead-Free (Bi 1/2na 1/2) 0.94ba 0.06tio 3/Zno Ceramic Composites, Zhongming Fan, Lin Zhou, Tae-Hoon Kim, Ji Zhang, Shan-Tao Zhang, Xiaoli Tan

Xiaoli Tan

(Bi 1/2Na 1/2)TiO 3-based solid solutions, one of the major systems of lead-free piezoelectric ceramics, exhibit a low thermal depolarization temperature ( T d~100°C). It was reported that by incorporating 30 mol% ZnO particles to form a ceramic composite of (Bi 1/2Na 1/2) 0.94Ba 0.06TiO 3/ZnO, the depolarization process can be shifted up to ~250 °C. In the present work, a variety of advanced transmission electron microscopy techniques, including in situ heating, annular bright-field, high-angle annular dark-field, geometric phase analysis, energy-dispersive spectrum and electron energy-loss spectroscopy, are employed to investigate the ...


Crystal Growth And Magnetic Structure Of Mnbi2 Te 4, J.-Q. Yan, Q. Zhang, T. Heitmann, Zengle Huang, K. Y. Chen, J.-G. Cheng, Weida Wu, David Vaknin, B. C. Sales, Robert J. Mcqueeney Jun 2019

Crystal Growth And Magnetic Structure Of Mnbi2 Te 4, J.-Q. Yan, Q. Zhang, T. Heitmann, Zengle Huang, K. Y. Chen, J.-G. Cheng, Weida Wu, David Vaknin, B. C. Sales, Robert J. Mcqueeney

Ames Laboratory Accepted Manuscripts

Millimeter-sized MnBi2Te4 single crystals are grown out of a Bi-Te flux and characterized using magnetic, transport, scanning tunneling microscopy, and spectroscopy measurements. The magnetic structure of MnBi2Te4 below TN is determined by powder and single-crystal neutron diffraction measurements. Below TN = 24 K, Mn2+ moments order ferromagnetically in the ab plane but antiferromagnetically along the crystallographic c axis. The ordered moment is 4.04(13)μB/Mn at 10 K and aligned along the crystallographic c axis in an A-type antiferromagnetic order. Below TN, the electrical resistivity drops upon cooling or when going across the metamagnetic transition in increasing magnetic fields ...


Thermodynamic Stabilities Of Perfect And Vacancy-Defected Li2 Tio3 (001) Surfaces From First-Principles Analyses, Yan Jiang, Yanli Shi, Xiaogang Xiang, Jianqi Qi, Yong Han, Zhijun Liao, Tiecheng Lu May 2019

Thermodynamic Stabilities Of Perfect And Vacancy-Defected Li2 Tio3 (001) Surfaces From First-Principles Analyses, Yan Jiang, Yanli Shi, Xiaogang Xiang, Jianqi Qi, Yong Han, Zhijun Liao, Tiecheng Lu

Ames Laboratory Accepted Manuscripts

Lithium titanate (Li2TiO3) is an attractive ceramic material for various industrial applications, particularly as one of the most promising breeder blanket materials in future nuclear-fusion reactors. Previously reported studies mainly focus on sintered polycrystalline samples of Li2TiO3. Surface structure of the single-crystal form is rarely reported, although the information of surface structures and stabilities can be critical for further understanding the surface-associated processes. In this work, we perform extensive first-principles density-functional-theory (DFT) calculations to obtain the surface energies of Li2TiO3 (001) with different surface terminations. For four perfect (defect-free) Li-, O-, or LiTi-terminated (001) surfaces, Li- or O-terminated (001) surfaces ...


Electronic Transport Behavior Of Adatom- And Nanoparticle-Decorated Graphene, Jamie Anne Elias May 2019

Electronic Transport Behavior Of Adatom- And Nanoparticle-Decorated Graphene, Jamie Anne Elias

Arts & Sciences Electronic Theses and Dissertations

To induce a non-negligible spin-orbit coupling in monolayer graphene, for the purposes of realizing the Kane-Mele Hamiltonian, transition metal adatoms have been deposited in dilute amounts by thermal evaporation in situ while holding the device temperature near 4K. Electronic transport studies including measurements such as gate voltage dependent conductivity and mobility, weak localization, high field magnetoresistance (Shubnikov de Haas oscillations), quantum Hall, and nonlocal voltage were performed at low temperature before and after sequential evaporations. Studies of tungsten adatoms are consistent with literature regarding other metal adatoms on graphene but were unsuccessful in producing a spin-orbit signature, at least partially ...