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Full-Text Articles in Physics

Competing Magnetic Phases And Itinerant Magnetic Frustration In Srco2 As2, Bing Li, Benjamin G. Ueland, W. T. Jayasekara, D. L. Abernathy, N. S. Sangeetha, David C. Johnston, Qing-Ping Ding, Yuji Furukawa, Peter P. Orth, Andreas Kreyssig, Alan I. Goldman, Robert J. Mcqueeney Aug 2019

Competing Magnetic Phases And Itinerant Magnetic Frustration In Srco2 As2, Bing Li, Benjamin G. Ueland, W. T. Jayasekara, D. L. Abernathy, N. S. Sangeetha, David C. Johnston, Qing-Ping Ding, Yuji Furukawa, Peter P. Orth, Andreas Kreyssig, Alan I. Goldman, Robert J. Mcqueeney

Ames Laboratory Accepted Manuscripts

Whereas magnetic frustration is typically associated with local-moment magnets in special geometric arrangements, here we show that SrCo2As2 is a candidate for frustrated itinerant magnetism. Using inelastic neutron scattering (INS), we find that antiferromagnetic (AF) spin fluctuations develop in the square Co layers of SrCo2As2 below T approximate to 100 K centered at the stripe-type AF propagation vector of (1/2, 1/2), and that their development is concomitant with a suppression of the uniform magnetic susceptibility determined via magnetization measurements. We interpret this switch in spectral weight as signaling a temperature-induced crossover from an instability toward ferromagnetism ordering to ...


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 ...


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 ...


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 ...


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 ...


Intelligent Metasurfaces With Continuously Tunable Local Surface Impedance For Multiple Reconfigurable Functions, Fu Liu, Odysseas Tsilipakos, Alexandros Pitilakis, Anna C. Tasolamprou, Mohammad Sajjad Mirmoosa, Nikolaos V. Kantartzis, Do-Hoon Kwon, Maria Kafesaki, Costas M. Soukoulis, Sergei A. Tretyakov Apr 2019

Intelligent Metasurfaces With Continuously Tunable Local Surface Impedance For Multiple Reconfigurable Functions, Fu Liu, Odysseas Tsilipakos, Alexandros Pitilakis, Anna C. Tasolamprou, Mohammad Sajjad Mirmoosa, Nikolaos V. Kantartzis, Do-Hoon Kwon, Maria Kafesaki, Costas M. Soukoulis, Sergei A. Tretyakov

Ames Laboratory Accepted Manuscripts

Electromagnetic metasurfaces can be characterized as intelligent if they are able to perform multiple tunable functions, with the desired response being controlled by a computer influencing the individual electromagnetic properties of each metasurface inclusion. In this paper, we present an example of an intelligent metasurface that operates in the reflection mode in the microwave frequency range. We numerically show that, without changing the main body of the metasurface, we can achieve tunable perfect absorption and tunable anomalous reflection. The tunability features can be implemented using mixed-signal integrated circuits (ICs), which can independently vary both the resistance and reactance, offering complete ...


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 Apr 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

Ames Laboratory Accepted Manuscripts

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 ...


Connection Between Mott Physics And Crystal Structure In A Series Of Transition Metal Binary Compounds, Nicola Lanatà, Tsung-Han Lee, Yong-Xin Yao, Vladan Stevanović, Vladimir Dobrosavljević Mar 2019

Connection Between Mott Physics And Crystal Structure In A Series Of Transition Metal Binary Compounds, Nicola Lanatà, Tsung-Han Lee, Yong-Xin Yao, Vladan Stevanović, Vladimir Dobrosavljević

Ames Laboratory Accepted Manuscripts

The choice that a solid system “makes” when adopting a crystal structure (stable or metastable) is ultimately governed by the interactions between electrons forming chemical bonds. Here we analyze six prototypical binary transition metal compounds and shed light on the connection between Mott physics and the behavior of the energy as a function of the spatial arrangement of the atoms in these systems. Remarkably, we find that the main qualitative features of this complex behavior in the Mott phase of these systems can be traced back to the fact that the strong d-electron correlations influence substantially the charge transfer ...


From Tb3ni2 To Tb3coni: The Interplay Between Chemistry, Structure, And Magnetism, Clemens Ritter, Alessia Provino, Francois Fauth, Sudesh K. Dhar, Vitalij K. Pecharsky, Pietro Manfrinetti Feb 2019

From Tb3ni2 To Tb3coni: The Interplay Between Chemistry, Structure, And Magnetism, Clemens Ritter, Alessia Provino, Francois Fauth, Sudesh K. Dhar, Vitalij K. Pecharsky, Pietro Manfrinetti

Ames Laboratory Accepted Manuscripts

Formation, crystal structure, and macroscopic and microscopic magnetism of the binary Tb3Ni2 and derivative pseudobinary Tb3CoxNi2−x phases have been investigated using an array of experimental methods. While Tb3Ni2 crystallizes in the monoclinic Dy3Ni2 structure type (mS20, C2/m), the substitution of Co for Ni results in a structural transition into the rhombohedral Er3Ni2 type (hR45, R¯3h) at x(Co)≈0.34 and beyond in the Tb3CoxNi2−x system. In both the monoclinic and rhombohedral phases, the addition of Co leads to an anisotropic change of lattice parameters and unexpected reduction of the cell volume. Measurements of bulk properties ...


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

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

Ames Laboratory Accepted Manuscripts

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 ...


Effects Of Dopants On The Glass Forming Ability In Al-Based Metallic Alloy, Yang Sun, Feng Zhang, Lin Yang, Huajing Song, Mikhail I. Mendelev, Cai-Zhuang Wang, Kai-Ming Ho Feb 2019

Effects Of Dopants On The Glass Forming Ability In Al-Based Metallic Alloy, Yang Sun, Feng Zhang, Lin Yang, Huajing Song, Mikhail I. Mendelev, Cai-Zhuang Wang, Kai-Ming Ho

Ames Laboratory Accepted Manuscripts

The effect of dopants on the metallic glass forming ability is usually considered based on the analysis of changes in the liquid structure or thermodynamics. What is missing in such considerations is an analysis of how a dopant changes the properties of the crystal phases which can form instead of the glass. In order to illuminate this aspect we performed molecular dynamics simulations to study the effects of Mg and Sm dopants on the crystal nucleation in Al. The simulation data were found to be consistent with the experimental observations that addition of Mg to Al does not lead to ...


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 Feb 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

Ames Laboratory Accepted Manuscripts

(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 ...


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 Jan 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

Ames Laboratory Accepted Manuscripts

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 ...


Nonlinearity In The Dark: Broadband Terahertz Generation With Extremely High Efficiency, Ming Fang, Nian-Hai Shen, Wei E. I. Sha, Zhixiang Huang, Thomas Koschny, Costas M. Soukoulis Jan 2019

Nonlinearity In The Dark: Broadband Terahertz Generation With Extremely High Efficiency, Ming Fang, Nian-Hai Shen, Wei E. I. Sha, Zhixiang Huang, Thomas Koschny, Costas M. Soukoulis

Ames Laboratory Accepted Manuscripts

Plasmonic metamaterials and metasurfaces offer new opportunities in developing high performance terahertz emitters and detectors beyond the limitations of conventional nonlinear materials. However, simple meta-atoms for second-order nonlinear applications encounter fundamental trade-offs in the necessary symmetry breaking and local-field enhancement due to radiation damping that is inherent to the operating resonant mode and cannot be controlled separately. Here we present a novel concept that eliminates this restriction obstructing the improvement of terahertz generation efficiency in nonlinear metasurfaces based on metallic nanoresonators. This is achieved by combining a resonant dark-state metasurface, which locally drives nonlinear nanoresonators in the near field, with ...


On Loss Compensation, Amplification And Lasing In Metallic Metamaterials, Sotiris Droulias, Thomas Koschny, Maria Kafesaki, Costas M. Soukoulis Jan 2019

On Loss Compensation, Amplification And Lasing In Metallic Metamaterials, Sotiris Droulias, Thomas Koschny, Maria Kafesaki, Costas M. Soukoulis

Ames Laboratory Accepted Manuscripts

The design of metamaterials, which are artificial materials that can offer unique electromagnetic properties, is based on the excitation of strong resonant modes. Unfortunately, material absorption—mainly due to their metallic parts—can damp their resonances and hinder their operation. Incorporating a gain material can balance these losses, but this must be performed properly, as a reduced or even eliminated absorption does not guarantee loss compensation. Here we examine the possible regimes of interaction of a gain material with a passive metamaterial and show that background amplification and loss compensation are two extreme opposites, both of which can lead to ...


Relaxation Dynamics Of Zero-Field Skyrmions Over A Wide Temperature Range, Licong Peng, Ying Zhang, Liqin Ke, Tae-Hoon Kim, Qiang Zheng, Jiaqiang Yan, X.-G. Zhang, Yang Gao, Shouguo Wang, Jianwang Cai, Baogen Shen, Robert J. Mcqueeney, Adam Kaminski, Matthew J. Kramer, Lin Zhou Nov 2018

Relaxation Dynamics Of Zero-Field Skyrmions Over A Wide Temperature Range, Licong Peng, Ying Zhang, Liqin Ke, Tae-Hoon Kim, Qiang Zheng, Jiaqiang Yan, X.-G. Zhang, Yang Gao, Shouguo Wang, Jianwang Cai, Baogen Shen, Robert J. Mcqueeney, Adam Kaminski, Matthew J. Kramer, Lin Zhou

Ames Laboratory Accepted Manuscripts

The promise of magnetic skyrmions in future spintronic devices hinges on their topologically enhanced stability and the ability to be manipulated by external fields. The technological advantages of nonvolatile zero-field skyrmion lattice (SkL) are significant if their stability and reliability can be demonstrated over a broad temperature range. Here, we study the relaxation dynamics including the evolution and lifetime of zero-field skyrmions generated from field cooling (FC) in an FeGe single-crystal plate via in situ Lorentz transmission electron microscopy (L-TEM). Three types of dynamic switching between zero-field skyrmions and stripes are identified and distinguished. Moreover, the generation and annihilation of ...


Intercalated Rare-Earth Metals Under Graphene On Sic, Nathaniel A. Anderson, Myron Hupalo, David Keavney, Michael C. Tringides, David Vaknin Nov 2018

Intercalated Rare-Earth Metals Under Graphene On Sic, Nathaniel A. Anderson, Myron Hupalo, David Keavney, Michael C. Tringides, David Vaknin

Ames Laboratory Accepted Manuscripts

Intercalation of rare earth metals (RE = Eu, Dy, and Gd) is achieved by depositing the RE metal on graphene that is grown on silicon-carbide (SiC) and by subsequent annealing at high temperatures to promote intercalation. STM images of the films reveal that the graphene layer is defect free and that each of the intercalated metals has a distinct nucleation pattern. Intercalated Eu forms nano-clusters that are situated on the vertices of a Moirè pattern, while Dy and Gd form randomly distributed nano-clusters. X-ray magnetic circular dichroism (XMCD) measurements of intercalated films reveal the magnetic properties of these REs nano-clusters ...


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 Oct 2018

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

Ames Laboratory Accepted Manuscripts

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 ...


Magnetic And Electrocatalytic Properties Of Transition Metal Doped Mos2 Nanocrystals, L. M. Martinez, J. A. Delgado, C. L. Saiz, A. Cosio, Y. Wu, D. Villagran, Kinjal Gandha, C. Karthik, I. C. Nlebedim, S. R. Singamaneni Oct 2018

Magnetic And Electrocatalytic Properties Of Transition Metal Doped Mos2 Nanocrystals, L. M. Martinez, J. A. Delgado, C. L. Saiz, A. Cosio, Y. Wu, D. Villagran, Kinjal Gandha, C. Karthik, I. C. Nlebedim, S. R. Singamaneni

Ames Laboratory Accepted Manuscripts

In this paper, the magnetic and electrocatalytic properties of hydrothermally grown transition metal doped (10% of Co, Ni, Fe, and Mn) 2H-MoS2 nanocrystals (NCs) with a particle size 25–30 nm are reported. The pristine 2H-MoS2 NCs showed a mixture of canted anti-ferromagnetic and ferromagnetic behavior. While Co, Ni, and Fe doped MoS2 NCs revealed room temperature ferromagnetism, Mn doped MoS2 NCs showed room temperature paramagnetism, predominantly. The ground state of all the materials is found to be canted-antiferromagnetic phase. To study electrocatalytic performance for hydrogen evolution reaction, polarization curves were measured for undoped and the doped MoS2 NCs. At ...


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 Oct 2018

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

Ames Laboratory Accepted Manuscripts

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 ...


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 Oct 2018

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

Ames Laboratory Accepted Manuscripts

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 ...


Enhanced Thermoelectric Performance Of Mg2 Si1−X Snx Codoped With Bi And Cr, Vikram, Duane D. Johnson, Aftab Alam Sep 2018

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

Ames Laboratory Accepted Manuscripts

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 ...


All-Solid-State Asymmetric Supercapacitor Based On Porous Cobalt Selenide Thin Films, Xincheng Zhang, Jiangfeng Gong, Kaixiao Zhang, Weihua Zhu, Jing-Chang Li, Qingping Ding Sep 2018

All-Solid-State Asymmetric Supercapacitor Based On Porous Cobalt Selenide Thin Films, Xincheng Zhang, Jiangfeng Gong, Kaixiao Zhang, Weihua Zhu, Jing-Chang Li, Qingping Ding

Ames Laboratory Accepted Manuscripts

As a significant semiconductor material, cobalt selenide has enormous potential and extensive application prospects in the field of solar cells, photocatalysis and supercapacitor. In this paper, porous CoSe thin films were successfully fabricated on stainless-steel sheet using a facile, effective electrodeposition technique. Electrochemical tests reveal that the specific capacitance reaches as high as 510 F g−1 at the current density of 1 A g−1 with the capacitance retention of 91% over 5000 cycles. An asymmetric all-solid-state supercapacitor is fabricated using CoSe thin film as the positive electrode and activate carbon as the negative electrode. The combined solid device ...


Disorder-Driven Transition From S(+/-) To S(+ +) Superconducting Order Parameter In Proton Irradiated Ba(Fe1-Xrhx)(2)As-2 Single Crystals, G. Ghigo, D. Torsello, G. A. Ummarino, L. Gozzelino, Makariy A. Tanatar, Ruslan Prozorov, Paul C. Canfield Sep 2018

Disorder-Driven Transition From S(+/-) To S(+ +) Superconducting Order Parameter In Proton Irradiated Ba(Fe1-Xrhx)(2)As-2 Single Crystals, G. Ghigo, D. Torsello, G. A. Ummarino, L. Gozzelino, Makariy A. Tanatar, Ruslan Prozorov, Paul C. Canfield

Ames Laboratory Accepted Manuscripts

Microwave measurements of the London penetration depth and critical temperature T c were used to show evidence of a disordered-driven transition from s ± to s + + order parameter symmetry in optimally doped Ba ( Fe 1 − x Rh x ) 2 As 2 single crystals, where disorder was induced by means of 3.5 MeV proton irradiation. Signatures of such a transition, as theoretically predicted [V. D. Efremov et al., Phys. Rev. B 84, 180512(R) (2011)], are found as a drop in the low-temperature values of the London penetration depth and a virtually disorder-independent superconducting T c . We show how these experimental ...


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 2018

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

Ames Laboratory Accepted Manuscripts

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.


Finite-Size Effects In Metasurface Lasers Based On Resonant Dark States, Sotiris Droulias, Thomas Koschny, Costas M. Soukoulis Aug 2018

Finite-Size Effects In Metasurface Lasers Based On Resonant Dark States, Sotiris Droulias, Thomas Koschny, Costas M. Soukoulis

Ames Laboratory Accepted Manuscripts

The quest for subwavelength coherent light sources has recently led to the exploration of dark-mode based surface lasers, which allow for independent adjustment of the lasing state and its coherent radiation output. To understand how this unique design performs in real experiments, we need to consider systems of finite size and quantify finite-size effects not present in the infinite dark-mode surface laser model. Here we find that, depending on the size of the system, distinct and even counterintuitive behavior of the lasing state is possible, determined by a balanced competition between multiple loss channels, including dissipation, intentional out-coupling of coherent ...


Magnetic Properties Of Single Crystalline Itinerant Ferromagnet Alfe2b2, Tej Lamichhane, Li Xiang, Qisheng Lin, Tribhuwan Pandey, David S. Parker, Tae-Hoon Kim, Lin Zhou, Matthew J. Kramer, Sergey L. Bud’Ko, Paul C. Canfield Aug 2018

Magnetic Properties Of Single Crystalline Itinerant Ferromagnet Alfe2b2, Tej Lamichhane, Li Xiang, Qisheng Lin, Tribhuwan Pandey, David S. Parker, Tae-Hoon Kim, Lin Zhou, Matthew J. Kramer, Sergey L. Bud’Ko, Paul C. Canfield

Ames Laboratory Accepted Manuscripts

Single crystals of AlFe2B2 have been grown using the self-flux growth method, and then we measured the structural properties, temperature- and field-dependent magnetization, and temperature-dependent electrical resistivity at ambient as well as high pressure. The Curie temperature of AlFe2B2 is determined to be 274 K. The measured saturation magnetization and the effective moment for the paramagnetic Fe ion indicate the itinerant nature of the magnetism with a Rhode-Wohlfarth ratio MCMsat≈1.14. Temperature-dependent resistivity measurements under hydrostatic pressure show that transition temperature TC is suppressed down to 255 K for p=2.24 GPa pressure with a suppression rate of ...


A Review Of Equation-Of-State Models For Inertial Confinement Fusion Materials, J. A. Gaffney, Duane D. Johnson, Andrey Smirnov, Et Al. Aug 2018

A Review Of Equation-Of-State Models For Inertial Confinement Fusion Materials, J. A. Gaffney, Duane D. Johnson, Andrey Smirnov, Et Al.

Ames Laboratory Accepted Manuscripts

Material equation-of-state (EOS) models, generally providing the pressure and internal energy for a given density and temperature, are required to close the equations of hydrodynamics. As a result they are an essential piece of physics used to simulate inertial confinement fusion (ICF) implosions. Historically, EOS models based on different physical/chemical pictures of matter have been developed for ICF relevant materials such as the deuterium (D2) or deuterium-tritium (DT) fuel, as well as candidate ablator materials such as polystyrene (CH), glow-discharge polymer (GDP), beryllium (Be), carbon (C), and boron carbide (B4C). The accuracy of these EOS models can directly affect ...


Structures And Magnetic Properties Of Iron Silicide From Adaptive Genetic Algorithm And First-Principles Calculations, Zejin Yang, Shunqing Wu, Xin Zhao, Manh Cuong Nguyen, Shu Yu, Tongqi Wen, Ling Tang, Fuxiang Li, Kai-Ming Ho, Cai-Zhuang Wang Aug 2018

Structures And Magnetic Properties Of Iron Silicide From Adaptive Genetic Algorithm And First-Principles Calculations, Zejin Yang, Shunqing Wu, Xin Zhao, Manh Cuong Nguyen, Shu Yu, Tongqi Wen, Ling Tang, Fuxiang Li, Kai-Ming Ho, Cai-Zhuang Wang

Ames Laboratory Accepted Manuscripts

We performed a systematic search for low-energy structures of binary iron silicide over a wide range of compositions using the crystal structure prediction method based on adaptive genetic algorithm. 36 structures with formation energies within 50 meV/atom (11 of them are within 20 meV) above the convex hull formed by experimentally known stable structures are predicted. Magnetic properties of these low-energy structures are investigated. Some of these structures can be promising candidates for rare-earth-free permanent magnet.