The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform

Carmine Ortix - One of the best experts on this subject based on the ideXlab platform.

  • topological semimetals in the snte material class nodal lines and weyl points
    Physical Review Letters, 2019
    Co-Authors: Alexander Lau, Carmine Ortix
    Abstract:

    We theoretically show that IV-VI semiconducting compounds with low-temperature Rhombohedral Crystal structure represent a new potential platform for topological semimetals. By means of minimal k·p models, we find that the two-step structural symmetry reduction of the high-temperature rocksalt Crystal structure, comprising a Rhombohedral distortion along the [111] direction followed by a relative shift of the cation and anion sublattices, gives rise to topologically protected Weyl semimetal and nodal line semimetal phases. We derive general expressions for the nodal features and apply our results to SnTe, showing explicitly how Weyl points and nodal lines emerge in this system. Experimentally, the topological semimetals could potentially be realized in the low-temperature ferroelectric phase of SnTe, GeTe, and related alloys.

Christopher S. Lynch - One of the best experts on this subject based on the ideXlab platform.

  • A Model for Simulating Polarization Switching and AF-F Phase Changes in Ferroelectric Ceramics
    Journal of Intelligent Material Systems and Structures, 1998
    Co-Authors: Wei Chen, Christopher S. Lynch
    Abstract:

    A computational micromechanics model for polyCrystalline ferroelectric ceramics developed by Chen and Lynch (1997) is modified and applied to the simulation of ferroelectric and ferroelastic switching of the tetragonal and the Rhombohedral Crystal structures, and to antiferroelectric to ferroelectric phase changes. Interactions between different grains in the ceramic are considered. Two switching criteria are used, one for ferroelectric switching and one or phase changes. Experimental results for both types of materials are simulated.

  • A micro-electro-mechanical model for polarization switching of ferroelectric materials
    Acta Materialia, 1998
    Co-Authors: Wei Chen, Christopher S. Lynch
    Abstract:

    Abstract Ferroelectric and ferroelastic switching are the major source of nonlinearity and hysteresis in ferroelectric materials subjected to high electric field or mechanical stress. A computational micromechanics model for polyCrystalline ferroelectric ceramics is developed based on consideration of the constitutive behavior of single Crystals. This model simulates the tetragonal and the Rhombohedral Crystal structures. Saturation of the linear piezoelectric effect is included. Interaction between different grains in the polyCrystalline ceramic is considered. A switching criterion is developed that accounts for different energy levels associated with 90° and 180° switching for the tetragonal structure (or 70.5°, 109.5°, and 180° for the Rhombohedral structure). Experimental results on 8/65/35 PLZT are simulated and a parametric study of the effects of Crystal structure, intergranular interaction, and phase transformation is performed.

1–45. (10) Binnemans, K. Interpretation Of Europium (iii - One of the best experts on this subject based on the ideXlab platform.

  • Striking similarity of ferroelectric aging effect in tetragonal, orthorhombic and Rhombohedral Crystal structures
    Physical Review B - Condensed Matter and Materials Physics, 2008
    Co-Authors: 94 (10). (1) Brajesh, K.; Abebe, M.; Ranjan, R. Structural , 1–11. (2) Khatua, D. K.; Senyshyn, A.; Ranjan, R. Long-p, 2–6. (3) Khatua, D. K.; Kalaskar, A.; Ranjan, R. Tuning, 1–10. (4) Rao, B. N.; Olivi, L.; Sathe, V.; Ranjan, R. E, 1–8. (5) Brajesh, K.; Tanwar, K.; Abebe, M.; Ranjan, R., 1–15. (6) Rao, B. N.; Datta, R.; Chandrashekaran, S. S.;, 1–6. (7) Ranjan, R.; Hackl, R.; Chandra, A.; Schmidbaue, S. J. Environmental Science Performance And Stability In Lead Free Ceramics. Energy Environmenal Sci (8) Zheng, T.; Wu, H.; Yuan, Y.; Lv, X.; Li, Q.; M, 3170–3178. (9) Du, P.; Guo, Y.; Lee, S. H.; Yu, J. S. Broad N, 1–45. (10) Binnemans, K. Interpretation Of Europium (iii
    Abstract:

    A series of Mn-doped alkaline niobate-based and lead zirconic titanate ferroelectrics that possess tetragonal, orthorhombic, and Rhombohedral perovskite structures was fabricated, and the aging behavior of their hysteresis loop and electrostrain was studied. We found that after aging, all the samples showed a similar double hysteresis loop and large recoverable electrostrain behavior, regardless of their Crystal structure and of their ionic species. The striking similarity of the aging effect in different ferroelectric phases suggests that there exists a common physical origin of aging in ferroelectric perovskites. Based on a symmetry-conforming short-range ordering mechanism of point defects, we provided a unified microscopic explanation for the aging effect in the tetragonal, orthorhombic, and Rhombohedral ferroelectrics.

Akhilesh Kumar Singh - One of the best experts on this subject based on the ideXlab platform.

  • Crystallite size strain analysis of nanoCrystalline La0.7Sr0.3MnO3 perovskite by Williamson-Hall plot method
    2018
    Co-Authors: Dinesh Kumar, Narendra Kumar Verma, Chandra Bhal Singh, Akhilesh Kumar Singh
    Abstract:

    The nanoCrystalline Sr-doped LaMnO3 (La0.7Sr0.3MnO3 = LSMO) perovskite manganites having different Crystallite size were synthesized using the nitrate-glycine auto-combustion method. The phase purity of the manganites was checked by X-ray diffraction (XRD) measurement. The XRD patterns of the sample reveal that La0.7S0.3MnO3 Crystallizes into Rhombohedral Crystal structure with space group R-3c. The size-dependence of structural lattice parameters have been investigated with the help of Rietveld refinement. The structural parameters increase as a function of Crystallite size. The Crystallite-size and internal strain as a function of Crystallite-size have been calculated using Williamson-Hall plot.The nanoCrystalline Sr-doped LaMnO3 (La0.7Sr0.3MnO3 = LSMO) perovskite manganites having different Crystallite size were synthesized using the nitrate-glycine auto-combustion method. The phase purity of the manganites was checked by X-ray diffraction (XRD) measurement. The XRD patterns of the sample reveal that La0.7S0.3MnO3 Crystallizes into Rhombohedral Crystal structure with space group R-3c. The size-dependence of structural lattice parameters have been investigated with the help of Rietveld refinement. The structural parameters increase as a function of Crystallite size. The Crystallite-size and internal strain as a function of Crystallite-size have been calculated using Williamson-Hall plot.

  • Synthesis, structural and optical properties of (ALa)(FeMn)O6 (A = Ba and Sr) double perovskites
    2018
    Co-Authors: Dinesh Kumar, V. Sudarshan, Akhilesh Kumar Singh
    Abstract:

    Here, we report structural and optical properties of ALaFeMnO6 (A = Ba and Sr) double perovskite synthesized via auto-combustion followed by calcinations process. Rietveld refinement of structure using x-ray diffraction data reveals that BaLaFeMnO6 Crystallizes into cubic Crystal structure with space group Pm-3m while SrLaFeMnO6 Crystallizes into Rhombohedral Crystal structure having space group R-3c. The absorption spectrum measurement using UV-Vis spectroscopy reveals that these samples are prefect insulator having energy band gap between conduction and valence band of the order of 6 eV.

  • Crystallite size strain analysis of nanoCrystalline La0.7Sr0.3MnO3 perovskite by Williamson-Hall plot method
    2018
    Co-Authors: Dinesh Kumar, Narendra Kumar Verma, Chandra Bhal Singh, Akhilesh Kumar Singh
    Abstract:

    The nanoCrystalline Sr-doped LaMnO3 (La0.7Sr0.3MnO3 = LSMO) perovskite manganites having different Crystallite size were synthesized using the nitrate-glycine auto-combustion method. The phase purity of the manganites was checked by X-ray diffraction (XRD) measurement. The XRD patterns of the sample reveal that La0.7S0.3MnO3 Crystallizes into Rhombohedral Crystal structure with space group R-3c. The size-dependence of structural lattice parameters have been investigated with the help of Rietveld refinement. The structural parameters increase as a function of Crystallite size. The Crystallite-size and internal strain as a function of Crystallite-size have been calculated using Williamson-Hall plot.

Jesús A. Blanco - One of the best experts on this subject based on the ideXlab platform.

  • Exploring the magneto-volume anomalies in Dy2Fe17 with unconventional Rhombohedral Crystal structure
    Acta Materialia, 2013
    Co-Authors: Pablo Álvarez-alonso, Pedro Gorria, Jose Luis Sanchez Llamazares, Gabriel J. Cuello, Inés Puente Orench, Jorge Sánchez Marcos, Gaston Garbarino, Marian Reiffers, Jesús A. Blanco
    Abstract:

    Abstract We have synthesized the Dy 2 Fe 17 alloy with an unconventional Crystal structure ( R 3 ¯ m space group). Neutron powder thermo-diffraction and X-ray powder diffraction under high pressure (up to 15 GPa) show that the Rhombohedral Crystal structure is stable. Likewise, the alloy with the usual hexagonal Crystal structure ( P 6 3 / mmc ), the Rhombohedral variant of Dy 2 Fe 17 compound, exhibits a collinear ferrimagnetic order below the Curie temperature ( T C  ≈ 363 K), with antiparallel mutual alignment of the Dy and Fe sublattices. Additionally, we have observed two distinctive issues related to magneto-volume anomalies: (i) the pressure dependence of the cell volume at room temperature shows the existence of a critical pressure at which the compound is no longer ferrimagnetic; and (ii) the cell volume shows invar-like behaviour in a wide temperature range (2–290 K), with a minimum at T  ≈ 380 K. The spontaneous volume magnetostriction reaches ω S  = 1.6 × 10 −2 at 2 K that decreases to zero at T  ≈ 500 K (≈1.4 T C ), which is associated with the existence of short-range magnetic correlations.

  • NanoCrystalline Pr2Fe17 studied by neutron powder diffraction
    Journal of Physics: Conference Series, 2010
    Co-Authors: Pedro Gorria, Pablo Álvarez-alonso, Jose Luis Sanchez Llamazares, Jorge Sánchez Marcos, Jesús A. Blanco
    Abstract:

    We have used neutron powder diffraction to make a comprehensive study of the Crystal structure in Pr2Fe17 nanoCrystalline compounds. These nanostructured materials have been obtained by high-energy ball milling from an arc-melted bulk polyCrystalline alloy. The Th2Zn17-type Rhombohedral Crystal structure of the starting bulk alloy is maintained after milling for 10 and 20 hours. The studied alloys are ferromagnetic below TC = 286?1 K (bulk) and TC ? 300?20 K (milled). These materials exhibit strong magneto-volume anomalies below TC, such as a negative coefficient of thermal expansion (?V ? -30 ? 10?6 K?1).

  • Crystal structure, magnetocaloric effect and magnetovolume anomalies in nanostructured Pr2Fe17
    Acta Materialia, 2009
    Co-Authors: Pedro Gorria, Pablo Álvarez-alonso, Jose Luis Sanchez Llamazares, Jorge Sánchez Marcos, María José Sanzo Pérez, Jesús A. Blanco
    Abstract:

    Abstract Using high-energy ball milling, nanostructured Pr2Fe17 powders can be obtained from their arc-melted bulk alloys. High-resolution X-ray and neutron powder diffraction experiments reveal that the Th2Zn17-type Rhombohedral Crystal structure is maintained, after milling for 10 h, with almost unchanged values for both Crystalline lattice parameters (Δa; Δc