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We report inelastic light scattering experiments on CaFe_2As_2 in the temperature range of 4 to 290 K. In in-plane polarizations two Raman-active phonon modes are observed at 189 and 211 cm-1, displaying A_1g and B_1g symmetries,…

Superconductivity · Physics 2009-11-13 K. -Y. Choi , D. Wulferding , P. Lemmens , N. Ni , S. L. Bud'ko , P. C. Canfield

In this work we explore the phase diagram of the binary Nb-S system from ambient pressures up to 250 GPa using $ab$ $initio$ evolutionary crystal structure prediction. We find several new stable compositions and phases, especially in the…

Materials Science · Physics 2021-01-13 Roman Lucrezi , Christoph Heil

We present details of synthesis optimization and physical properties of nearly single phase carbon doped MgB2 with a nominal stoichiometry of Mg(B{0.8}C{0.2})2 synthesized from magnesium and boron carbide (B4C) as starting materials. The…

Superconductivity · Physics 2009-11-07 R. A. Ribeiro , S. L. Bud'ko , C. Petrovic , P. C. Canfield

We present x-ray powder diffraction (XRPD) and neutron diffraction measurements on the slightly underdoped iron pnictide superconductor Ba(1-x)K(x)Fe2As2, Tc = 32K. Below the magnetic transition temperature Tm = 70K, both techniques show an…

We synthesized single crystalline and policrystalline MgB_2 under ambient pressures. The single crystals of MgB_2 were of good quality, where the crystal structure refinements were successfully converged with R = 0.020. The specific heat of…

Superconductivity · Physics 2009-11-07 Y. Machida , S. Sasaki , H. Fujii , M. Furuyama , I. Kakeya , K. Kadowaki

It is shown that the transition to the low temperature superconducting state in a 3D metal at high magnetic field is smeared dramatically by thermal fluctuation of the superconducting order parameter. The resulting superconducting-to-normal…

Superconductivity · Physics 2013-05-29 T. Maniv , V. Zhuravlev

Materials with honeycomb lattice structures exhibit unique electronic properties arising from their distinctive atomic arrangements. Their weakly coupled nature facilitates modulation by external stimuli, which leads to a diverse range of…

Magnetotransport properties of GaMnAs single layers and InGaMnAs/InGaAs superlattice structures were investigated at temperatures from 4 K to 300 K and magnetic fields up to 23 T to study the influence of carriers confinement through…

Materials Science · Physics 2007-05-23 C. Hernandez , F. Terki , S. Charar , J. Sadowski , D. Maude , V. Stanciu , P. Svedlindh

Measurements of single crystalline MgB2 with torque magnetometry in fields up to 90 kOe reveal a sharp peak in the irreversible torque at about 0.85 Hc2. In the region between peak onset and maximum, pronounced history effects occur. Angle…

Superconductivity · Physics 2008-11-28 M. Angst , R. Puzniak , A. Wisniewski , J. Jun , S. M. Kazakov , J. Karpinski

A long-standing question for avant-grade data storage technology concerns the nature of the ultrafast photoinduced phase transformations in the wide class of chalcogenide phase-change materials (PCMs). Overall, a comprehensive understanding…

We measured the complex dynamic elastic modulus of MgB2 between 1.3 and 650 K at frequencies included between 5 and 70 kHz. The main purpose of this work is to search for possible lattice instabilities, which could contribute to enhance the…

Superconductivity · Physics 2010-07-23 F. Cordero , R. Cantelli , G. Giunchi , S. Ceresara

Sr3Ir4Sn13 is an interesting compound showing a coexistence of structural phase transition and superconductivity. The structural phase transition at 147 K leads to the formation of a superlattice. We performed optical spectroscopy…

Superconductivity · Physics 2014-07-23 A. F. Fang , X. B. Wang , P. Zheng , N. L. Wang

Measurements of the superconducting transition temperatures for Al-doped, C-doped and neutron-damaged-annealed MgB2 samples under pressure up to ~8 kbar are presented. The dT_c/dP values change systematically with the decrease of the…

Superconductivity · Physics 2009-11-10 S. L. Bud'ko , R. H. T. Wilke , M. Angst , P. C. Canfield

We report investigation of structural phase transitions in technologically important material sodium niobate as a function of temperature on heating over 300-1075 K. Our high resolution powder neutron diffraction data show variety of…

Materials Science · Physics 2015-05-20 S. K. Mishra , R. Mittal , V. Yu. Pomjakushin , S. L. Chaplot

We have measured the Raman spectra of polycrystalline MgB$_{2}$ from 25 {\cm} to 1200 {\cm}. When the temperature was decreased below the superconducting transition temperature $T_c$, we observed a superconductivity-induced redistribution…

Superconductivity · Physics 2016-08-31 X. K. Chen , M. J. Konstantinovic , J. C. Irwin , D. D. Lawrie , J. P. Franck

We present a joint experimental and theoretical study of the superconducting phase of the layered binary silicide BaSi2. Compared with the layered AlB2 structure of graphite or diboride-like superconductors, in the hexagonal structure of…

We present the structural, electronic and superconducting properties of Li2B2 under pressure within the framework of the density functional theory. The structural parameters, electronic band structure, phonon frequency of the E2g phonon…

Superconductivity · Physics 2014-01-08 Edgar Martínez-Guerra , Filiberto Ortíz-Chi , Stefano Curtarolo , Romeo de Coss

The lattice parameters of MgB2 up to pressures of 8 GPa were determined using high-resolution x-ray powder diffraction in a diamond anvil cell. The bulk modulus, B0, was determined to be 151 +-5 GPa. Both experimental and first-principles…

Materials Science · Physics 2019-08-17 T. Vogt , G. Schneider , J. A. Hriljac , G. Yang , J. S. Abell

The system MgxB2 has been investigated to investigate possible nonstoichiometry in MgB2. When synthesized at 850oC, MgB2 is a line compound with a possible Mg vacancy content of about 1%. Small changes in lattice constants as a function of…

Superconductivity · Physics 2009-11-07 D. G. Hinks , J. D. Jorgensen , Hong Zheng , S. Short

Currently, superconductivity in two-dimensional (2D) materials is a hot topic of research owing to their potential technological applications. Here, we report observation of superconductivity in a 2D Nb2C MXene with transition temperature…