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A series of doping experiments are reported for MgB2 conductors that have been synthesized using doped boron fibers prepared by chemical vapor deposition(CVD) methods. Undoped MgB2 samples prepared from CVD prepared fibers consistently give…

MgB2 thin films were deposited using Pulsed Laser Deposition (PLD) and ex-situ annealing in Mg atmosphere. The films presented critical temperatures up to 36K and turned out to be preferentially c-oriented both on Al2O3 (r-cut) and MgO(100)…

We report the fabrication of MgB2 with bulk superconducting properties by conventional solid state methods at temperatures as low as 550 C. Mg deficiencies of the type Mg1-xB2 were tested. Tc was found to decrease by about 1K at large x,…

Superconductivity · Physics 2009-11-07 N. Rogado , M. A. Hayward , K. A. Regan , Yayu Wang , N. P. Ong , John M. Rowell , R. J. Cava

The recent discovery of intermediate-temperature superconductivity (ITC) in MgB2 by Akimitsu et al. and its almost simultaneous explanation in terms of a hole-carrier-based pairing mechanism by Hirsch, has triggered an avalanche of studies…

Superconductivity · Physics 2009-11-07 S. X. Dou , X. L. Wang , J. Horvat , D. Milliken , E. W. Collings , M. D. Sumption

In the present paper we report an in-situ high-energy X-ray diffraction analysis of MgB2 tapes during the preparation process. The experiment was performed in a specifically designed furnace working in reducing atmosphere, compatible with…

High energy milling of MgB2 pre-reacted powder renders the material largely amorphous through extreme mechanical deformation and is suitable for mechanically alloying MgB2 with dopants including carbon. Bulk samples of milled C and MgB2…

Superconductivity · Physics 2009-11-10 B. J. Senkowicz , J. E. Giencke , S. Patnaik , C. B. Eom , E. E. Hellstrom , D. C. Larbalestier

In high-quality c-axis-oriented MgB2 thin films, we observed high critical current densities (Jc) of 16 MA/cm^2 at 15 K under self fields comparable to those of cuprate high-temperature superconductors. The extrapolated value of Jc at 5 K…

Superconductivity · Physics 2009-11-07 Hyeong-Jin Kim , W. N. Kang , Eun-Mi Choi , Mun-Seog Kim , Kijoon H. P. Kim , Sung-Ik Lee

An extended magneto-optical (MO) analysis of samples cut from high-density pellets of MgB2 is reported. For sake of comparison some magnetic measurements and critical values are also shown. Notwithstanding the fact that the optical and SEM…

Fine grained polycrystalline samples of MgB(2) superconductor were synthesized from the elements to contain < 5 % of impurity phases, according to X-ray powder diffractometry. The superconductive transition was sharp with a midpoint Tc =…

Superconductivity · Physics 2007-05-23 J. R. Thompson , M. Paranthaman , D. K. Christen , K. D. Sorge , H. J. Kim , J. G. Ossandon

This paper presents a brief review on the reported anisotropic properties of MgB2, in the superconducting state (e.g. upper critical field Hc2, field penetration depth, coherence length, energy gap) as well as in the normal state (e.g.,…

Superconductivity · Physics 2007-05-23 O. F. de Lima

We report the study of the polycrystalline MgB2 phase formation during the fabrication processes. Three major phases are identified in different sintering temperature ranges according to the corresponding superconducting properties and the…

Condensed Matter · Physics 2009-11-10 Qing-rong Feng , Chinping Chen , Jun Xu , Ling-wen Kong , Xiu Chen , Yong-zhong Wang , Zheng-xiang Gao

Fe-sheathed MgB2 tapes were prepared through the in situ powder-in-tube technique by 5 at.% ZrSi2, ZrB2 and WSi2 doping, respectively. The doping effect of these compounds on the microstructure and superconducting properties of MgB2 tapes…

Superconductivity · Physics 2009-11-10 Yanwei Ma , H. Kumakura , A. Matsumoto , H. Hatakeyama , K. Togano

Magnetization studies have been carried out on superconducting MgB$_2$ (T$_c$=37K) in the temperature range of 2-50K and in magnetic field up to 5 Tesla. From these measurements, values of the lower critical field H$_c1$(0), upper critical…

Superconductivity · Physics 2007-05-23 Amish G. Joshi , C. G. S. Pillai , P. Raj , S. K. Malik

We present the results of a spectroscopic study of state-of-the-art MgB2 single crystals, carried out by using a modified point-contact technique. The use of single crystals allowed us to obtain point contacts with current injection either…

Superconductivity · Physics 2009-11-07 D. Daghero , R. S. Gonnelli , G. A. Ummarino , V. A. Stepanov , J. Jun , S. M. Kazakov , J. Karpinski

Bulk samples of MgB2 have been formed by hot isostatic pressing (HIPping) of commercial powder at 100MPa and 950=B0C. The resulting material is 100% dense with a sharp superconducting transition at 37.5K. Microstructural studies have…

Superconductivity · Physics 2009-11-07 T C Shields , K Kawano , D Holdom , J S Abell

We succeeded in the synthesis of high-Jc MgB2 bulks via high energy ball-milling of elemental Mg and B powder at ambient temperatures. Alternatively to longtime mechanical alloying technique, the mixed powder was ball-milled for only 1h and…

Superconductivity · Physics 2008-01-14 Y. F. Wu , Y. Feng , G. Yan , J. S. Li , H. P. Tang , S. K. Chen , Y. Zhao , M. H. Pu , H. L. Xu , C. S. Li , Y. F. Lu

Single crystals of MgB2 have been grown at high pressure via the peritectic decomposition of MgNB9. The crystals are of a size up to 1.5x0.9x0.2 mm3 with a weight up to 0.23 mg, and typically have transition temperatures between 37 and 39…

Superconductivity · Physics 2009-11-10 J. Karpinski , S. M. Kazakov , J. Jun , M. Angst , R. Puzniak , A. Wisniewski , P. Bordet

X-ray diffraction, transmission electron microscopy, and magnetization measurements are employed to study the structural and magnetic properties of Mn-rich (Mn,Ga)As nanocrystals embedded in GaAs. These nanocomposites are obtained by…

We prepared and characterized monofilamentary MgB2 wires with a mechanically reinforced composite sheath of Ta(Nb)/Cu/steel, which leads to dense filaments and correspondingly high transport currents up to Jc = 10^5 A/cm^2 at 4.2 K, self…

Superconductivity · Physics 2009-11-07 W. Goldacker , S. I. Schlachter , S. Zimmer , H. Reiner

We report on the superconducting performance of the ex-situ SiC doped MgB2 monofilamentary tapes. Polycrystalline powders of MgB2 doped with 5 and 10 wt% SiC were synthesized by conventional solid-state reaction route and characterized for…

Superconductivity · Physics 2014-05-19 Gennaro Romano , Arpita Vajpayee , Maurizio Vignolo , V. P. S. Awana , Carlo Frederghini
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