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Despite the intense activity in the year since the discovery of superconductivity in MgB2, key parameters, in particular the upper and lower critical fields Hc2 and Hc1 and their anisotropies, are not well-established, largely because of…

Superconductivity · Physics 2009-11-07 G. K. Perkins , J. Moore , Y. Bugoslavsky , L. F. Cohen , J. Jun , S. M. Kazakov , J. Karpinski , A. D. Caplin

We investigated the annealing effects on the physical properties of SrFe$_2$(As$_{1-x}$P$_x$)$_2$ ($x=0.35$). The superconducting transition temperature ($T_c$) increased from 26 K to 33 K by annealing. The X-ray diffraction measurement…

Superconductivity · Physics 2015-06-15 T. Kobayashi , S. Miyasaka , S. Tajima , T. Nakano , Y. Nozue , N. Chikumoto , H. Nakao , R. Kumai , Y. Murakami

Magnetic ions (Mn) were substituted in MgB_2 single crystals resulting in a strong pair-breaking effect. The superconducting transition temperature, T_c, in Mg_{1-x}Mn_xB_2 has been found to be rapidly suppressed at an initial rate of 10…

The review considers bulk MgB2-based materials in terms of their structure, superconducting and mechanical properties. Superconducting transition temperatures of 34.5-39.4 K, critical current densities of 1.8-1.0 x E6 A/sq.cm in self field…

Superconductivity · Physics 2009-12-25 T. A. Prikhna

We studied the influence of sample preparation and defects in the superconducting properties samples using atomic ratios of Mg:B=1:1 and Mg:B=1:2. Samples were characterized by SEM, and XRD, and the magnetization properties were examined in…

Single crystals of MgB2 and Mg(B1-xCx)2 have been grown using cubic anvil technique. Tc values vary in a wide range (39-9 K) with carbon content varying from 0 up to 16%. Using SiC as the precursor leads to C and not to Si substituted…

Superconductivity · Physics 2016-08-31 S. M. Kazakov , J. Karpinski , J. Jun , P. Geiser , N. D. Zhigadlo , R. Puzniak , A. V. Mironov

The effect of annealing at room temperature on the fluctuation conductivity (FLC) $\sigma^\prime(T)$ and pseudogap (PG) $\Delta^*(T)$ in the basal ab plane of $ReBa_2Cu_3O_{7-\delta}$ (Re = Ho) single crystals with a lack of oxygen has been…

Annealing Mg-implanted homoepitaxial GaN at temperatures at or above 1400 {\deg}C eliminates the formation of inversion domains and leads to improved dopant activation efficiency. Extended defects in the form of inversion domains contain…

The anisotropy gamma of the superconducting state of high quality single-crystals of MgB2 was determined, using torque magnetometry with two different methods. The anisotropy of the upper critical field was found to be temperature…

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

The angular and temperature dependence of the upper critical field Hc2 in MgB2 was determined from torque magnetometry measurements on single crystals. The Hc2 anisotropy gamma_H was found to decrease with increasing temperature, in…

Superconductivity · Physics 2009-11-07 M. Angst , R. Puzniak , A. Wisniewski , J. Roos , H. Keller , P. Miranovic , J. Jun , S. M. Kazakov , J. Karpinski

We have performed a systematic study of the evolution of the superconducting and normal state properties of neutron irradiated MgB$_2$ wire segments as a function of fluence and post exposure annealing temperature and time. All fluences…

Superconductivity · Physics 2009-11-11 R. H. T. Wilke , S. L. Bud'ko , P. C. Canfield , J. Famer , S. T. Hannahs

The dependence of Tc for MgB2 on purely hydrostatic or nearly hydrostatic pressure has been determined to 23 GPa for single-crystalline and to 32 GPa for polycrystalline samples, and found to be in good agreement. Tc decreases from 39 K at…

We report on study of the electronic anisotropy of the newly discovered MgB2 superconductor using the in-plane resistivity measurements in magnetic field applied perpendicular and parallel to Mg and B planes of MgB2 single crystals. The…

Superconductivity · Physics 2009-11-07 Yu. Eltsev , S. Lee , K. Nakao , N. Chikumoto , S. Tajima , N. Koshizuka , M. Murakami

The dependence of Tc on nearly hydrostatic pressure has been measured for an isotopically pure (11B) MgB2 sample in a helium-loaded diamond-anvil-cell to nearly 20 GPa. Tc decreases monotonically with pressure from 39.1 K at ambient…

Superconductivity · Physics 2009-11-07 S. Deemyad , J. S. Schilling , J. D. Jorgensen , D. G. Hinks

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 recently discovered superconductivity in MgB2 has created the world sensation. In spite of the relatively high superconducting transition temperature Tc=39K, the superconductivity is understood in terms of rare two gap superconductor…

Superconductivity · Physics 2007-05-23 T. Dahm , A. I. Posazhennikova , K. Maki

The electrical resistivity $\rho$ and upper critical field $H_{c2}$ were measured in MgB$_2$ disordered by nuclear reactor neutrons. We found that superconducting temperature $T_c$ decreases under irradiation from 40 to 5 K. Despite strong…

Far-infrared reflectivity studies on the polycrystalline intermetallic compound MgB_2 with a superconducting transition temperature T_c=39 K were performed at temperatures 20 K to 300 K. We observe a significant raise of the…

We have studied the evolution of superconducting and normal state properties of neutron irradiated Mg(B$_{.962}$C$_{.038}$)$_2$ wire segments as a function of post exposure annealing time and temperature. The initial fluence fully…

We present the results of measurements of the thermal and electrical conductivity in the basal plane of single-crystalline MgB_2 between 2 and 300 K. The analysis of the temperature dependence of the thermal conductivity gives supporting…

Superconductivity · Physics 2007-05-23 A. V. Sologubenko , J. Jun , S. M. Kazakov , J. Karpinski , H. R. Ott