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The temperature dependence of the magnetic field distribution in the mixed superconducting phase of randomly oriented MgB$_2$ powder was probed by $% ^{11}$B NMR spectroscopy. Below the temperature of the second critical ($B_{% {c2}}$)…

Superconductivity · Physics 2009-11-07 G. Papavassiliou , M. Pissas , M. Fardis , M. Karayanni , C. Christides

The temperature dependence of the London penetration depth ($\lambda$) and coherence length ($\xi$) has been deduced from Hall probe magnetization measurements in high quality MgB$_2$ single crystals in the two main crystallographic…

Superconductivity · Physics 2009-11-10 L. Lyard , P. Szabo , T. Klein , J. Marcus , C. Marcenat , B. W. Kang , K. H. Kim , H. S. Lee , S. I. Lee

Data on macroscopic superconducting anisotropy of MgB$_2$ are reviewed. The data are described within a weak coupling two-gaps anisotropic s-wave model of superconductivity. The calculated ratio of the upper critical fields…

Superconductivity · Physics 2009-11-07 V. G. Kogan , S. L. Bud'ko

Magnetization and muon spin relaxation on MgB2 were measured as a function of field at 2 K. Both indicate an inverse-squared penetration depth strongly decreasing with increasing field H below about 1 T. Magnetization also suggests the…

We have studied the anisotropy of the London penetration depth, which was obtained from reversible magnetization measurements with the magnetic field both parallel and perpendicular to the c-axis. The anisotropy of the London penetration…

Superconductivity · Physics 2009-11-10 Heon-Jung Kim , Byeongwon Kang , Min-Seok Park , Kyung-Hee Kim , Hyun Sook Lee , Sung-Ik Lee

We report measurements of the temperature dependent anisotropies ($\gamma_\lambda$ and $\gamma_\xi$) of both the London penetration depth $\lambda$ and the upper critical field of MgB$_2$. Data for $\gamma_\lambda=\lambda_c/\lambda_a$ was…

Superconductivity · Physics 2009-11-11 J. D. Fletcher , A. Carrington , O. J. Taylor , S. M. Kazakov , J. Karpinski

We present data on temperature-dependent anisotropy of the upper critical field of MgB$_2$ obtained from the analysis of measurements on high purity, low resistivity polycrystals. The anisotropy decreases in a monotonic fashion with…

Superconductivity · Physics 2009-11-07 Sergey L. Bud'ko , Paul C. Canfield

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

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

The magnetic penetration depth, $\lambda^{-2}(T)$, in the basal plane of a magnesium diboride (MgB$_2$) film was measured using a two-coil mutual inductance technique at 50 kHz. This film has $T_c\simeq 38$ K, $\Delta T_c \leq 1$ K, and…

The bulk upper critical field H_{c2}(T) of superconducting MgB_2 and its anisotropy are established by analyzing experimental data on the temperature and magnetic field dependences of the ab-plane thermal conductivity of a…

Superconductivity · Physics 2009-11-07 A. V. Sologubenko , J. Jun , S. M. Kazakov , J. Karpinski , H. R. Ott

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

In-plane electrical transport properties of MgB2 single crystals grown under high pressure of 4-6 GPa and temperature of 1400-1700oC in Mg-B-N system have been measured. For all specimens we found sharp superconducting transition around…

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

Heat-capacity measurements of a 39 microgramm MgB_2 single crystal in fields up to 14 T and below 3 K allow the determination of the low-temperature linear term of the specific heat, its field dependence and its anisotropy. Our results are…

Superconductivity · Physics 2009-11-07 F. Bouquet , Y. Wang , I. Sheikin , T. Plackowski , A. Junod , S. Lee , S. Tajima

Single crystals of the oxypnictide superconductors SmFeAsO_(0.8)F_(0.2) and NdFeAsO_(0.8)F_(0.2) with T_c in the range of 44 K to 48 K were investigated by torque magnetometry. An analysis of the data in terms of a recently proposed model…

Superconductivity · Physics 2009-03-23 S. Weyeneth , R. Puzniak , N. D. Zhigadlo , S. Katrych , Z. Bukowski , J. Karpinski , H. Keller

The recently discovered superconductivity in MgB2 has captured world attention due to its simple crystal structure and relatively high superconducting transition temperature Tc=39K. It appears to be generally accepted that it is…

Superconductivity · Physics 2009-11-07 A. I. Posazhennikova , T. Dahm , K. Maki

The two-gap structure in the superconducting state of MgB_2 gives rise to unusual thermodynamic properties which depart markedly from the isotropic single-band BCS model, both in their temperature- and field dependence. We report and…

Superconductivity · Physics 2009-11-07 F. Bouquet , Y. Wang , I. Sheikin , P. Toulemonde , M. Eisterer , H. W. Weber , S. Lee , S. Tajima , A. Junod

The superconducting phase diagram of MgB2 was determined from magnetization, magneto-transport and the first single-crystal specific heat measurements. A zero-temperature in-plane coherence length of 8 nm is determined. The superconducting…

Magnesium diboride MgB2 has been an extraordinarily hot research topic since the discovery of superconductivity below 40 K, due to the vast amount of unusual properties originating from the involvement in superconductivity of two sets of…

Superconductivity · Physics 2007-05-23 M. Angst , R. Puzniak

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
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