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Anisotropy of the Upper Critical Field and Critical Current in Single Crystal MgB$_2$

L. Lyard·P. Samuely·P. Szabo·T. Klein·C. Marcenat·L. Paulius·K. H. P. Kim·C. U. Jung·H. -S. Lee·B. Kang·S. Choi·S. -I. Lee·J. Marcus·S. Blanchard·A. G. M. Jansen·U. Welp·G. Karapetrov·W. K. Kwok
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Abstract

We report on specific heat, high magnetic field transport and $ac-$susceptibility measurements on magnesium diboride single crystals. The upper critical field $H_{c2}$ for magnetic fields perpendicular and parallel to the Mg and B planes is presented for the first time in the entire temperature range. A very different temperature dependence has been observed in the two directions which yields to a temperature dependent anisotropy with $Γ\sim$ 5 at low temperatures and about 2 near $T_c$. A peak effect is observed in susceptibility measurements for $H \sim $2 T parallel to the $c-$axis and the critical current density presnts a sharp maximum for $H$ parallel to the ab-plane.

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L. Lyard, P. Samuely, P. Szabo, T. Klein, C. Marcenat, L. Paulius, K. H. P. Kim, C. U. Jung, H. -S. Lee, B. Kang, S. Choi, S. -I. Lee, J. Marcus, S. Blanchard, A. G. M. Jansen, U. Welp, G. Karapetrov, W. K. Kwok. 2002-09-18. Anisotropy of the Upper Critical Field and Critical Current in Single Crystal MgB$_2$. https://doi.org/10.1103/physrevb.66.180502

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