%0 Journal Article
%T Thermodynamic and Transport Properties of Superconducting $Mg^{10}B_2$
%A D. K. Finnemore
%A J. E. Ostenson
%A S. L. Bud'ko
%A G. Lapertot
%A P. C. Canfield
%J Physics
%D 2001
%I arXiv
%R 10.1103/PhysRevLett.86.2420
%X Transport and thermodynamic properties of a sintered pellet of the newly discovered $MgB_2$ superconductor have been measured to determine the characteristic critical magnetic fields and critical current densities. Both resistive transition and magnetization data give similar values of the upper critical field, $H_{c2}$, with magnetization data giving $dH_{c2}/dT=0.44~T/K$ at the transition temperature of $T_c=40.2 K$. Close to the transition temperature, magnetization curves are thermodynamically reversible, but at low temperatures the trapped flux can be on the order of one Tesla. The value of $dH_c/dT$ at $T_c$ is estimated to be about $12~mT/K$, a value similar to classical superconductors like Sn. Hence, the Ginsburg-Landau parameter $\kappa \sim 26$. Estimates of the critical supercurrent density, $J_c$, using hysteresis loops and the Bean model give critical current densities on the order of $10^5~A/cm^2$. Hence the supercurrent coupling through the grain boundaries is comparable to intermetallics like $Nb_3Sn$.
%U http://arxiv.org/abs/cond-mat/0102114v1