Penetration depth and anisotropy inMgB2

Abstract

The penetration depth $\lambda$ of ${\mathrm{MgB}}_2$ was deduced from both the ac susceptibility $\chi$ and the magnetization $M\left(H\right)\mathrm{}$ of sorted powders. The good agreement between the two sets of data without geometric correction for the grain orientation suggests that ${\mathrm{MgB}}_2$ is an isotropic superconductor.