Studies on the Anisotropic Properties of MgB2

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., magnetoresistance, compressibility, thermal expansion). So far, the reported results have been obtained using aligned crystallites, c-axis oriented thin films and sub-millimeter crystals. Since impurity scattering affects directly the gap anisotropy it could be one of the main reasons for the different values observed in the Hc2 anisotropy ratio, ranging between 1.3 and 2.6.