Anisotropy and internal field distribution of MgB2 in the mixed state at low temperatures

摘要

Magnetization and muon spin relaxation on MgB2 were measured as a function offield at 2 K. Both indicate an inverse-squared penetration depth stronglydecreasing with increasing field H below about 1 T. Magnetization also suggeststhe anisotropy of the penetration depth to increase with increasing H,interpolating between a low Hc1 and a high Hc2 anisotropy. Torque vs anglemeasurements are in agreement with this finding, while also ruling out drasticdifferences between the mixed state anisotropies of the two basic length scalespenetration depth and coherence length.