Author/Authors :
Wosnitza، نويسنده , , J. and Wanka، نويسنده , , S. and Beckmann، نويسنده , , D. and Hagel، نويسنده , , J. and Balthes، نويسنده , , E. and Schweitzer، نويسنده , , D. and Strunz، نويسنده , , W. and Keller، نويسنده , , H.J.، نويسنده ,
Abstract :
We present dc-magnetization and ac-susceptibility measurements of the organic superconductors κ-(ET)2X with X = I3, Cu(NCS)2, and Cu[N(CN)2]Br. For all investigated materials the lower critical field perpendicular to the highly conducting planes, Bcl⊥, tends to zero already 0.5 K below Tc. This might be an indication for fluctuation effects of single vortices expected for 2D superconductors. Pinning effects lead to an apparent increase of Bcl towards lower temperatures and they play an important role for the temperature and frequency dependence of the irreversibility field Birr determined by ac-susceptibility.
