CROSSING POINT OF THE MAGNETIZATION IN HIGH-TEMPERATURE SUPERCONDUCTORS

The magnetisation curves M(H,T) of the most anisotropic high temperatu re superconductors cross in a single point M(T*), independently of th e magnetic field H that is applied perpendicular to the superconductin g planes. This property may be very generally derived from the singula r part of the free energy of a two-dimensional (2D) superconductor wit h fluctuations at T-c. Correspondingly, three-dimensional (3D) superco nductors have a crossing point in the quantity M/H(1/2)at T-c, with an amplitude proportional to the anisotropy ratio gamma=(m(c)/m(ab))(1/2 ). (C) 1998 Elsevier Science B.V.