Magnetization experiments around T-c in cuprate superconductors: thermal fluctuation, random orientation and inhomogeneity effects

We present some measurements of the crossing point of the excess magnetizat ion vs. temperature curves, (Delta M*, T*), and of the Meissner fraction, c hi(FC)(T), in granular La1.9Sr0.1CuO4 (LaSCO) samples, before and after gra in alignment. These results show that once Delta M* and chi(FC) are adequat ely and separately corrected for random grain orientation and demagnetizing effects, the remaining extrinsic effects on Delta M-ab* (associated with s tructural and, mainly, stoichiometric inhomogeneities) may be taken into ac count through chi(ab)(FC)(T*). The intrinsic Delta M-ab* values agree with the predictions based on thermal fluctuations of pancakes. (C) 2000 Elsevie r Science B.V. All rights reserved.