COMPARATIVE-STUDY OF GLOBAL AND LOCAL MAGNETIZATION MEASUREMENTS ON SINGLE-CRYSTALLINE HIGH-T-C SUPERCONDUCTORS

The mixed state of several (RE)Ba2Cu3O7-delta single crystals (RE = Y, Yb) was investigated by various measuring techniques. Using an 8 T SQU ID magnetometer as a reference, we compare the current densities evalu ated from global magnetization measurements (SQUID, torque and VSM) an d from a local technique (Hall probe array), Taking the specific time scales of the various measurements into consideration, we obtain excel lent agreement at all temperatures from 5 to 77 K. Magneto-optical ima ges of the flux density gradients confirm that the current densities c an be calculated on the basis of an extended Bean model, The establish ed correspondence between global and local techniques is of fundamenta l relevance for future experimental work on the subject. (C) 1998 Else vier Science B,V. All rights reserved.