Relaxation effects in high T_csuperconductors

The relaxation of the isothermal d.c. magnetization M in zero-field cooled Ba-La-Cu-O and Sr-La-Cu-O specimens has been investigated at temperatures T ⋘ Tcin magnetic fields 0 ≤ H < 400 Oe. The results show that the value of ôM changes logarithmically with time following the law M lm (t/t0) with great accuracy over an observation time of 50 000 s. At H = 0, the relaxation rate of the remanent magnetization ôM/ô ln t increases with temperature and with the third power of the field to which the specimen has been previously cycled. © 1988 IOP Publishing Ltd.