VANISHINGLY SMALL MAKI-THOMPSON SUPERCONDUCTING FLUCTUATION IN THE MAGNETORESISTANCE OF HIGH-T-C SUPERCONDUCTORS

The magnetoresistance (MR) of high-T-c cuprate superconductors (HTSC's ) is Studied. We have shown that the Zeeman term of the Maki-Thompson (MT) process could not be detected in the longitudinal MR of 90 K YBCO crystals. We show here that the MT process is thought to be also negl igible in the transverse MR of 90 K and Zn-doped YBCO crystals. The MR , which has been assigned previously to a MT-orbital process, is more naturally understood as normal-state orbital MR that is proportional t o the square of the Hall angle. We conclude that the MT-fluctuation is vanishingly small, at least above T-c, in these HTSC's. In addition t o the Hall measurements, MR measurements also support the hypothesis o f two distinct relaxation times in HTSC's.