Effect of DPPH radical adsorption on the superconducting properties of HTSC bismuth ceramics

Measuring the AC susceptibility and registering the ESR spectra of the stab le 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical at 77.3-125 K, we have stu died the effect of the radical on the current properties of the intergranul ar contacts in the superconducting ceramics Bi1.8Pb0.3Sr1.9Ca2.8Cu3.4Oy. Cr itical current in the ceramics is decreased by the magnetic field generated by the radical spin. The effect of the field on the critical current corre sponds to the location of the adsorbed radical at a distance of 56 Angstrom from the superconducting phase. (C) 2000 Published by Elsevier Science B.V .