ELECTRON SPIN-LATTICE RELAXATION IN OXIDE SUPERCONDUCTORS AND FULLERIDES

Using the original technique of measuring very short spin-lattice rela xation times T-1, the electron-spin relaxation has been investigated i n a number of HTSC materials and related phases. The relaxation of Gd3 + ions in GdBa2Cu3O6+x is shown to be affected by both quasiparticle a nd antiferromagnetic fluctuations, the latter being increased at lower oxigen content. The pseudo-spin gap of about 200 K is found for both contributions. For Cu2+ EPR in YBaCuO, the T-1 values reveal several t ypes of paramagnetic centers including the ''green phase'' Y2BaCuO5. I n the fulleride RbC50, the measuring of T-1 and T-2 yielded additional support for ID conductivity and allowed to monitor the metal-insulato r phase.