Paramagnetic resonance of Cu2+ ions in the superconductor Y0.2Ba0.8CuOx

A strong paramagnetic resonance signal characteristic of Cu2+ ions in x2-y2 states is observed in the high-Tc 90 K superconductor Y0.2Ba0.8CuOx. The line intensity of the ioniclike signal shows a deviation from Curie behavior at TTc. It is speculated that the phase that is responsible for the signal is an example of an Anderson lattice with an unusually high Kondo temperature. © 1987 The American Physical Society.