MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS III: Electron Spin Resonance Studies of Y2Ba1Cu1O5 and Gd2Ba1Cu1O5

The ESR of Cu 2+ and Gd 3+ ion in Y 2 Ba 1 Cu 1 O 5 and Gd 2 Ba 1 Cu 1 O 5 has been studied at temperatures from 4 K to room temperature. Particular emphasis has been paid to the ESR linewidths (∆H PP ) and g-values of the ions. The ∆H PP and g-values for Y 2 Ba 1 Cu 1 O 5 were found to have anomalous increments near 15 K, close to the Néel temperature of Y 2 Ba 1 Cu 1 O 5. Similarly, ∆H PP for Gd 2 Ba 1 Cu 1 O 5 had peaks near 12 K. Our analysis reveals that the ESR signal from Gd 2 Ba 1 Cu 1 O 5 is dominated by the Gd 3+ ESR. However, the magnetic ordering may be caused by both Gd-Gd and Gd-Cu interactions.