Electron paramagnetic resonance of Gd3+ ions in the superconductor GdBa2Cu3Ox

EPR from Gd3+ ions in the high-Tc90 K superconductor GdBa2Cu3Ox is reported. The temperature dependence of the linewidth and intensity of the Gd3+ ions in the vicinity of Tc are related to the corresponding characteristics of the Cu2+ ions. © 1987 The American Physical Society.