Electron paramagnetic resonance, electrical resistivity, and magnetization studies in the high Tc superconductors EuBa2Cu3O9-x and EuBa2 (Cu1-yMy)3O9-x (M = Cr, Mn, Fe, Co, Ni, OR Zn)

We have measured electron paramagnetic resonance (EPR), electrical resistivity, and dc magnetic susceptibility from 2 K - 300 K for the high Tc oxide superconductor EuBa2Cu3O9-x, either undoped or doped with 3d ions (Cr, Mn, Fe, Ni, Co, or Zn), which presumably substitute at the Cu sites. We have observed an EPR line at low temperatures (T ≤ 40 K), which exhibits an increase in intensity and decrease in field for resonance as the temperature is lowered. The EPR linewidth is also temperature dependent and exhibits a minimum at about 15 K. In some of the samples another EPR signal is observed over the entire temperature range studied, with properties that depend on sample preparation conditions. This signal is likely to be due to small amounts of an additional phase. The behavior and origin of these EPR signals are discussed. The variation of Tc with 3d ion concentration over the range (1 - 8%) is also presented. © 1987