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 T//c oxide superconductor EuBa//2Cu//3O//9// minus //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 less than equivalent to 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 T//c with 3d ion concentration over the range (1 - 8%) is also presented.