MOSSBAUER STUDY OF YBA2(CU1-XFEX)3O7-DELTA - SUPERCONDUCTIVITY AND MAGNETIC ORDER

The electronic and magnetic properties of the ceramic superconductor YBa//2(Cu//1// minus //xFe//x)//3O//7// minus //67 with x equals 0. 010, 0. 017, 0. 033 and 0. 067 have been studied microscopically by Mossbauer technique. We have shown that Fe's are substituted for both Cu 1 and Cu 2 sites. We have also shown that the samples with x greater than 0. 01 undergo a magnetic transition at low temperatures without destroying the superconductivity, and that the magnetic transition temperature T//M increases with x. The coexistence argued that spin fluctuations of Cu are related to the superconductivity.