Mössbauer measurements on170Yb3+ substituted into YBa2Cu3O7

We present some results obtained by Mössbauer spectroscopy on Yb³⁺ when substituted into YBa₂Cu₃O _x -like compounds. For the fully substituted compound YbBa₂Cu₃O₇, we describe the properties of the rare earth sublattice magnetic ordering which coexists with superconductivity. From measurements at the dilute substitution level, we study the Yb³⁺ crystal field properties and the thermal dependence of the Yb³⁺ paramagnetic relaxation rate. By making use of the molecular field produced on the Yb³⁺ probe by the magnetically correlated Cu(2), we examine the evolution of the Cu(2)-based magnetism as a function of carrier density and study the phase separation which occurs in the superconducting samples with intermediate oxygen levels. We also examine how the properties of the Yb³⁺ probe are influenced by the substitution of Pr³⁺ or Zn²⁺ (these substitutions are known to considerably influence the superconducting properties).