Crystal structure and magnetic properties of Tb-doped Ru-1222 ruthenocuprates

The effects of Tb doping on the structural, superconducting, and magnetic properties of (Ru0.9Nb0.1)Sr2(Gd1.34−xTbxCe0.66)Cu2Oz and RuSr2(Eu1.34−xTbxCe0.66)Cu2Oz (x=0, 0.34) systems were investigated. It was found that Tb doping in both systems results in a significant suppression of superconductivity and an enhancement of the magnetic ordering temperature, as well as an enhancement of the weak-ferromagnetic component of field-cooled magnetization. The Rietveld refinements of the X-ray diffraction data at room temperature showed that both a and c lattice parameters decrease and the rotation angle of the RuO6 octahedron around the crystallographic c-axis decreases by Tb doping in both systems. The superconducting and magnetic behaviors induced by the Tb doping are discussed in conjunction with the change in hole concentration and the local structural changes in the Ru sublattice induced by Tb doping.