Effect of Ni and Zn substitution on the physical and electrical properties of NdBaSrCu3O7−δ high temperature superconductor

Abstract

Polycrystalline NdBaSrCu[Formula: see text]MxO[Formula: see text] samples ([Formula: see text] or Zn for [Formula: see text]) were prepared via solid-state reaction and examined by X-ray diffraction (XRD), Scanning electron microscopy (SEM), AC susceptibility and electrical resistance (dc) measurements. This study is focused on the effect of magnetic and non-magnetic particles substitution on the superconductivity of this tetragonal NdBaSrCu3O[Formula: see text] sample. There is no significant dependence of doping concentration for the changes of a-, b-lattice parameter but c-lattice parameter increased with both Ni and Zn substituted samples contrary to the ionic size considerations of the dopants. Results showed decrease of the critical temperature, [Formula: see text] and critical current density [Formula: see text] with increase of both doping contents. [Formula: see text] is the peak temperature of the imaginary part of the complex AC susceptibility, [Formula: see text]. Decrease of [Formula: see text] is related to the disruption of spin correlation of the CuO2 planes. Both doping only affect the [Formula: see text] without changing the transition width. The results showed that both Ni and Zn substitutions alter the quantity of spin-singlet pairs but have no effect on the size of the spin gap in the ladder. However, Zn doping more clearly lowered the [Formula: see text] than Ni doping. It is proposed that Zn, a non-magnetic dopant, caused a greater induction of unpaired charge carriers.