Magnetic pair-breaking effects: Moment formation and critical doping level in superconducting La1.85Sr0.15Cu1−xAxO4 systems (A=Fe,Co,Ni,Zn,Ga,Al)

Abstract

We have conducted a systematic study on the effect of Cu-site doping in ${\mathrm{La}}_{1.85}$ ${\mathrm{Sr}}_{0.15}$ ${\mathrm{CuO}}_4$ system. The relations between ${\mathit{T}}_{\mathit{c}}$ and doping level as well as the critical doping levels ${\mathit{x}}_{\mathit{c}}$ have been determined accurately for the Fe-, Co-, Ni-, Zn-, Ga-, and Al-doped systems. Every dopant either carries an intrinsic magnetic moment or induces a net moment on the Cu-${\mathrm{O}}_2$ plane. The size of the moment is correlated with the suppression of superconductivity, consistent with the magnetic-pair-breaking effect. The ground states of the dopants have also been determined.