Effect of 3d Metal (Co and Ni) Doping on the Superconductivity of FeSe0.5Te0.5

TL;DR

This study investigates how doping FeTe0.5Se0.5 with small amounts of Co and Ni affects its crystal structure and superconducting properties, revealing that Ni suppresses superconductivity more rapidly than Co due to increased in-plane disorder.

Contribution

It provides new insights into how 3d metal doping influences the structural and superconducting characteristics of FeTe0.5Se0.5, highlighting the different effects of Co and Ni.

Findings

Ni suppresses Tc faster than Co

Lattice parameters decrease with doping, not monotonically

In-plane disorder impacts superconductivity

Abstract

We report the effect of 3d metal Cobalt (Co) and Nickel (Ni) doping on the FeTe0.5Se0.5 superconductor with the nominal composition range Fe1-xMxTe0.5Se0.5 (M = Co, Ni and x = 0.00, 0.01 0.02, 0.05, and 0.10). Samples are synthesized through standard solid state reaction route and all are crystallize in single phase tetragonal structure with space group P4nmm. The lattice parameters 'a', 'c' and volume decrease with increase in Co and Ni content, although not monotonically. In fact the 'a' lattice parameter of Co doped samples is nearly unaffected for Co doped samples. The superconducting transition temperature (Tc) is measured from both DC and AC magnetic susceptibility, which decrease with increase in Ni or Co content. Both Co and Ni suppress Tc and drive the system into the normal state. Interestingly, Ni suppresses the superconductivity much faster than the Co. This indicates less effect on in-plane Fe-Se distances and thus reduced disorder in case of Co when compared with Ni substation at Fe site in FeTe0.5Se0.5 superconductor. It is concluded that in-plane disorder on superconducting Fe-Se and Fe-Se-Se planes directly affects superconductivity in FeTe0.5Se0.5 superconductor.