BaT2As2 Single Crystals (T = Fe, Co, Ni) and Superconductivity upon Co-doping

TL;DR

This paper investigates the structural, magnetic, and superconducting properties of BaT2As2 (T=Fe, Co, Ni) single crystals, revealing superconductivity upon Co-doping and highlighting differences from cuprate systems.

Contribution

It provides new insights into the effects of Co-doping on BaFe2As2, demonstrating bulk superconductivity and analyzing disorder tolerance in Fe-based superconductors.

Findings

BaFe2As2 exhibits a magnetic transition at 132 K.

BaNi2As2 shows a structural transition at 131 K and superconductivity below 0.69 K.

Co-doped BaFe2As2 becomes superconducting at 22 K.

Abstract

The crystal structure and physical properties of BaFe2As2, BaCo2As2, and BaNi2As2 single crystals are surveyed. BaFe2As2 gives a magnetic and structural transition at TN = 132(1) K, BaCo2As2 is a paramagnetic metal, while BaNi2As2 has a structural phase transition at T0 = 131 K, followed by superconductivity below Tc = 0.69 K. The bulk superconductivity in Co-doped BaFe2As2 below Tc = 22 K is demonstrated by resistivity, magnetic susceptibility, and specific heat data. In contrast to the cuprates, the Fe-based system appears to tolerate considerable disorder in the transition metal layers. First principles calculations for BaFe1.84Co0.16As2 indicate the inter-band scattering due to Co is weak.