Competition and coexistence of antiferromagnetism and superconductivity in underdoped Ba(Fe0.953Co0.047)2As2

TL;DR

This study investigates how antiferromagnetism and superconductivity coexist and compete in underdoped Ba(Fe0.953Co0.047)2As2, revealing phase transitions and the interplay of magnetic and superconducting states.

Contribution

It provides detailed experimental evidence of the phase transitions and coexistence of AFM and SC in underdoped iron pnictide, highlighting the competition between these orders.

Findings

Two separate phase transitions: structural at 60 K and magnetic at 47 K.

Superconductivity appears below 15 K in the orthorhombic phase.

Reduction of Fe magnetic moment and spin gap formation below Tc.

Abstract

Neutron and x-ray diffraction studies show that the simultaneous first-order transition to an orthorhombic and antiferromagnetic (AFM) ordered state in BaFe2As2 splits into two transitions with Co doping. For Ba(Fe0.953Co0.047)2As2, a tetragonal-orthorhombic transition occurs at TS = 60 K, followed by a second-order transition to AFM order at TN = 47 K. Superconductivity (SC) occurs in the orthorhombic state below TC = 15 K and coexists with AFM. Below TC, the static Fe moment is reduced and a 4 meV spin gap develops indicating competition between coexisting SC and AFM order.