Coexistence and competition of the short-range incommensurate antiferromagnetic order with superconductivity in BaFe2-xNixAs2

TL;DR

This study uses neutron scattering to show that in BaFe2-xNixAs2, long-range antiferromagnetic order and superconductivity do not coexist, but short-range incommensurate AF order coexists and competes with superconductivity without a magnetic quantum critical point.

Contribution

It provides new insights into the phase relationship between antiferromagnetism and superconductivity in iron pnictides, highlighting the role of short-range AF order.

Findings

Long-range AF order and superconductivity do not coexist.

Incommensurate short-range AF order coexists and competes with superconductivity.

No evidence of a magnetic quantum critical point.

Abstract

Superconductivity in the iron pnictides develops near antiferromagnetism, and the antiferromagnetic (AF) phase appears to overlap with the superconducting phase in some materials such as BaFe2-xTxAs2 (where T = Co or Ni). Here we use neutron scattering to demonstrate that genuine long-range AF order and superconductivity do not coexist in BaFe2-xNixAs2 near optimal superconductivity. In addition, we find a first-order-like AF to superconductivity phase transition with no evidence for a magnetic quantum critical point. Instead, the data reveal that incommensurate short-range AF order coexists and competes with superconductivity, where the AF spin correlation length is comparable to the superconducting coherence length.