Can antiferromagnetism and superconductivity coexist in the high-field paramagnetic superconductor Nd(O,F)FeAs?

TL;DR

This study investigates whether antiferromagnetism and superconductivity can coexist in Nd(O,F)FeAs, finding that they do not coexist and that magnetic behavior below Tc is dominated by Nd ions, with superconductivity and antiferromagnetism being mutually exclusive.

Contribution

The paper provides experimental evidence that superconductivity in Nd(O,F)FeAs cannot coexist with antiferromagnetic order, clarifying the magnetic state of this high-field superconductor.

Findings

Superconductivity with Tc ~ 51K does not coexist with antiferromagnetic order.

Magnetization exhibits Curie-Weiss behavior indicating antiferromagnetism above Tc.

Below Tc, magnetic behavior is consistent with paramagnetism or spin glass state.

Abstract

We present measurements of the temperature and field dependencies of the magnetization M(T,H) of Nd(O0.89F0.11)FeAs at fields up to 33T, which show that superconductivity with the critical temperature Tc ~ 51K cannot coexist with antiferromagnetic ordering. Although M(T,H) at 55 < T < 140K exhibits a clear Curie-Weiss temperature dependence corresponding to the Neel temperature TN ~ 11-12K, the behavior of M(T,H) below Tc is only consistent with either paramagnetism of weakly interacting magnetic moments or a spin glass state. We suggest that the anomalous magnetic behavior of an unusual high-field paramagnetic superconductor Nd(O1-xFx)FeAs is mostly determined by the magnetic Nd ions.