Microscopic coexistence of superconductivity and antiferromagnetism in underdoped Ba(Fe1-xRux)2As2

TL;DR

This study uses NMR to reveal microscopic coexistence of antiferromagnetism and superconductivity in underdoped Ba(Fe$_{1-x}$Ru$_x$)$_2$As$_2$, showing both phases coexist below 15 K with detailed magnetic properties.

Contribution

It provides direct microscopic evidence of coexistence of antiferromagnetism and superconductivity in Ru-doped BaFe$_2$As$_2$, advancing understanding of phase interplay in iron-based superconductors.

Findings

Antiferromagnetic transition at ~60 K.

Superconducting transition at ~15 K.

Microscopic coexistence of both phases below T_C.

Abstract

We use $^{75}$As nuclear magnetic resonance (NMR) to investigate the local electronic properties of Ba(Fe$_{1-x}$Ru$_{x}$)$_2$As$_2$ ($x =$ 0.23). We find two phase transitions, to antiferromagnetism at $T_N \approx$ 60 K and to superconductivity at $T_C \approx$ 15 K. Below $T_N$, our data show that the system is fully magnetic, with a commensurate antiferromagnetic structure and a moment of 0.4 $\mu_B$/Fe. The spin-lattice relaxation rate $1/^{75}T_1$ is large in the magnetic state, indicating a high density of itinerant electrons induced by Ru doping. On cooling below $T_C$, $1/^{75}T_1$ on the magnetic sites falls sharply, providing unambiguous evidence for the microscopic coexistence of antiferromagnetism and superconductivity.