EuFe$_2$As$_2$ under high pressure: an antiferromagnetic bulk superconductor

TL;DR

This study demonstrates that EuFe$_2$As$_2$ becomes a bulk superconductor under high pressure, maintaining antiferromagnetic order, with a critical temperature around 30 K, revealed through susceptibility and resistivity measurements.

Contribution

It provides experimental evidence of pressure-induced bulk superconductivity in EuFe$_2$As$_2$ and explores the coexistence of superconductivity with antiferromagnetic order.

Findings

Superconductivity appears at 28 kbar with T_c ~30 K.

Antiferromagnetic order persists in the superconducting phase.

Resistivity shows nearly linear temperature dependence down to T_c.

Abstract

We report the ac magnetic susceptibility $\chi_{ac}$ and resistivity $\rho$ measurements of EuFe$_2$As$_2$ under high pressure $P$. By observing nearly 100% superconducting shielding and zero resistivity at $P$ = 28 kbar, we establish that $P$-induced superconductivity occurs at $T_c \sim$~30 K in EuFe$_2$As$_2$. $\rho$ shows an anomalous nearly linear temperature dependence from room temperature down to $T_c$ at the same $P$. $\chi_{ac}$ indicates that an antiferromagnetic order of Eu$^{2+}$ moments with $T_N \sim$~20 K persists in the superconducting phase. The temperature dependence of the upper critical field is also determined.