Robust magnetic order of Ce 4f-electrons coexisting with superconductivity in CeFeAsO$_{1-x}$F$_x$

TL;DR

This study investigates the coexistence of magnetic order of Ce 4f-electrons with superconductivity in CeFeAsO$_{1-x}$F$_x$, revealing that Ce magnetic order persists under high magnetic fields even when superconductivity is suppressed.

Contribution

It demonstrates the robustness of Ce 4f-electron magnetic order coexisting with superconductivity under high magnetic fields in CeFeAsO$_{1-x}$F$_x$.

Findings

Ce magnetic order remains unchanged up to 40T.

Superconductivity is suppressed but Ce magnetic order persists.

Zero resistance appears below Ce magnetic transition temperature.

Abstract

The electrical resistance of CeFeAsO$_{1-x}$F$_x$ (x = 0.06 and 0.08) has been measured in a magnetic field up to 40T. At zero field, the sample with x = 0.06 shows a structural phase transition around T$_S$~100K, followed by a spin-density-wave (SDW) transition around T$_{SDW}$~30K. For x = 0.08, the structural phase transition is suppressed down to T$_S$~60K without a clear anomaly associated with the Fe-SDW transition, and superconductivity shows up at T$_C$~25K. At lower temperatures, both samples show a clear resistive peak around T$_N$~4K, which is associated with the antiferromagnetic (AFM) transition of Ce-4f electrons. Strikingly, zero resistance is recovered upon further lowering temperature below T$_N$ for x = 0.08. Moreover, we found that the AFM transition of Ce 4f-electrons at 4K hardly changes with applying a magnetic field up to 40T, even in the case of x = 0.08, where superconductivity has been partially suppressed at such a large field.