Charge doping versus disorder in CeFeAsO: do the in- and out-of-plane dilutions play the same role?

TL;DR

This study shows that in CeFeAsO, in-plane and out-of-plane chemical dilutions similarly suppress the spin-density-wave phase, but in-plane disorder more effectively reduces the superconducting transition temperature, with magnetic order of Ce ions remaining stable.

Contribution

It provides direct experimental evidence that in-plane and out-of-plane chemical dilutions have identical effects on SDW suppression in CeFeAsO, highlighting the different impacts on superconductivity and magnetic order.

Findings

In-plane and out-of-plane dilutions similarly suppress SDW.

In-plane disorder more effectively suppresses T_c.

Ce magnetic order remains stable across the phase diagram.

Abstract

We provide direct experimental evidence for the identical effect of the in-plane Fe$_{1-x}$Co$_{x}$ and of the out-of-plane O$_{1-x}$F$_{x}$ chemical dilutions on the itinerant spin-density-wave (SDW) magnetic phase in CeFeAsO. Remarkably, the suppression of SDW is not sensitive at all to the different kinds of disorder introduced in the two cases. Still, it is clearly shown that the sizeable in-plane disorder induced by the Fe$_{1-x}$Co$_{x}$ substitution is highly effective in suppressing $T_{\textrm{c}}$. Differently from what is observed in CeFeAsO$_{1-x}$F$_{x}$, the ordered magnetic phase of the Ce sublattice is preserved throughout the whole phase diagram in CeFe$_{1-x}$Co$_{x}$AsO ($x \leq 0.2$). An intriguing effect is encountered, whereby the magnetic coupling among Ce$^{3+}$ ions is enhanced by the superconducting phase.