Role of in-plane and out-of-plane dilution in CeFeAsO: Charge doping versus disorder

Abstract

We provide direct experimental evidence for the identical effect of the in-plane Fe${}_{1\ensuremath{-}x}$Co${}_{x}$ and of the out-of-plane O${}_{1\ensuremath{-}x}$F${}_{x}$ chemical dilution 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 sizable in-plane disorder induced by the Fe${}_{1\ensuremath{-}x}$Co${}_{x}$ substitution is highly effective in suppressing ${T}_{\mathrm{c}}$. Differently from what is observed in CeFeAsO${}_{1\ensuremath{-}x}$F${}_{x}$, the ordered magnetic phase of the Ce sublattice is preserved throughout the whole phase diagram in CeFe${}_{1\ensuremath{-}x}$Co${}_{x}$AsO ($x\ensuremath{\leqslant}0.2$). An intriguing effect is encountered, whereby the magnetic coupling among Ce${}^{3+}$ ions is enhanced by the superconducting phase.