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

We provide direct experimental evidence for the identical effect of the in-plane Fe1-xCox and of the out-of-plane O1-xFx 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 Fe1-xCox substitution is highly effective in suppressing Tc. Differently from what is observed in CeFeAsO1-xFx, the ordered magnetic phase of the Ce sublattice is preserved throughout the whole phase diagram in CeFe1-xCoxAsO (x?0.2). An intriguing effect is encountered, whereby the magnetic coupling among Ce3+ ions is enhanced by the superconducting phase.