T. Shang, L. Yang, Y. Chen, J. L. Zhang, L. Jiao, J. Chen, J. Dai, H. Q. Yuan
We report the tunable interplay between 3d- and 4f-electrons and the relevant physical properties in polycrystalline CeFe$_{1-x}$Co$_x$AsO ($0\leq x \leq 1$) by means of measuring the electrical resistivity $\rho(T)$, magnetic susceptibility $\chi(T)$ and specific heat $C(T)$. CeFeAsO undergoes a spin-density-wave (SDW) transition associated with Fe 3d-electrons around 150 K, which is rapidly suppressed by Fe/Co substitution. Superconductivity appears in a narrow doping range of $0.05 < x < 0.2$, showing a maximum transition temperature of $T_\textup{sc}\approx$ 13.5 K around $x = 0.1$. On the other hand, Ce 4f-electrons form an antiferromagnetic (AFM) state over the entire doping range; the N\'{e}el temperature $T_\textup{N}^\textup{Ce}$ increases upon suppressing the SDW transition of Fe and then remains nearly unchanged with further increasing Co concentration up to $x\simeq0.8$ ($T_\textup{N}^\textup{Ce}\approx$ 4K). On the Co-rich side ($x \geq 0.75$), Co 3d-electrons are ferromagnetically ordered; its Curie temperature reaches $T_\textup{C}^\textup{Co} \approx$ 75 K at $x = 1$. Furthermore, evidence of Co-induced polarization on Ce-moments is observed in this regime. Our results suggest that the effects of both electron hybridizations and magnetic exchange coupling between the 3d-4f electrons give rise to a rich phase diagram in the alloy CeFe$_{1-x}$Co$_x$AsO.
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http://arxiv.org/abs/1212.0221
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