Tunable interplay between 3d and 4f electrons in Co-doped iron pnictides

Abstract

We study the interplay of 3d and 4f electrons in the iron pnictides CeFe${}_{1-x}$Co${}_x$AsO and GdFe${}_{1-y}$Co${}_y$AsO, which correspond to two very different cases of $4f$-magnetic moment. Both CeFeAsO and GdFeAsO undergo a spin-density-wave (SDW) transition associated with Fe 3d electrons at high temperatures, which is rapidly suppressed by Fe/Co substitution. Superconductivity appears in a narrow doping range: $0.05<x<0.2$ for CeFe${}_{1-x}$Co${}_x$AsO and $0.05<y<0.25$ for GdFe${}_{1-y}$Co${}_y$AsO, showing a maximum transition temperature $T_{\text{sc}}$ of about 13.5 K for Ce and 19 K for Gd. In both compounds, the $4f$-electrons form an antiferromagnetic (AFM) order at low temperatures over the entire doping range and Co 3d electrons are ferromagnetically ordered on the Co-rich side; the Curie temperature reaches $T_{\text{C}}^{\text{Co}}\approx$ 75 K at $x=1$ and $y=1$. In the Ce-compounds, the Néel temperature $T_{\text{N}}^{\text{Ce}}$ increases upon suppressing the SDW transition of Fe and then remains nearly unchanged with further increasing Co concentration up to $x\simeq 0.8$ ($T_{\text{N}}^{\text{Ce}}\approx$ 4 K). Furthermore, evidence of Co-induced polarization on Ce-moments is observed on the Co-rich side. In the Gd-compounds, the two magnetic species of Gd and Co are coupled antiferromagnetically to give rise to ferrimagnetic behavior in the magnetic susceptibility on the Co-rich side. For $0.7\le y<1.0$, the system undergoes a possible magnetic reorientation below the Néel temperature of Gd ($T_{\text{N}}^{\text{Gd}}$). 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 rare-earth iron pnictides.

13 pages, 15 figures

References in corpus (21)

• Superconductivity at 43 K in Samarium-arsenide Oxides $SmFeAs{O}_{1-x}{F}_x$
• High-temperature superconductivity in iron-based materials
• Superconductivity at 41 K and its competition with spin-density-wave instability in layered CeO${}_{1-x}$F${}_x$FeAs
• Structural and magnetic phase diagram of CeFeAsO1-xFx and its relationship to high-temperature superconductivity
• Competing Orders and Spin-Density-Wave Instability in La(O${}_{1-x}$F${}_x$)FeAs
• Superconductivity in iron-based F-doped layered quaternary compound Nd[O1-xFx]FeAs
• Thorium-doping induced superconductivity up to 56 K in Gd1-xThxFeAsO
• Nearly Isotropic superconductivity in (Ba,K)Fe2As2
• Upper critical fields and thermally-activated transport of Nd(O_0.7F_0.3)FeAs single crystal
• Superconductivity in Co-doped LaFeAsO
• High - Temperature Superconductivity in Iron Based Layered Compounds
• Effect of Co doping on superconductivity and transport properties in SmFe${}_{1-x}$Co${}_x$AsO
• Superconductivity induced by cobalt doping in iron-based oxyarsenides
• Superconductivity at 53.5 K in GdFeAsO1-delta
• Itinerant Ferromagnetism in layered crystals LaCoOX (X = P, As)
• Interplay of Rare Earth and Iron magnetism in RFeAsO with R = La, Ce, Pr, and Sm: A muon spin relaxation study and symmetry analysis
• CeFePO: A Heavy Fermion Metal with Ferromagnetic Correlations
• Universal behavior of the upper critical field in iron based superconductors
• The crystalline electric field as a probe for long range antiferromagnetic order and superconductivity in CeFeAsO${}_{1-x}$F${}_x$
• Ferromagnetism and superconductivity in P-doped CeFeAsO
• Interplay between 3d and 4f magnetism in CeCoPO

Cited by in corpus (12)

• The phase diagrams of iron-based superconductors: theory and experiments
• Charge doping versus disorder in CeFeAsO: do the in- and out-of-plane dilutions play the same role?
• Magnetic structures, spin-flop transition and coupling of Eu and Mn magnetism in the Dirac semimetal EuMnBi${}_2$
• Revisiting the phase diagram of LaFe${}_{1-x}$Co${}_x$AsO on single crystals by thermodynamic methods
• Tunable magnetic orders in CePd${}_2$As${}_{2-x}$P${}_x$
• Magnetic polarization of Ir in underdoped, non-superconducting Eu(Fe${}_{0.94}$Ir${}_{0.06}$)${}_2$As${}_2$
• Spin reorientation of the Fe moments in Eu${}_{0.5}$Ca${}_{0.5}$Fe${}_2$As${}_2$: Evidence for a strong interplay of Eu and Fe magnetism
• Electron doping of the iron-arsenide superconductor CeFeAsO controlled by hydrostatic pressure
• Robust magnetic order of Ce 4f-electrons coexisting with superconductivity in CeFeAsO${}_{1-x}$F${}_x$
• Tuning the magnetocrystalline anisotropy in $R$CoPO by means of $R$ substitution: a ferromagnetic resonance study
• Evolution of superconductivity in PrFe1-xCoxAsO with x = 0.0 to 1.0
• Magnetocrystalline anisotropic effect in GdCo${}_{1-x}$Fe${}_x$AsO ($x=0,0.05$)