Structural and magnetic phase diagram of CeFeAsO1− xFx and its relation to high-temperature superconductivity

Abstract

Recently, high-transition-temperature (high-Tc) superconductivity was discovered in the iron pnictide RFeAsO(1-x)F(x) (R, rare-earth metal) family of materials. We use neutron scattering to study the structural and magnetic phase transitions in CeFeAsO(1-x)F(x) as the system is tuned from a semimetal to a high-Tc superconductor through fluorine (F) doping, x. In the undoped state, CeFeAsO develops a structural lattice distortion followed by a collinear antiferromagnetic order with decreasing temperature. With increasing fluorine doping, the structural phase transition decreases gradually and vanishes within the superconductivity dome near x=0.10, whereas the antiferromagnetic order is suppressed before the appearance of superconductivity for x>0.06, resulting in an electronic phase diagram remarkably similar to that of the high-Tc copper oxides. Comparison of the structural evolution of CeFeAsO(1-x)F(x) with other Fe-based superconductors suggests that the structural perfection of the Fe-As tetrahedron is important for the high-Tc superconductivity in these Fe pnictides.

Electronic and magnetic phase diagram of β-Fe1.01Se with superconductivity at 36.7 K under pressure

“…The temperature regime where we observe the linear resistivity is correlated to the region where NMR has detected the presence of increasing spin fluctuations in β-Fe 1.01 Se [13]. In contrast to our findings for β-Fe 1.01 Se, for LaO 1-x F x FeAs and Ba 1-x K x Fe 2 As 2 the linear resistivity behavior and the orthorhombic structural distortion are intimately correlated to the presence of a long range ordered spin density wave which sets in at or slightly below the temperature of the structural phase transition [3,22,23].…”

“…Superconductivity has recently been discovered in iron arsenides [1][2][3][4][5][6], with superconducting transition temperatures (T c 's) as high as 55 K [6]. The superconductivity in this class of materials is unexpected because most Fe-based compounds display strong magnetic behavior.…”

Visualizing the microscopic coexistence of spin density wave and superconductivity in underdoped NaFe1−xCoxAs

“…8), together with nuclear magnetic resonance 6 and neutron scattering 7 on similar compounds, reveal the coexistence of the two phases. In an intermediate case, neutron scattering in CeFeAsO 1 À x F x reveals a continuous transition, but the SDW and SC regimes only touch at a quantum critical point 3 .…”

“…A key question here is whether the magnetic order and superconductivity can coexist microscopically or mutually exclude each other. So far the available experimental methods used to answer this question are either spatially averaged probes or local ones without control of probing position, thus a consensus is still lacking [3][4][5][6][7][8][9] . Experiments on various iron pnictide compounds have revealed at least three categories of behaviour.…”

Magnetic order in orbital models of the iron pnictides

“…[3][4][5][6] Although this already provides strong motivation to study the magnetism of the pnictides, the unusual magnetic properties are of interest in their own right. 7,8 It is now well established that the undoped cuprates are AFM Mott insulators.…”