Muon spin rotation study of magnetism and superconductivity in BaFe2-xCoxAs2 and Pr1-xSrxFeAsO

Abstract

We present a muon spin rotation (\muSR) study of the magnetic and superconducting properties of single crystals of electron-doped BaFe2-xCoxAs2 with x=0.08, 0.20, and 0.25 (Tc=9, 25 and 20K) and of polycrystalline hole-doped Pr1-xSrxFeAsO with x=0 and 0.2 (Tc=15 K). In the former series we observe some interesting parallels with the electron doped SmFeAsO1-xFx 1111-type system [A.J. Drew et al., to appear in Nature Materials 2009 and arXiv:0807.4876]. In particular, we obtain evidence that strongly disordered static magnetism coexists with superconductivity on a microscopic scale in underdoped samples and even at optimum doping there is a slowing down (or enhancement) of dynamic magnetic correlations below Tc\approx25K. To the contrary, for the hole-doped Pr1-xSrxFeAsO samples we obtain evidence for a mesoscopic phase segregation into regions with nearly unperturbed AF order and others that are non magnetic and most likely superconducting. The observed trend resembles the one that was previously reported for hole-doped Ba1-xKxFe2As2 [A.A. Aczel et al., Phys. Rev. B 78, 214503 (2008); J.T. Park et al., arXiv:0811.2224] and thus seems to be fairly common in these hole doped systems.

17 pages, 6 figures

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• Direct observation of the flux-line vortex glass phase in a type II superconductor
• Structural and electronic response upon hole-doping of rare-earth iron oxyarsenides Nd1-xSrxFeAsO (0 < x < 0.2)
• Synthesis, structural and transport properties of the hole-doped Superconductor Pr_{1-x}Sr_xFeAsO
• Competition/Coexisitence of Magnetism and Superconductivity in Iron Pnictides Probed by Muon Spin Rotation
• Determination of characteristic muon precession and relaxation signals in FeAs and FeAs2, possible impurity phases in pnictide superconductors

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• Measurement of a Sign-Changing Two-Gap Superconducting Phase in Electron-Doped Ba(Fe_{1-x}Co_x)_2As_2 Single Crystals using Scanning Tunneling Spectroscopy
• Muon spin rotation study of magnetism and superconductivity in Ba(Fe1-xCox)2As2 single crystals
• Incommensurate spin density wave in Co-doped BaFe2As2
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• Gap structure in the electron-doped Iron-Arsenide Superconductor Ba(Fe0.92Co0.08)2As2: low-temperature specific heat study
• Quasiparticle interference in iron-based superconductors
• Transfer of optical spectral weight in magnetically ordered superconductors
• Tuning of competing magnetic and superconducting phase volumes in LaFeAsO$_0.945F_0.055 by hydrostatic pressure
• A brief review on muSR studies of unconventional Fe and Cr-based superconductors
• Phase diagram of superconductivity and antiferromagnetism in single crystals of Sr(Fe1-xCox)2As2 and Sr1-yEuy(Fe0.88Co0.12)2As2
• Calorimetric Evidence for Nodes in the Overdoped Ba(Fe${}_{0.9}$Co${}_{0.1}$)${}_2$As${}_2$
• Effect of SDW fluctuations on the specific heat jump in iron pnictides at a superconducting transition
• Fe-spin reorientation in PrFeAsO : Evidences from resistivity and specific heat studies
• Doping dependence of antiferromagnetism in models of the pnictides
• Competing superconducting and magnetic order parameters and field-induced magnetism in electron doped Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• High-Pressure Evolution of the Specific Heat of a Strongly Underdoped Ba(Fe0.963Co0.037)As2 Iron-Based Superconductor
• Anomalous local magnetic field distribution and strong pinning in CaFe1.94Co0.06As2 single crystals
• Coupled Magnetic and Superconducting Transitions in Sr${}_2$VO${}_3$FeAs Under Pressure
• Cooperative order in the weakly magnetic domain of LaFeAsO${}_{1-x}$F${}_x$ near the doping phase boundary