Dresden 2009 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 40: Superconductivity: Ferropnictides 1

TT 40.6: Talk

Thursday, March 26, 2009, 15:15–15:30, HSZ 03

Electronic phase separation in the slightly underdoped iron pnictide superconductor Ba_1−xK_xFe₂As₂ — •Ji Tae Park¹, D. S. Inosov¹, Ch. Niedermayer², G. L. Sun¹, D. Haug¹, N. B. Christensen², R Dinnebier¹, A. V. Boris¹, A. J. Drew³, L. Schulz³, T. Shapoval⁴, U. Wolff⁴, V. Neu⁴, X. Yang¹, C. T. Lin¹, B. Keimer¹, and V. Hinkov¹ — ¹Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, Stuttgart, Germany — ²ETHZ & PSI, Villigen PSI, Switzerland — ³Department of Physics, University of Fribourg, Chemin du Musée 3, Fribourg, Switzerland — ⁴IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden, Germany

We performed a combined study of the slightly underdoped novel iron pnictide superconductor Ba_1−xK_xFe₂As₂ by means of X-ray powder diffraction, neutron scattering, muon spin rotation (µSR), and magnetic force microscopy (MFM). Commensurate static magnetic order sets in below T_m ∼ 70 K as inferred from the emergence of the magnetic (1 0 3) reflection in the neutron scattering data and from the observation of damped oscillations in the zero-field-µSR asymmetry. Transverse-field µSR below T_c shows a coexistence of magnetically ordered and non-magnetic states, which is also confirmed by MFM imaging. This coexistence could be explained by electronic phase separation into antiferromagnetic and superconducting/normal state regions on a scale of several tens of nanometers indicating that such mesoscopic phase separation can be considered an intrinsic property of some iron pnictide superconductors.