Volume 87, Number 3, August 2009
|Number of page(s)||6|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||18 August 2009|
Homogeneous vs. inhomogeneous coexistence of magnetic order and superconductivity probed by NMR in Co- and K-doped iron pnictides
Laboratoire de Spectrométrie Physique, UMR5588 CNRS and Université J. Fourier Grenoble, 38402 Saint Martin d'Hères, France, EU
2 Laboratoire National des Champs Magnétiques Intenses, UPR 3228 CNRS 25 avenue des martyrs, BP 166, 38042 Grenoble Cedex 9, France, EU
3 Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Science - P.O. Box 603, Beijing 100190, China
Corresponding author: firstname.lastname@example.org
Accepted: 23 July 2009
In Ba(Fe0.95Co0.05)2As2 all of the 75As NMR intensity at the paramagnetic resonance position vanishes abruptly below = 56 K, indicating that magnetic (spin-density wave) order is present in all of the sample volume, despite bulk superconductivity below Tc = 15 K. The two phases thus coexist homogeneously at the microscopic scale. In Ba0.6K0.4Fe2As2, on the other hand, the signal loss below 75 K is not complete, revealing that magnetic order is bound to finite-size areas of the sample, while the remaining NMR signal shows a clear superconducting response below Tc = 37 K. Thus, the two phases are not homogeneously mixed, at least for this potassium concentration. For both samples, spatial electronic and/or magnetic inhomogeneity is shown to characterize the NMR properties in the normal state.
PACS: 74.25.Ha – Magnetic properties / 75.30.Fv – Spin-density waves / 76.60.-k – Nuclear magnetic resonance and relaxation
© EPLA, 2009
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