Eur. Phys. J. B 73, 161-166 (2010)
https://doi.org/10.1140/epjb/e2009-00414-x

Absence of large nanoscale electronic inhomogeneities in the Ba(Fe_1-xCo_x)₂As₂ pnictide

¹ Laboratoire de Physique des Solides, Univ. Paris-Sud, UMR 8502 CNRS, 91405 Orsay Cedex, France
² Service de Physique de l'État Condensé, Orme des Merisiers, CEA Saclay (CNRS URA 2464), 91191 Gif-sur-Yvette Cedex, France

Corresponding author: bobroff@lps.u-psud.fr

Received: 23 July 2009
Revised: 2 November 2009
Published online: 4 December 2009

Abstract

⁷⁵As NMR and susceptiblity were measured in a Ba(Fe_1-xCo_x)₂As₂ single crystal for x = 6% for various field H values and orientations. The sharpness of the superconducting and magnetic transitions demonstrates a homogeneity of the Co doping x better than ±0.25%. On the nanometer scale, the paramagnetic part of the NMR spectra is found very anisotropic and very narrow for H||ab which allows to rule out the interpretation of reference [J. Phys. Soc. Jpn 78, 013711 (2009); Phys. Rev. B 79, R 140506 (2009)] in terms of strong Co induced electronic inhomogeneities. We propose that a distribution of hyperfine couplings and chemical shifts due to the Co effect on its nearest As explains the observed linewidths and relaxations. All these measurements show that Co substitution induces a very homogeneous electronic doping in BaFe₂As₂, from nano to micrometer lengthscales, on the contrary to the K doping.