Absence of large nanoscale electronic inhomogeneities in the Ba[.sub.2][As.sub.2] pnictide

• Published in: The European physical journal. B, Condensed matter physics Vol. 73; no. 2; pp. 161 - 166
• Main Authors: Laplace, Y, Bobroff, J, Rullier-Albenque, F, Colson, D, Forget, A
• Format: Journal Article
• Language: English
• Published: Springer 15.01.2010
• Subjects: Anisotropy; Cobalt; Nanotechnology; Superconductors
• ISSN: 1434-6028; 1434-6036
• DOI: 10.1140/epjb/e2009-00414-x

[sup.75]As NMR and susceptiblity were measured in a Ba[([Fe.sub.1- x][Co.sub.x]).sub.2][As.sub.2] 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 Ba[Fe.sub.2][As.sub.2] from nano to micrometer lengthscales, on the contrary to the K doping.