Magnetic fluctuations in BaFe2−xNixAs2 superconductors

Anomalies found in the electronic conductivity and the elastic constants C33 and C44 around the superconducting phase transition in the underdoped BaFe1.93Ni0.07As2 compounds are re-examined. The large anomalies in the elastic constants C33 and C44 modes and the unusual temperature dependence of the real part σ1 of the electronic conductivity found around the superconducting phase transition TC ~ 16 K are attributed to magnetic fluctuations. The establishment of a magnetic order at TM ~ 21 K results in a marked decrease of the scattering of electronic carriers.