Variation in Electronic State of Ba(Fe_1-<i>x</i>Co_<i>x</i>)₂As₂Alloy as Investigated in Terms of Transport Properties

Abstract

We investigate the in-plane transport properties of the electron-doped iron arsenide superconductor Ba(Fe 1- x Co x ) 2 As 2 (0≤ x ≤1). We observe a non-Fermi-liquid behavior characterized by an incoherent resistivity and a low-temperature increase in Hall coefficient ( R H ) at x ≤0.14. We discuss this feature in terms of antiferromagnetic fluctuations. We find that the effective carrier density per Fe/Co atom n eff = - V /( e R H ) ( V is the volume per Fe/Co atom and e is the elementary electric charge) at 250 K exhibits a nonmonotonic x dependence with a minimum value at x ∼0.1, which is considered to reflect the disappearance of hole Fermi surfaces. We discuss the interrelationships among superconductivity, magnetism, and band nesting.