Evolution of superconductivity and antiferromagnetic order in Ba(Fe0.92-xCo0.08 Vx)2As2

The vanadium doping effects on the superconductivity and magnetism of iron pnictides are investigated in Ba(Fe0.92-xCo0.08Vx)2As2 by transport, susceptibility, and neutron scattering measurements. The doping of magnetic impurity V causes a fast suppression of superconductivity with TC reduced at a rate of approximately 7.4 K/1% V. On the other hand, for x?0.02, long-range C-type antiferromagnetic order is recovered upon V doping, in contrast to the x=0 sample with no detectable magnetic order. The value of ordered magnetic moments of Ba(Fe0.92-xCo0.08Vx)2As2 follows a domelike evolution versus doping concentration x. A possible Griffiths-type antiferromagnetic region of multiple coexisting phases in the phase diagram of Ba(Fe0.92-xCo0.08Vx)2As2 is identified, in accordance with previous theoretical predictions based on the cooperative behavior of magnetic impurities and conduction electrons mediating the Ruderman-Kittel-Kasuya-Yosida interactions between them.