Coexistence of Competing Antiferromagnetic and Superconducting Phases in the Underdoped Ba(Fe_0.953Co_0.047)₂As₂ Compound Using X-ray and Neutron Scattering Techniques

Neutron and x-ray diffraction studies show that the simultaneous first-order transition to an orthorhombic and antiferromagnetic (AFM) ordered state in BaFe₂As₂ splits into two transitions with Co doping. For Ba(Fe_0.953Co_0.047)₂As₂, a tetragonal-orthorhombic transition occurs at T_S=60  K, followed by a second-order transition to AFM order at T_N=47  K. Superconductivity occurs in the orthorhombic state below T_C=17  K and coexists with AFM. Below T_C, the static Fe moment is reduced along with a redistribution of low energy magnetic excitations indicating competition between coexisting superconductivity and AFM order.