From Ising Resonant Fluctuations to Static Uniaxial Order in Antiferromagnetic and Weakly Superconducting CeCo(In1-xHgx)5 (x=0.01)

CeCo(In0.990Hg0.010)(5) is a charge doped variant of the d-wave CoCoIn5 superconductor with coexistent antiferromagnetic and superconducting transitions occurring at T-N = 3.4 and T-c = 1.4 K, respectively. We use neutron diffraction and spectroscopy to show that the magnetic resonant fluctuations present in the parent superconducting phase are replaced by collinear c-axis magnetic order with three-dimensional Ising critical fluctuations. No low-energy transverse spin fluctuations are observable in this doping-induced antiferromagnetic phase and the dynamic resonant spectral weight predominately shifts to the elastic channel. Static (tau > 0.2 ns) collinear Ising order is proximate to superconductivity in CeCoIn5 and is stabilized through hole doping with Hg.