Occurrence of magnetism in CeMIn5 - xHgx(M = Rh, Ir)

The physical properties of CeM(In 1-x Hg x ) 5 (M = Rh, Ir) including specific heat and magnetic susceptibility are reported. Two magnetic phases exist in CeRhIn(In 1-x Hg x ) 5 with some evidence of a change from incommensurate magnetic order to a commensurate structure near 10% nominal Hg substitution. In CeIr(In 1-x Hg x ) 5 , an antiferromagnetic quantum critical point near x = 3% (followed by robust long-range antiferromagnetism for x > 5%) appears to be separated from superconductivity in CeIrIn 5 . The multitude of magnetic ground states observed in the CeM(In 1-x Hg x ) 5 materials is quite sensitive to doping and magnetic fields.