UC Irvine

The heavy-fermion superconductor CeCo In5 is believed to be close to a magnetic instability, but no static magnetic order has been found. Cadmium doping on the In site shifts the balance between superconductivity and antiferromagnetism to the latter with an extended concentration range where both types of order coexist at low temperatures. We investigated the magnetic structure of nominally 10% Cd-doped CeCo In5, being antiferromagnetically ordered below TN ≈3 K and superconducting below Tc ≈1.3 K, by elastic neutron scattering. Magnetic intensity was observed only at the ordering wave vector QAF = (1 2, 1 2, 1 2) commensurate with the crystal lattice. Upon entering the superconducting state, the magnetic intensity seems to change only little. The commensurate magnetic ordering in CeCo (In1-x Cdx) 5 is in contrast to the incommensurate antiferromagnetic ordering observed in the closely related compound CeRh In5. Our results give insights into the interplay between superconductivity and magnetism in the family of CeT In5 (T=Co, Rh, and Ir) based compounds. © 2007 The American Physical Society.