Spurious magnetism in high-Tc superconductor

One challenge in condensed-matter physics is to unravel the interplay between magnetism and superconductivity in copper oxides with a high critical temperature ( T c ). Kang et al. 1 claim to have revealed a quantum phase transition from the superconducting to an antiferromagnetic state in the electron-doped material Nd 2-x Ce x CuO 4 (NCCO) based on the observation of magnetic-field-induced neutron scattering intensity at (1/2,1/2,0), (1/2,0,0), and related reflections. Here we argue that the observed magnetic intensity is due to a secondary phase of (Nd,Ce) 2 O 3 . We therefore contend that the effect is spurious and not intrinsic to superconducting NCCO.