The suppression of superconductivity in MgCNi3 by Ni-site doping

The effects of partial substitution of Cu and Co for Ni in the intermetalli c perovskite superconductor MgCNi3 are reported. Calculation of the expecte d electronic density of states suggests that electron (Cu) and hole (Co) do ping should have different effects. For MgCNi3-xCux, solubility of Cu is li mited to approximately 3% (x = 0.1). and T-c decreases systematically from 7 to 6 K. For MgCNi3-xCox, solubility of Co is much more extensive, but bul k superconductivity disappears for Co doping of 1% (x = 0.03). No signature of long range magnetic ordering is observed in the magnetic susceptibility of the Co doped material. (C) 2001 Elsevier Science Ltd. All rights reserv ed.