Ni-site Doping Effect of New Antiperovskite Superconductor ZnNNi3

A new superconductor ZnNNi3 with Tc of about 3 K has the same anti-perovskite-type such as MgCNi3 and CdCNi3. For this new superconductor, we have studied the Ni-site doping effect with the formula of ZnNNi3-xMx. The dopant elements M are chosen to be Cu, Co, Fe, Mn, Cr, and V In Mn and Fe doping, only by x=0.05 doping, the superconductivity rapidly disappears. The superconductivity survives in V, Cr, Co, and Cu cases up to x=0.1, 0.3, 0.5 and 0.05 doping, respectively. This result suggests that the magnetic character is associated with the origin of superconductivity. Interestingly, in Co-doping case, the superconductivity and ferromagnetism coexist at low temperature. It has been revealed that form EPMA analysis the coexistence is originated from the spatial phase separation of superconducting ZnNNi3 and ferromagnetic ZnN(Co2.6Ni0.4), suggesting the existence of miscibility gap of ZnN(Ni, Co)3 solid solution.