Electronic structure and magnetism in superconductor ZnNNi 3: A comparative study with ZnCNi 3 and ZnNi 3

Abstract

We have investigated the structural, electronic, and magnetic properties of a newly discovered antiperovskite superconductor ZnNNi 3 and related compounds ZnCNi 3 and ZnNi 3 by using full-potential linearized augmented plane-wave method with the generalized gradient approximation (GGA). It is found that the electronic structures of ZnNNi 3 and ZnCNi 3 are very similar, existing a characteristic density of states (DOS) peak just below the Fermi level, which is dominated by Ni d bands with a small contribution from N/C p states. Contrarily, the band structure and Fermi surface in ZnNi 3 is changed considerably. Based on the free electron model, the Sommerfeld coefficients and the molar Pauli paramagnetic susceptibility for these compounds are evaluated. The spin-polarized calculations and the fixed spin-moment calculations indicate that both ZnNNi 3 and ZnCNi 3 are not near magnetism, while ZnNi 3 shows a typically ferromagnetic behavior. Furthermore, we also investigated the influence of N/C-defect on the electronic and magnetic properties. We found that ZnCNi 3 is more sensitive to the defect than ZnNNi 3, which well explains the fact why superconductivity has not yet been observed in ZnCNi 3.