A pseudopotential approach to the superconducting state parameters of (Ni33Zr67)1-xMx (M = Ti, V, Co, Cu) ternary metallic glasses

Superconductivity in ternary metallic glasses has been investigated using the model pseudopotential approach, which has been found quite successful in explaining superconductivity in metals, binary alloys and binary glasses. It is observed that this simple methodology successfully explains superconducting behaviour of ternary glasses without requiring the solution of Dirac equation for a many body problem or estimation of various interactions as required in ab-initio pseudopotential theory. In the present work superconducting state parameters of fourteen metallic glasses of (Ni-Zr)-M system (M=Ti, V, Co, Cu) have been determined in the BCS-Eliashberg-McMillan framework. It is observed that addition of V, Co, and Cu as the third element (M) to a binary metallic glass (Ni-33 Zr-67) causes the parameters lambda, T-c, alpha, and N0V to decrease, and Coulomb pseudopotential (mu*) to increase with concentration of M, showing that the presence of third element (M) causes suppression of superconducting behaviour of the alloy. The decrease in T, with increasing concentration of third element (M) may be attributed to the modifications in density of states at the Fermi level N(E-F), and probable changes in the band structure of the alloy due to addition of the third element (M). Slight difference is noticed when Ti is added to the Ni-33 Zr-67 alloy. In this case T-c rises initially and then decreases with concentration of M, showing a peak at about x = 0.05. This indicates that on addition of Ti, 3d states grow near the Fermi level and hence contribute substantially to N(EF), favouring superconducting behaviour in this case. The present results for T-c show an excellent agreement with the experimental data. Quadratic T-c equations have been proposed, which provide successfully the T-c values of ternary metallic glasses under consideration.