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

Abstract

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 (Ni3a Zr67) causes the parameters A, To, a, and NoV to decrease, and Coulomb pseudopotential (#*) 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 Tr with increasing concentration of third element (M) may be attributed to the modifications in density of states at the Fermi level N(EF), 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 Ni33 Zr67 alloy. In this case Tc 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 Tc show an excellent agreement with the experimental data. Quadratic Tc equations have been proposed, which provide successfully the Tr values of ternary metallic glasses under consideration.

Superconducting state parameters of binary metallic glasses

“…The Ashcroft's empty core (EMC) model potential is a simple one-parameter model potential [28], which has been successfully found for various metallic complexes [5][6][7][8][9][10][11][12][13][14][15][18][19][20][21][22][23][24][25][26][27]. When used with a suitable form of dielectric screening functions, this potential has also been found to yield good results in computing the SSPs of metallic glasses [5][6][7][8][9][10][11][12][13][14][15][18][19][20][21][22][23][24][25][26][27] 25 metallic glass, the model potential parameter C is fitted with the experimental data of the electron-phonon coupling strength λ, which came from the experimental tunneling data [37]. After fitting the model potential parameter C , same C is then used in the computation of the SSPs of binary metallic glasses.…”

“…Experiments also show that the superconducting transition temperature T C is grater for amorphous metals than for crystals, which also depends on the composition of the metallic element in the crystalline as well as amorphous phases . Though the pseudo-potential theory is found very successful in studying the various properties of metallic glasses, there have been very few random attempts to study the superconducting state parameters (SSPs) of binary metallic glasses based on model potential [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. The application of a pseudo-potential to a binary metallic glass involves the assumption of pseudoions with average properties, which are assumed to replace two types of ions in the binary systems.…”

“…The theoretical investigation of the SSPs of Cu-Zr metallic glasses has been reported by Sharma et al. [18][19][20]. In most of these studied, Ashcroft's empty core (EMC) model potential [28] is adopted in the calculation.…”

Superconducting state parameters of bulk amorphous alloys

“…During last several years, the superconductivity remains a dynamic area of research in condensed matter physics with continual discoveries of novel materials and with an increasing demand for novel devices for sophisticated technological applications [1][2][3][4][5][6][7][8][9][10]. There are very few scattered attempts to study the superconducting state parameters of bulk amorphous alloys based on model potential [7][8][9][10].…”

“…There are very few scattered attempts to study the superconducting state parameters of bulk amorphous alloys based on model potential [7][8][9][10]. Hence, we thought it worthwhile to undertake the investigation of the superconducting state parameters of (Ni33Zr67)1 -xVx (x = 0, 0.05, 0.1, 0.15) bulk amorphous alloys on the basis of well recognized empty core (EMC) pseudopotential of Ashcroft [11].…”