Superconductivity in the cobalt-doped V3Si A15 intermetallic compound

The A15 structure of superconductors is a prototypical type-II superconductor that has generated considerable interest since the early history of superconducting materials. This paper discusses the superconducting properties of previously unreported V3-x Co (x) Si (0 <= x <= 0.30) alloys. It is found that the lattice parameter decreases with increasing cobalt-doped content and leads to an decreased residual resistivity ratio value of the V3-x Co (x) Si system. Meanwhile, the superconducting transition temperature (T-c ) also decreases with increasing cobalt-doped content. Furthermore, the fitted data show that the increase of cobalt-doped content also reduces the lower/upper critical fields of the V3-x Co (x) Si system. Type-II superconductivity is demonstrated in all V3-x Co (x) Si samples. With higher Co-doped content, V3-x Co (x) Si (0.15 <= x <= 0.30) alloys may have superconducting and structural phase transitions in low-temperature regions. As the electron/atom ratio increases, the T-c variation trend of V3Si is as pronounced as in crystalline alloys and monotonically follows the trend observed for amorphous superconductors.