Superconducting and electrical properties of amorphous zirconium-transition metal binary alloys

In order to clarify the compositional effect on the superconductivity of zirconium-transition metal (M) binary amorphous alloys, the superconducting properties and electrical resistance of the alloys were examined as functions of the concentration, group number and periodicity of the M elements.T _c for Zr₇₅M₂₅ alloys rises in the order Ru > Rh > Ir > Co > Os > Ni > Pt > Cu > Pd > Fe > Au, i.e. as the group number decreases when the periodicity belongs to the 5th period, and with decreasing M content for Zr_100–X M _X alloys. The highT _c attained in the present work is 4.55 K for Zr₈₀Rh₂₀, 4.38 K for Zr₇₅Rh₂₅ and 4.47 K for Zr₇₅Ru₂₅. The temperature gradient of the upper critical magnetic field (H _c2) near the transition temperature (T _C) tends to increase with increasing zirconium content, and the resistive state due to the flux flow phenomena appears in a wide sweeping field. Following the sharp and large decrease of the flux flow resistance due to a peak effect, the resistance recovers sharply nearH _c2. The peak effect was found to occur more distinctly for the alloys containing a magnetic element of iron or cobalt, probably because of the suppression of the pair-breaking effect due to magnetic scattering by the application of the high field nearH _c2. The dominating factor for the compositional effect onT _C is inferred to originate from the variation of through for Zr_100–x M _X alloys and from that of through N(E_f) for Zr₇₅M₂₅ alloys. Additionally, it has been found for the Zr-M amorphous alloys that the electrical resistivity(T) exhibits a maximum value at temperature ranging from 2T _C to 3T _C, suggesting that the hump phenomenon in (T) appeared through the generation of the superconducting fluctuations. The temperature coefficient of resistivity (tcr) defined by 1/R₂₅₀(dR/dT) shows negative values ranging from 1.05×10^–4 to 1.75×10^–4 K ^–1 andT _C was found to rise through the increase in with the increase in the negative value of the tcr.