Upper critical fields and superconducting transition temperatures of some zirconium-base amorphous transition-metal alloys

Abstract

Superconducting upper critical fields H, 2(T), transition temperatures T"and normalstate electrical resistivities p"have been measured in the amorphous transition-metal alloy series Zri "Co, Zri "Ni", (Zri "Ti")Q7gNiQ22, and (Zri "Nb")Q78NiQ22. Structural integrity of these melt-spun alloys is indicated by x-ray, density, bend-ductility, normal-state electrical resistivity, superconducting transition width, and mixed-state flux-pinning measurements.

X-ray Diffraction Study of Amorphous NixZr(100-x)-Alloys Prepared by Melt-Spinning

“…This is in good agreement with results concerning the variation of the supercon ducting transition temperature [3][4][5], magnetic sus ceptibility [4,6], crystallization temperature [7], and electrical resistivity [4] in the same concentration region. Therefore, we state that the variations in macroscopic physical parameters are directly related to changes in structure, i.e.…”

Superconductivity and short-range order in metallic glassesFexNi1−xZr2

“…The normal state resistivity ρ n is calculated from resistance measurements performed at room temperature on long ribbons (> 30 cm) such as to minimize geometrydependent effects. ρ n of the order 1.68 µΩm is obtained for all alloys; these values are close to values reported for similar alloys 3,6,7,9 . Since ρ n is related to the GSRO, the constant ρ n throughout this composition range brings further confirmation of the constant GSRO.…”

“…The slope of the upper critical field as a function of temperature close to T c , dBc2 dT Tc , is determined from a single set of measurements of the resistance as a function of temperature at different magnetic fields. We obtain dBc2 dT Tc ≃ −2.4 T/K as typical in amorphous alloys (see for instance 9,23,24 ). We also report values for the penetration depth λ (0), coherence length ξ G (0) (analogous to BCS ξ 0 but including correction due to short mean free path, as indicated by Gor'kov 25,26 ), and GinzburgLandau coherence length ξ GL (0) and GL parameter κ evaluated from expressions for superconductors in the dirty limit 27 .…”

“…Moreover, several superconducting properties, for instance the shape and width of the B c2 transition, or magnetization hysteresis loops are direct consequences of the homogeneity of the material and its flux trapping capacities. Binary and pseudo-binary compounds composed of the early transition (ET) metal Zr and late transition (LT) metal Cu, Ni, Co and Fe in the form LT x ET 1−x and (LT a x LT b 1−x ) y ET 1−y have shown excellent glass-forming abilities over a wide compositional range 3,7,9,10,11 . In this article, we study such a pseudobinary compound, namely Fe x Ni 1−x Zr 2 superconducting glasses with 0 ≤ x ≤ 0.6, based on electric transport and local magnetization measurements.…”

“…Although these first attempts at making amorphous alloys were plagued by the inconvenient instability of the amorphous phase at room temperature, they have served to expose the differences between superconductivity in amorphous materials and in their crystalline counterpart. Nowadays, several techniques based on the rapid cooling of the melt are used to fabricate stable amorphous alloys and the past 25 years have seen the publication of many studies about superconductivity in such metallic glasses, especially those composed of transition metal alloys 3,4,5,6,7,8,9 . These studies have, among other things, discussed the importance of including effects due to spin fluctuations in the predictions of T c , especially in alloys containing Ni, Co, or Fe.…”