Enhanced superconductivity in Hf-base metallic glasses

Abstract

A systematic study of electrical resistivity of Hf100−xFex (x = 20,25), Hf100−xCux(x = 30,40,50) and Ti65Cu35 metallic glasses has been done in the temperature range 0.3–290 K, and in magnetic fields B≤5 T. All Hf-base alloys are superconducting with Tc≥0.44 K, which is well above the Tc of pure crystalline Hf (0.13 K). From the initial slopes of the upper critical fields, (dHc2/dT)Tc, and resistivities we determined the dressed electronic densities of states, Nγ(EF), for all alloys. Both Tc and Nγ(EF) decrease with increasing x (Fe and Cu content). The results are compared with those for corresponding Zr-base metallic glasses and ion-implanted Hf films.

Properties and atomic structure of amorphous early transition metals

“…LTSH yields the Debye temperature, Â D , and dressed DOS at E F , N ␥ (E F ) = (1 + ep )N(E F ) (with ep the electron-phonon enhancement), while T c enables [2] the calculation of ep . N ␥ (E F ) can also be calculated from the normal state resistivity r, density , and the temperature dependence of the upper critical field, H c2 (T) [9]:…”

“…The absence of any hcp atomic arrangements in a-TEs and their alloys has a profound influence on their DOS and interatomic bonding and, hence, affects all properties of glassy TE-TL alloys. Quite large N(E F ) and its simple variation with x strongly affect the magnetic and superconducting properties of glassy TE-TL alloys [5,9]. As shown in Fig.…”

“…Casting with controlled parameters resulted in ribbons with closely similar cross-sections (∼2 mm × 0.03 mm) and, thus, with the glassy phase having broadly the same degree of quenched-in disorder. As-cast samples were used for actual measurements and their fully amorphous structures were verified by X-ray diffraction [9]. The superconducting transition temperatures Tc were determined either resistively, or via ac susceptibility measurements [3,9].…”

“…As-cast samples were used for actual measurements and their fully amorphous structures were verified by X-ray diffraction [9]. The superconducting transition temperatures Tc were determined either resistively, or via ac susceptibility measurements [3,9]. The magnetic susceptibility was measured with a SQUID magnetometer MPMS [10] in a magnetic field B ≤ 5.5 T over the temperature range of 5-300 K. The Young's modulus, E, was cal- Table 1 The parameters of amorphous Ti, Zr and Hf compared with those for different crystalline phases of the same metals.…”

“…The majority of the results for TE-TL metallic glasses have been obtained for Zr-TL alloys, so that a comparison between the alloy systems based on different TE is seldom possible [2,4,9]. Here, we report new results for the magnetic, superconducting and mechanical properties of several Ti-Cu and Hf-Cu glassy alloys and combine these results with the literature data for Ti-TL and Hf-TL metallic glasses in order to observe how a change in TE (Ti → Zr → Hf) affects these properties for glassy TE-TL alloys.…”