Jagoda Lukatela

The electrical resistivity of hydrogen-doped ZrCo metallic glasses☆

Abstract The results are presented for the temperature dependence of the electrical resistivity in hydrogen-doped ZrCo metallic glasses in the range 1.42–290 K for various dopant concentrations. In the ZrCo system, which is superconducting at low temperatures, the hydrogen reduces both the effective electron diffusion constant and the screening of the Coulomb interaction, thus leading to a decrease in the conductivity and a suppression of the superconducting transition temperature.

The influence of hydrogen on the superconducting transition temperature in hydrogen-doped Zr80Co20 metallic glasses

Abstract We report the results of a study of electrical resistivity and of the superconducting transition temperature, Tc, in hydrogen-doped ( Zr 80 Co 20 ) 1−x H x (x=0, 0.02, 0.048, 0.11) metallic glasses. The increase of the room-temperature resistivity and its temperature coefficient are explained as a consequence of increased disorder due to hydrogen doping. The temperature dependence of the resistivity has been analysed using theoretical models of weak-localisation and electron–electron interaction in disordered three-dimensional conductors. The hydrogen dopant lowers Tc and broadens the superconducting transition region. We discuss the effect of different hydrogen environments on Tc of (Zr80Co20)1−xHx metallic glasses.

Electronic properties and localization effects in some hydrogen-doped 4d-3d metallic glasses☆

Abstract Magnetoresistance and magnetic susceptibility data obtained on hydrogen-doped samples of ZrNi and ZrCu systems are reported. A mobile-stage sample container in conjunction with a 6 T superconducting coil was used to measure magnetoresistance at temperatures down to 1.7 K with a relative precision of 10−6. The temperature profile of the magnetic susceptibility was also measured down to 2 K by Faradays method using a Cahn electrobalance combined with a conventional magnet. A precision range of 10−7 J T−2 mol−1 was maintained in this measurement. The samples were produced by the common melt-spinning method and were used in the as-obtained condition. Hydrogen strongly influences the quantum-mechanical interference at defects, considerably enhances the quasi-elastic electron scattering and depresses the relative contribution of the spin-orbit interaction. The Maki-Thompson interaction is likewise depressed with increasing hydrogen concentration. The results can be interpreted on the basis of current theoretical concepts based on weak localization in three-dimensional systems in the presence of strong spin-orbit interaction and superconducting fluctuations. The magnetic susceptibility data are interpreted in terms of the hydrogen influence on the electronic density of states at the Fermi level.

Magnetic field dependence of the resistivity in hydrogen-doped Zr-Fe metallic glass

We present the results for the magnetic field dependence of the electrical resistivity in hydrogen-doped Zr 68 Fe 32 metallic glasses. The undoped sample is paramagnetic down to very low temperatures ( < 1 K) because of pronounced spin fluctuations. The observed magnetoresistance is positive and increases with hydrogen concentration. The results have been analyzed using a renormalized expression for the magnetoresistivity which takes into account the exchange enhancement of the spin-splitting contributions (through the Stoner factor) to the usual weak localization and electron-electron interaction terms. The magnetoresistivity enhancement of hydrogen-doped Zr 68 Fe 32 has been attributed to the increase of the Stoner factor (1 - I) -1 , and of the spin-scattering rate τ s -1 . That increase indicates enhancement of spin fluctuations with hydrogen.

The resistivity and the magnetoresistivity of hydrogen-doped Zr67Co33 metallic glass

Abstract The electrical resistivity of hydrogen-doped Zr 67 Co 33 metallic glass has been measured at temperatures between 1.7 K and 4.2 K and in magnetic fields up to 9 T for various dopant concentrations. The temperature and magnetic field dependence have been analyzed using the theoretical models of weak-localization and electron-electron interaction in disordered three-dimensional conductors. Doping the samples with hydrogen increases disorder. In a Zr 67 Co 33 system, which becomes superconducting at 2.74 K, hydrogen reduces both the effective electron diffusion constant and the screening of the Coulomb interaction, leading to a decrease in conductivity and suppression of the superconducting transition temperature. The relative contributions of the spin-orbit and the Maki-Thompson interaction to the magnetoresistivity are also depressed.

The Effect of Absorbed Hydrogen on the Chemical Short-Range Order in Zr68Fe32 Metallic Glass

Electrical resistivity and x-ray diffraction measurements have been made on the hydrogen-doped (Zr68Fe32)1-xHx metallic glass. We find that the relationship between /(273 K) and the hydrogen concentration of the sample is linear for n(H)/n(Zr68Fe32) < 0.13 then saturates at /(Zr68Fe32)  0.35, for 0.28<n(H)/n(Zr68Fe32)<0.48 whereas for larger hydrogen content /(Zr68Fe32) increases. The position of the first and second broad maximum diffraction halo in XRD spectra of (Zr68Fe32)1-xHx metallic glasses is shifted to smaller values of 2 with increasing hydrogen concentration. Thus, the nearest-neighbour distance increases from r=(0.2460.001) nm in Zr68Fe32 to r=(0.2550.001) nm in (Zr68Fe32)0.60H0.40. These values correspond to the Zr-Fe nearest-neighbour distance. In the paramagnetic Zr68Fe32 system the hydrogen produces a pronounced positive anomaly in the electrical resistivity below about 50 K leading to a maximum in (T) before the curve resumes a monotonic decrease with increasing temperature. This is attributed to the increase of the screening parameter for the Coulomb interaction F* associated with the enhancement of the spin fluctuations with hydrogen concentration.

Hydrogen-induced degradation of Tc in Zr-Ni and Zr-Cu metallic glasses.

We have studied the effect of hydrogen doping of Zr-3d metallic glasses on the superconducting transition temperature T_c. It is shown that the degrad

The influence of localization and electron-electron interaction on the superconducting transition temperature in hydrogen-doped Zr-(3d,4d) metallic glasses

Abstract Hydrogen doping has been used to vary continously the superconducting transition temperature, Tc, in Zr-3d metallic glasses. Thus, by changing the hydrogen concentration, the influence of electron localization and electron-electron interaction on Tc could be deduced quantitatively. We have found that hydrogen enhances localization by providing additional centres for quasielastic scattering. The slowing of the electron diffusion enhances the repulsive Coulomb interaction. Thus, a decrease of Tc with the dopant was explained as being caused partly by an increase of the effective Coulomb potential and partly by a decrease of the electron-phonon coupling constant.