Electrical resistivity of amorphous alloys

Amorphous alloys of Ga, Sn, Pb and Bi with Cu, Ag and Au are produced by evaporation on a cold substrate. The residual resistivity, the temperature dependence of the resistivity, the transition temperature of superconductivity and the temperature of the amorphous-crystalline transformation are measured. We observe e.g. that the residual resistivity increases with the noble metal concentration, and that the temperature coefficient of the resistivity of the Au alloys is always negative. In these two respects amorphous alloys differ in behaviour from the corresponding liquid alloys. These observations can be correlated with the atomic energy levels of the free atoms.     

Electrical resistivity of amorphous Sn-Cu alloys

The residual resistivity of amorphous Sn-Cu alloys increases with the Cu-concentration. Both positive and negative temperature coefficients are observed. The positive temperature coefficient and the transition temperature of superconductivity depend linearly on the Cu-concentration and both vanish simultaneously.     

On the resistivity minimum in amorphous ferromagnetic alloys

We present a theoretical approach which, taking into account the amorphous nature of the system and the correlations between nearest-neighbour magnetic ions, gives a plausible explanation of some features present in the electrical resistivity of amorphous ferromagnetic alloys with transition metals.     

Pressure dependence of the resistivity of several amorphous alloys

Measurements under hydrostatic pressure of the electrical resistance of a series of metglas alloys and one alloy of NiY have been made in the range 0–5 kbar and 77–300 K. In general the behaviour fits no general pattern, except that Metglas 2204 (BeTiZr) obeys a simple prediction of the Ziman model as found by Nagel for thermopower.     

The electrical resistivity of amorphous alloys at low temperatures

Measurements of the temperature- and magnetic field dependence of the electrical resistance of some metallic glasses are presented. The data obtained for Cu₅₇Zr₄₃, Cu₄₀Zr₆₀ and Pd₃₀Zr₇₀ demonstrate that deviations from the high temperature behaviour extrapolated to low temperatures are caused by superconducting effects. The paraconductivity which is strongly enhanced in amorphous alloys is shown to agree quite well with theoretical models. The normal state resistance does not saturate down to temperatures of about 2 K. It still exhibits a negative temperature coefficient of the resistivity.     

Critical behavior of electrical resistivity in amorphous Fe-Zr alloys

Electrical resistivity (ρ) of the amorphous (a-)Fe_100−c Zr _c (c=8.5, 9.5 and 10) alloys has been measured in the temperature range 77 to 300 K, which embraces the second-order magnetic phase transition at the Curie temperature point T _c. Analysis of the resistivity data particularly in the critical region reveals that these systems have a much wider range of critical region compared to other crystalline ferromagnetic materials. The value of T _c and specific heat critical exponent, α has the same values as those determined from our earlier magnetic measurements. The value of α for all the present investigated alloys are in close agreement with the values predicted for three-dimensional (3D) Heisenberg ferromagnet systems, which gives contradiction to the earlier results on similar alloys. It is observed from the analysis that the presence of quenched disorder does not have any influence on critical behavior.     

The pressure dependence of resistivity in amorphous copper-zirconium alloys

The variation of electrical resistance with hydrostatic pressure has been measured at room temperature for a number of amorphous Cu-Zr alloys. In each case the resistance falls to a lower value so that the volume dependence of resistance is positive. No correlation is found with the thermoelectric power of these materials and, in a detailed analysis, it is argue that for such transition metal alloys, such a simple correlation is most unlikely.     

Calculation of the electrical resistivity of amorphous Sn-noble metal alloys

The absolute value and temperature dependence of the electrical resistivity of amorphous AuSn and CuSn alloys have been calculated on the basis of the generalized Faber-Ziman theory. The partial structure factors of the amorphous AuSn alloys were calculated for a modified microcrystallite model using the electron diffraction data for the average structure factor. The experimentally observed difference of the temperature dependence of the resistivity in the AuSn and the CuSn series is found to be largely due to the different atomic pseudopotentials for the noble metal component in these alloys.     

Superconductivity and phase compositions in annealed amorphous Nb-Si alloys under high pressure

We report the results of amorphous Nb₈₁Si₁₉ and Nb₇₇Si₂₃ alloys annealed at high pressure but at a pressure lower than that used to synthesize single-phase A15 Nb₃Si. The lower pressure gives rise to the decomposition of the alloys into a multi-phase state consisting of A15 Nb₃Si, Γ-Nb₅Si₃, L1₂-type Nb₃Si and Nb. The lattice constants are smaller and T_c higher than those obtained for the single-phase samples. We predict the T_c of stoichiometric A15 Nb₃Si to be 25 K.     

Surface and bulk crystallization of amorphous alloys Ni-Si-B probed by electrical resistivity

Electrical resistivity measurements are tested as a sensitive probe of the crystallization processes in amorphous metallic alloys of Ni₇₈Si₇B₁₅, rendering the determination of nucleation rates at the surface and in bulk. It is shown that the increase in the electrical resistivity just below the crystallization temperature is mainly due to nucleation phenomena. Moreover, the Avrami coefficient, calculated from resistivity data, provides information about types of crystallization mechanisms, dimensionality of the crystallite growth and the sequence of crystallization stages.     

Electrical resistivity and thermoelectric power of amorphous niobium-nickel alloys synthetized by vapour quenching

Thin film samples (10–20 thick) of niobium-nickel alloys in the composition range Nb-5 to 95 at % Ni were vapour quenched by R. F. sputtering onto fused quartz substrates held at a temperature of 450 K. It was found that fully glassy alloys were synthetized in the composition range Nb-30 to 85 at % Ni, 2·5 times larger than reported for splat-quenched alloys. Crystallization temperatures exhibited maxima near the eutectic composition and are comparable to those of splat-quenched materials. At room temperature, the electrical resistivity of these alloys lies between 176–210 cm, and the absolute thermoelectric power S between 2·20–2·52 V/K. On increasing the temperature from 4·2 to 775 K, up to which the amorphous alloys are stable, the resistivity of the alloy with=0·50 decreases by about 1·5%; the value of d/dT progressively increases with increasing Ni content, becoming positive at 0·50dS/dT of all alloys lies between 6–8·5×10^–3V deg^–2. The electrical behaviour of these alloys may be treated in terms of electron scattering in disordered structures assuming the nearly free-electron model, in a manner analogous to Ziman's theory of electronic transport in liquid metals.     

Superconductivity and spin-glass regime in amorphous La80Au20 alloys doped with Gd

Magnetization and resistivity measurements are performed on amorphous La₈₀Au₂₀ alloys doped with Gd impurities. The anomalous behavior observed in the dependence of the superconducting transition temperature on Gd concentration is related to the onset of spin-spin correlations among the Gd impurities. This study suggests the co- existence of superconductivity and spin-glass regime in several previously investigated superconductors doped with Gd.     

Correlation between the residual resistivity and the temperature resistance minimum in amorphous alloys

A simple formula for the correlation between the residual resistivity and the temperature resistivity minimum in amorphous transition metal-metalloid alloys is derived by means of the Ziman potential scattering theory and the Kondo spin-flip scattering theory.The author would like to thank Dr.O.Hudak for helpful discussions.     

Superconductivity in the amorphous Pd−Si−H alloys with noble-metal substitutes

Hydrogen (or deuterium) was implanted into amorphous Pd-noble metal-Si alloys at low temperatures. In all cases superconductivity resulted. Silicon concentration was varied between 17.1 and 20.1 at.%. The transition temperature,T _c , was primarily influenced by the silicon concentration with small decreases upon addition of noble metals. All the deuteriated alloys show lowerT _c 's compared to the corresponding hydrogenated ones, manifesting normal isotope effect.     

The pressure- and temperature dependence of the electrical resistivity of some amorphous Fe-B alloys

We report measurements of the electrical resistivity of the amorphous alloys Fe₄₀Ni₄₀P₁₄B₆ (Metglas 2826). Fe₃₂Ni₃₆Cr₁₄P₁₂B₆ (Metglas 2826A) Fe₈₀B₂₀ (Metglas 2605) and Fe₇₅B₂₅ as a function of pressure and temperature. The pressure is varied between 0 and 12 GPa, the temperature between 1.2 and 380 K. At low temperatures the pressure dependence yields additional information on the scattering mechanism.     

Crystal-field induced anomalies in the thermoelectric power and electrical resistivity of amorphous cerium alloys

The amorphous alloys Ce₇₂Cu₂₈, Ce₈₀Au₂₀ and Ce₈₉Al₁₁ exhibit a pronounced maximum in the thermoelectric power near 50 K, together with a step-like increase of the electrical resistivity. This is interpreted in terms of a model invoking Kondo scattering from the cerium 4f states split by the local crystal fields of the amorphous matrix. The data for the alloys with Cu and Au indicate a narrow distribution of the overall crystalfield splittings. This hints at a rather uniform structural short-range order.     

Recovery of electrical resistivity in amorphous pdsi alloys after low temperature neutron irradiation

Measurements of electrical resistivity after low temperature fast neutron irradiation are made for amorphous Pd₈₀Si₂₀ and Pd₈₀Ni₂Sl₁₈ and then Pd₈₀Si₂₀ annealed at 230°C and 360°C, and the isochronal annealing curves are obtained. The resistivity increase of Pd₈₀Si₂₀ annealed at 360°C is about 10 times larger than that of amorphous alloys and no defined annealing stage is observed in amorphous alloys and Pd₈₀Si₂₀ annealed at 360°C. For amorphous Pd₈₀Si₂₀, about 60% of the resistivity increase by irradiation remains after annealing up to room temperature and these are discussed by the structural relaxation.     

Superconductivity in amorphous Cr films

Superconducting transition has been observed for the first time in amorphous Cr films prepared by co-sputtering of Cr and BN. Superconducting transition temperatures (Tc) up to 1.14 K have been observed with an orbital contribution (i.e.(dH_c2⊥/dT)_Tc) as large as 49 kOe K^-1. The electronic specific heat coefficient (γ) has been estimated to be about 1.6 times as large as that of amorphous Mo-BN (or Mo-metalloid) alloys. This finding, i.e. the low Tc with the large γ for amorphous Cr is inconsistent with data reported for amorphous alloys of 4d and 5d transition elements. This inconsistency implies a formation of local magnetic moments or spin fluctuation in the amorphous Cr film.     

Effect of transition metal additions on the resistivity of Fe83B17 amorphous alloys

Alloying effects of transition metals on Fe₈₃B₁₇ amorphous alloy were investigated. The resistivity versus temperature curves of Fe₈₃T₃B₁₇ between 4.2–300 K depend on the magnetic behaviour of the transition elements, while below 4.2 K show universal behaviour as it was suggested recently.