Structure and d.c. conductivity of amorphous Si1−xSnx alloys

Amorphous Si_1?xSn_x alloys have been prepared by vapor deposition at a pressure of about 10^?8 Torr on substrates maintained at 77 K. Density measurements and electron diffraction show that Sn atoms are substituted for Si in a random continuous network. The d.c. resistivity of samples of stabilized structure is correctly described by the variable range hopping formula. Structural changes are revealed by the variation of the resistivity at 77 K of samples annealed from 77 K to the crystallization temperature.     

Electrical resistivity of ternary glassy and liquid Pd-alloys

The electrical resistivity of liquid (Pd₁₀₀Cu_100?x)₈₀Ge₂₀ alloys has been measured as a function of temperature. For Cu-rich negative temperature coefficients and for Pd-rich alloys positive temperature coefficients of the electrical resistivity have been observed. This behavior is very similar to recent observed resistivity temperature curves of glassy (Pd₁₀₀Cu_100?x)₈₀P₂₀ alloys. An explanation of the resistivity behavior in terms of liquid metals theory is suggested.     

替代式合金系统的电阻率

本文将文献[1]的无序晶态合金电阻率理论推广到包含长程有序的系统,从而建立了适用于晶态金属,无序及有序替代式合金的Ziman型电阻率理论。根据这个理论我们详细讨论了这类系统电阻率的温度依赖性。文中着重指出:合金系统结构因子的超结构峰对电阻率有重要贡献。这个贡献在低温下是一个T²项,它比电子-电子散射引起的T²项大得多,因而合金系统电阻率在T<<Θ(Θ是德拜温度)时有ρ≈ρ₀+ρ_a(T/Θ)²+ρ_i(T/Θ)⁵的形式。据此,许多A-15化合物正常态电阻率在低温下的反常行为很容易解释。作为例子,我们将低温电阻率的理论表达式与V₃Si的测量值作了比较,符合得很好。     

Normal state resistivity and Tç studies of superconducting Ti1−xSbx system

The superconducting transition temperature (T_c) and the temperature dependence of the normal state resistivity of the Ti_1?xSb_x system between T_c and 300 K have been studied. The T_c values are found to depend on the heat treatment of the samples. Below 40 K, all alloys show a T² dependence of the resistivity. However, the sample with x = 0.53 is not superconducting and shows a different behaviour of the resistivity.     

Superconductivity and the b.c.c. to A-15 transformation in Nb-Au alloys2

Nb-Au alloys near the composition Nb₃Au can be quenched from the high temperature α solid solution phase field, retaining the b.c.c. structure. We report results on their superconducting, mechanical and physical properties as a function of composition. Short low temperature anneals transform these materials to the equilibrium A-15 structure with T_c up to 11K. We report results on the superconducting and physical properties of the transformed A-15 structure materials and describe how the properties of the transformed materials are affected by annealing temperature and time.     

Magnetic and electrical properties of amorphous PdCoP alloys

Magnetic susceptibility and electrical resistivity measurements were performed (Pd_100?xCo_x)₈₀P₂₀ alloys where 15 < x < 50. The magnetic properties show that these alloys undergo a ferromagnetic transition between 272 and 399 K as the cobalt concentration increases from 15 to 50 atomic %. Below 20 atomic % Co the short-range exchange interactions which produce the ferromagnetism are unable to establish a long-range magnetic order and a peak in the magnetization shows up at the lowest temperature range under an applied field of 6.0 kOe. The electrical resistivity of these alloys has been measured from 4.2 K up to the vinicity of the melting point (900 K). The electrical resistivity data could be interpreted by the coexistence fo a Kondo-like minimum and ferromagnetism. The minimum becomes less important as the transition metal concentration increases. The coefficients of In T and T² become smaller and concentration dependent. The spin ordering in such alloys can be simulated as either the ordering due to an applied “external field” or as an increase in “internal fields”. These are due to an increase in transition metal concentration. The negative magnetoresistivity is a strong indication of the existence of localized moment.     

Note on measurements of the electrical resistivity of CrMn alloys

Various experimental results on CrMn alloys are reviewed in order to discuss recent precise measurements of the electrical resistivity in the vicinity of the spin ordering transition temperature T_N. Different critical exponents λ have been observed for the electrical resistivity temperature derivate in alloys of similar composition. Apparent discepancies arte interpreted following recent theoretical work.     

The impurity resistivity and resistivity minima in AlCr and AlMn alloys

The impurity resistivity of $\text{Al}$Cr between 1.5 and 50°K was determined with a characteristic temperature for the T² variation θ₁=960±40°K. The behaviour of the resistivity minimum both in $\text{Al}$Cr and $\text{Al}$Mn alloys with impurity concentration provides evidence that a T³ phonon resistivity is found also in aluminium with anomalous impurity resistivity.     

The effect of pressure on the resistivity of a gold-chromium Kondo alloy and on the low temperature phonon resistivity of pure gold

The electrical resistivity of the Kondo alloy Au (20ppm Cr) and of pure gold has been determined in the temperature range 1.3 – 20 K at pressures up to 80 kbar. For pure gold the pressure dependence of the temperature dependent part of the lattice resistivity can be explained fairly well by the Bloch-Grüneisen theory. Expressions for the volume dependence of the ideal lattice resistivity and of the Debye-temperature for gold are derived. — The Kondo temperatureT _K of Au(Cr) is found to increase with pressure to more than twice the value atp=0 kbar.Therefrom the volume dependence of the effective exchange constantJ is calculated. The results are similar as in other Kondo alloys described previously.     

Cu3Au的电阻率和长程有序

基于作者最近发展的晶态合金电阻理论,本文对Cu₃Au电阻率的温度系数随长程有序度增加而增大的现象给出一个解释,用一个简单的模型赝势计算Cu₃Au的ρT及(dρT/dT),所得结果与实验资料一致。 关键词：     

Magnetic and electrical transport properties of amorphous Zr-Fe alloys

Amorphous Zr_1?xFe_x samples were prepared in the composition range 0.2 ? x ? 0.9 either by means of vapour deposition or melt spinning. The electrical resistivity was determined in the range 4.2–300 K. Negative temperature coefficients were observed in the whole concentration range. The extended Ziman theory (diffraction model) was found to be able to explain these results only if the effective valence of the Fe atoms involves not only s electrons but also d electrons. The magnetic properties and the ⁵⁷Fe Mössbauer effect of the Zr_1?xFe_x alloys were studied in the range 4.2–300 K. The Fe-rich alloys are ferromagnetic. The Fe moment vanishes in alloys of an Fe concentration lower than about 50 at%. In most alloys (x ? 0.8) the Curie temperature is below room temperature and continuously decreases with Zr concentration. By means of Mössbauer spectroscopy and magnetic measurements it is shown that compositional short-range order (CSRO) is present to a higher degree in melt-spun alloys than in vapour-deposited alloys. The effect of sign and magnitude of the heat of solution on CSRO and the magnetic properties is discussed.     

EDXRF measurements on gold diffusion-doped Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy

Gold (Au) diffusion in superconducting Bi_1.8Pb_0.35Sr_1.9Ca_2.1Cu₃O_y was investigated over the temperature range 500-800 °C by the energy dispersive X-ray fluorescence (EDXRF) technique. It is found that the Au diffusion coefficient decreases as the diffusion-annealing temperature decreases. The temperature dependences of Au diffusion coefficient in grains and over grain boundaries are described by the relations D₁=6.7×10⁻⁵exp(−1.19 eV/k_BT) and D₂=9.7×10⁻⁴exp(−1.09 eV/k_BT), respectively. The diffusion doping of Bi-2223 by Au causes a significant increase of the lattice parameter c by about 0.19%. For the Au-diffused samples, dc electrical resistivity and transport critical current density measurements indicated the critical transition temperature increased from 100 to 104 K and the critical current density increased from 40 to 125 A cm⁻², in comparison with those of undoped samples. From scanning electron microscope (SEM) and X-ray diffraction (XRD) measurements it is observed that Au doping of the sample also improved the surface morphology and increased the ratio of the high-T_c phase to the low-T_c phase. The possible reasons for the observed improvement in microstructure and superconducting properties of the samples due to Au diffusion are also discussed.     

Analysis of the spin splitting of maxima of quantum oscillations of the resistivity of n-Bi-Sb semiconductor alloys in a magnetic field parallel to the bisector axis

In samples of semiconductor alloys n-Bi_0.93Sb_0.07 with different electron concentrations (n ₁ = 8 × 10¹⁵ cm^?3, n ₂ = 1.2 × 10¹⁷ cm^?3, and n ₃ = 1.9 × 10¹⁸ cm^?3), dependences of the electrical resistivity on magnetic fields up to 45 T parallel to the current and the bisector axis (H ‖ C ₁ ‖ j) have been measured at temperatures of 1.5, 4.5, and 10 K. The obtained dependences ρ₂₂(H) demonstrate quantum oscillations of the resistivity (Shubnikov-de Haas effect), and, in high magnetic fields, there is a resistivity maximum far away from other maxima. On assumption that this maximum is related to the spin-split Landau level N = 0^? for electrons of the main ellipsoid, the spin-splitting parameters are calculated for electrons of the main ellipsoid: γ₁ = 0.87, γ₂ = 0.8, and γ₃ = 0.73. Using these values, the oscillation maxima can be reliably related to the numbers of split Landau levels for electrons of the main and secondary ellipsoids. The dependences of the resistivity ρ₁₁ and the Hall coefficient R _31.2 on magnetic field have been measured in a transverse magnetic field at H ‖ C ₁ and j ‖ C ₂ on the sample with the electron concentration n ₄ = 1.4 × 10¹⁷ cm^?3. Using similar analysis, the spin-splitting parameter is found to be γ₄ = 0.85, which is close to the value of γ₂ = 0.8 obtained for the sample with close electron concentration (n ₂ = 1.2 × 10¹⁷ cm^?3) during the measurements in a longitudinal magnetic field. The quantum oscillation maxima of Hall coefficient R _31.2 are shifted to the range of high magnetic fields as compared to the quantum oscillation maxima of resistivity ρ₁₁.     

Spin-disorder resistivity in Ni2Mn(Sn1−xInx) heusler alloys

Electrical resistivity measurements have been performed on Ni₂Mn(Sn_1?xIn_x) Heusler alloys, where x = 0, 0.02, 0.05, 0.10 and 0.15, in the temperature range of 4–300 K. The experimental data clearly show the existence of two distinct kinds of resistivity behaviour, both described by an aTⁿ law, for 7 ? T ? 20 K. Between 170 and 300 K the data are well described by an AT + BT² phenomenological fit, and the results obtained are in good agreement with an interpretation based on electron-phonon and spin-disorder scattering.     

Anomalous electrical conduction in disordered and non-crystalline metallic conductors

Many disordered and non-crystalline metallic conductors are characterized by both a negative temperature coefficient (α = ?^-1 d?/dT) of resistivity ? over a wide range of temperatures T and a gradual leveling-off of ? at low temperatures. Experimental results will be presented to show that ? varies as -?n T (for T ? the Debye temperature) in contrast to the prediction of existing theories. This anomalous electron transport can be understood in terms of an attractive interaction between conduction electrons and localized excitations arising from a structural indeterminacy in the atomic arrangement. The possibility of using this scattering mechanism to explain the unusual deviation from linear T dependence of resistivity (the bulge effect) in many structurally unstable superconductors such as A-15 Nb₃Ge, V₃Si, bcc Nb and alloys containing the ω-phase is also discussed.     

The elastic behaviour of In-Tl alloys in the vicinity of the martensitic transition

To test further the prediction of collapse of the [110], q|| [11&#x0304;0] acoustic mode at the martensitic phase transition, pulse superposition measurements of ultrasonic wave velocities have been made in indium-thallium alloys containing 25 and 27 at. % thallium. These alloys are f.c.c. at room temperature and transform on cooling to the f.c.t. phase at 196 ± 2°K and 127 ± 2°K, respectively. Results show that $\text{1}\text{2}$(C₁₁ ? C₁₂) goes to zero within experimental error at the transition temperature. The room temperature elastic constants of the tetragonal 11.5 and 15 at. % thallium alloys are also reported.     

Thermoelectric properties of Bi-Sb semiconducting alloys prepared by quenching and annealing

Bi_100−xSb_x (x=8-17) alloys were prepared by direct melting of constituent elements, which was followed by quenching and annealing. The synthesis of high-homogeneity alloys was confirmed by X-ray diffraction, differential thermal analyses and electron microprobe analysis. The semiconducting and thermoelectric properties of the samples were investigated by measuring Hall coefficient, electrical resistivity and Seebeck coefficient in the temperature range from 20 to 300 K for both the as-quenched and annealing samples. The properties change gradually with the Sb concentration x, which is attributed to the variation of the energy gap. The Hall mobility was enhanced by annealing, which leads to a small electrical resistivity and a large Seebeck coefficient. Consequently, large values of about 8.5 mW/mK² for the power factor were obtained in the annealed alloys of x=8,12, and 14.     

Electron transport properties of Co71−xFexCr7Si8B14 (x=0, 2, 3.2, 4, 6,8 and 12 at%) amorphous alloys during devitrification

The investigation addresses the electron transport properties of Co_71−xFe_xCr₇Si₈B₁₄ (x=0, 2, 3.2, 4, 6, 8 and 12 at%) amorphous alloys. The variation in electrical resistivity of as-cast amorphous materials with thermal scanning from room temperature to 1000 K was measured. The CoFe-based alloys revealed an initial decrease in temperature coefficient of resistivity (TCR), a characteristic of spin-wave phenomena in glassy metallic systems. This behaviour in the present alloys was in a sharp contrast to the Co-based amorphous materials that indicate the drop in resistivity much below room temperature. In the studied alloys, the variation in initial TCR values and the full-width at half-maxima determined from X-ray diffraction of as-quenched materials exhibited a similar trend with increasing Fe content, indicating the compositional effect of near neighbouring atoms. After the initial decrease in resistivity, all the alloys indicated a subsequent increase at T_min. The Curie temperature (T_C), which was measured from thermal variation of ac susceptibility showed non-monotonic change with Fe content. In the temperature range between T_min and T_C the relative scattering by electron-magnon and electron-phonon resulted in the non-monotonic change in Curie temperature. At crystallization onset (T_X1) all the alloys except there with X=6, showed a sharp decrease in electrical resistivity which was attributed to ordering phenomena. In contrast to this resistivity decrease, X=6 alloy exhibited a drastic increase in resistivity around T_X1 observed during amorphous to nanocrystalline transformation. Such nanocrystalline state was observed by Transmission electron microscopy.     

Measurement of surface resistivity/conductivity of metallic alloys in aqueous solutions by optical interferometry techniques

Optical interferometry techniques were used for the first time to measure the surface resistivity/conductivity of the pure aluminium (in seawater at room temperature), UNS No.304 stainless steel (in seawater at room temperature), and pure copper (in tap water at room temperature) without any physical contact. This was achieved by applying an electrical potential across the alloys and measuring the current density flow across the alloys, during the cyclic polarization test of the alloys in different solutions. In the mean time, optical interferometry techniques such as holographic interferometry were used in situ to measure the orthogonal surface displacement of the alloys, as a result of the applied electrical potential. In addition, a mathematical model was derived in order to correlate the ratio of the electrical potential to the current density flow (electrical potential/electronic current flow = resistance) and to the surface (orthogonal) displacement of the metallic samples. In other words, a proportionality constant (surface resistivity or conductivity = 1/surface resistivity) between the measured electrical resistance and the surface displacement (by the optical interferometry techniques) was obtained. Consequently the surface resistivity (ρ) and conductivity (σ) of the pure aluminium (in seawater at room temperature), UNS No.304 stainless steel (in seawater at room temperature), and pure copper (in tap water at room temperature) were obtained. Also, electrical resistivity values (ρ) from other source were used for comparison sake with the calculated values of this investigation. This study revealed that the measured value of the resistivity for the pure aluminium (7.7 × 10¹⁰ Ω cm in seawater at room temperature) is in good agreement with the one found in literature for the aluminium oxide, 85% Al₂O₃ (5 × 10¹⁰ Ω cm in air at temperature 30 °C). Unfortunately, there is no measured value for the resistivity of cupric oxide (CuO), cuprous oxide (Cu₂O), or even the oxide of the UNS No.304 stainless steel in literature comparing those values with the measured values in this study.     

Core level binding energy shifts in Ni on Au and Au on Ni overlayers

Core level binding energy shifts of the Ni-2p and Au-4? lines have been measured for Ni on Au and Au on Ni overlayers down to mean coverages of less than 0.1 monolayers. When normalized to the maximum shift at submonolayer coverage the Ni on Au and Au on Ni shifts show the same dependence as function of the monolayer coverage. Using the thermodynamical approach for the calculation of binding energy shifts in metals, recently developed by Mårtensson and Johansson, the submonolayer shifts together with experimental results of core level binding energy shifts in dilute NiAu and AuNi alloys are used to calculate surface segregation energies in these alloys. They are compared with semiempirical determinations of these energies by Seah.