Temperature dependence of the electrical resistivity in amorphous metals

In amorphous metals the electrical resistivity increases linearly in the temperature range from 2 to 40 K. This result differs fundamentally from the nonlinear behaviour known for crystalline metals and it suggests the conduction electrons not to be scattered by the vibrations of the amorphous point lattice. The temperature dependent part of the resistivity in amorphous metals is explained with scattering of conduction electrons by fluctuations ofp-electrons.     

Temperature dependence of the contribution to the transport coefficients of nearly ferromagnetic metals from electron-paramagnon scattering

We present calculations of the temperature dependence of the contribution from electron-paramagnon scattering to the electrical and thermal resistivity of a simple model of a nearly ferromagnetic metal. The purpose of the work is to explore the behavior of these quantities when the temperature is the order of or greater than the spin fluctuation temperature T_sf. As the temperature T is raised from zero through T_sf, the electrical resistivity varies more slowly with temperature than the T² law characteristic of the regime T?T_sf. When T?T_sf, the electrical resistivity becomes proportional to T, although this asymptotic behavior is approached very slowly. The Lorenz number rises monotonically with temperature, and appears to approach the ideal Sommerfeld value when T?T_sf, although this limit is also approached slowly.     

On the concentration dependence of transport coefficients in amorphous transition metal alloys

We discuss the concentration dependence of resistivity of CuTM (TM  Ti, Zr, Hf) amorphous alloys within a framework of a two-band model in which the s-states dominate conduction at the Cu end while the conduction of the d-states becomes increasingly important at TM rich end. We present a simple empirical relation that well describes the concentration dependence of the Hall coefficient and its sign reversal.     

Electron transport in amorphous metals

Electron transport measurements—resistivity, thermopower, magnetoresistivity and Hall effect—in non-magnetic amorphous metals are surveyed and compared with predictions from several theoretical models proposed to describe electron scattering in highly disordered metals.     

Comments on the temperature dependence of the electronic transport coefficients in ferromagnetic f-electron metals

Possibilities of formulation of a theory capable of describing the temperature behaviour of the electronic transport coefficients of f-electron crystal field-free systems on a broad temperature scale are discussed. The approach used by Balberg to study the spin-fluctuation resistivity in the vicinity of T_c is shown to be valid on the broad temperature scale if the scattering cross section is appropriately treated. The results of this approach are compared to that of de Gennes and Friedel and supplementary results for the thermoelectric power are presented.     

Temperature and thickness dependence of low temperature transport in amorphous silicon thin films: A comparison to amorphous germanium

The temperature and thickness dependence of the low temperature electrical transport of amorphous silicon thin films measured in-situ in ultra-high vacuum are presented. As for a-Ge there is an extended range of $\text{ln ? ∝ T}{}^{\mathrm{<mtext>?1</mtext><mtext>4</mtext>}}$ for thick films with $\text{ln ? ∝ S}{}_2\text{T}{}^{\mathrm{<mtext>?1</mtext><mtext>3</mtext>}}$ for thin films with $\text{S}{}_2\text{∝ d}{}^{\mathrm{<mtext>?1</mtext><mtext>3</mtext>}}$ as expected from a variable range tunneling mechanism.     

Temperature dependence of EXAFS in amorphous arsenic

EXAFS measurements at different temperatures on amorphous arsenic are reported. The low values of the EXAFS mean square relative displacement σ² for the first coordination shell are consistent with a distribution of As₄ pyramidal units throughout the amorphous network, giving a locally very ordered first shell, whose disorder is essentially dynamic in character. The temperature dependence of the vibrational contribution to the EXAFS Debye-Waller factor is well described by an Einstein oscillator model.     

Evidence that the Born approximation is unreliable for calculating transport coefficients of liquid metals

The validity of the Born approximation formula for the electrical resistivity of a liquid metal has recently been questioned by Greenfield. However, it has been suggested that Greenfield underestimated the volume dependence of the potential. We demonstrate that the influence of the volume dependence of the potential is indeed small, and we thus confirm Greenfield's conclusion that the Born approximation formula fails to give the correct temperature dependence of the resistivity. This failure is shown to occur both for the constant-pressure and for the constant-volume cases.     

Temperature dependence of photodegradation in amorphous hydrogenated silicon

Measurements of steady-state photoconductivity with respect to light-induced defect generation in amorphous hydrogenated silicon (a-Si: H) show that the power index of the time evolution (long-term observation) of the photodegradation is determined by the exposure temperature and the material.     

Temperature dependence of liquid volume

It is shown that the temperature dependence of the liquid volume is well described by the equation $ V = A + BT + CT^2 + V_e \exp ( - E/RT), $ V = A + BT + CT^2 + V_e \exp ( - E/RT), where A, B, C, V _e , and E are constants. This equation reflects two processes owing to which the liquid volume increases with temperature, namely, anharmonic oscillations of molecules and formation of “holes.”     

Temperature dependence of liquid viscosity

Least squares programs were used to evaluate the correlation between recent experimental results and theoretical, semi-theoretical, or empirical relations between liquid viscosity and temperature. It was found that none of these describes the experimental dependence in the whole range of temperature. A new dependence based on the free volume concept and cell-hole liquid theory is proposed. The theory permits linearization of the viscosity-temperature data in the range (T_i, T_i+1), where the T_i's are the liquid-liquid transition temperatures. It was demonstrated that these transitions, both in small molecular and in polymeric liquids, occur in discrete steps: T_i = a_iT_g, where T_g is the glass transition temperature and the a_i's are numerical parameters. Not all the transitions T_i were apparent in all liquids. Transition T₂ = 1.26T_g was observed for most polymeric liquids. On the basis of thermal analysis it was demonstrated that the T_i's coincide with the temperatures at which small changes in the apparent specific heat were detected. These temperatures can be assigned to the maximum rate of crystallization and melting temperatures of the metastable and stable crystalline forms.     

Temperature dependence of the self-broadening coefficients of ethane

Using a diode-laser spectrometer, self-broadening coefficients have been measured at three temperatures (246.2, 226.2 and 150.2 K) for 11 spectral lines in the ν₉ fundamental band of ¹²C₂H₆. The collisional widths have been obtained by fitting each experimental absorption profile with a Rautian model. The temperature dependence exponent n was also determined for each line, and found to be constant within experimental uncertainties. The mean value is equal to n = 0.676.     

Temperature dependence of low angle structure factors of liquid alkali metals using electron-ion plasma model

The analytic solution of EIP model in the MSA via the OCP criterion yields temperature dependent results in RPA quite satisfactorily at high temperatures. The same set of parameters produces low and high angle structural properties. The model can work almost near to the critical point if the ion-core radius is allowed to vary systematically in the regionρ<2ρ _c,ρ _c being the critical density. The model can also accommodate the general scaling behaviour observed for the structure factors of liquid alkali metals.     

Molecular dynamics simulation of self-diffusion coefficients for liquid metals

The temperature-dependent coefficients of self-diffusion for liquid metals are simulated by molecular dynamics meth ods based on the embedded-atom-method （EAM） potential function. The simulated results show that a good inverse linear relation exists between the natural logarithm of self-diffusion coefficients and temperature, though the results in the litera ture vary somewhat, due to the employment of different potential functions. The estimated activation energy of liquid metals obtained by fitting the Arrhenius formula is close to the experimental data. The temperature-dependent shear-viscosities obtained from the Stokes-Einstein relation in conjunction with the results of molecular dynamics simulation are generally consistent with other values in the literature.     

Temperature dependence of hyperfine fields at impurities in metals

A model is developed to account for the spin-densities at dilute non- magnetic impurities in ferromagnetic metals which exhibits a non-linear dependence of the hyperfine field on the host magnetization. The theory is used to calculate the hyperfine field at an interstitial positive muon in gadolinium.