Magnetoresistance measurements in Al-Ge alloys after neutron irradiation at 4.6 K

The influence of different structural defects, introduced by irradiation in a series of AlGe alloys is established by measuring the longitudinal magnetoresistance. The validity of Kohler's rule is absolute for both pure and alloyed samples that have been irradiated by neutrons at 4.6 K, while the rule breaks down after annealing at different temperatures.The origin of the breakdown of Kohler's rule appears to be the anisotropic scattering of the electrons on the clusters formed after annealing. This scattering depends on the size of the clusters which varies with the concentration of foreign atoms.     

Magnetic susceptibility and electrical resistivity of dilute liquid copper - iron alloys

Electrical resistivity and magnetic susceptibility measurements on dilute liquid CuFe alloys are reported. Small additions of Fe increase the resistivity of liquid Cu in a drastic manner, whereas the temperature coefficient is found to be decreased. Due to the localized magnetic moments of the impurity atoms the diamagnetism of Cu is converted into a strong temperature-dependent paramagnetism indicating about 3.5 unpaired d electrons per Fe atom. The electronic properties of CuFe resemble those of liquid CuMn and AuFe which, in the solid state, are known for their Kondo-like behaviour. The experimental findings are tentatively interpreted in terms of spin-disorder scattering with special emphasis on the negative temperature coefficient of the impurity resistivity.     

The influence of irradiation temperature (4.2 and 77 K) on the resistivity recovery of pure and Ge alloyed aluminum

An examination of the resistivity increment of pure and Ge alloyed aluminum neutron irradiated at 77 K and 4.6 K followed by an anneal at 77 K was carried out. In the first treatment, the resistivity increment, for pure and germanium alloyed aluminum, was found smaller than that corresponding to the second treatment.     

Surface scattering of electrons on copper whiskers and its influence on the electrical resistivity at 4.2 K

The effect of specimen size on the electrical resistivity at 4.2 K of copper whiskers having transverse dimensions in the order of the electron mean-free path was measured. The experimental data are interpreted by means of a modified Nordheim formula adapted to the exact theory of Dingle. Assuming for copper the value of the productQ ₀·λ obtained from the free electron model a specularity parameterp for the surface scattering of conduction electrons is deduced from the diameter dependence of the sample resistivity. Values ofp=0.45 (up to 0.66 in an individual case) andp=0.18 are calculated exhibiting that significant specular reflection is present. Differences in the amount of specular reflection appear to arise from differences in the microscopically observed surface conditions of the whiskers.     

The electrical resistivity of barium and yttrium at high pressure

Electrical resistivity data suggest that yttrium and barium become d-metals under pressure. This behavior correlates with the pressure-induced superconductivity.     

Investigation of the transition to superplastic behaviour by measurements of electrical resistivity annealing curves

Superplastic behaviour of the Zn-0·25 wt. % Cd alloy is studied by means of electrical resistivity measurements accompanied by dynamical tensile tests and optical metallography. Specimens of the alloy were deformed at various strain rates and temperatures and then step-by-step annealed up to 520 K, the electrical resistivity changes due to annealing being recorded. It is shown that the resistivity annealing curves are strongly influenced by the value of strain, strain rate and deformation temperature. A good correlation between the mechanical characteristics of the alloy and the resistivity changes caused by annealing has been observed.     

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.     

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.     

Electron-electron interactions and the electrical resistivity of lithium at low temperatures

The electron-electron interactions in lithium metal have been examined keeping in view the recent developments. The contribution of the electron-electron Umklapp scattering processes in the electrical resistivity of lithium at low temperatures has been evaluated using a simplified spherical Fermi surface model with isotropic transition probability. Our values of the electrical resistivity so obtained compare fairly well with the experimental results for lithium.      

Magnetic susceptibility and electrical resistivity of Ni-Al alloys at high temperatures

Magnetic susceptibility and electrical resistivity of the Ni-Al alloy system are studied in wide temperature (700–800°C) and concentration (up to 25 at. %) intervals. It is shown that in the region of solid solutions, temperature dependencies are sufficiently well described by a modified Curie-Weiss law, taking into account the existence of a temperature-independent contribution. For liquid alloys, calculation of the dependence of the electrical resistivity on composition is performed according to the Faber-Ziman-Evans method. Magnetic and electrical characteristics obtained are explained on the basis of a modified Anderson model, with the interaction of virtual bound states of nickel with collective valent electrons of aluminum taken into account.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 23–28, March, 1982.     

高压下锐钛矿TiO2的电阻率及能带结构的研究

应用在位电阻率测量方法研究高压下锐钛矿TiO2的电学性质。通过研究电阻率随压力变化的异常变化点,观察到了TiO2从锐钛矿－柯铁矿－斜锆石的相变。卸压后,电阻率数值和初始值相差2个数量级,说明该相变为不可逆相变。结合第一性原理计算结果表明,柯铁矿结构更小的带隙是导致TiO2电阻率减小的根本原因。     

Electron interactions and the electrical resistivity of alkali metals at low temperatures

The contribution of the electron-electron umklapp scattering processes to the electrical resistivity of sodium, potassium, rubidium and cesium at low temperatures has been evaluated using a simplified spherical Fermi-surface model with an isotropic transition probability. Our values of the electrical resistivity so obtained compare fairly well with the recent experimental values for sodium, potassium and rubidium. Our theoretical results have also been compared with the other available data in the literature due to Lawrence and Wilkins and MacDonald and Geldart.     

高压下锐钛矿TiO2的电阻率及能带结构的研究

应用在位电阻率测量方法研究高压下锐钛矿TiO2的电学性质. 通过研究电阻率随压力变化的异常变化点, 观察到了TiO2从锐钛矿-柯铁矿-斜锆石的相变. 卸压后,电阻率和初始值相差2个数量级, 说明该相变为不可逆相变. 结合第一性原理计算结果表明, 柯铁矿结构更小的带隙是导致TiO2电阻率减小的根本原因.     

Role of nickel and manganese in recovery of resistivity in iron-based alloys after low-temperature proton irradiation

This study investigates the recovery of electric resistivity in pure iron, Fe–0.6Ni and Fe–1.5Mn as related to isochronal annealing following 1 MeV proton irradiation at lower temperature than 70 K, focusing on the relationship between solute atoms and irradiation defects. Both nickel and manganese prevent stage I_D recovery, which corresponds to correlated recombination. Stage II recovery is also changed by the addition of a solute, which corresponds to the migration of small interstitial clusters. In both pure iron and Fe–0.6Ni, no evident difference was observed in the stage III region, which corresponds to the migration of vacancies. In contrast, two substages appeared in the Fe–1.5Mn at a higher temperature than stage III_B appeared in pure iron. These substages are considered to represent the release of irradiation-induced defects, which was trapped by manganese.     

Mössbauer effect studies of the recovery of iron after heavy-ion implantation at 7 K

Mössbauer effect measurements were performed with sources of¹³³Xe implanted at 7 K in polycrystalline iron foils by means of an isotope separator. Information about the direct environment of an implanted radioactive probe atom is obtained through the hyperfine interaction of the daughter nucleus (¹³³Cs) with its surroundings. The Mössbauer spectra were analyzed on the basis of an earlier model, assuming three visible spectral components with high, intermediate and low hyperfine fields and recoilless fractions, respectively, and a fourth, invisible component with a recoilless fraction very close to zero. Annealing experiments showed no evidence for post-implantation recovery stage I in the iron foils, while recovery stage II only gave rise to small changes in the site occupations. These results can be explained in terms of the high energy density locally deposited in the lattice by each implanted atom, leading to stage I recovery during the very short time that is necessary for the thermal dissipation of this energy. Quantitatively, these results are confirmed by calculations of Sigmund on heavy-ion induced elastic-collision spikes in solids. After annealing at room temperature the site occupations agree with those obtained directly with room temperature implanted sources. In previous experiments we have shown that different results are obtained for annealing and for implantation at 200°C. From these results we estinate the migration energy of vacancies in iron at 1.27±0.09 eV.     

Behavior of the electrical resistivity at phase transitions in binary alloys

The excess resistivity of binary alloys is calculated in the Born approximation for the scattering of quasifree electrons from the atomic disorder. can be represented as the convolution of the structure functionS(q) and the fourier transform of the effective potential. The critical anomaly of is derived from scaling expressions forS(q), both for alloys which undergo unmixing and for order-disorder transitions. The variation of with concentration and temperature in the vicinity of a critical point is obtained. The time-dependence of the resistivity of alloys after a sudden quench into the two-phase region is also calculated, using computer simulation data forS(q,t), and a maximum of is found for zones with linear dimension of 8–12 lattice spacings. All these results are in fair agreement with the available experiments. As a further possible application, we obtain the critical exponent for the nonlinear relaxation of the resistivity of an alloy close to the order-disorder transition.