The 27 Al and 63 Cu spin-lattice relaxation rates were found to contain a large T 2 term over a wide temperature range below 400 K in several thermodynamically stable quasicrystalline alloys, including i-AlCuRu, i-AlPdRe, i-AlCuFe, and the crystalline approximant phase a-AlMnSi. The relaxation mechanism is proven to be electronic in origin. Such nonlinear temperature dependence is shown to be a clear signature of sharp features in the density of states at the Fermi level. The estimated width of this sharp feature is on the order of 20 meV. [S0031-9007(97)

The activation volume ΔV for chemical diffusion in Ag50Au50 alloy has been determined from the pressure dependence of the rate of decrease in amplitude of composition-modulated thin films. Based on resistivity measurements, it is argued that the technique yields the bulk chemical diffusion coefficient, in close agreement with the experimental results. Eight measurements of the diffusion coefficient were made, four as a function of temperature (237–309 °C) at atmospheric pressure and four as a function of pressure (0–0.85 GPa) at constant temperature (269.5 °C). The samples, 2000–3000-Å-thick multilayers of alternating silver and gold, with periods between 72 and 160 Å, were made with a newly built UHV sputter-deposition apparatus. The bulk chemical interdiffusion activation energy (1.5 eV) and activation volume (0.72 Ω) agree with those expected from other interdiffusion and tracer measurements.

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The analysis of the original measurements of the subsurface electrical potential in oriented single crystals of AgC1 [Hudson, Farlow, and Slifkin, Phys. Rev. B 36, 4651 (1987)] has been corrected for two previously neglected effects. The resulting values for the surface potential Ns have been reanalyzed to resolve the Frenkel-pair formation enthalpy and entropy into the contributions from the two distinct defects comprising the pair. It is shown that the effects of divalent impurities and of impurity-vacancy association are important even for temperatures that appear intrinsic in Arrhenius ionic-conductivity

Because an external magnetic field does no work on moving charges, it is argued that independently migrating point defects in an ionic crystal cannot exhibit any Hall effect, to first order. This is in sharp contrast to the cooperative motions displayed by superionic conductors. Experimental results on interstitial migration in AgBr and a-AgI agree with these expectations.

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