Investigation On The Electrical Transport And Thermal Properties Of Disordered Alloys

The temperature dependence of specific heat and thermal conductivity of (Cu₅₀Zr₅₀)₉₄Al₆ bulk metallic glasses was analyzed systematically. The electrical transport properties of the Ag3Sn polycrystalline samples and the Cu-Zr amorphous thin films were studied, respectively.The heat capacity measurements on (Cu₅₀Zr₅₀)₉₄Al₆ bulk metallic glasses indicated that localized vibration modes exist in these alloys. Comparing the heat capacity data with theoretical predication, we find that the vibrational density of states of localized vibration modes has a Gaussian distribution. As for the thermal conductivity, besides Rayleigh-type point defect scattering and electron-phonon scattering, the resonant scattering due to the interaction between phonons and localized vibration modes also plays an important role in the phonon transport process. The annealed sample (the annealing temperature is lower than the glass transition temperature) still keeps amorphous structure, and the intensity of Boson peak of the sample increases and position of peak moves to lower energy. The variation of the Boson peak can be described by the transformation of the continuous medium.We have systemically investigated the electrical transport properties of Ag3Sn bulk metallic samples with different disorder levels. The temperature dependence of resistivity reveals concave function characteristic from 305 down to 2 K, which can be quantitatively described by Fisk and Webb's"parallel resistor"formula. The lower temperature resistivity of all the samples varies as T2 dependence, whose origination is not very clear yet. The normalized magnetoresistance is positive for all the samples. The normalized magnetoresistance in low field (B<1 T) obeys Kohler rule, that is, it has a quadratic dependence on the applied field. In high field (B>1 T), the magnetoresistance data show linear dependent on field, which is not very well understood. The electron weak localization effect and the electron-electron interaction play important roles in the electrical transport properties of Cu-Zr amorphous thin film. We find there exist three distinct temperature regions, in which the conductivity variation with temperature follows T 1/2, T and T 1/2 law, respectively. The electron dephasing time can be obtained from the magnetoresistance measurement. The electron inelastic scattering mainly come from the interaction between the electrons and the transverse phonons. The spin-obit scattering rate is strongly dependent on the Zr content of the samples.