In this thesis, we performed a detailed study of the thermal conductivity in a wide range of quasicrystals. Three systems were studied: AlPdMn, AlCuFe and AlPdRe, and the samples were in both single and polycrystalline form. A further variable was added by introducing a controlled level of defects. / At low temperatures (below 20K), the thermal conductivity is defect limited, being controlled by boundary scattering, two level systems, stacking faults and dislocations. At high temperatures (above 20K), we find the thermal conductivity is limited by intrinsic properties of the quasicrystalline structure and phonon-phonon scattering. / From fitting the thermal conductivity to a detailed model we are able to predict the maximum thermal conductivity of a perfect quasicrystal.

In this Ph.D thesis the conductance fluctuations of different physical origins in semi-conductor nanostructures were studied using both diagrammatic analytical methods and large scale numerical techniques. In the "mixed" transport regime where both mesoscopic and ballistic features play a role, for the first time I have analytically calculated the non-universal conductance fluctuations. This mixed regime is reached when impurities are distributed near the walls of a quantum wire, leaving the center region ballistic. I have discovered that the existence of a ballistic region destroys the universal conductance fluctuations. The crossover behavior of the fluctuation amplitude from the usual quasi-1D situation to that of the mixed regime is clearly revealed, and the role of various length scales are identified. My analytical predictions were confirmed by a direct numerical simulation by evaluating the Landauer formula. In another direction, I have made several studies of conductance or resistance oscillations and fluctuations in systems with artificial impurities in the ballistic regime. My calculation gave explanations of all the experimental results concerning the classical focusing peaks of the resistance versus magnetic field, the weak localization peak in a Sinai billiard system, the formation of a chaotic billiard, and predicted certain transport features which were indeed found experimentally. I have further extended the calculation to study the Hall resistance in a four-terminal quantum dot in which there is an antidot array. From my numerical data I analyzed the classical paths of electron motion and its quantum oscillations. The results compare well with recent experimental studies on similar systems. Since these billiard systems could provide quantum chaotic dynamics, I have made a detailed study of the consequence of such dynamics. In particular I have investigated the resonant transmission of electrons in these chaotic systems, and found that the level-s

Quantum corrections to the conductivity have been studied at low temperatures down to 0.15K and fields up to 8.8T in two different disordered systems, namely amorphous Ca-Al alloys doped with Ag and Au and icosahedral Al-Cu-Fe alloys. In the former the influence of spin-orbit scattering on the enhanced electron-electron contribution to the resistivity has been, for the first time, clearly displayed. As the spin-orbit scattering rate increases, this contribution decreases rapidly to finally vanish at extremely high spin-orbit scattering rates. Furthermore the analysis shows that the current weak localization theory gives an accurate description of the experiments irrespective of the level of spin-orbit scattering. / In icosahedral Al-Cu-Fe alloys, detailed study of the low temperature resistivity shows that the magnetoresistance and the temperature dependence of the resistivity data are consistent with the predictions of quantum corrections to the conductivity theories. The success of these theories in this alloy system is attributed to intense electron scattering due to disorder. The spin-orbit scattering and the electron wave-function dephasing rates are extracted from fitting the magnetoresistance. The dephasing rate is found to vary as AT$ sp{p}$ with $p sim1.5$; a characteristic of electron-electron scattering in the strong disorder limit. An antilocalization effect has also been directly observed in the temperature dependence of the resistivity in one of the samples.

Time resolved small angle x-ray scattering (SAXS) using synchrotron radiation was applied to the study of the kinetics of spinodal decomposition (SD) in an AlZn binary alloy at critical composition quenched into the immiscible region. These millisecond time scale measurements, performed at the National Synchrotron Light Source (Brookhaven National Labs., N.Y.), constitute the first direct experimental verification in a binary alloy of the theory proposed by Langer, Bar-on and Miller in 1975 for SD. A scheme based on the composition distribution functional is proposed to account for the decomposition taking place during the quench. The interatomic mobility, a free energy gradient coefficient and two coefficients that suffice to determine a coarse-grained (intensive) free energy have been obtained in the framework of this theory. The mobilities obtained compare well with tracer diffusion measurements reported in literature. A dependence of the coarse-grained free energy coefficients on the coarse-graining length is found and a procedure is proposed to uniquely choose the values of these coefficients based on the predicted integrated intensity from the equilibrium concentrations and on the measured integrated intensities. / Late-stage coarsening regimes were also investigated. In these regimes, growth exponents higher than the value 1/3 predicted by the Lifshitz-Slyozov-Wagner theory are obtained. These higher values, comprised between 0.40 and 0.45 are consistent with predictions that alloys in which elastic effects are important can present a transition regime from a $t sp{1/3}$ growth law to a $t sp{1/2}$ law. The structure factors do not quite scale. They also present a shoulder at high wavevectors, a feature not reported before in metallic alloys.

The effects of short range order on the structural and transport properties of the $ rm Cu sb{1-x}Ni sb{x}Zr sb2$ amorphous metallic alloy system are studied. Depending on composition, these amorphous alloys crystallize into different structures. CuZr$ sb2$ has the I4/mmm (C11) structure and NiZr$ sb2$ has the I4/mcm (C16) structure. It is believed that the short range order in the amorphous phase is related to the final crystalline phase. A careful study (using differential scanning calorimetry, X-ray diffraction on as made and crystallized states, room temperature magnetic susceptibility and resistivity, and a determination of the superconducting transition temperature of as-made and annealed states) has been done to see what transport properties are affected. / It is observed that there is a linear increase in the values of the susceptibility, resistivity, and superconducting transition temperature of the system from CuZr$ sb2$ to NiZr$ sb2.$ This is attributed to an increase of the electronic density of states as the concentration of Ni increases. There is little or no influence on transport properties due to topological short range order.

Electrochemical methods have been used to measure the solubility and diffusivity of hydrogen in amorphous $Ni sb{60}Zr sb{40}$ over a wide range of hydrogen concentrations. It is found that Sievert's law is not obeyed and that the concentration of hydrogen in the metallic glass varies as $P sp{1/4}$, P being the pressure of hydrogen. In the concentration range of hydrogen measured, the diffusion constant of hydrogen increases by more than a factor of ten. A Gaussian distribution of hydrogen binding energy was used to explain the concentration dependence of chemical potential. A possible explanation to the concentration dependence of diffusion coefficient was also given.

We have used a new type of torque magnetometer: a piezoresistive cantilever. It detects the force and torque applied to the end of the cantilever beam by changes in its resistance. We report the first use of this device at temperatures below 1 K. We observed a hysteretic behavior of the resistance at low magnetic field (less than 10 mT) in that temperature range. At higher field it has a smoothly varying magnetoresistance which permitted us to measure the de Haas-van Alphen (dHvA) effect in two superconductors: $ kappa$-(BEDT-TTF)$ sb2$Cu(NCS)$ sb2$ and Sr$ sb2$RuO$ sb4.$ These measurements demonstrated that a large excitation current can be used if the sample is well thermalized but that torque interactions (TI) can affect the signal. TI can be reduced by the use of feedback. We also present measurements above 75 K of $H sb{c1}$ of YBa$ sb2$Cu$ sb3$O$ sb{6.9}$ obtained by modulating the field and measuring the torque signal at an harmonic of the modulation frequency.

Spin fluctuations (SF) are magnetization fluctuations in a metal. They have been proposed as the fundamental origins of the finite temperature properties of transition metals. This thesis presents amorphous iron-zirconium ($a$-Fe$ sb{x}$Zr$ sb{100-x}$) as an ideal system in which to study SF. $a$-Fe$ sb{x}$Zr$ sb{100-x}$ transforms from an exchange-enhanced paramagnet to a weak ferromagnet with increasing $x$, while the atomic structure remains virtually unchanged. The enhancement by SF of the effective electron mass has been studied in $a$-Fe$ sb{x}$Zr$ sb{100-x}$ by low temperature calorimetry. We report the first observation of the complete quenching or suppression of SF in a metal, achievable by either raising the temperature, or by applying a high magnetic field. This complete quenching allows us to rule out the formation of super-paramagnetic clusters, the only other plausible explanation of the data. $a$-Fe$ sb{x}$Zr$ sb{100-x}$, therefore, shows the clearest evidence to date of SF in the electronic properties.

Soft magnetic $ rm Ni sb{ it x}Co sb{ it 100-x}$/Cu multilayers in the range x = 20 to 80 have been prepared by DC-magnetron sputtering. NiCo alloys were chosen because of their small magnetoelastic parameters around the range x = 70-80 and very small lattice mismatch between NiCo and Cu. This combination of parameters should lead to good giant magnetoresistance (GMR) with a small saturation field. Structural characterization reveals that high quality layered structures were obtained. Quantitative interpretation of the superlattice structure parameters, such as interface roughness, interfacial mixing profiles and layer-thickness disorders, have been carried out by modelling the X-ray diffraction data. / GMR was found to be largest at x = 80 with well-defined oscillations as a function of the thickness of the Cu layer, mirroring the interlayer magnetic coupling. In particular, GMR with small saturation fields around Cu thickness near the second MR maximum (t$ sb{Cu}$ = 20A) will be technologically important because of the very high magnetic field sensitivity. Correlating the multilayer structure to the GMR allow us to optimize the structural parameters by enhancing the spin-dependent interfacial scattering in a high quality layered structure. Direct observation of the simple antiferromagnetic order has been achieved by the presence of the (0,0,${1 over2})$ wavevector in small angle neutron scattering experiments. A near-perfect antiferromagnetic spin arrangement is found for a Cu thickness t$ sb{Cu}$ = 20 A, that can be readily aligned ferromagnetically in a small external field of less than 200 Oe. / A complementary system, FM/Ag (FM = $ rm Ni sb{81}Fe sb{19}, Ni sb{80}Co sb{20}$ and $ rm Ni sb{66}Co sb{18}Fe sb{16})$ granular multilayer prepared by annealing multilayers, has also been studied. Enhanced magnetoresistance observed in these systems is shown to be controlled by the size, concentration and thermal stability of the magnetic precipitates in a nonmagnetic matrix. For a particular multilayer structure with a magnetic layer of 20 A, annealed at around 325$ sp circ$C, a GMR of $ sim$4% with a characteristic saturation field of 10 Oe was found, leading to a high magnetoresistive sensitivity of $ sim$0.4%/Oe at room temperature.

This exploratory study examined the predictive ability of perceived work environment characteristics on employees' level of motivation to learn and growth need strength. It looked at motivation to learn within the context of two types of training: formal training and on-the-job training. It also examined the existence of group differences in motivation and in perceptions of the work environment. The sample was 117 middle management staff at a Canadian research university, varying in age, level of education, job classification, work unit, and job and institutional tenure. Data was collected using a questionnaire consisting of scales from the management and educational literature. Using multiple regression analysis and MANOVAs, workplace environmental characteristics were found to be predictors of employee motivation. The best predictor of motivation to learn was a composite measure of incentives, while the best predictor of growth need strength was a composite measure of lack of independence and freedom of choice. No group differences in motivational characteristics were found, however, there were differences in perceptions of the work environment.