Effect of diffusive scattering on giant magnetoresistance in magnetic multilayers

Dramatic changes in resistance due to external magnetic fields or giant magnetoresistance (GMR) have provided revolutionary advances in disciplines ranging from computer memory to land mine detection. This thesis explores the crucial role of interfaces in producing GMR in systems such as magnetic multilayers and spin valves where magnetic layers (Co or Fe) are separated by simple metal layers of Cu or Cr.; A semi-classical Boltzmann transport model is used to model GMR in Co|Cu magnetic multilayers. Parameters required to fit experimental results indicate minority carriers in Co have a very small mean free path and experience enhanced diffusive scattering at layer interfaces. Parameters fitted for magnetic multilayers (>100 layers) are used to calculate the GMR in corresponding spin valve systems. The model provides GMR and resistivity values in good agreement with current experimental results for spin valves.; Scattering at a single interface is examined using two techniques to provide a better theoretical basis for treatment of interfaces in semi-classical calculations. An analytical Green's function approach is developed that treats the interface as a sheet of randomly placed point scatterers. This formalism provides closed forms for interface specularity parameters that depend on electron momentum and interface roughness. The specularity parameters for transmission and reflection differ in functional form, a fact neglected in current Boltzmann models. The layered Korringa Kohn Rostoker method (LKKR) is also used to examine transport across free electron and Co|Cu interfaces. The interdiffused region is treated as an alloy layer under the Coherent Potential Approximation (CPA). Specularity parameters found using this technique for free electrons agree well with analytical Green's function results. The LKKR also provides the first energy dependent specularity parameters for a real material interface.; The electronic properties of FeCr alloys are examined using the LKKR-CPA. Heat capacity measurements of FeCr multilayers indicate the presence of an enhanced density of states possibly due to the formation of interdiffused alloy layers. Density of states and magnetic moments are calculated for alloys with varying Cr concentrations. Our calculations do not produce the density of states enhancement observed. Calculated magnetic moments agree well with available experimental data.