Correlation between the magnetorefractive effect, giant magnetoresistance, and optical properties of Co-Ag granular magnetic films

Giant magnetoresistance (GMR), optical properties, and the infrared magnetorefractive effect (MRE) are studied in reflection for granular films of composition Co_xAg_1-x with x ranging from 0.1 to 0.7. From ellipsometry measurements it is shown that it is necessary to take into account finite-size effects in order to successfully model the optical data demonstrating the importance of the microstructure to the MRE. The ellipsometry data enable the variation in optical properties with Co concentration to be determined and incorporated into a model of the MRE. The MRE itself is calculated with a frequency- and spin-dependent conductivity. Both the experimental and theoretical analyses reveal a correlation between GMR and the MRE demonstrating the feasibility of using the MRE as a contactless method for measuring the GMR and for extracting fundamental spin-dependent scattering parameters.