Correlation of Giant Magnetoresistance with Infrared Magnetorefractive Spectra

In this paper contactless measurements of magnetoresistance (MR) using electromagnetic radiation are attractive for in-situ probing of MR. The magnetorefractive effect (MRE) relates the MR to reflection in the far infrared (IR). An extended Drude model is used to describe the spin-dependent conduction and incorporated into the complex dielectric function. The reflectance, transmittance and emittance are determined by the complex dielectric function, hence enabling (IR) optics to sense MR. A wide variety of MR materials have now been studied using the MRE. For this technique to be useful, a simple relationship between the IR reflection and the electrical MR is required. Using CoFe/Cu multilayers, we test such a relationship as predicted by simulations. The MRE is defined as the change in the IR spectrum in a magnetic field.