By starting with the Boltzmann equation, we calculate the transport properties of magnetic multilayers for currents perpendicular to the layers. Our model takes into account both volume and interface spin-dependent scattering. We show that the macroscopic equations already used by Johnson et al. or van Son et al. are justified if the spin-diffusion length is much longer than the mean free path, even for individual layer thicknesses of the order of the mean free path. But, second, we show that Johnson's assumption of additive effects from independent interfaces in multilayers is incorrect and we obtain different results by taking into account the interplay between successive interfaces. The simple expressions derived for individual thicknesses much shorter than the spin-diffusion length are in agreement with the analysis of experimental results already proposed. It turns out that data on the perpendicular magnetoresistance can be used to separate clearly the volume and interface contributions to the spindependent scattering.
We show theoretically that the change in the magnetization structure of magnetic metallic multilayers under the application of a magnetic field shall be generally associated with a significant change of the refractive index. This constitutes a new magnetooptical effect: the magnetorefractive effect.Optical transmission measurements under an applied magnetic field through [Ni80Fe20/Cu/Co/Cu] multilayers, in the light wavelength region between 2 μm and 20 μm, clearly demonstrate the existence of the predicted effect and are found in reasonnable agreement with the theoretical calculations.
The domain morphology in CoPt multilayers has been investigated by means of magnetic force microscopy for a broad range of thickness parameters. Following hard-axis saturation, complex closure domains, isolated reversed domains, and segmented and fully developed stripe patterns are clearly identified down to stripe widths of the order of 50 nm. Pending full numerical simulations, the stripe width behavior versus Co and Pt thicknesses has been confronted to the predictions of a purely magnetostatic model. The data are consistent with the existence of a single and physically realistic characteristic length, which, however, is viewed as mostly casual. Likely reasons are discussed.
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