QUANTUM EFFECTS IN THE GIANT MAGNETORESISTANCE OF MAGNETIC MULTILAYERED STRUCTURES

We present an analytical quantum statistical theory of giant magnetore sistance in magnetic multilayers (current Bowing in the plane of the l ayers) which takes into account both spin-dependent scattering of cond uction electrons (s, d or hybridized sd electrons) and spin-dependent potential barriers between successive layers. The model also includes quantization of the momentum of conduction electrons in the direction perpendicular to the plane of the layers (k(z)). The influence of the following parameters is discussed: ratio of spin-up to spin-down mean free paths, height of potential barriers between adjacent materials an d thicknesses of the various layers. It is shown that the main contrib ution to the giant magnetoresistance is spin-dependent scattering rath er than spin-dependent potential barriers. In fact, if the mean free p aths of spin-up and spin-down electrons in the magnetic material are s ignificantly different, the presence of potential barriers (spin-depen dent or not) can only decrease the magnetoresistance amplitude. Furthe rmore, the quantization of component momentum k(z), leads to well-defi ned oscillations of magnetoresistance with respect to thicknesses of t he various layers. It should be possible to observe these quantum osci llations experimentally.