QUANTUM SINGULARITIES IN THE ANGULAR-DEPENDENCE OF GIANT MAGNETORESISTANCE IN ULTRATHIN FERROMAGNETIC SANDWICHES

We present an analytical quantum statistical theory of the angular var iation of the giant magnetoresistance (GMR) in thin ferromagnetic sand wiches (current flowing in the plane of the layers). Both spin-depende nt scattering of conduction electrons and the existence of spin-depend ent potential barriers between the successive layers are taken into ac count. We show that quantum singularities can arise in the variation o f the electrical resistivity of the structure with the angle between t he magnetizations in the ferromagnetic layers. These singularities res ult from the quantization of the momentum of electrons in the directio n perpendicular to the plane of the layers.