THEORY OF THE NEGATIVE MAGNETORESISTANCE OF FERROMAGNETIC-NORMAL METALLIC MULTILAYERS (INVITED)

Transport properties for a system consisting of a ferromagnetic-normal metallic multilayer are theoretically examined. The in-plane conducta nce of the film is calculated for two configurations; the ferromagneti c layers aligned (i) parallel and (ii) antiparallel to each other. The results explain the giant negative magnetoresistance encountered in t hese systems when an initial antiparallel arrangement is changed into a parallel configuration by application of an external magnetic field. The calculation depends on (a) geometric parameters (the thicknesses of the layers); (b) intrinsic metal parameters (number of conduction e lectrons, magnetization and effective masses in the layers); (c) bulk sample properties (conductivity relaxation times); and (d) interface s cattering properties (diffuse scattering versus potential scattering a t the interfaces). It is found that a large negative magnetoresistance requires, in general, considerable asymmetry in the interface scatter ing for the two spin orientations. All qualitative features of the exp eriments are reproduced. Quantitative agreement can be achieved with s ensible values of the parameters. The effect can be conceptually expla ined based on considerations of phase-space availability for an electr on of a given spin orientation as it travels through the multilayer sa mple in the various configurations.