  We address two finite size effects in perpendicular transport through
magnetic multilayers. When the magnetic layer thickness in spin valves becomes
of the order or smaller than the spin-flip diffusion length, structural
asymmetries affect the transport properties. A magnetic layer with thickness
approaching the magnetic coherence length becomes transparent for spin currents
polarized perpendicular to the magnetization. We use the generalized
magnetoelectronic circuit theory to investigate both effects on the angular
magnetoresistance (aMR) and spin transfer torque. We analyze recent aMR
experiments to determine the spin-flip diffusion length in the ferromagnet as
well as the interface spin-mixing conductance and propose a method to measure
the ferromagnetic coherence length.
