  We use a quantum mechanical treatment of a ballistic spin current to describe
novel aspects of spin transfer to a ferromagnetic multilayer. We demonstrate
quantum phenomena from spin transmission resonance (STR) to magnetoelectric
spin echo (MESE), depending on the coupling between the magnetic moments in the
ferromagnetic thin films. Our calculation reveals new channels through which
the zero spin transfer occurs in multilayers: the STR and MESE. We also
illustrate that counter-intuitively, a negative spin torque can act initially
on the second moment in a bilayer system.
