Conductance modulation by spin precession in noncollinear ferromagnet normal-metal ferromagnet systems

We study diffusive transport through ferromagnet normal-metal ferromagnet systems, with arbitrary but fixed magnetization directions of the ferromagnetic reservoirs and orientations of a magnetic field applied to the normal metal. For noncollinear configurations, the complex mixing conductance G↑↓ describes the transport of spins noncollinear to the magnetizations of the ferromagnetic reservoirs. When Im G↑↓Þ0, the total conductance of the system in the presence of a magnetic field can be asymmetric with respect to time reversal. The total conductance changes nonmonotonically with the magnetic field strength for different magnetic configurations. This modulation of the conductance is due to the precession of the spin accumulation in the normal metal. The difference between the conductance of the parallel and antiparallel configurations can be either positive or negative as a function of the applied magnetic field. This effect should be best observable on Al single crystals attached to ferromagnetic electrodes by means of tunnel junctions or metallic contacts.