ac transport in ferromagnetic tunnel junctions

To study possible capacitive effects, we incorporate the effect of electron interaction on the ac spin-polarized tunnelling. Under steady-state nonequilibrium conditions, the voltage-induced charge accumulated at the interface is a sum of two terms, decaying with length scales of the order of the screening length and the spin diffusion length. As a result, the effective width of the capacitor is changed by an additional term. This additional term is a function of the magnetic configurations on opposite sides of the junction and a magnetocapacitance is introduced. (C) 2002 American Institute of Physics.