Effect of the classical ampere field in micromagnetic computations of spin polarized current-driven magnetization processes

Magnetization reversal by spin polarized current flowing perpendicular to pillar nanostructures with different geometries and materials is studied by means of a micromagnetic model. The spin transfer torque is included as an additional term in the Gilbert equation following previous theoretical calculations by Slonczewski. The ampere field (H(Amp)) due to the current and the dipolar antiferromagnetic coupling between the ferromagnetic layers are also taken into account. The H(Amp) plays a crucial role; in fact it can speed, retard or even inhibit the magnetization switching process depending on the kind of structure under test. The studied nanostructures are circular and elliptic nanopillars of Co/Cu/Co and permalloy/Cu/permalloy.