  This paper describes a numerical experiment of magnetization switching driven
by spin-polarized current in high-TMR magnetic tunnel junctions (TMR>100%).
Differently from other works, the current density distribution throughout the
cross-sectional area of the free-layer is here computed dinamically, by
modeling the ferromagnet/insulator/ferromagnet trilayer as a series of parallel
resistances. The validity of the main postulated hypothesis, which states that
the current density vector is perpendicular to the sample plane, has been
verified by numerically solving the Poisson equation. Our results show that the
nonuniform current density distribution is a source of asymmetry for the
switching. Furthermore, we found out that the switching processes are
characterized by well defined localized pre-switching oscillation modes.
