  Perpendicular MgO-based Magnetic Tunnel Junctions are optimal candidates as
building block of Spin Transfer Torque (STT) magnetoresistive memories.
However, up to now, the only STT is not enough to achieve switching current
density below 106 A/cm2. A recent work [Wang et al., Nature Mater., vol. 11, pp
64-68, Jan. 2012] has experimentally demonstrated the possibility to perform
magnetization switching assisted by an electric-field at ultra-low current
density. Theoretically, this switching has been studied by using a macrospin
approach only. Here, we show a full micromagnetic study. We found that the
switching occurs via a complex nucleation process including the nucleation of
magnetic vortexes.
