  We investigate current-induced magnetization switching for a multilayer
structure that allows a reduced switching current while maintaining high
thermal stability of the magnetization. The structure consists of a
perpendicular polarizer, a perpendicular free-layer, and an additional
free-layer having in-plane magnetization. When the current runs perpendicular
to the structure, the in-plane free-layer undergoes a precession and supplies
an internal rf field to the perpendicular free-layer, resulting in a reduced
switching current for one current polarity. For the other polarity, the
in-plane free-layer almost saturates perpendicular to the plane and acts as
another perpendicular polarizer, which also reduces the switching current.
