  We demonstrate current-induced bipolar switching in in-plane magnetized
spin-valve devices that incorporate a perpendicularly magnetized spin
polarizing layer. Further, hysteretic transitions into a state with
intermediate resistance occur at high currents, again for both current
polarities. These transitions are shown to be consistent with a macrospin model
that considers a spin-polarized current that is tilted with respect to the free
layer plane, due to the presence of spin-transfer torque from the polarizing
layer. These unique switching characteristics, which have their origin in the
noncollinear layer magnetizations, are of interest for magnetic random access
memory and spin-torque oscillator devices.
