Bipolar switching in an orthogonal spin transfer spin valve device

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.