Effect of polarizer dynamics on current-induced behaviors in magnetic nanopillars

Magnetoelectronic nanodevices such as magnetic random access memory include two essential magnetic layers: a polarizing reference layer and a free layer whose configuration can be changed by spin-polarized current via spin-transfer effect. We present measurements of current-induced behaviors in nanodevices with fixed dimensions of the free layer, and varied dimensions of the polarizer. Current-induced precession occurs only at positive current for sufficiently thick polarizer, and only at negative current for thin polarizer, with an abrupt transition between these regimes. Bipolar current-induced precession was observed for a small range of extended polarizer thickness but the amplitude of precession in these devices is reduced. These behaviors are interpreted in terms of the coupling between magnetic layers caused by spin transfer. We suggest a device architecture utilizing the coupling for improved efficiency.