CHARACTERIZATION OF MAGNETIC DYNAMICS EXCITED BY SPIN TRANSFER TORQUE IN A NANOMAGNET

This dissertation presents our investigation of the effects of spin transfer torque on a nanoscale ferromagnet. Spin transfer torque is generated by the transfer of angular momentum from spin polarized electrons to a ferromagnet. This torque provides an efficient means to manipulate the dynamic motion of the magnetization of a nanomagnet, and can be strong enough to induce magnetization reversal or steady-state precession. We have developed new techniques to characterize such dynamics induced by spin transfer torque. In the first study, we perform an experiment demonstrating that spin transfer from a microwave current pulse can produce a resonant excitation of a nanomagnet and improve switching characteristics in combination with a square current pulse. With the assistance of a microwave-frequency pulse, the switching time is reduced and achieves a narrower distribution than when driven by a square current pulse alone, and this can permit significant reductions in the integrated power required for switching. In the second study, we develop a single-shot electrical technique to captur