Critical Current Enhancement In Magnetic Spin-Transfer Nano-Devices Through Doping With The Rare Earth Terbium

Abstract

In this thesis, we fabricate magnetic nanopillars and dramatically enhance their damping through terbium doping in order to suppress the various spin-transfer effects, to the potential benefit of magnetic hard drive read head technology. This enhancement is much stronger at lower temperatures, and we can understand the 1/T temperature dependence observed through the application of established theory from the iron garnets. We also show that terbium doping can address technological problems with hard drive read heads. In particular, by inhibiting the microwave noise until a higher turn-on current is reached, without compromising the ability of the device to switch with reasonable power in times scales as short as 1 nsec, terbium-doped structures point the way forward for future designs. Finally, we make direct FMR measurements of the Gilbert phenomenological damping parameter at the center of these effects, and these measurements also suggest cobalt-iron alloys as systems for potential follow-up work.