Switching Current vs. Magnetoresistance in Magnetic Multilayer Nanopillars

We study current-driven magnetization switching in nanofabricated magnetic trilayers, varying the magnetoresistance in three different ways. First, we insert a strongly spin-scattering layer between the magnetic trilayer and one of the electrodes, giving increased magnetoresistance. Second, we insert a spacer with a short spin-diffusion length between the magnetic layers, decreasing the magnetoresistance. Third, we vary the angle between layer magnetizations. In all cases, we find an approximately linear dependence between magnetoresistance and inverse switching current. We give a qualitative explanation for the observed behaviors, and suggest some ways in which the switching currents may be reduced.