Current-Driven Magnetic Excitations in Permalloy-Based Multilayer Nanopillars

Abstract

We study current-driven magnetization switching in nanofabricated Ni84Fe16/Cu/Ni84Fe16 trilayers at 295 K and 4.2 K. The shape of the hysteretic switching diagram at low magnetic field changes from 295 K to 4.2 K. The reversible behavior at higher field involves two phenomena, a threshold current for magnetic excitations closely correlated with the switching current, and a peak in differential resistance characterized by telegraph noise, with average period that decreases exponentially with current and shifts with temperature. We interpret both static and dynamic results at 295 K and 4.2 K in terms of thermal activation over a potential barrier, with a current dependent effective magnetic temperature.

4 pages, 4 Figures