Current-sweep-rate dependence of spin-torque driven dynamics in magnetic nanopillars

PAPER: B. O’Gorman, S. Dietze, and M. Tsoi,

“Current-sweep-rate dependence of spin-torque driven dynamics in magnetic nanopillars”,

J. Appl. Phys. 105, 07D111 (2009).

POSTER: 53^rd Magnetism and Magnetic Materials Conference

Austin, Texas, November 10-14, 2008

ABSTRACT:

We report on the measurements of current-driven dynamics in magnetic nanopillars as a function of the current-sweep-rate. These measurements were intended to verify the recently predicted thermal-activation nature of current-induced precessional states in spin-valve multilayers. For a fixed temperature and field (applied perpendicular to the layers), the critical current for dynamic excitations was found to increase logarithmically with the sweep-rate as expected for a thermally activated process. However, we observed little if any dependence of this behavior on temperature. We discuss the implications of this in terms of a simple model of spin-torque driven magnetization dynamics.

We thank J. Sun for the nanopillar samples and discussions and S. Zhang for valuable suggestions. This work was supported in part by NSF Grant DMR-06-45377