Dynamics of spin torque switching in all-perpendicular spin valve nanopillars

• Published in: Journal of magnetism and magnetic materials 2014-05, Vol.358-359, p.233-258
• Main Authors: Liu, H., Bedau, D., Sun, J.Z., Mangin, S., Fullerton, E.E., Katine, J.A., Kent, A.D.
• Format: Article
• Language: English
• Subjects: Activation; Ballistic magnetization reversal; Condensed Matter; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dynamics; Electronic transport in condensed matter; Exact sciences and technology; Giant magnetoresistance; Macrospin dynamics; Magnetic properties and materials; Magnetic random access memory; Magnetization dynamics; Magnetization reversal; Magnetotransport phenomena, materials for magnetotransport; Materials Science; Mathematical analysis; Mathematical models; Nanostructure; Perpendicular magnetic anisotropy; Physics; Spin polarized transport; Spin transfer torque; Spin transfer torque switching; Spin valve; Spin valves; Spintronics; Switching
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2014.01.061

We present a systematic experimental study of the spin-torque-induced magnetic switching statistics at room temperature, using all-perpendicularly magnetized spin-valves as a model system. Three physical regimes are distinguished: a short-time ballistic limit below a few nanoseconds, where spin-torque dominates the reversal dynamics from a thermal distribution of initial conditions; a long time limit, where the magnetization reversal probability is determined by spin-torque-amplified thermal activation; and a cross-over regime, where the spin-torque and thermal agitation both contribute. For a basic quantitative understanding of the physical processes involved, an analytical macrospin model is presented which contains both spin-torque dynamics and finite temperature effects. The latter was treated rigorously using a Fokker–Plank formalism, and solved numerically for specific sets of parameters relevant to the experiments to determine the switching probability behavior in the short-time and cross-over regimes. This analysis shows that thermal fluctuations during magnetization reversal greatly affect the switching probability over all the time scales studied, even in the short-time limit.