Averaged equation for energy diffusion on a graph reveals bifurcation diagram and thermally assisted reversal times in spin-torque driven nanomagnets

Katherine A. Newhall, Eric Vanden Eijnden

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Abstract

Driving nanomagnets by spin-polarized currents offers exciting prospects in magnetoelectronics, but the response of the magnets to such currents remains poorly understood. We show that an averaged equation describing the diffusion of energy on a graph captures the low-damping dynamics of these systems. From this equation we obtain the bifurcation diagram of the magnets, including the critical currents to induce stable precessional states and magnetization switching, as well as the mean times of thermally assisted magnetization reversal in situations where the standard reaction rate theory of Kramers is no longer valid. These results match experimental observations and give a theoretical basis for a Néel-Brown-type formula with an effective energy barrier for the reversal times.

Original languageEnglish (US)
Article number184105
JournalJournal of Applied Physics
Volume113
Issue number18
DOIs
StatePublished - May 14 2013

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torque
magnets
diagrams
magnetization
critical current
reaction kinetics
damping
energy

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

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abstract = "Driving nanomagnets by spin-polarized currents offers exciting prospects in magnetoelectronics, but the response of the magnets to such currents remains poorly understood. We show that an averaged equation describing the diffusion of energy on a graph captures the low-damping dynamics of these systems. From this equation we obtain the bifurcation diagram of the magnets, including the critical currents to induce stable precessional states and magnetization switching, as well as the mean times of thermally assisted magnetization reversal in situations where the standard reaction rate theory of Kramers is no longer valid. These results match experimental observations and give a theoretical basis for a N{\'e}el-Brown-type formula with an effective energy barrier for the reversal times.",
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