Time-Domain Studies of Very-Large-Angle Magnetization Dynamics Excited by Spin Transfer Torques

TL;DR

This paper investigates the nonlinear, large-angle magnetization dynamics in nanomagnets driven by spin-transfer torque, revealing step-like switching behavior, non-periodic resistance variations, and rapid mode switching through time-domain measurements.

Contribution

It provides new time-resolved experimental insights into the complex magnetization dynamics induced by spin-transfer torque, including mode switching and nonlinear behaviors.

Findings

Step-like dependence of reversal time on magnetic field.

Observation of non-periodic large-amplitude resistance variations.

Detection of rapid switching between precessional modes.

Abstract

We describe time-domain measurements which provide new information about the large-angle nonlinear dynamics of nanomagnets excited by spin-transfer torque from a spin-polarized current. Sampling-oscilloscope measurements, which average over thousands of experimental time traces, show that the mean reversal time for spin-transfer-driven magnetic switching has a step-like dependence on magnetic field, because an integer number of precession cycles is required for reversal. Storage-oscilloscope measurements of individual experimental traces reveal non-periodic large-amplitude resistance variations at values of magnetic field and current in a crossover region between the regimes of spin-transfer-driven switching and steady-state precession. We also observe directly the existence of time-dependent switching, on the nanosecond scale, between different precessional modes and between a precessional mode and a static state, at particular values of magnetic field and current bias.