Time-resolved spin-torque switching in MgO-based perpendicularly magnetized tunnel junctions

TL;DR

This study investigates nanosecond spin-torque switching in MgO-based perpendicularly magnetized tunnel junctions, revealing domain wall dynamics and complex reversal behaviors with implications for spintronic device performance.

Contribution

It provides the first detailed analysis of domain wall motion and Walker regime dynamics during spin-torque switching in pMTJs, supported by a simplified single-wall model.

Findings

Switching involves domain wall nucleation and propagation at ~40 m/s.

Reversal exhibits Walker regime oscillations and back-and-forth wall motion.

Back-hopping increases with voltage, linked to layer instability.

Abstract

We study ns scale spin-torque-induced switching in perpendicularly magnetized tunnel junctions (pMTJ). Although the switching voltages match with the macrospin instability threshold, the electrical signatures of the reversal indicate the presence of domain walls in junctions of various sizes. In the antiparallel (AP) to parallel (P) switching, a nucleation phase is followed by an irreversible flow of a wall through the sample at an average velocity of 40 m/s with back and forth oscillation movements indicating a Walker propagation regime. A model with a single-wall locally responding to the spin-torque reproduces the essential dynamical signatures of the reversal. The P to AP transition has a complex dynamics with dynamical back-hopping whose probability increases with voltage. We attribute this back-hopping to the instability of the nominally fixed layers.