Spin Inertia as a Driver of Chaotic and High-Speed Ferromagnetic Domain Walls

TL;DR

This paper investigates how spin inertia influences ferromagnetic domain wall dynamics, revealing chaotic behavior without damping and enhanced velocities with damping, which could improve racetrack memory performance.

Contribution

It introduces the concept of spin inertia as a key factor in domain wall motion, showing its effects on chaos and velocity enhancement in ferromagnetic systems.

Findings

Inertial effects induce chaotic domain wall dynamics without damping.

Finite damping and field-like driving increase domain wall velocity.

Spin inertia causes domain wall width contraction at low driving.

Abstract

Ferromagnetic domain walls -transitional regions between magnetic domains- are an essential ingredient for racetrack memory, a device concept that promises to deliver faster and more compact memory storage compared to other non-volatile memory devices. Motivated by recent experiments that have found inertial effects in spin dynamics, we explore its consequences on domain wall motion. We find that the inertial dynamics of the individual magnetic moments induce massive dynamics of the domain wall. We investigate these massive dynamics driven by a magnetic field, spin-transfer torque, and spin-orbit torque. We show that, in the absence of Gilbert damping, the domain wall dynamics become chaotic, resembling that of an electron in a two-dimensional crystal. For finite damping, field-like driving of the inertial domain wall significantly increases its velocity compared to conventional massless dynamics, potentially enabling faster racetrack operations. Additionally, in the limit of low driving, we observe that the domain wall width contracts due to the spin inertia of the ferromagnet.