Magnetic Droplet Solitons

TL;DR

Magnetic droplet solitons are dynamic magnetic textures formed by spin wave interactions in thin films, with recent experimental advances enabling their visualization, control, and potential use as microwave oscillators in neuromorphic computing.

Contribution

This review summarizes recent experimental progress in understanding and controlling magnetic droplet solitons, highlighting their unique properties and potential applications.

Findings

First direct x-ray images of droplets

Determined threshold and sustaining currents

Observed drift instabilities affecting lifetime

Abstract

Magnetic droplet solitons are dynamical magnetic textures that form due to an attractive interaction between spin waves in thin films with perpendicular magnetic anisotropy. Spin currents and the spin torques associated with these currents enable their formation as they provide a means to excite non-equilibrium spin wave populations and compensate their decay. Recent years have seen rapid advances in experiments that realize and study magnetic droplets. Important advances include the first direct x-ray images of droplets, determination of their threshold and sustaining currents, measurement of their generation and annihilation time and evidence for drift instabilities, which can limit their lifetime in spin-transfer nanocontacts. This article reviews these studies and contrasts these solitons to other types of spin-current excitations such as spin-wave bullets, and static magnetic textures, including magnetic vortices and skyrmions. Magnetic droplet solitons can also serve as current controlled microwave frequency oscillators with potential applications in neuromorphic chips as nonlinear oscillators with memory.