Generation and annihilation time of magnetic droplet solitons

TL;DR

This paper measures the creation and destruction times of magnetic droplet solitons, revealing nanosecond-scale annihilation and microsecond-scale generation, crucial for their application in high-frequency nanodevices.

Contribution

It provides the first direct measurements of the timescales for droplet soliton nucleation and annihilation using current pulses, supported by micromagnetic simulations.

Findings

Annihilation occurs in a few nanoseconds.

Generation can take from several nanoseconds to a microsecond.

Generation time depends on pulse amplitude and initial magnetic state.

Abstract

Magnetic droplet solitons were first predicted to occur in materials with uniaxial magnetic anisotropy due to a long-range attractive interaction between elementary magnetic excitations, magnons. A non-equilibrium magnon population provided by a spin-polarized current in nanocontacts enables their creation and there is now clear experimental evidence for their formation, including direct images obtained with scanning x-ray transmission microscopy. Interest in magnetic droplets is associated with their unique magnetic dynamics that can lead to new types of high frequency nanometer scale oscillators of interest for information processing, including in neuromorphic computing. However, there are no direct measurements of the time required to nucleate droplet solitons or their lifetime---experiments to date only probe their steady-state characteristics, their response to dc spin currents. Here we determine the timescales for droplet annihilation and generation using current pulses. Annihilation occurs in a few nanoseconds while generation can take several nanoseconds to a microsecond depending on the pulse amplitude. Micromagnetic simulations show that there is an incubation time for droplet generation that depends sensitively on the initial magnetic state of the nanocontact. An understanding of these processes is essential to utilizing the unique characteristics of magnetic droplet solitons oscillators, including their high frequency, tunable and hysteretic response.