Kavli Affiliate: David A. Muller
| First 5 Authors: Jiangteng Liu, Ryan Schoell, Xiyue S. Zhang, Hongbin Yang, M. B. Venuti
| Summary:
A promising architecture for next-generation, low energy spintronic devices
uses skyrmions — nanoscale whirlpools of magnetic moment — as information
carriers. Notably, schemes for racetrack memory have been proposed in which
skyrmions and antiskyrmions, their antiparticle, serve as the logical bits 1
and 0. However, major challenges exist to designing skyrmion-antiskyrmion based
computing. The presence of both particles in one material is often mutually
exclusive such that few systems have been identified in which they coexist, and
in these systems their appearance is stochastic rather than deterministic.
Here, we create a tunable skyrmion-antiskyrmion system in FeGe films through
ion-irradiation and annealing, and detail the structural properties of the
films under these various conditions. Specifically, we irradiate epitaxial
B20-phase FeGe films with 2.8 MeV Au$^{4+}$ ions, showing evidence that the
amorphized regions preferentially host antiskyrmions at densities controlled by
the irradiation fluence. In this work, we focus on a subsequent, systematic
electron diffraction study with in-situ annealing, demonstrating the ability to
recrystallize controllable fractions of the material at temperatures ranging
from approximately 150$^{circ}$ C to 250$^{circ}$ C, enabling further
tunability of skyrmion/antiskyrmion populations. We describe the
crystallization kinetics using the Johnson-Mehl-Avrami-Kolmogorov model,
finding that growth of crystalline grains is consistent with
diffusion-controlled one-to-two dimensional growth with a decreasing nucleation
rate. The procedures developed here can be applied towards creation of
skyrmion-antiskyrmion systems for energy-efficient, high-density data storage,
spin wave emission produced by skyrmion-antiskyrmion pair annihilation, and
more generally testbeds for research on skyrmion-antiskyrmion liquids and
crystals.
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