SIUC Physics Seminar
School of Physics and Applied Physics, Southern Illinois University--Carbondale

2025 April 11 Friday 4:00 PM:
Physics Seminar in Neckers 440

Title: Introduction to Magnetic Skyrmions
Speaker: Thayne Dean and Lance Griswold
Affiliation: Southern Illinois University--Carbondale


Abstract: First theorized in 1961 by Tony Skyrme in high-energy physics, Skyrmions has been observed in condensed matter physics, particularly in magnetic systems. Often likened to bubbles in a magnetic field, magnetic skyrmions are topologically stable vortexes ranging in size from the ten-nanometer scale to about 2 micrometers. The most interesting feature of the skyrmions is that they can behave as particles that can be moved, created, or destroyed and manipulated by an electrical current, making them suitable for information storage, memory, logic, or neuro-inspired technologies. Experimentally first observed in 2009 in bulk MnSi, one of the key interactions necessary for stabilizing skyrmions is the Dzyaloshinksii-Moriya interaction (DMI), of the type Dij·(Si x Sj). DMI is much weaker than ferromagnetic Heisenberg exchange interaction Jij(Si·Sj), implying low Curie temperature and not observed in centrosymmetric materials. Therefore, room-temperature skyrmions are hard to find in bulk systems. At thin film interfaces between two materials, inversion symmetry is broken, generating an effective interfacial DMI that stabilizes skyrmions. In the past decade or so, several bilayer systems, e.g., Co/Pt, have shown room-temperature skyrmions with relatively small sizes.


Thayne Dean: (theory) Micromagnetic simulations of magnetic skyrmions:
In the first part of our presentation, we will investigate the formation, stability, and dynamics of skyrmions in both bilayer and bulk magnetic systems using micromagnetic simulations via MuMax3, a micromagnetic simulation program. We explore how the skyrmion size and behavior depend on DMI, Heisenberg exchange interactions, and anisotropy parameters. Our simulations reveal key distinctions in skyrmion size and mobility, showing how multilayer materials can be manipulated to tailor skyrmion properties. We will provide simulation results outlining the Skyrmion Hall effect. This unexpected phenomenon results in neutral skyrmions drifting to the edge of the sample, similar to the charge carriers in the Hall effect. These findings contribute to a deeper understanding of skyrmionic systems and will be extended to compositionally graded materials that interest our group.

Lance Griswold: (experiment) Towards compositionally graded thin films in search for stable magnetic skyrmions:
In the second half of the presentation, we will provide a brief review of the experimental literature on bulk and thin films and outline the issues with skyrmions for applications regarding its size, stability, and motion. We will then motivate that a system with a graded DMI structure can provide skyrmions with small size and high stability. Essentially, we wish to create a two-dimensional DMI profile. Such structures can be grown using thin film engineering techniques that are accessible to our group. I will share some preliminary results with compositionally graded Co-Pt thin films. Our future experimental work will involve imaging the skyrmions, measuring the DMI (x,y) profile, and investigating its dynamical behavior to minimize the Skyrmion Hall effect.

Last updated on by K V Shajesh (kvshajesh@gmail.com).