Doctoral thesis: Elizaveta Tremsina

Date: April 17th, 2025 11AM

Location: RLE Haus/Allen 36-428

Name: Elizaveta (Liza) Tremsina

Advisor: Geoffrey S.D. Beach

Spin Dynamics Lab, DMSE

Title: “Atomistic Study of Traveling Skyrmions in Multi-Sublattice Magnetic Materials”

The development of novel energy-efficient computing hardware is imperative for the reduction of the carbon footprint and for the extension of computing, mobile and wearable device lifespan. Recent advances have been focused on turning to novel material systems, and one such avenue is magnetic thin films. Spin polarized transport phenomena are now widely researched in metals, semiconductors, and oxide materials for spintronic applications where electronic spin, instead of the conventional charge, is used as the information-carrier. Using these magnetic material systems as hardware components, namely memory cells, artificial neurons, or synapses, one can create a computing architecture that behaves in ways emulating the human brain. Bits of information can be encoded by magnetic twisted textures called skyrmions, which can be efficiently driven by applying electrical current. Recently, emphasis has been placed on investigating antiferromagnetic and ferrimagnetic skyrmions, as opposed to the single-sublattice ferromagnetic ones studied earlier, due to their potential for more rapid dynamics and magnetic stability.

However, there is a pressing need for a thorough and detailed understanding of the intricacies of skyrmion motion, in particular, limiting velocity, optimization of trajectory, controlled mobility and, notably, the observed dynamic distortions of skyrmion profiles. For this reason, experimental studies are simply not enough to provide a complete picture, since the material parameter space for systems hosting skyrmions is quite large. For this reason, systematic modelling of these phenomena is imperative, to not only quantitatively understand the fundamental physical mechanisms attributed to dynamic distortions and velocity limits, but also help guide material optimization for maximizing skyrmion speed and stability through informed materials selection.

We perform a comprehensive study combining simulation-based as well as analytical approaches, of the spin-orbit torque motion of skyrmions in a wide host of magnetic materials, ranging from crystalline antiferromagnetic to ferrimagnetic, to ferromagnetic. We systematically analyze the relationship between physical distortions of the skyrmion profiles, based on the action of local Thiele forces, and internal elastic tension forces. Our results significantly augment the current understanding of skyrmion distortions from past experimental observations and simulations studies. This work provides a more quantitative and nuanced explanation of the nature of magnetization profile distortions and the direct connection with asymmetric local Thiele forces which are in a dynamic balance with skyrmions’ internal restoring forces. These results expand the understanding of fundamental properties of magnetic skyrmions, as well as their potential use in spintronics applications.

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Details

• Date: Thursday, April 17
• Time: 11:00 am - 12:00 pm
• Category: Thesis Defense
• Location: RLE Haus/Allen 36-428