Electronic Theses and Dissertations Archive

Date

2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Physics

Committee Chair

Shawn Pollard

Abstract

Motivated by the growing demand for energy-efficient spintronic technologies, this work combines nanofabrication, magneto-optical characterization, and micromagnetic modeling to explore the interplay between ferrimagnetism and topological spin textures in rare earth–transition metal (RE–TM) alloys, with emphasis on how rare-earth alloying influences the behavior of magnetic vortices and Bloch point-mediated magnetic states. The first portion of this work demonstrates a direct measurement of exchange stiffness reduction in PyGd alloys through field-driven vortex displacement and magnetic transmission soft x-ray microscopy, revealing the emergence of highly deformed noncoaxial vortex structures as Gd concentration increases. The second portion investigates stochastic magnetization reversal and vortex propagation in Gd- and Tb-based ferrimagnets, showing that Gd alloying promotes increasingly stochastic behavior and random pinning near magnetic compensation, whereas Tb alloying produces comparatively deterministic and reproducible vortex propagation despite enhanced anisotropy. Finally, finite-temperature micromagnetic simulations are used to establish an initial phase map of Bloch-point-mediated topology in ferrimagnetic microdisks, identifying transitions between traditional vortices, noncoaxial vortices, and Bloch-point states. Together, these results demonstrate how selective rare-earth alloying provides a powerful pathway for engineering topological spin textures and diverse functionality in ferrimagnetic materials, offering insight relevant to next generation spintronic devices.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to ProQuest/Clarivate.

Notes

Embargoed until 01-31-2027

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Available for download on Sunday, January 31, 2027

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