Doctoral Dissertations

Date of Award

5-2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Materials Science and Engineering

Major Professor

Dustin A. Gilbert

Committee Members

Philip D. Rack, Haixuan Xu, Lisa M Debeer-Schmitt

Abstract

Non-collinear magnetic structures, where the magnetic moments do not align along a single axis, can lead to interesting physical phenomena and potential device applications. In this dissertation, two specific non-collinear magnetic textures are studied which includes soft/hard bilayer and skyrmions. Soft/hard magnetic bilayer thin films have been widely used in data storage technologies and permanent magnet applications. Here, we use polarized neutron reflectometry (PNR) to study magnetic configuration in soft-hard bilayer heterostructure thin films designed with different sample geometry and material properties under a range of temperatures and fields. Comparing the PNR results to the micromagnetic simulations reveals that the interfacial magnetic configuration is highly dependent on thickness and saturation magagnetization of soft layer materials and external factors (field and temperature) and has a relatively weak dependence on hard layer properties. Magnetic skyrmions, another example of non-collinear structures, exhibit unique, technologically relevant pseudo-particle behaviors which arise from their topological protection, including well-defined, three-dimensional dynamic modes that occur at microwave frequencies. In this work, we use small angle neutron scattering (SANS) to capture the dynamics in hybrid skyrmions and investigate the spin wave structure. Performing simultaneous ferromagnetic resonance and SANS, the diffraction pattern shows a large increase in low-angle scattering which is present only in the resonance condition. This scattering pattern is best fit using a mass fractal model, which suggests the spin waves form a long-range fractal network. Overall, this dissertation contributes to a deeper understanding of the complex behavior and potential applications of non-collinear magnetic structures, particularly in soft/hard bilayer heterostructures and magnetic skyrmions.

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