Author ORCID Identifier

https://orcid.org/0000-0003-2392-9915

Year of Publication

2021

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Arts and Sciences

Department/School/Program

Physics and Astronomy

First Advisor

Dr. Lance E. De Long

Abstract

Artificial spin ices (ASI) have been shown to exhibit dynamic magnetic responses that are dramatically different from plane magnetic thin films. A number of magnetic ASI have been fabricated and measured in recent years. However, some important effects including influence of vertex and geometrical distortion on their dynamic response have not been addressed. This dissertation adopts Ferromagnetic Resonance (FMR) spectroscopy to study magnetization dynamics in fabricated artificial spin ices with a contentiously distorted Honeycomb geometry with the specific goal of exploring how the vertex and lattice distortion affect the dynamic magnetic response. Samples were patterned using electron beam lithography techniques. FMR spectroscopy was developed by designing a new printed microwave transmission line. The transmission line was fabricated using photolithography technique. A Vector Network Analyzer (VNA) and an electromagnet were used to measure the FMR spectrum of the samples. Object Oriented Micromagnetic Framework (OOMMF) and Fast Fourier Transform (FFT) were used to simulate the magnetization texture and FMR spectrum of the samples. The experimental and simulation findings demonstrated the importance of the vertex in the dynamic response of artificial spin ices such that previous research findings were modified. Moreover, Fibonacci-distortion was applied on the geometrical lattice (Honeycomb) of Kagome ASI that offers a mathematical algorithm to design artificial spin ice. The FMR spectra for different degrees of distortion severity were measured. We found that the geometrical distortion is a suitable algorithm to achieve the desired FMR spectrum and multi-step magnetization reversal process for engineering applications. Furthermore, FMR data aided with simulations in the magnetization reversal regime suggest that the distortion can cause the artificial spin ice to relax in partially long-range magnetic order.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2021.106

Funding Information

This study was supported by:

The U.S. National Science Foundation Grant DMR-1506979 (Jan 2016-May 2021)

The University of Kentucky Center for Advanced Materials (Jan 2016-May 2021)

The University of Kentucky Center for Computational Sciences (Jan 2016-May 2021)

The University of Kentucky Center for Nanoscale Science and Engineering (Jan 2016-May 2021)

The U.S. Department of Energy Office of Science under Contract No. DE-AC02-06CH11357 (Jan 2018-May 2021)

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