Author ORCID Identifier

https://orcid.org/0000-0001-5195-913X

Date Available

7-4-2022

Year of Publication

2022

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy (PhD)

College

Arts and Sciences

Department/School/Program

Physics and Astronomy

Advisor

Dr. Lance De Long

Abstract

Artificial spin ices are magnetic metamaterials consisting of nanomagnet arrays in a 2-D lattice. Typically, these nanomagnet arrays are binary macrospins that can only be in an up or down state similar to the Ising spins. They have been intensively used to study magnetic frustration and ordering phenomena in a controlled environment. The hexagonal artificial spin ice and square artificial spin ice are among the most heavily studied systems. In this dissertation, we designed a modified square artificial spin ice system by an ordered substitution of a double-segment for a nanomagnet array in the unit cell of square artificial spin ice. The samples were patterned by using an electron-beam lithography tool. The substitution of double segment introduces extra degrees of frustration. We adopted ferromagnetic resonance (FMR) spectroscopy to study magnetization dynamics in modified square spin ice with the specific goal of exploring how this substitution affects the FMR modes and magnetic order. We measured the FMR spectrum by using a photo-lithographically printed microwave transmission line, a vector network analyzer (VNA), and an electromagnet. We analyzed the FMR spectrum by using Object Oriented Micromagnetic Framework (OOMMF) software and Fast Fourier Transform (FFT). Using different field protocols, we found that the MSqASI system adopts dipole order (where two segments of the double-segment have parallel moments) and quadrupole order (where two segments of the double-segment have antiparallel magnetizations).

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2022.007

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