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ADDITIONAL SOURCES TO THE SIGNAL: SPIN PUMPING IN SPIN TORQUE FERROMAGNETIC RESONANCE AND STUDENT-LEVEL VARIABLES IN LINEAR MIXED-EFFECTS MODELS

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Abstract

In this dissertation I will present my work in both the fields of spintronics and physics education research. In the first section, I present a method to account for spin pumping in spin torque ferromagnetic resonance (ST-FMR) measurements. A spin current can be generated via the spin Hall effect (SHE), which is typically transverse to the charge current in a nonmagnetic metal (NM) such as Pt or W. This spin current can pass into an adjacent ferromagnet (FM), transferring angular momentum, and inducing precession of the magnetic moment. Using an oscillating current, an oscillating resistance is produced due to anisotropic magnetoresistance, which results in a DC mixing voltage that can be measured via ST-FMR. I will adapt the ST-FMR model to include extraneous sources of the DC mixing voltage signal from spin pumping. Using fabricated NM/FM thin film heterostructures, I will show experiments where spin pumping is a large measurable effect that cannot be ignored. The signal due to spin pumping can be used to get an estimation of the damping-like spin torque efficiency. In the second section of this thesis, I will compare the learning outcomes of two types of active engagement instruction in our introductory electricity and magnetism (E&M) physics class. Previous research has focused primarily on comparing traditional lectures to various active engagement types, but little is known about how different types of active engagement compare to each other. This study aims to dissect two distinct implementations of active engagement by using scores from the Conceptual Survey of Electricity and Magnetism (CSEM) and final course grades as measures of improved student understanding. Several semesters used an active learning style that was more focused on conceptual understanding and several semesters used an active learning style that emphasized problem-solving during class. I use linear mixed-effects modeling to assess learning outcomes while accounting for student-level preparatory and demographic variables. I find that both active learning styles led to similar learning outcomes. Additionally, the estimated performance gaps on the survey, such as a gender gap, were found to be not statistically related to instruction method, as measured by interaction terms in the model. Finally, I show the use of a graphical technique to identify specific trends in student responses to the CSEM pre- and post-test while incorporating all types of student responses. This technique does not distill responses to just "correct" or "incorrect", which is common in test and item level analysis of concept inventories.

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166 pages

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Date Issued

2021-12

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Keywords

active learning; linear mixed-effects models; nanofabrication; spin Hall effect; spin pumping; spin torque ferromagnetic resonance

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Committee Chair

Ralph, Dan

Committee Co-Chair

Committee Member

Mueller, Erich
Holmes, Natasha Grace

Degree Discipline

Physics

Degree Name

Ph. D., Physics

Degree Level

Doctor of Philosophy

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Government Document

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Attribution-NonCommercial-NoDerivatives 4.0 International

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dissertation or thesis

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