Graduation Year

2018

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Physics

Major Professor

Manh-Huong Phan, Ph.D.

Co-Major Professor

Hariharan Srikanth, Ph.D.

Committee Member

Dario Arena, Ph.D.

Committee Member

Jing Wang, Ph.D.

Committee Member

Jiangfeng Zhou, Ph.D.

Keywords

amorphous alloys, magnetic anisotropy, magnetoimpedance, surface magnetic domains

Abstract

Amorphous and nanocrystalline transition metal magnetic alloys (TMMAs) have been the subjects of fundamental and applied study due to their unique structure. The lack of long-range order in these materials sets the stage for their soft magnetic properties to be tuned for a variety of technological applications, such as sensitive magnetic field sensors, high frequency transformers, and stress sensors. Fundamental investigation of the magnetic and structural properties of these materials is also motivated by their unique amorphous or nanocrystalline-embedded amorphous matrix morphology, which has consequences on both the magnetism seen from both the atomic and macro-scale. The surfaces of these materials become important to their high frequency applications, where the skin depth of the excitation field is distributed near the surface. In conjunction with high frequency magnetoimpedance measurements, surface sensitive probes of magnetism and structure must be employed to provide a complete picture of the relationship between the surface and dynamic magnetism. This dissertation focuses on the surface impact of chemical composition, annealing conditions, and coatings on TMMAs on their magnetoimpedance response through multiple surface sensitive techniques such as atomic/magnetic force microscopy, magneto-optical Kerr effect, and scanning/transmission electron microscopy. These tools provide a view into the relationship between the nanostructure, microstructure and soft magnetic properties that make these materials highly desired for fundamental study and technological application.

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