Graduation Year
2026
Document Type
Thesis
Degree
M.S.
Degree Name
Master of Science (M.S.)
Degree Granting Department
Physics
Major Professor
Dario Arena, Ph.D.
Committee Member
Sarath Witanachchi, Ph.D.
Committee Member
Humberto Rodriguez Gutierrez, Ph.D.
Keywords
Ferromagnetism, Spintronics, Thin Films, Transitional metals dichalcogenides
Abstract
Interfaces dominate the behavior of ultrathin ferromagnets, where interfacial spin-orbit coupling(SOC) can strongly influence both magnetic anisotropy and magnetization dynamics. This thesis compares how a heavy-metal interface (Pt) and a semiconducting two-dimensional transition-metal dichalcogenide (TMD) interface (MoSe2) modify the static and dynamic magnetic properties of ultrathin Co. To isolate interface-driven effects, the heterostructure architecture is kept fixed (sapphire substrate and Si3N4 cap) while only the seeding/interface layer beneath Co is varied. MoSe2 is studied in two thickness conditions (monolayer and bilayer) to test layer-dependent trends.
Layer thicknesses are determined by X-ray reflectivity. Static magnetic properties are measured by in-plane vibrating sample magnetometry to extract Ms and comparative loop metrics. Magnetization dynamics is quantified using broadband ferromagnetic resonance (FMR) in in-plane and out-of-plane configurations. From the FMR dispersion, the spectroscopic g-factor and effective magnetization Meff are extracted, enabling evaluation of an effective perpendicular anisotropy contribution. Linewidth analysis yields the Gilbert damping parameter α, with out-of-plane results emphasized to minimize extrinsic broadening. Interface-induced relaxation is quantified through the damping enhancement relative to the Co reference and interpreted within the spin-pumping framework to obtain an effective spin mixing conductance.
The results show that MoSe2 seeding produces a significant damping enhancement comparable to Pt, indicating that a semiconducting van der Waals interface can provide strong SOC-related relaxation channels in ultrathin Co. In contrast, MoSe2 modifies anisotropy and loop hardness differently from the heavy-metal benchmark, and the extracted parameters depend on MoSe2 layer number. These findings support TMD interfaces as promising alternatives to heavy metals for SOC-active interface engineering in spintronic and opto-spintronics heterostructures.
Scholar Commons Citation
Almuhanna, Ibrahim, "Spin Pumping and Interfacial Anisotropy in Ultrathin Cobalt Heterostructures" (2026). USF Tampa Graduate Theses and Dissertations.
https://digitalcommons.usf.edu/etd/11223
