Author ORCID Identifier
0009-0006-4592-0304
Defense Date
2025
Document Type
Thesis
Degree Name
Master of Science
Department
Mechanical and Nuclear Engineering
First Advisor
Dr. Jayasimha Atulasimha
Abstract
Magnetic materials face two critical challenges that limit the scalability of modern energy and information technologies: supply-chain vulnerabilities associated with rare-earth permanent magnets, and excessive energy consumption in current-driven spintronic switching. While rare-earth-based magnets achieve energy products of 30–50 MGOe, global dependence on limited sources motivates the development of earth-abundant alternatives. Simultaneously, conventional spin-orbit-torque and spin-transfer-torque switching mechanisms consume orders of magnitude more energy than CMOS transistors, necessitating new low-power switching paradigms. This thesis addresses these challenges through micromagnetic simulation-based investigations of rare-earth-free permanent magnets and energy-efficient magnetic switching mechanisms. Using MuMax3, optimized ferromagnetic nanostrip arrays exploiting shape anisotropy are shown to achieve energy products of approximately 12 MGOe using earth-abundant FeCo-like compositions, corresponding to ~35–40% of rare-earth magnet performance. The results establish a fundamental upper limit imposed by dipole–dipole interactions, while proposed extensions incorporating exchange bias, defect pinning, and interface roughness optimization are expected to enhance energy products through cooperative multi-mechanism anisotropy. For energy-efficient switching, this work investigates hybrid surface acoustic wave (SAW) and spin-orbit torque (SOT) driven magnetization reversal in nanoscale magnetic elements. SAW-induced strain dynamically modulates magnetic anisotropy, creating temporal windows in which weak SOT enables deterministic switching with substantially reduced current density. Simulations demonstrate current reduction from ~3 × 10¹² A/m² to ~0.5 × 10¹² A/m² with sub-1.5 ns switching times. Additionally, a previously unexplored regime involving velocity mismatch between SAWs and spin waves is identified, leading to shock-like interactions that may enable ultrafast switching and controlled spin-wave generation for magnonic applications.
Rights
© The Author Shouvik Sarker
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
12-12-2025