Domain Wall Based Magnonics in Iron Garnet

Abstract

Magnonic devices leverage magnons, quantized spin waves, as the mechanism to process and transfer information. In materials with low Gilbert damping, these spin wave-based systems enable ultra-fast operation while eliminating thermal heating and leakage currents inherent to conventional electron-based microelectronics. To maximize energy efficiency and processing speed, materials like iron garnets, ferrimagnetic insulators with tunable magnetic properties, are essential. Key magnetic parameters, including saturation magnetization, perpendicular magnetic anisotropy, coercivity, and Gilbert damping, can be tailored through elemental substitution or strain engineering in thin films. Furthermore, relativistic domain wall velocities reported in yttrium iron garnet (YIG), bismuth substituted YIG, and thulium iron garnet lay the foundations for high-speed operation. These unique attributes position garnets as ideal materials for the development of magnonic devices that integrate efficiency, speed, and versatility. This thesis presents my research on integrating thin film garnets into a domain wall based magnonic devices. It begins by exploring the magnetic characterization of thin film iron garnets, including the growth process, temperature dependent magnetic behavior, and tunable magnetic anisotropy. Next, we report on magnonics within the garnet, focusing on the interactions between spin waves and domain walls. Finally, we demonstrate a write mechanism for a magnonic device driven by spin wave-induced domain wall motion, providing detailed characterization of the device behavior and performance. These results underscore the potential of iron garnets for magnonic-based device applications and offer insights into the efficiency of write mechanism, paving the way for energy-efficient high-speed spintronic technologies.