Prototyping passive and active cavity magnonic devices

Abstract

Microwave technologies form the foundation of modern communication, radar, and sensing systems. Magnetic materials, particularly ferrites, have long served as key components in microwave devices such as isolators, filters, and oscillators. Their low loss and frequency tunability remain essential for controlling and manipulating microwave signals. In recent years, cavity magnonics has emerged as a promising platform that harnesses the interaction between microwave cavity and magnetic excitations. The interaction produces hybridized states that combine the mobility of photons with the coherence of spins, enabling new device concepts and functionalities. Originally studied in spintronics, cavity magnonics has since revealed novel effects that go beyond the capabilities of conventional microwave components. This thesis investigates two such phenomena: non-reciprocal transmission and coherent microwave emission. First, an isolator prototype is demonstrated, achieving strong signal isolation with low insertion loss, representing a step toward compact and efficient non-reciprocal devices. Next, a microwave oscillator is developed and coupled to ferrite material, revealing a phase noise suppression effect that produces a sharp emission spectrum, establishing a pathway to low-noise microwave sources. Together, the thesis demonstrates how cavity magnonic systems can progress from proof-of-concept studies to practical device applications, opening new opportunities for the development of next-generation microwave electronics.