Ferrimagnetic Insulator Enabled Quantum Spintronic Effects and Devices

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In this proposed research, the PI proposes to first synthesize epitaxial magnetic insulator or FMI films (e.g. Y3Fe5O12 or YIG) using pulsed laser deposition, fabricate FMI-based nanoscale spintronic devices, and investigate the unique physical properties and novel functionalities of these spintronic devices. FMI thin films have not been well studied or widely used in electronic devices, but have become increasingly important because they could enable a host of brand new spintronic devices. For example, in FMI, spin waves or magnons can be excited, transmitted, and exploited to efficiently drive domain walls via spin momentum transfer in nanoscale devices that can potentially serve as non-volatile memory. Another example is that the spin current carried by a heat current in FMI can be converted into a voltage signal which is known as the spin Seebeck effect. Furthermore, by bringing FMI in proximity to materials that have the Dirac energy dispersion (e.g. graphene and topological insulators), the exchange interaction at the interface can result in the quantized anomalous Hall effect, an effect produced by quantized edge channels in the devices. These novel phenomena have been recently predicted or are currently being explored experimentally. The PI aims to study FMI materials and FMI-enabled quantum spintronic devices in this proposed research. Intellectual merit: The proposed research will integrate several unique materials (e.g. FMI, graphene, and topological insulators) to discover distinct collective phenomena and functionalities, although many properties of individual materials are being vigorously investigated by researchers including the PI himself. This proposed research will likely yield very exciting new results that can advance our fundamental understanding of materials, their interfaces, and related new physics. Currently, the experimental work in this particular area is scarce. This proposed research represents a significantly new effort aiming to advance the field. Broader impacts: The broad impacts of this proposed research contain the following two aspects. First, Spintronics is a relatively young and thriving field. A primary objective of Spintronics is to introduce new spin related functionalities to existing devices, such as spin-based non-volatile memory devices that are ubiquitous in our modern lives. The proposed research will explore new device concepts for spintronic non-volatile memory and quantum information processing. The breakthroughs will likely inspire the researchers in industrial labs to develop more energy efficient and high-performance non-volatile memory devices. The PI himself has extensive experience in adopting new concepts for advanced device applications. Second, this proposed research will integrate the undergraduate and graduate education with the cutting-edge research activities. In particular, the PI will actively engage into this research the under-represented minority students which make up a significant portion of the student population in PI?s institution. Aligned with PI?s departmental ambitious goal in involving all physics majors in undergraduate research, which has been aggressively pushed by the PI in the past four years as the chair of the Undergraduate Advising Committee, the PI will continue to recruit more undergraduates into this and other funded research projects. The PI will incorporate the outcomes of this proposed research into the new graduate and undergraduate courses that he recently developed and taught. He will continue to pursue the education and outreach activities with K-12 that he initiated independently or jointly with the Physics Department.