Collaborative Research: Epitaxial spin heterostructures for energy efficient magnetic memory

Nontechnical description

This project aims to revolutionize computer memory by developing new materials and devices for high-density magnetic random-access memory. The project focuses on enabling these devices using thin layers of special materials, called van der Waals heterostructures, on a wafer scale. This wafer-scale approach is crucial for practical applications in the semiconductor industry, unlike current lab methods that rely on delicate, small flakes of two-dimensional materials prepared by exfoliation.

Achieving highly efficient switching in these magnetic random-access memory devices is essential for future “memory-in-computing” technologies, which promise faster and more energy-efficient computing. This research will address critical challenges in material development and device fabrication, ultimately paving the way for transformative advancements in computing.

Additionally, the project will provide invaluable training for students, equipping them with essential skills for the semiconductor industry and contributing to the development of a highly skilled workforce. Technical description

This research will address the limitations of conventional spin-orbit torque switching in magnetic random access memory devices by developing wafer-scale epitaxial van der Waals spin heterostructures. Current spin-orbit torque efficiency in three-dimensional materials is restricted by intrinsic and extrinsic factors, such as low spin Hall angles and imperfect interface spin transparency.

Recent studies on exfoliated two-dimensional materials suggest the potential to surpass these three-dimensional limitations. This project seeks to achieve material breakthroughs by growing epitaxial van der Waals heterostructures with exceptional structural, electronic, and magnetic properties, including atomically sharp interfaces, on a wafer scale.

These heterostructures will consist of a two-dimensional ferromagnetic material with room-temperature Curie temperature and tunable perpendicular magnetic anisotropy, epitaxially grown via molecular beam epitaxy onto a topological quantum material with strong spin-orbit coupling. Topological insulators (e.g., Bi2Te3) and semimetals (e.g., WTe2) will provide the spin-momentum locking necessary for high intrinsic spin-orbit torque efficiency.

The ferromagnetic component, Fe3GaTe2, a recently discovered two-dimensional ferromagnet, exhibits a Curie temperature of approximately 380 K, among the highest reported for two-dimensional magnets. Furthermore, like Fe3GeTe2, Fe3GaTe2 possesses strong perpendicular magnetic anisotropy, a crucial property for high-density memory devices. Successfully integrating these components into a wafer-scale heterostructure via molecular beam epitaxy represents a significant scientific advancement compared to devices made with exfoliated flakes.

The combined expertise of the PI and Co-PI in molecular beam epitaxy, nanofabrication, and spintronics will ensure the project’s success. The resulting epitaxial heterostructures will have a profound impact on nanoscale magnetism, spintronics, and related fields. First-principles calculations will be employed to provide theoretical insights into the fundamental properties and behavior of these novel materials, guiding the optimization of material growth and device design.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.