Electrical switching of magnetic devices by voltage-controlled proton insertion for low-power, high-performance data storage and computing

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

As conventional silicon-based electronics approaches fundamental physical limits, new materials and devices are urgently needed to meet the growing demand for low-power, high-performance data storage and processing technologies in today's information-based society. Magnetic materials, in which both the charge and the spin of the electron can be harnessed simultaneously, provide a path to enable a new generation of advanced 'spintronic' devices with capabilities beyond those that can be achieved using the electron charge alone. The ability to electrically gate charge transport was key to the electronics revolution, but at present, no mechanism exists to effectively gate magnetism in materials. This project seeks fundamental understanding and practical application of a new mechanism to control magnetism electrically that can enable an unprecedented level of control with fast response, low gate voltage and power input, and robustness over many cycles. The transformative aspect is the use of protons instead of electrons to mediate changes in magnetic properties in solid materials by injecting them towards and away from a magnetic thin film using a small applied voltage. This new control mechanism could deliver superior functionality to enable future memory, logic, and other spin-based technologies that would have tremendous fundamental, technological, and societal impact. The project provides a fertile training ground for undergraduate and graduate students in key interdisciplinary nanotechnologies, and will include an international collaboration that provides international scientific exposure for the supported graduate student. Educational innovation will be achieved through project-centric curriculum development at the undergraduate level. Outreach and diversity activities will include hosting high school teachers through the National Science Foundation Research Experience for Teachers program and by developing and delivering a 'Magnetism in Action' program at a local elementary school classroom for hands-on explorations in science, technology, engineering, and mathematics (STEM). Technical: The objective of the proposed program is to enable a new means to electrically gate magnetism and spin transport in spintronic devices by exploiting reversible hydrogen insertion in all-solid-state thin-film heterostructures. In ultrathin ferromagnetic films adjacent to a heavy metal like Pt and Pd, broken inversion symmetry and spin-orbit coupling give rise to a wealth of phenomena such as perpendicular anisotropy, chiral and other exchange interactions, and spin-orbit torques. These same metals are well-known hydrogen storage materials that undergo a reversible transition between metallic and metal-hydride phases with correspondingly substantial changes to structural and electronic properties. The transformative aspect of the proposed research is to harness electrochemical water splitting in the ambient atmosphere catalyzed by a rare-earth oxide/noble metal interface, to act as a solid-state proton pump capable of driving H+ ions through the gate oxide and into/out of the heavy-metal adjacent to a ferromagnet. Heterostructures will be designed to examine and optimize low-voltage gating of critical magnetic properties, to assess the reaction and diffusion kinetics, to identify and mitigate device failure modes, and to apply this knowledge to exemplary devices in which spin waves can be electrically gated in dynamic magnonic waveguides and crystals. The proposed research will establish a revolutionary new approach that will enable new devices and spin-based architectures, while providing a powerful knob to explore the origins of some of the most important interactions being studied in nanomagnetism today. The project moreover provides new interdisciplinary insights by combining spintronics with solid-state ionics, two traditionally distinct disciplines, which will lead to synergistic approaches to tackle key fundamental and technological challenges. 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.