Voltage-based switching of memory elements based-on spin dephasing, diffusion and switching in ferrimagnetic metals

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Our economy and society rely heavily on information technology, which consumes an ever-growing amount of energy to process and store the world’s information. This makes energy-efficient, non-volatile memory systems a critical goal for future computers. Magnets, where information is encoded in bits typically formed from ferromagnetic materials with “north” and “south” poles with very much reduced size, currently store a huge amount of information. However, these memory systems rely on magnetic fields to manipulate the poles, giving a technology with non-volatile storage but limited size and energy efficiency. This project aims to achieve a low-current, based on materials with properties of antiferromagnets and ferromagnets, called a ferrimagnet by using all electrical means of manipulating nanoscale non-volatile magnetic memory. A ferrimagnet has vanishing magnetization at a certain temperature which can be shifted with carefully engineered applied electric field. This project will provide fundamental scientific knowledge and demonstration of this principle, for the fabrication of energy efficient, non-volatile, nanoscale magnetic memory and switching devices. The project will involve graduate and undergraduate students training and outreach activities involving collaboration with the student physics club, online spintronics seminar series and brown bag seminars. This project focuses on ferrimagnetic metal alloys and bilayers, with the overall goal of demonstrating voltage-based switching of memory elements using a detection scheme based on the anomalous Hall effect, and of spin transport sensors such as non-local spin valves. One specific focus is on a design of a new experiment to measure both the spin dephasing length and the spin diffusion length in ferrimagnetic metals. These measurements for a single material, will provide critical information for a range of spintronic systems and devices. The project will also explore voltage manipulation via electrolytic gating using an ionic gel. The project explores temperature-driven switching of the ferrimagnet as a first step toward eventual voltage-gated switching, which could also prove useful for applications in sensing. Research activities will involve characterization and development of ferrimagnetic metals, including SQUID magnetometry and thermoelectric and thermal conductivity measurements using unique micro- and nanomachined measurement tools. The project has four main thrusts: (1) Developing, optimizing, and characterizing materials for ferrimagnetic spintronics, (2) Measuring the spin dephasing and diffusion lengths in ferrimagnetic metals, (3) Using a ferrimagnet to Realize Voltage-Driven Deterministic Magnetic Switching, and 4) Tuning spin direction in a ferrimagnetic non local spin valve.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.