SHF: Small: Collaborative Research: Skyrmion Mediated Eenergy-efficient VCMA Switching of 2-Terminal p-MTJ Memory

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State of the art magnetic memory devices use electrical current to switch the magnetization of a nano-magnet from 'up' to 'down' state or vice versa and thus encode the binary bits 1 and 0 respectively. Unlike devices based on widely-used CMOS (Complementary Metal Oxide Semiconductor) technology, such a device, based on technology called spin transfer torque random access memory (STT-RAM), is non-volatile, a significant advantage. However, these devices consume about 1000 times the energy that CMOS devices use for switching. If electrical field is used to control magnetization, these devices could be a hundred times more energy-efficient. However, development of such control methods are impeded by the level of errors introduced due to the presence of material defects and room temperature thermal noise in the material. This project seeks to demonstrate new techniques that makes the switching and control process robust to such defects, thus achieving the energy savings needed for this technology to be competitive with CMOS devices. The project would also help mentor undergraduate summer research, various K-12 workshops (including a K-12 research experience for underrepresented sections in partnership with Richmond Minorities in Engineering Program) on nano-magnetic computing. This project aims to demonstrate that forcing the magnetization through an intermediate so-called "magnetic skyrmion state", where the magnetization spirals from pointing up/down at the core to pointing down/up at the periphery of a circular nano-magnet, makes the switching process extremely robust as well as eliminates the need for any extra magnetic field. The development of such device, if successful, could make the energy efficient Voltage Control of Magnetic Anisotropy (VCMA) switching technique viable for practical memory devices while needing only modest changes to existing STT-RAM fabrication process. The key technical approach in this research project will address gaps in knowledge as well as demonstrate a proof of concept for skyrmion mediated nano-magnetic memory device. The project plans to 1) investigate the growth of various material systems and interfaces and characterize their magnetic properties to develop an optimized memory device that is energy efficient, scalable and has low switching error, 2) demonstrate proof of concept VCMA switching of a nano-magnetic memory cell ~100 nm diameter mediated by a skyrmion state and characterize its switching error, and 3) perform rigorous modeling of skyrmion mediated magnetization dynamics in the presence of thermal noise and defects to understand why the intermediate skyrmion state makes the magnetization reversal robust and study further scaling of these devices. Students will be trained on complementary thin film growth, nano-fabrication, magnetic characterization and micromagnetic modeling in this project.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.