Ultra-fast energy efficient ferrimagnetic memory

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The goal of this project is to achieve an in-depth understanding of the physics of a new class of magnetic material: ferri-magnets, and to create a new kind of memory device to resolve the bottleneck in speed and energy beyond today's technologies. The success of the proposed research will surely set an important milestone for next-generation information and communications technology. The research is closely aligned with industrial needs to provide new directions, which may thus fuel another wave of innovation for socio-economic growth. The impact is transformative because it aims at the discovery of novel functional nanomaterials as well as the new physics for high density, high speed, and ultra-high efficient devices. The forefront research will also have a vast educational impact since the research trains students with various education levels, from high school to undergraduate/graduate school (including women and minorities) as well as school teachers in this inter- and multi-disciplinary and emerging fields of physical science, engineering, and computer science, through PI's participation of the outreach programs at UCLA. The training in these emerging disciplines will provide a diverse human capital, versed in scientific methods and experienced in the applications. The educational impact is further amplified by the existing outreach programs established in the UCLA NSF Engineering Research Center. Ultra-fast and energy-efficient memory devices are critical to resolving the limit of speed and energy dissipation for today's computing challenges in the era of big data and artificial intelligence. The proposed research is aimed at realizing a radically different class of memory devices based on insulating ferrimagnetic materials, which can operate at terahertz speed due to the enormous internal exchange field. In particular, these materials usually have low damping, enabling high energy efficiency. The major tasks are to understand and control the dynamics of nearly compensated ferri-magnets and to build ferri-magnetic prototype memories. To accomplish the objective, the proposed research will investigate a series of new insulating ferri-magnets from three perspectives: (1) understanding the fundamental switching mechanism and the interfacial exchange coupling between a compensated ferrimagnet and a large spin-orbit-coupling layer through electrical characterizations, pump-probe, x-ray, and neutron techniques; (2) enabling electrical manipulation of the compensated ferrimagnetic order to be demonstrated by anomalous Hall and magnetoresistance effects; (3) realizing their ultrafast dynamics using electronic ultrashort pulses and optical pump-probing in the picosecond regime. Fundamentally, the research will enable the understanding of the interface coupling and the ferri-magnetic dynamics, resulting in new switching mechanisms. It may provide a new framework for employing spintronics in quantum technology.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.