Magnetic Skyrmion for Nonvolatile Low-Power Spin-Orbitronics Applications

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

This proposal aims to resolve the challenging issues related to the scaling of complementary metal-oxide-semiconductor (CMOS): power dissipation and variability. To achieve this goal, the proposed research explores the possibilities to build magnetic memory devices based on magnetic skyrmions for room-temperature applications featuring in nonvolatile, high density and low-power consumption. A magnetic skyrmion is a particle-like, topologically protected magnetic domain. As a nonvolatile information carrier, each individual skyrmion in a memory device can enable high-density, low-power operations due to the small size, the low driving current density and the extra topological protection. The proposed research will establish a framework for magnetic memory devices using topologically protected spin texture as the information carrier. The impact will be transformative and thus enables the construction of novel magnetic memory. The high-density memory will help accelerate the progress of the big data and internet-of-things era. Meanwhile, when integrated with the CMOS semiconductor technology, it potentially resolves the energy dissipation challenge and thus further advances the technology node. Additionally, this interdisciplinary research also has a vast educational impact, as the new knowledge from the spin orbit coupling engineering will have emerging educational meaning for new students. Students with education level from high school to undergraduate/graduate students, and postdocs (including women and minorities) will be exposed and trained in this inter- and multi-disciplinary and emerging fields of physical science and engineering as well as computer science through PI's participation of the high school and freshman outreach programs at UCLA. The training of students in these emerging disciplines will provide diverse human capital, versed in scientific method and experienced in the applications. The educational impact is further amplified by current outreach programs through the California NanoSystems and the NSF-ERC on Translational Applications of Nanoscale Multiferroic Systems. Although skyrmions can intrinsically exist in a group of so-called helimagnetic materials (B-20) compounds, skyrmions in magnetic multilayers or interfaces will be more compatible with existing magnetic recording/memory technologies. Thus, the proposed project focuses on the study of skyrmion creation, manipulation and detection in ferromagnetic layer/heavy-material (FM/HM) thin-film systems. This system provides the possibility to furthest adjust and tune the skyrmion properties for application purposes. The creation and annihilation of single, individual skyrmions will be experimentally realized and theoretically analyzed dynamically and statically. The manipulation of skyrmions can be controlled by currents via spin-orbit torque coming from the relativistic spin-orbit coupling (SOC). Each individual skyrmion can be detected using magnetoresistance effect via magnetic tunnel junctions. Single spin textures of single Skyrmions will be modeled via micromagnetic simulation. Knowledge and experience learnt from this study will enable electrically encoding and decoding of information; the use of commonly accessible thin film material systems with low-temperature process in this research automatically ensures devices to be fully compatible with current CMOS or magnetic recording technology. The proposed research is transformative since it invokes many unique innovations from (1) interfacial Dzyaloshinskii-Moriya interaction in FM/HM heterostructures to create skyrmion with controllable sizes; (2) effectively manipulation of skyrmion motion by the current-induced spin-orbit torque at the FM/HM interface; (3) the use of high-quality MTJ for information encoding and detection; (4) nanostructure engineering and voltage-controlled magnetic anisotropy (VCMA).