Abstract
Spintronic devices generate and manipulate spin-polarized currents of electrons in atomically engineered heterostructures that allow for novel physical phenomena that make possible spin-valves and magnetic tunnel junction devices. These devices have already had major impact in memory-storage applications in the form of highly sensitive magnetic field sensors that allowed for massive increases in the storage capacity of magnetic disk drives, and, more recently, in the form of a high performance non-volatile magnetic random access memory (MRAM). Beyond these established devices, magnetic racetrack memory has great potential as a highly capacious, solid state, non-volatile memory-storage device that could even replace magnetic hard disk drives1. Racetrack memory stores data in the form of chiral magnetic domain walls that are moved by current-induced spin-transfer and spin-obit torques along magnetic nano-wires that form the racetracks. Recently, it has been demonstrated that racetracks can be reduced to nanoscopic dimensions that are needed for real world applications2. To date, most work on racetrack memory has relied on 2D forms of racetrack. Even more interesting forms of racetrack memory are based on 3D structures, as originally foreseen1. Here we discuss several forms of 3D racetrack memory. First, we discuss the fabrication of ultrathin membranes formed from the racetrack thin film structure that are disposed on surfaces with pre-patterned vertical structures3,4. Secondly, we discuss 3D racetrack devices that are printed via a multi-photon super-resolution microscope that we developed5. This instrument has a voxel size of just 50 nm with which we can create scaffolds formed from an insulating polymeric material on which we use sputtering techniques to deposit the racetrack structures. These 3D racetracks can be printed in various geometrical forms, including racetracks that have twists, both right-handed or left-handed, and racetracks with curvatures along and across the racetracks. We show that these geometries give rise to novel exchange interactions that strongly influence the current induced motion of chiral domain walls in the 3D racetracks.
References:
1. Parkin, S. S. P., Hayashi, M. & Thomas, L. Magnetic Domain-Wall Racetrack Memory. Science 320, 190–194 (2008). https://doi.org/10.1126/science.1145799
2. Jeon, J.-C., Migliorini, A., Yoon, J., Jeong, J. & Parkin, S. S. P. Multi-core memristor from electrically readable nanoscopic racetracks. Science 386, 315–322 (2024). https://doi.org/10.1126/science.adh3419
3. Gu, K. et al. 3D racetrack memory devices designed from freestanding magnetic heterostructures. Nat. Nanotechnol. 17, 1065–1071 (2022).
4. Gu, K. et al. Atomically-Thin Freestanding Racetrack Memory Devices. Adv. Mater. 37, 2505707 (2025). https://doi.org/https://doi.org/10.1002/adma.202505707
5. Farinha, A. M. A., Yang, S.-H., Yoon, J., Pal, B. & Parkin, S. S. P. Interplay of geometrical and spin chiralities in 3D twisted magnetic ribbons. Nature 639, 67–72 (2025). https://doi.org/10.1038/s41586-024-08582-8
Biography
Stuart Parkin received his B.A. in Physics and Theoretical Physics in 1977 and his Ph.D. in 1980 from the University of Cambridge, UK. Parkin is an elected Fellow or Member: Royal Society (London), Royal Academy of Engineering, National Academy of Sciences, National Academy of Engineering, German National Academy of Science - Leopoldina, Royal Society of Edinburgh, Indian Academy of Sciences, and TWAS - academy of sciences for the developing world. Parkin’s awards include the Materials Research Society Inaugural Outstanding Young Investigator Award (1991); American Physical Society International Prize for New Materials (1994); Europhysics Prize for Outstanding Achievement in Solid State Physics (1997); IUPAP Magnetism Prize and Neel Medal (2009); von Hippel Award - Materials Research Society (2012); Swan Medal - Institute of Physics (London) (2013); Alexander von Humboldt Professorship − International Award for Research (2014); Millennium Technology Award (2014); ERC Advanced Grant - SORBET (2015); King Faisal Prize for Science 2021; ERC Advanced Grant – SUPERMINT (2022); 2024 APS Medal for Exceptional Achievement in Research; and 2024 Charles Stark Draper Prize of the National Academy of Engineering. Parkin has received 4 honorary doctorates. Parkin was named a “Highly Cited Researcher” for the years 2018-2025 and a Citation Laureate™ for 2023 by Clarivate.
Anyone interested is welcome to attend.