Interplay of geometrical and spin chiralities in 3D racetracks and twisted structures

Racetrack Memory is an emerging spintronic memory-storage technology that encodes data in moveable magnetic domain walls (DWs). Chiral DWs can be moved at high speeds along nanoscopic magnetic “tracks” using spin torques derived from spin currents. Each racetrack can be designed to hold tens to hundreds of DWs, thereby, allowing for massive data storage capacities. We have recently demonstrated scaling of racetracks to technologically relevant dimensions.¹ The greatest potential of Racetrack Memory lies in building three-dimensional (3D) forms of the magnetic racetracks. Using freestanding membranes, just a few nanometers thick, that are comprised of complex thin film magnetic heterostructures that form the racetrack, we recently demonstrated the first 3D Racetrack Memory. The membranes are floated off a substrate and positioned on pre-patterned surfaces with micron sized protrusions, thereby forming 3D structures in which we demonstrated current induced DW motion with high velocities. More complex 3D racetracks can be formed by using 3D printing techniques. We have developed a custom-designed, multiphoton lithography 3D printing instrument based on a modified super-resolution microscope with a 50 nm voxel size. Using this system, we have fabricated 3D scaffolds with various geometrical shapes including curved surfaces with torsions and twists. The tiny voxel size allows for very smooth surfaces on which we deposit complex thin film heterostructures that form the 3D magnetic racetracks. The current induced motion of DWs in these structures depends on their chirality and configuration (up/down or down/up) and the geometrical chiral twists and curvatures of the ribbons.² We have shown that the interplay of spin and geometrical chirality can result in non-reciprocal DW motion, i.e. DW filter or diode. Our results show that the interplay between 3D geometrical and spin chiralities leads to novel functionalities that allow for innovative spintronic phenomena and devices.



1 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).

2 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).