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Spin-orbitronics and Racetrack Memory

Physikalisches Kolloquium

Over the past few years there have been remarkable discoveries in spin-based phenomena that rely on spin-orbit coupling that could spur the development of advanced magnetic memory devices1-4.  One of the most exciting of these is Racetrack Memory5 that stores digital data in the form of the presence or absence of chiral domain walls.  These domain walls are shifted to and fro, synchronously, along magnetic nano-wires – the racetracks - using current pulses.  The magnetic data are thereby shifted to reading and writing devices built into each racetrack so that the data can be written and read.  Recent discoveries in the emerging field of spin-orbitronics makes possible the current induced motion of chiral domain walls at high speeds that exceed 1 km/s in atomically engineered racetracks.  The same Dzyaloshinskii-Moriya exchange interactions that stablilize chiral Néel domain walls in such racetracks also enable the formation of topological spin textures such as skyrmions.   Recently we have discovered magnetic antiskyrmions in a tetragonal Heusler compound, using Lorentz transmission electron microscopy6.  Such antiskyrmions are potential storage elements in racetrack memories.  These recent discoveries in spin-orbitronics makes Racetrack Memory extremely attractive as a dense, high performance, low energy consuming, non-volatile memory technology1 that could make computing systems more compact and yet more powerful.

1  Parkin, S. S. P. & Yang, S.-H. Memory on the Racetrack. Nat. Nano.10, 195-198, (2015).

2  Yang, S.-H., Ryu, K.-S. & Parkin, S. S. P. Domain-wall velocities of up to 750 ms−1 driven by exchange coupling torque in synthetic antiferromagnets. Nat. Nano.10, 221-226, (2015).

3  Garg, C., Yang, S.-H., Phung, T., Pushp, A. & Parkin, S. S. P. Dramatic influence of curvature of nanowire on chiral domain wall velocity. Sci. Adv. 3, e1602804, (2017).

4   Ryu, K.-S., Thomas, L., Yang, S.-H. & Parkin, S. S. P. Chiral spin torque at magnetic domain walls. Nat. Nano.8, 527–533, (2013).

5  Parkin, S. S. P., Hayashi, M. & Thomas, L. Magnetic Domain-Wall Racetrack Memory. Science320, 190-194, (2008).

6  Nayak, A. K. et al. Magnetic antiskyrmions above room temperature in tetragonal Heusler materials. Nature548, 561-566, (2017).

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