报告题目: Chiral spin-orbitronics
Max Planck Institute for Microstructure Physics, Halle (Saale), Germany
Martin Luther University Halle-Wittenberg
报告内容简介: 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 devices. These include the formation of chiral spin textures in the form of Néel domain walls and topological spin textures, skyrmions, that are stabilized by a Dzyaloshinskii-Moriya exchange interaction. The Dzyaloshinskii-Moriya exchange interaction is derived from broken symmetries and spin-orbit interactions at interfaces or within the bulk of materials. Another important consequence of spin-orbit effects are the unexpectedly highconversion efficiencies of charge current to chiral spin current from topological spin textures and in conventional metals, via the spin Hall effect1,2. Such spin currents lead to giant spin-orbit torques thatcan be used to switch the magnetization in three terminal magnetic tunnel junction memory elements or can be used to move domain walls in Racetrack Memory memory-storage devices. Indeedrecord-breaking current-induced domain wall speeds exceeding 1,000 m/sec have recently been reported in atomically engineered synthetic antiferromagnetic racetracks in which the domain walls are “invisible” with no net magnetization3,4. More complex non-collinear spin textures include the recent discovery of antiskyrmions5 in a Heusler compound.
1 Zhang, W. et al. Giant facet-dependent spin-orbit torque and spin Hall conductivity in the triangular antiferromagnet IrMn3. Sci. Adv.2, e1600759, (2016).
2 Demasius, K.-U. et al. Enhanced spin-orbit torques by oxygen incorporation in tungsten films. Nat. Commun.7, 10644, (2016).
3 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).
4 Garg, C., Yang, S.-H., Phung, T., Pushp, A. & S.P.Parkin, S. Dramatic influence of curvature of nanowire on chiral domain wall velocity. Sci. Adv. 3, e1602804, (2017).
5 Nayak, A. K. et al.Magnetic Antiskyrmions Beyond Room Temperature in Tetragonal Heusler Materials. Nature548, 561-566 (2017).
报告人简介:Prof. Stuart Parkin’s research interests include oxide thin film heterostructures, high-temperature superconductors, and, magnetic thin film structures and spintronic materials and devices for advanced sensor, memory, and logic applications. Parkin’s discoveries in magneto-resistive thin film structures enabled a more than 1000-fold increase in the storage capacity of magnetic disk drives. Most recently, Parkin’s has proposed and demonstrated a novel storage-class memory device, “Racetrack Memory”, that is an innately 3D solid-state device with the storage capacity of a disk drive but with much higher performance and reliability. Parkin’s other major research interest is cognitive - bio-inspired materials - that could enable ultra-low power computing technologies. Parkin has published more than 500 papers and has 110 issued patents. His h impact factor is 99 (Google Scholar) and he has ~52,000 citations.