Quench-switching of antiferromagnets explored with high spatial and temporal resolution

• Applicants: Dr. Bernd Kästner; Professor Jairo Sinova, Ph.D.; Professor Dr. Jörg Wunderlich
• Subject Area: Theoretical Condensed Matter Physics ; Experimental Condensed Matter Physics
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 452301518

The joint German-Czech project AFQuench aims to provide a full microscopic physical understanding of the novel switching mechanism in antiferromagnets, where the system is controlled by electrical and optical pulses and driven into high-resistive nano-fragmented domain states. Prior to this discovery, the field of antiferromagnetic spintronics focused on switching the states of the antiferromagnet by exploiting direct analogies with the ferromagnetic spintronics counterpart, aiming to control the orientation of the magnetic order by means of spin-orbit torque. This success promoted antiferro- magnets as active elements in electronic memory devices, bringing with them many advantages such as insensitivity to magnetic fields and THz scale dynamics. However, similarly to ferromagnets, the inherent weakness of low resistivity read-out signals remained. The newly discovered quench- switching mechanism represents a new branch of research in antiferromagnetic spintronics and has no direct analogue in the entire field of magnetism. This switching avoids many of the weaknesses of the reorientation-switching mechanism and it allows for dc and fs-laser pulses to be used, bridging ultrafast opto-spintronics and spin-electronics. Based on the preliminary microscopy studies of the Czech-German team, we ascribe these unparalleled electrical and optical device characteristics to pulse-quenching the antiferromagnet into metastable nano-fragmented domain states. Beyond these initial observations, there is at present little known about the dynamics and the specific physical origin of the new mechanism. The project is based on the synergy of expertise of the Czech and German partners in the development and application of complementary, beyond state-of-the-art space and time-resolved imaging techniques: (i) Scanning near-field magneto-Seebeck microscopy with 10 nm resolution, (ii) Lorentz transmission electron microscopy with atomic resolution, (iii) sub-ps THz/optical pump-probe technique, and (iv) scanning near-field THz/optical microscopy with simultaneous high spatial and temporal resolutions, all underpinned by (iv) multi-scale theoretical modelling. The potential impact of our project is multidisciplinary with implications ranging from memory-logic devices beyond conventional digital electronics (artificial intelligence architectures) and ultra-fast optical switching, to magnetic microscopies exceeding the state-of-the-art limits of spatial and temporal resolutions.

• DFG Programme: Research Grants
• International Connection: Czech Republic
• Partner Organisation: Czech Science Foundation
• Cooperation Partners: Professor Dr. Lukas Nádvorník; Kamil Olejník, Ph.D.