Ultrafast magnetic order dynamics in antiferromagnets

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The possibility of writing all-optically magnetic structures on a sub-picosecond time scale paves the way to ultra-fast magnetic information storage. Regarding the materials used, the focus in the field of purely optically induced switching dynamics was primarily on ferrimagnets such as GdFeCo, since it has already been shown that the magnetization can be switched with a single laser pulse lasting less than 100 femtoseconds. However, the materials investigated so far are only of limited use for commercial spintronic devices, which is why the search for other materials that could be used for ultra-fast information processing continues.In the last application period, our focus was therefore on the ferromagnet FePt - a material that is already used in magnetic data storage due to its high magnetic anisotropy. By adding antiferromagnetically coupling elements such as Tb, Gd, and Cr, the transition from poorly switching ferromagnets to ultra-fast switching ferrimagnets should be investigated. It turned out that FeCrPt in particular is promising in this respect, and first results on polarization-dependent switching could be achieved.In our renewal proposal, we want to shift our focus to antiferromagnets. While antiferromagnets have so far mainly been used as purely passive elements in combination with ferromagnets in spintronics, the interest of international research is currently shifting in the direction of active antiferromagnetic components. It has now been shown that antiferromagnetic textures can be written and read electrically as an indispensable functionality of antiferromagnets for spintronics. However, the laser-induced, ultra-fast switching behavior has so far only been examined to a limited extent. In this joint project we want to investigate the ultrafast dynamics of antiferromagnets through a combination of sample preparation and characterization, optical measurements of the laser-induced spin dynamics and quantitative numerical simulation methods.The main goals of our joint project are the microscopic understanding of laser-induced switching in thin antiferromagnetic layers such as CrPt or dielectric oxides (garnets, orthoferrites), the investigation of the influence of hot electrons and/or spin currents from a metallic top layer on the switching behavior, and multiscale simulations, on the one hand to verify the model assumptions and on the other hand to contribute to the understanding of the static and time-resolved experiments.