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Raw data for the publication titled 'Ultrafast Unidirectional Spin Hall Magnetoresistance Driven by a Terahertz Light Field,' including the data presented in Figures 2 through 4.

The year 2023 was highly successful, marked by significant high-level publications and the acquisition of new projects. The latter is increasingly crucial given the tight budget in 2023, which is expected to become even tighter in 2024 due to rising costs and well-deserved salary increases for our employees. As a result, we must reduce the number of our non-permanent scientific staff, which will impact future productivity. Despite these challenges, our performance in 2023 remained outstanding with a total of 178 refereed publications and an average impact factor of 8.1. Notable publications include 8 from the Nature Publishing Group, 7 from Advanced (Functional) Materials, 4 from ACS Nano, and 2 from Angewandte Chemie. Our excellence was further recognized by the HZDR Research Award, which again went to our Institute, this time awarded to Dr. Oleksii Volkov and Dr. Oleksandr Pylypovskyi from the Department of Intelligent Materials and Devices for their theoretical and experimental investigations into chiral symmetry breaking in magnetic 3D textures. Furthermore, Dr. Lukas Körber, who completed his PhD in 2023 with summa cum laude, was the recipient of both the Helmholtz Doctoral Award in the research field of Matter and the HZDR Doctoral Award. Prof. Manfred Helm was honored as an APS Fellow. In 2023, the majority of newly approved projects are financed by the Saxonian Ministry of Science, Culture and Tourism and the Helmholtz Initiative and Networking Fund which is a confirmation of the application relevance of our research. Our infrastructure upgrades are progressing as planned. The new AMS (Accelerator Mass Spectrometry) building was handed over to us in fall 2023. This year, we anticipate the arrival of our new 1 MV accelerator, which will be a dedicated AMS system. We aim to achieve full user operation by 2025. Finally, we extend our heartfelt thanks to all partners, friends, and organizations who supported our progress in 2023. We are particularly grateful to

Electric fields operating at THz frequencies hold significant promise for inducing ultrafast coherent excitations in magnetic heterostructures. Through the utilization of ferromagnetic/heavy metal (FM/HM) heterostructures, we have demonstrated that THz radiation (0.1 – 30 THz) exhibits combined functionality of microwaves and visible light. 1) Similar to microwaves, THz fields can effectively generate spin currents through the spin-Hall effect (SHE), resulting in an excitation of THz-frequency magnon modes. 2) Akin to visible light excitation, THz fields deposit heat, leading to the demagnetization of FM layers. Harnessing the THz-induced demagnetization as a spin current source within FM/HM heterostructures, we exploit the half-cycle THz electric field to incite spin currents, which subsequently transformed into picosecond charge currents through the inverse SHE within the HM layer. This conversion process results in the emission of a THz second harmonic signal, offering the THz spintronic frequency conversion.

Cr2O3 is an exceptional antiferromagnet with an easy axis of anisotropy that exhibits a magnetoelectric effect at room temperature [1]. Although there are technological challenges to use it for applications because of the relatively low bulk Neel temperature of TN = 308 K, there are demonstrations that TN can be substantially enhanced by strain in thin films. The morphology and growth procedure of such samples allow the appearance of flexomagnetic effects and pinning of domain walls at grain boundaries [2,3]. Here, we propose a material model of granular antiferromagnetic films and apply it to maze-like domain patterns in thin Cr2O3 samples [4]. The domain pattern is obtained by means of the nitrogen vacancy magnetometry and compared with spin-lattice simulations. We analyze the statistics of the size and self-similarity of the domain wall patterns to correlate the experimental measurements with the parameters of the theoretical model and compare the domain wall patterns with predictions made by a machine learning approach. The estimated inter-grain coupling is characterized by a substantial reduction of the effective exchange coupling to about 10% of the bulk value, with a wide standard deviation. Based on the material model, we provide design rules for the granular AFM recording media.

Antiferromagnets (AFMs) as materials with a high degree of magnetic compensation and complex dynamics attract attention for fundamental research and use in high-speed and low-energy-cosuming electronics. Technologically relevant AFM thin films usually possess a granular crystal structure, which alters the properties of domain walls and skyrmions [1,2]. Here, we provide a material model of a granular AFM and describe domain wall pinning at grain boundaries [3]. The model is applied to Cr2O3 films with a maze-like domain pattern visualized using nitrogen vacancy magnetometry. Using the statistical analysis of domain size and measuring the self-similarity parameters of the domain wall pattern, we estimate the material parameters characterizing the inter-grain coupling. Namely, for the films with a grain size of about 50 nm, the distribution of exchange bonds between grains is characterized by an average of 10% from the bulk value and a wide standard deviation, including a small amount of ferromagnetic bonds. The presented approach is compatible with machine learning techniques. Based on the material model, we provide design rules for the granular AFM recording media. [1] Jing et al, Phys. Rev. B 103, 174430 (2021) [2] Veremchuk et al, ACS Appl. El. Mat. 4, 2943 (2022); Erickson et al, RCS Adv. 13, 178 (2023) [3] Pylypovskyi et al, Phys. Rev. Appl. 20, 014020 (2023)

Atomic scale reordering of lattices can induce local modulations of functional material properties, such as reflectance and ferromagnetism. Pulsed femtosecond laser irradiation enables lattice reordering in the picosecond range. However, the dependence of the phase transitions on the initial lattice order as well as the temporal dynamics of these transitions remain to be understood. This study investigates the laser-induced atomic reordering and the concomitant onset of ferromagnetism in thin Fe-based alloy films with vastly differing initial atomic orders. The optical response to single fs laser pulses on selected prototype systems, one that initially possesses positional disorder, Fe60V40, and a second system initially in a chemically ordered state, Fe60Al40, has been tracked with time. Despite the vastly different initial atomic orders the structure in both systems converges to a positionally ordered but chemically disordered state, accompanied by the onset of ferromagnetism. Time-resolved measurements of the transient reflectance combined with simulations of the electron and phonon temperature reveal that the reordering processes occur via the formation of a transient molten state with an approximate lifetime of 200 ps. These findings provide insights into fundamental processes involved in laser-induced atomic reordering, paving the way for controlling material properties in the picosecond range.

The integration of heterogeneous modular units for building large-scale quantum networks requires engineering mechanisms that allow a suitable transduction of quantum information. Magnon-based transducers are especially attractive due to their wide range of interactions and rich nonlinear dynamics, but most of the work to date has focused on linear magnon transduction in the traditional system composed of yttrium iron garnet and diamond, two materials with difficult integrability into wafer-scale quantum circuits. In this work, we present a different approach by utilizing wafer-compatible materials to engineer a hybrid transducer that exploits magnon nonlinearities in a magnetic microdisc to address quantum spin defects in silicon carbide. The resulting interaction scheme points to the unique transduction behavior that can be obtained when complementing quantum systems with nonlinear magnonics.