Nanomagnetism and spintronics of Cr2O3 thin-film 
magnetoelectric antiferromagnets

Thin film magnetoelectric antiferromagnets (AF) is a viable material science platform for prospective high speed and energy efficient spintronic devices for memory and logic applications. To explore their application potential, it is necessary to understand modifications of the magnetic properties of AF thin films with respect to their bulk counterparts. Here, we will discuss spintronics, magnetometry and microscopy of bulk α-Cr2O3 single crystals [1] and relate them to the properties of α-Cr2O3 thin films [2-5]. In transport experiments, we access the magnetic state of the Cr2O3 relying on the spin Hall physics in a Pt thin film brought in proximity to the insulating antiferromagnet [2-4]. The analysis of the transport data is backed up by the real space imaging of AF domain patterns using NV microscopy [1,5]. Considering grainy morphology of thin films, we address questions regarding the change of the intergranular exchange [5], criticality behavior and switching of the order parameter [2] and physics of the readout signal in α-Cr2O3 interfaced with Pt [3]. In particular, the possibility to read-out the antiferromagnetic order parameter all-electrically enables a new recording concept of antiferromagnetic magnetoelectric random access memory (AF-MERAM) [3]. Furthermore, relying on the elasticity of antiferromagnetic domain walls in Cr2O3 single crystals and exploring their efficient pinning at lithographically defined mesa structures, the concept of domain wall based antiferromagnetic memory was put forth [1].

1. N. Hedrich, K. Wagner, O. V. Pylypovskyi, B. J. Shields, T. Kosub, D. D. Sheka, D. Makarov, P. Maletinsky, Nature Physics, (2021), doi:10.1038/s41567-020-01157-0.
2. T. Kosub, M. Kopte, F. Radu, O. G. Schmidt, D. Makarov, Physical Review Letters, 115 (2015) 097201.
3. T. Kosub, M. Kopte, R. Hühne, P. Appel, B. Shields, P. Maletinsky, R. Hübner, M. O. Liedke, J. Fassbender, O. G. Schmidt, D. Makarov, Nature Communications, 8 (2017) 13985.
4. R. Schlitz, T. Kosub, A. Thomas, S. Fabretti, K. Nielsch, D. Makarov, S. T. B. Goennenwein, Applied Physics Letters, 112 (2018) 132401.
5. P. Appel, B. J. Shields, T. Kosub, R. Hübner, J. Fassbender, D. Makarov, P. Maletinsky, Nano Letters, 19 (2019) 1682.