epitaxial films using nitrogen-vacancy scanning microscopy*

Antiferromagnetic (AFM) magnetoelectric chromia (Cr₂O₃) allows voltage-control of the Néel vector in the presence of an applied magnetic field (H) [1]. Boron doping further allows the realization of voltage controlled Néel vector switching at zero H [2], a promising finding to AFM spintronics. B-doping is also believed to break the local symmetry allowing for the formation of polar nanoregions giving rise to transient polarization, and to in-plane 90°_­ rotation of the Néel vector into a new stable state (vs 180⁰ in undoped film) [2]. However, it is not clear how the voltage reversibly switches the Néel vector from in-plane to out-of-plane. In this study we use nitrogen vacancy (NV) scanning microscopy [3, 4] to image the surface/boundary magnetization in 200-nm thick B-Cr₂O₃ films grown by pulsed laser deposition on Al₂O₃ substrates. The acquired B_NV images confirm the presence of homogeneously magnetized domains with domain sizes ∼40-500 nm. We discuss the effect of voltage applied along micro-structured Pt Hall bars deposited on B-Cr₂O₃/V₂O₃ structures on the switching of AFM domains. [1] N. Wu et al., Phys. Rev. Lett. 106, 087202 (2011). [2] A. Mahmood et al. Nat. Comm. 12, 1674 (2021). [3] P. Appel et al., Nano Lett. 19, 1682 (2019). [4] A. Erickson et al., RSC Advances, Under review (2022).