Symmetry-guided Analogy between Bulk Magnetoelectric Responses and Surface Magnetization in Antiferromagnets

Theoretical [1-2] and experimental [3-4] investigations have shown that antiferromagnets (AFMs) can have a non-vanishing magnetic dipole moment per unit area, named “surface magnetization”, on specific surface orientations. In this talk I will discuss how, based on symmetry arguments, a surface magnetization can counter-intuitively arise even in nominally magnetically compensated surfaces. I will show how surface magnetization can be interpreted in terms of ferro-like and ferri-like bulk linear and higher-order magnetoelectric responses by discussing two examples, namely (-120) Cr₂O₃ and (110) FeF₂ surfaces, where induced surface magnetization arises due to spin canting (in Cr₂O₃) and to the inequivalence of the magnetic sublattices (in FeF₂) produced by symmetry lowering at the surface [5].

[1] A. F. Andreev, JETP Lett. 63, 756 (1996)

[2] K. D. Belashchenko, Phys. Rev. Lett. 105, 147204 (2010)

[3] P. Appel et al., Nano Lett. 19, 1682 (2019)

[4] M. S. Wornle et al., Phys. Rev. B 103, 094426 (2021)

[5] S. F. Weber, A. Urru, S. Bhowal, C. Ederer, and N. A. Spaldin, arXiv:2306.06631 (2023)