Verification of the polar-discontinuity mechanism for ultrathin magnetization suppression

Determine whether the polar-discontinuity mechanism, including the predicted surface metallicity and associated recovery of antiferromagnetic stability below approximately four ErFeO₃ unit cells, accounts for the suppression of magnetization in the thinnest ErFeO₃/SrTiO₃ films.

Background

The paper considers a polar-discontinuity scenario in which alternating charged (ErO)¹⁺ and (FeO₂)¹⁻ planes generate a potential gradient across the ErFeO₃ film. The associated band bending could promote surface metallicity and itinerant ferromagnetic exchange at intermediate thicknesses, whereas reduced band bending in the thinnest films could restore antiferromagnetic stability and thereby explain the experimentally observed reduction of magnetization at approximately 1.2 nm thickness.

This interpretation remains unresolved because the experiments did not detect the surface metallicity required by the scenario. The authors therefore present the polar-discontinuity mechanism only as a theoretical possibility rather than a confirmed explanation, leaving its experimental verification and relevance to the ultrathin magnetization suppression open.

References

We stress that no signature of the surface metallicity required by this scenario has been resolved in the present experiments; the polar-discontinuity picture is therefore retained only as a theoretical possibility rather than a confirmed mechanism.

— Giant Magnetization Enhancement at Ultrathin Limit of an Orthoferrite  (2610.11217 - Oh et al., 8 Oct 2026) in Supplementary Note S1, “Polar-discontinuity scenario in the ErFeO₃/SrTiO₃ film geometry”