Emergent exchange bias in ultra-thin La0.67Sr0.33MnO3 films driven by ferro-antiferromagnetic phase coexistence

Inés García-Manuz; Gabriel Caballero; Jose Luis F. Cunado; Miguel Romera; Mariela Menghini; Carlos León; Jacobo Santamaría; Julio Camarero; Paolo Perna; Fernando Ajejas

arXiv · 2607.12669

Emergent exchange bias in ultra-thin La0.67Sr0.33MnO3 films driven by ferro-antiferromagnetic phase coexistence

Inés García-Manuz·Gabriel Caballero·Jose Luis F. Cunado·Miguel Romera·Mariela Menghini·Carlos León·Jacobo Santamaría·Julio Camarero·Paolo Perna·Fernando Ajejas

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Abstract

Ultra-thin La0.67Sr0.33MnO3 (LSMO) films are generally regarded as single-phase ferromagnets, yet their reduced dimensionality enhances the impact of oxygen stoichiometry and local structural distortions. Here we demonstrate that LSMO layers with thicknesses between 3 and 17 nm develop a robust and thickness-independent exchange bias (EB) despite the absence of an engineered ferromagnetic-antiferromagnetic (FM-AFM) interface. Angular magneto-optical Kerr effect measurements reveal a reproducible hysteresis-loop shift that reverses sign upon 180-degree rotation, confirming its intrinsic origin. X-ray photoelectron spectroscopy shows a thickness-independent Mn2+ fraction (about 20 percent), indicating the presence of oxygen-deficient reduced regions embedded within the Mn3+/Mn4+ ferromagnetic matrix. A simple interfacial-exchange model suggests that only a sub-percent fraction of antiferromagnetic (or frustrated spin-ice-like) regions is required to generate the observed EB. These results demonstrate that ultra-thin LSMO can spontaneously host internal FM-AFM interfaces driven by oxygen deficiency, revealing an emergent route to exchange bias in nominally single-phase manganite films.

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Inés García-Manuz, Gabriel Caballero, Jose Luis F. Cunado, Miguel Romera, Mariela Menghini, Carlos León, Jacobo Santamaría, Julio Camarero, Paolo Perna, Fernando Ajejas. 2026-07-14. Emergent exchange bias in ultra-thin La0.67Sr0.33MnO3 films driven by ferro-antiferromagnetic phase coexistence. https://arxiv.org/abs/2607.12669

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