Oxygen stoichiometry-driven charge compensation and Ruddlesden–Popper defects in ferromagnetic high-entropy manganite thin films

communications materials Article A Nature Portfolio journal https://doi.org/10.1038/s43246-026-01190-1 Oxygen stoichiometry-driven charge compensation and Ruddlesden–Popper defects in ferromagnetic high-entropy manganite thin films Check for updates 1,2 3 4,9 1234567890():,; 1234567890():,; Zhibo Zhao , Moaz Waqar , Arun Kumar Jaiswal , Dirk Fuchs Xiaoqing Pan 3,6,7, Robert Kruk1 & Abhishek Sarkar 8 4 , Horst Hahn 1,2,5 , High-entropy oxides (HEOs) originate from an innovative materials design strategy that stabilizes single-phase solid solutions despite the inclusion of multiple principal elements into a single cation sublattice. While prior efforts have largely focused on cation disorder, the impact of anion defects on the structure and properties of HEOs remains unexplored. Here, we examine the influence of oxygen non-stoichiometry on the nanostructure and magnetic properties of single-crystal high-entropy manganite (HE-Mn) films, (Gd0.2La0.2Nd0.2Sm0.2Sr0.2)MnO3. The films were deposited on singlecrystal (LaAlO3)0.3(Sr2AlTaO6)0.7 (001) substrates under varying oxygen partial pressures p(O2). Phasepure cube-on-cube epitaxy is maintained across all growth conditions. However, distinct nanocolumnar Ruddlesden-Popper (RP) faults formed in oxygen deficient HE-Mn films. Unlike in conventional manganites, low-pressure-deposited films show no change in cation oxidation state, indicating the concurrent oxygen and manganese deficiency. This coupled cation-anion deficiency preserves the Mn3+/Mn4+ ratio and drives RP fault formation. Consequently, ferromagnetic ordering persists even in the low p(O2) HE-Mn films, demonstrating their resilience to oxygen nonstoichiometry. Additionally, an in-plane to out-of-plane magnetic anisotropy crossover was observed, likely arising from spatial variation in the c-axis lattice constant. These findings establish oxygen nonstoichiometry as an effective control parameter for defect nanostructuring and magnetic property tuning in HEO epitaxial films. High-entropy oxides (HEOs) are a promising class of functional materials that offer access to a vast compositional space, enabling fine-tuning of properties1–6. The uniqueness of HEOs lies in their ability to retain phasepurity despite the presence of multiple principal cations on a given lattice site1,7–11. Consequently, the vastness of accessible composition space in HEOs provides the platform for extensive functionality design. Already, HEOs are known for their enhanced electrochemical energy storage capabilities, high catalytic activities, superior ionic transport, tunable band gap and unique magnetic phenomena2,4,11–21. Most of the initial works on HEOs were carried out with powder or bulk ceramics22–24. Recent works have focused on the fabrication of epitaxial HEO thin films, where substrateinduced straining opens additional avenues for tuning their structure and properties25–28. Investigation on HEO thin films, although limited, showcases thickness and strain-dependent tuning of functional characteristics, 1 Institute of Nanotechnology, Karlsruhe Institute of Technology, Kaiserstrasse 12, 76131 Karlsruhe, Germany. 2KIT-TUD-Joint Research Laboratory Nanomaterials, Technical University Darmstadt, 64287 Darmstadt, Germany. 3Department of Materials Science and Engineering, University of California, Irvine, CA, 92697, USA. 4Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, Kaiserstrasse 12, 76131 Karlsruhe, Germany. 5Department of Materials Science & Engineering, The University of Arizona, Tucson, AZ, 85721, USA. 6Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA. 7Irvine Materials Research Institute, University of California, Irvine, CA, 92697, USA. 8Department of Materials Science and Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, 110016, India. 9Present address: Department of Quantum Matter Physics, University of Geneva, CH1211 e-mail: ; Geneva, Switzerland. Communications Materials | (2026)7:141 1 Article https://doi.org/10.1038/s43246-026-01190-1 Fig. 1 | Structural and surface topology characterization of the HE-Mn thin films. a HR-XRD, b XRR, and c ω-rocking curves, showcasing epitaxial growth of HE-Mn films deposited at different p(O2) on LSAT (001). d–f AFM micrographs of HE-Mn thin films deposited at different p(O2), indicating a smooth surface topology. such as magnetic transition temperatures, exchange bias, perpendicular magnetic anisotropy, etc26–29. Oxygen deficiency, which results in oxygen vacancies (VO) often accompanied by cation vacancies, profoundly impacts the structure and properties of oxide systems. Perovskite manganites are one such class of functional oxides, where the crystallographic structure, charge ordering, magnetic and electronic ground states are strongly affected by oxygen stoichiometry30,31. For instance, VO can induce a phase transition from perovskite to brownmillerite32. It is worth emphasizing that the structural modifications induced by VO are intricately connected to changes in electronic and magnetic properties. For instance, precise control of oxygen content can significantly influence transport properties by modifying charge carrier density and triggering phenomena like the metal-insulator transition and colossal magnetoresistance30. Furthermore, VO strongly affects the magnetism of manganite perovskites by modifying magnetic interactions, thereby influencing the Curie temperature (TC) and saturation magnetization (MS)31,33. In an earlier study, we explored HE-design strategy in combination with hole doping in manganite systems, (Gd0.25La0.25Nd0.25Sm0.25)1-xSrxMnO316. Investigations revealed a single homogenous crystallographic structure with magnetic inhomogeneities in HE-manganites (HE-Mn), which manifests itself through an enhancement of colossal magnetoresistance (CMR) along with dual magnetic transitions16. Similar enhanced CMR has also been reported in other HE-Mn compositions, such as (La0.2Nd0.2Pr0.2Sm0.2Eu0.2)1−xSrxMnO3, where a structural transition from orthorhombic to rhombohedral symmetry with increasing Sr content was additionally observed34. It should be noted magnetic properties of HE-Mn (including CMR) are typically compared with conventional perovskite manganites (e.g., La1−xSrxMnO3)16,34, rather than across different HEO classes, as magnetism in HEOs is highly structure dependent7,8,23,24. Even within perovskite-HEOs, A-site and B-site disorder can lead to contrasting magnetic behavior, with the B-site transition metal playing a dominant role7,23,24,29. Recently, we reported the influence of epitaxial strain on the structure and magnetism of HE-Mn, where strained thin films (Gd0.25La0.25Nd0.25Sm0.25)0.8Sr0.2MnO3 exhibited a single ferromagnetic Communications Materials | (2026)7:141 (FM) transition, unlike its bulk counterparts, along with a unique strain accommodation mechanism and substantial change in TC27. In this study, we utiliz (...truncated)