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La0.7Sr0.3MnO3 (LSMO) is a promising material for spintronic applications due to its robust ferromagnetism and complete spin polarization. However, these properties are known to degrade in thin films. Oxygen vacancies are believed to be a critical factor in this degradation, but experimentally isolating their effects has proven challenging. In this work, we use first-principles calculations to theoretically investigate how oxygen vacancies affect the magnetic structure of LSMO thin films. Our results reveal that oxygen vacancies act as scattering centers, leading to charge redistribution within the bulk layers. This redistribution disrupts the ferromagnetic double-exchange interaction and introduces competing super-exchange interactions, causing local spin flipping and ultimately reducing the overall magnetization. 

Abstract Multiferroics are a unique class of materials where magnetic and ferroelectric orders coexist. The research on multiferroics contributes significantly to the fundamental understanding of the strong correlations between different material degrees of freedom and provides an energy‐efficient route toward the electrical control of magnetism. While multiple ABO₃oxide perovskites are identified as being multiferroic, their magnetoelectric coupling strength is often weak, necessitating the material search in different compounds. Here, the observation of room‐temperature multiferroic orders in multi‐anion SrNbO_3−xN_xthin films is reported. In these samples, the multi‐anion state enables the room‐temperature ferromagnetic ordering of the Nb d‐electrons. Simultaneously, ferroelectric responses that originate from the structural symmetry breaking associated are found with both the off‐center displacements of Nb and the geometric displacements of Sr, depending on the relative O‐N arrangements within the Nb‐centered octahedra. The findings not only diversify the available multiferroic material pool but also demonstrate a new multiferroism design strategy via multi‐anion engineering.