Biaxial Strain Control of Helimagnetism via Chemical Expansion in Thin Film SrFeO3
Jennifer Fowlie, Jiarui Li, Danilo Puggioni, Lucas Barreto, Lin Ding Yuan, James M Rondinelli, Ronny Sutarto, Teak D Boyko, Fabio Orlandi, Pascal Manuel, …
We demonstrate control of helimagnetic order in biaxially strained SrFeO3 thin films using neutron diffraction and resonant soft x-ray scattering. SrFeO3, a negative charge-transfer oxide, exhibits a complex magnetic phase diagram that includes multi-q spin structures. Tensile epitaxial strain produces a pronounced shortening of the helimagnetic ordering length and a tilting of the magnetic ordering vector. We interpret this behavior in terms of chemical expansion: lattice dilation under tensile strain lowers the energetic cost of oxygen vacancies, leading to an expanded unit cell that modifies Fe-O hybridization and enhances superexchange relative to double exchange. These results reveal how epitaxial strain can indirectly tune helimagnetism through defect-driven chemical expansion, highlighting the strong coupling between lattice, chemistry, and magnetic order in transition-metal oxides. Our findings establish chemical expansion as an effective mechanism for engineering complex magnetic textures in oxide thin films, with implications for spintronic, magnonic, and quantum information applications.
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Biaxial Strain Control of Helimagnetism via Chemical Expansion in Thin Film SrFeO3