Strain-Preserving Transfer of Freestanding Oxide Membranes for Tunable Magnetic Anisotropy

Epitaxial strain has been widely used as an effective approach for harnessing magnetic anisotropy (MA) of complex oxide-based heterostructures, which enables essential building blocks for advanced spintronic applications. However, extending this strain engineering of MA to flexible magnetic systems and devices is largely hindered by strain relaxation during the exfoliation and transfer procedures of freestanding oxide membranes. To address this challenge, we develop an epoxy-assisted transfer (EAT) approach that effectively preserves the epitaxial strain state in freestanding oxide membranes. Using this approach, we impose compressive strain on the ferromagnetic freestanding La_2/3Sr_1/3Mn_0.9Ru_0.1O₃ films and achieve robust perpendicular magnetic anisotropy (PMA) up to 4.2 × 10⁵ J/m³. This strain-preserving transfer recipe can be further applied to a variety of ferromagnetic oxide membranes, such as La_2/3Ca_1/3MnO₃ and SrRuO₃, for stabilizing uniaxial in-plane MA and even tilted PMA. Our work addresses the long-standing trade-off between structural flexibility and control of MA in oxide-based heterostructures, offering versatile and innovative design strategies of flexible spintronic devices with customizable functionality.