Tuning of Electrical Transport Performance in La0.67Sr0.33MnO₃ Films by a Sr₄Al₂O₇ Buffer Layer for Freestanding Membrane-Based Devices

Strain engineering of the electrical and magnetic properties of perovskite manganites has attracted reasonable attention during the last decades. Here, we introduce a newly discovered Sr4Al2O7 as a buffer layer and achieve a successful tuning of the electrical transport properties of the La0.67Sr0.33MnO3 film grown by pulsed laser deposition via controlling the thickness and crystallinity of Sr4Al2O7. For a poorly crystallized Sr4Al2O7 buffer layer, the metallic and insulating state of La0.67Sr0.33MnO3 can be modulated by a small range of Sr4Al2O7 thickness, which is ∼2 nm for a film grown on LaAlO3 and ∼4 nm on SrTiO3 due to the different lattice mismatch. This Sr4Al2O7 buffer layer-controlled epitaxial growth and epitaxial strain provides a strategy to largely modulate the physics properties of perovskite manganites by a small change of the buffer layer. After dissolving Sr4Al2O7, the electrical transport properties of La0.67Sr0.33MnO3 can be preserved well in the freestanding films, showing the promising application potential for innovative electronic devices.