Stacking-engineered magnetic anisotropy in bilayer SrRuO3 freestanding membranes

The emergence of freestanding oxide membrane technology has enabled the layer-by-layer stacking of these materials in a manner analogous to two-dimensional (2D) van der Waals (vdW) heterostructures. Magnetic anisotropy is of great significance for magnetic materials and spintronics; however, investigations into the magnetic properties—particularly magnetic anisotropy—of such stacked oxide membranes remain scarce. Here, we fabricate bilayer SrRuO3 heterostructures by stacking two freestanding SrRuO3 membranes using water-soluble Sr3Al2O6 as a sacrificial layer. The freestanding SrRuO3 single layers exhibit two coexisting magnetic components with perpendicular and in-plane magnetic anisotropies. We demonstrate that stacking two SrRuO3 single layers leads to a substantial suppression of the perpendicular magnetic anisotropy. This behavior is consistently observed across bilayer SrRuO3 membranes spanning a wide range of thicknesses, establishing the universality of this phenomenon. Unlike traditional 2D-material stacking that yields weak interlayer vdW coupling, the present work induces easy-axis rotation via interlayer atomic bonding in the bilayer freestanding membranes. These findings provide a versatile strategy for engineering magnetic anisotropy in complex oxides for spintronic applications.