Tunable Electrical Transport and Magnetic Anisotropy in Textured SrRuO ₃ Films Mediated by Gap Control of Monolayer Ca ₂ Nb ₃ O ₁₀ Nanosheet Templates

The deterministic integration of functional oxide thin films on technologically relevant substrates is a longstanding challenge for oxide electronics. Two-dimensional Ca 2 Nb 3 O 10 nanosheets have emerged as versatile epitaxial templates, enabling high-quality film growth on arbitrary substrates by decoupling the overlying layer from the underlying support. However, the intrinsic gaps inherent in monolayer nanosheet assemblies originate from irregular geometry and stochastic deposition processes. These gaps create exposed substrate regions that introduce a second, distinct growth environment, whose influence on film properties remains poorly understood. Here, we demonstrate that these nanoscale gaps are not merely structural imperfections but rather tunable elements that govern the crystallinity, transport behavior, and magnetic anisotropy of SrRuO 3 thin films. By engineering Ca 2 Nb 3 O 10 nanosheets with controlled lateral size distributions (>20 μm and <2 μm) and systematically varying substrate coverage (≈90% and ≈95%), precise modulation of the crystallographic phase of gap-nucleated SrRuO 3 is achieved. The phase varies from amorphous on SiO 2 to polycrystalline on Si and Al 2 O 3, and coexists with c -axis-oriented epitaxy templated by the nanosheets. This coexistence gives rise to emergent phenomena including nonuniaxial magnetic anisotropy, two-channel anomalous Hall signatures, and stepwise magnetization reversal, all of which are tunable through coverage and substrate selection. Bilayer nanosheet coatings effectively eliminate gap contributions, restoring pristine in-plane easy magnetization axis and confirming complete film–substrate decoupling. Our findings establish a previously unrecognized design paradigm in which the deliberate control of nanosheet gaps enables the engineering of composite magnetic and electronic ground states in oxide thin films, providing a scalable route toward multifunctional spintronic devices on arbitrary substrates.