Cross‐sectional observations of YBa2Cu3Oy/La0.7Ca0.3MnOz/YBa2Cu3Oytrilayered films on MgO (100) substrates were performed using transmission electron microscopy. Each layer grows epitaxially with crystal orientations of YBa2Cu3Oy(100)∥ La0.7Ca0.3MnOz(110) ∥ YBa2Cu3Oy(100)∥ MgO(010). The Mn—O—Mn bond is parallel to the Cu—O—Cu bond. A reactant is absent at the interfaces and the La0.7Ca0.3MnOzlayer is continuous until a thickness of about 7 nm.