Interlayer‐Mediated Stabilization of Metastable <i>P</i>6₃<i>cm</i> ScFeO₃ on Al₂O₃

Abstract The metastable P 6 3 cm phase of ScFeO 3 has potential for multiferroic applications not possible in the ground state if stabilization routes can be identified. This work demonstrates that the P 6 3 cm phase of ScFeO 3 is stabilized on (0001) Al 2 O 3 by the spontaneous formation of two atomic layers of (111) Fm m FeO during pulsed laser deposition, as observed via scanning transmission electron microscopy and a shift in the Fe L‐edge on approaching the interface. The matching oxygen sublattice and reduced strain of the FeO interlayer enable a ScFeO 3 [110] || [2] FeO || Al 2 O 3 [110] orientation relationship despite a −17.1% lattice mismatch. Temperature‐dependent X‐ray diffraction further support interlayer‐mediated stabilization, as FeO forms above 850 °C, preceding the formation of the P 6 3 cm ScFeO 3 phase at 1000 °C. The identification of the FeO interlayer provides insights into the phase stabilization mechanism of P 6 3 cm ScFeO 3 and presents a strategy for stabilizing other metastable materials that lack epitaxial substrates.