Mechanism of the lattice relaxation in thin epitaxial films of iron oxides: Generalization from the case of ilmenite-hematite solid solution

► Overshoot of the in-plane lattice parameter above its expected value is observed for iron oxides. ► We use ilmenite-hematite solid solution for the experimental and theoretical descriptions of overshoot. ► We explain the overshoot in terms of the surface atom displacements at low thicknesses. ► This displacement is due to the strong lattice relaxation via the dislocation formation. ► The experimental results are in agreement with used theory.