Ferrimagnetic spinel CoFe 2 O 4 (CFO) films are integrated with Si(111) using Sc 2 O 3 buffer layers. The huge lattice mismatch (17%) between CFO and Sc 2 O 3 is accommodated by domain matching, and CFO grows epitaxially with (111) out-of-plane orientation and coexistence of A-and B-type in-plane crystal variants. CFO films have low roughness of 4 Å and saturation magnetization of about 300 emu/cm 3 . These properties make CFO films on Sc 2 O 3 -buffered Si(111) comparable to those grown on oxide single crystals and thus extend the possibilities of using spinel oxides in electronic devices. 1,4 But the future incorporation of spinel oxides as active materials in electronics will critically depend on its epitaxial integration with silicon, which requires a buffer layer to avoid chemical interaction and allows lattice matching. Epitaxy of CFO and similar spinels has been achieved on Si(001), using yttria-stabilized zirconia (YSZ) as buffer layer.5,6 (111) faces in spinels typically have the lowest surface energy and thus these oxides tend to form (111) facetted islands when they grow (001)-oriented, 7 or to grow (111)-oriented, 5,6 which breaks the in-plane symmetry at the interface from four-to three-fold forming four in-plane CFO crystal variants. Si(111) wafers, favouring (111) out-of-plane orientation, can thus be a better choice as substrate for epitaxial growth of spinel films with higher crystalline quality.Some oxides that grow epitaxially and two-dimensionally directly on Si (111) 14 Sc 2 O 3 is a candidate as high-k dielectric for replacing conventional gate oxides in metal oxide semiconductor field effect transistors (MOSFETs). Its additional use as buffer layer for integration of ferrimagnetic CFO on silicon could add functionalities to complementary MOS (CMOS) logic circuits. However, the possibility of epitaxial growth of CFO (cubic Fd3m, a CFO ¼ 8.3919 Å ) on Sc 2 O 3 is challenging due to huge lattice mismatch:(a Sc2O3 À a CFO )/a CFO ¼ 17.3%. Nevertheless, domain matching epitaxy (DME) 15 could be active thus still leaving some room for high quality epitaxy. In DME, the misfit between film and substrate is reduced by matching of m lattice planes of the film with n lattice planes of the substrate. 15 There will be misfit dislocations in the domains, but each block of m lattice planes of the film accommodates on n lattice planes of the substrate with low overall strain.Using pulsed laser deposition (PLD), we have grown high quality epitaxial CFO films on Sc 2 O 3 /Si(111). It will be shown that CFO films are (111) out-of-plane oriented, they present two crystal variants (denoted A and B, corresponding to [11-2]