Enhanced coercive and remanence fields for CoFe2O4 and BaFe12O19 bilayers deposited on (111) MgO

High quality epitaxial bilayer films of spinel CoFe2O4 (CoF) and M-type hexagonal ferrite BaFe12O19 (BaM) were deposited onto (111) magnesium oxide (MgO) substrate by pulsed laser ablation deposition. X-ray diffraction patterns of both BaM/CoF and CoF/BaM films showed only (0001) BaM, (111) CoF, and (111) MgO peaks. The highest coercive field of Hc=1.4 kOe was obtained for a BaM/CoF film where the CoF layer was deposited at 400 °C, which was higher than typical Hc values of ∼0.4 kOe found for single layer BaM films on (111) MgO. This was less than the Hc∼3.0 kOe found for (111) CoF films deposited at 400 °C, probably due to in situ annealing effects during the growth of the overlying BaM film at 900 °C. This Hc enhancement for BaM/CoF bilayers as compared to BaM/MgO films may provide a means to combine large coercive fields with high quality hexaferrite films.