We attempted to deposit a hexagonal barium ferrite (BaM) film with a thickness of less than 50 nm by using an alternate periodic atomic layer deposition method. BaM films from 11.5 to 115 nm thick were deposited at 630°C on a ZnFe2O4 (20nm) underlayer of (111) texture. Compared with films deposited by conventional sputtering, the film obtained in this study had excellent c-axis orientation and crystallinity. Even the BaM film with a thickness of 11.5 nm had clear X-ray diffraction peaks from the BaM c-plane. The crystallite size of the film decreased significantly as the thickness of the BaM layer decreased, and the typical crystallite size of the 11.5-nm-thick film was about 25 nm. The coercive force of the film in the perpendicular direction, however, decreased markedly as the thickness of the BaM layer decreased below 23 nm. A magnetic intermediate layer was produced in the film between the BaM layer and ZnFe2O4 underlayer, and thus the film had a double layer structure composed of a BaM layer with perpendicular magnetization and an intermediate layer with an in-plane magnetization.
