In order to obtain a hexagonal barium ferrite (BaM) film with large saturation magnetization, we attempted to reduce the thickness of a ZnO underlayer and to deposit BaM film on underlayers of various materials such as α-Fe₂O₃, amorphous barium ferrite (a-BaM), amorphous BaFe₆O₁₀ (a-BaFe₆O₁₀), and ZnFe₂O₄. The following results were obtained: (1) A ZnO underlayer less than 10 nm thick significantly degraded the c-axis orientation of the BaM films. (2) A BaM film with c-axis orientation was obtained only on ZnO, a-BaM/ZnO, and ZnFe₂O₄ underlayers. In particular, a film deposited on a (111)-oriented ZnFe₂O₄ underlayer had excellent c-axis orientation and magnetic properties. (3) The saturation magnetizations of films deposited on the various underlayers had low values below 260 emu/cc, and could not be increased by reducing the thickness of the ZnO underlayer or by depositing the film on an underlayer that did not contain ZnO.