Ba-ferrite films with small c-axis dispersion angle Δθ
50are suitable for ultrahigh density recording media. The dependences of partial oxygen gas pressure P
O2and total discharge gas pressure P
Totalon the characteristics of Ba-ferrite films were clarified. It was found that there were three regions, where films were composed of single layer of spinel type ferrite(P
O2≤0.002mTorr), mixed layer of spinel and magnetoplumbite type ferrites (

mTorr) and single layer of magnetoplumbite type ferrite (P
O2>0.3 mTorr). In the range of P
02between 0.005 and 0.2 mTorr, spinel-like ferrite layer plays very important role as an underlayer to decrease the Δθ
50of the Ba-ferrite layer. Films deposited at relatively low P
O2and P
Totalexhibit very smooth surface and Δθ
50as small as

.